subject:"RE\: EMC\-related safety issues"

Dear Ken
Sorry to be so late replying, but I have been unable to read any of the 
correspondence in this thread for a week.

In an attempt to spare the emc-pstc more of our arguing I will not reply in 
detail to three of your emails, one from the 6th Jan, and two from the 7th 
Jan, because they all deal with what I think is the core issue:

"Can the emissions from an 'intentional radiator' such as a laptop that is 
compliant with CISPR22 and/or FCC limits interfere with an electronic product 
that is not an intentional radio receiver and possibly cause a safety 
problem?"

Have I summarised the issue correctly?

I am of the opinion, and I think the other correspondents are too, that the 
answer is: "Yes they can in some circumstances but it should be unlikely 
these days". 

I think the reasons for this conclusion include...

a) Products with compliant fields at 10 metres distance might have 
considerably stronger fields closer to, especially in their near field.

b) The mandatory standards don't measure all the frequencies that could be 
emitted from the compliant laptop and possibly cause interference (e.g. audio 
frequency magnetic fields from fluctuating dc power supply currents can 
interfere directly with nearby audio or low-frequency transducer circuits).

c) Some circuits are very sensitive (especially some transducer amplifiers), 
or not well-designed for RF immunity, or both at the same time.

What do you think, Ken? 
What do the other emc-pstc members think?
Can we please finish this debate now?

Regards, Keith Armstrong
PS: I will not be able to reply to postings in this thread for about another 
week.

Re: EMC-related safety issues

Dear Ken
Sorry to have taken so long to reply to this. 
I haven't been able to read any of the contributions for a week.

I have to say that I don't recognise myself, or the IEE's guide on EMC and 
Functional Safety or the 30+ respected and senior engineers who contributed 
to it, or the IEE itself, in any way whatsoever in your descriptions below.

Have you read the IEEE's Ethical Policy? (That's the IEEE not the IEE).

What do you think of it?

Regards, Keith Armstrong
PS: I will not be able to reply to postings in this thread for about another 
week.

In a message dated 07/01/02 02:37:17 GMT Standard Time, 
ken.ja...@emccompliance.com writes:

> Subj:Re: EMC-related safety issues
> Date:07/01/02 02:37:17 GMT Standard Time
> From:ken.ja...@emccompliance.com (Ken Javor)
> To:cherryclo...@aol.com, j...@jmwa.demon.co.uk
> CC:emc-p...@majordomo.ieee.org
> 
> The question of ethics or morality is at the heart of this discussion which 
> makes it much more important than technical discussions about 
> electromagnetism, which is the ONLY reason I have pursued this so far.  I 
> was critical of the IEE safety guide on MORAL grounds.  It is part of the 
> morality which says that businessmen or producers are considered guilty 
> until proven innocent because of what they are - profit-making producers.  
> That it is immoral to make a profit and anyone doing so is taking advantage 
> of someone else.  This is not the morality which built the USA into the 
> world's wealthiest nation, but it is the morality which will reduce us to 
> the most impecunious.  The strict Muslim countries that have been in the 
> news of late forbid loaning of money at interest, because the Koran forbids 
> usury.  It is no accident that these countries all belong to the third 
> world.  Progress depends on the ability to raise capital.  The most 
> efficient way to do that is for people who have profited from past ventures 
> to invest those profits in new ventures.  That is what banks facilitate.  
> If there are no profits, then there is no money to borrow and to start a 
> venture and progress stops or becomes agonizingly slow.   A policy which 
> says that producers are liable for unlimited damages without needing to 
> show defect or negligence is on a moral level with the prohibition of 
> lending money at interest.  We have to decide if we wish to live in a 
> civilized world or not.  That is a question of moral significance.
> 
> The idea that businessmen are immoral greedy people who give no thought to 
> the quality of their products is an ugly lie spread by enemies of 
> capitalism.  A little thought will show that businessmen who operate like 
> this do not stay in business long because their products get a bad 
> reputation.  Certainly you can find examples of bad or ignorant behavior.  
> Does this justify policies which assume all businessmen are evil and that 
> they must be reined in by pure-hearted regulators?  What makes the 
> regulators pure-hearted?  That they don't make profit, but siphon profits 
> away?  What is the cost of the regulation relative to the benefit?  What 
> marvelous inventions didn't occur because the seed money necessary to 
> initiate a development wasn't there?   
> 
> When engineers make false claims that unintentional RE from ITE can cause 
> safety-critical circuits to fail catastrophically, we engage in another 
> moral transgression.  We attempt to get a short term gain at the cost of 
> long  term loss.  The short term gain is to make ourselves and our 
> profession look more important.  But the long term loss is that of the 
> little boy who cried wolf.  After a long enough period of false alarms, we 
> will lose the respect and ear of management and if we must raise a REAL 
> issue, it will fall on deaf ears.  I have no way of knowing, but I wonder 
> how many unfulfilled warnings the managers who OK'd the launch of 51L 
> (Challenger) had listened to prior to making their fateful decision.
> 
>

Re: EMC-related safety issues

Dear Ken
Sorry to have taken so long to reply to this. Pressure of work has kept me 
away from the thread for a week.

I don't know where you get your maths from.

The usual formula (commonly available in a number of variants) for the 
radiated emissions E in V/m at 10 metres due to a common-mode current is:

E = 1.26 10^-4 (f.L.ICM)

f = frequency in MHz
L = length of the radiating cable in metres
ICM = common-mode current in the cable in milliamps

Using L = 1.5 metres (not a long cable) and f = 100MHz, I find that 92dBuV/m 
(= 40mV/m) can be created at 10 metres distance by a CM current of just 2mA.

2mA is a far cry from your "significant fraction of an Ampere of common mode 
rf current".

Hence my serious concerns about your math.

I also don't agree with a number of other things in your analysis below, 
especially as you finish by saying: "If you consider that any signal with 
information content carried by 2 mV is shielded, the issue becomes, once 
again, a non-problem." 

I don't think you can make the assumption that cables carrying low level 
signals are shielded. 
Remember that this thread began with a discussion of EMC-related safety 
issues, and where safety is involved one shouldn't make assumptions that 
everyone else designs equipment as well as you would like them to.

If we consider a country such as the US with no mandatory EMC immunity 
regulations, and a measuring device that uses analogue technology and does 
not have to meet emissions standards, it is obvious that the lowest cost way 
to design and market it is to leave out all the shielding and filtering, and 
I would expect a proportion of manufacturers to do just that.

I will spare the emc-pstc a longer email by not responding to the other 
issues I don't agree with at this time. 

Maybe other contributors would like to support your analysis below? or not.

Regards, Keith Armstrong.
PS:  It will be another week before I can reply again to postings in this 
thread.

In a message dated 07/01/02 02:46:46 GMT Standard Time, 
ken.ja...@emccompliance.com writes:

> Subj:Re: EMC-related safety issues
> Date:07/01/02 02:46:46 GMT Standard Time
> From:ken.ja...@emccompliance.com (Ken Javor)
> Sender:owner-emc-p...@majordomo.ieee.org
> Reply-to:  HREF="mailto:ken.ja...@emccompliance.com";>ken.ja...@emccompliance.com 
> (Ken Javor)
> To:cherryclo...@aol.com
> CC:emc-p...@majordomo.ieee.org
> 
> 
> QUOTE: "And I don't think that 92dBuV/m is a high field strength to be 
> emitted by a PC placed nearby, or for a non-compliant laptop at 10 metres."
> 
> You may not think so, but I am sorry, the numbers just don't add up.  92 
> dBuV/m at 10 meters implies an effective radiated power of 5.3 mW.  
> Consider that the source is not an intentional antenna.  It will have no 
> more directivity than a dipole and its efficiency will be much less since 
> it isn't matched to the source.  If we simply assume no gain (meaning 
> matching losses just offset directivity) , that means 5.3 mW of rf power 
> are emitted from the EUT or its attached cables.  If one makes the 
> reasonable assumption that it is common mode rf current which is radiating, 
> then the potential associated with rf power will be a small number of 
> millivolts (in the frequency domain).  This in turn implies a significant 
> fraction of an Ampere of common mode rf current.  A highly unlikely 
> situation!  Once again, with an impossible conclusion, either the 
> assumption or the logic must be wrong.  You can choose to disbelieve, but 
> please point out where the logic has gone awry.  You have several times 
> cited Mr. Woodgate for non-constructive criticism.  Now I am asking you, 
> don't give more hearsay: explain where my physics is incorrect.  We are 
> engineers here, not pollsters. 
> 
> And if you are saying that specification level compliance at 10 meters can 
> scale up to 92 dBuV/m nearby, that is either false or misleading depending 
> on the frequency range.  At the low end, say 30 MHz, the area subtended by 
> position near the offending PC isn't large enough to efficiently radiate or 
> couple the field (the wavelength is 10 meters, and the other gentleman's 
> antenna factor calculation assumed a tuned dipole antenna in order to get a 
> small antenna factor).  So the field will not scale up  as per your 
> prediction, and the pickup mechanism will be nowhere near the antenna 
> factor that gentleman calculated.  In fact at 30 MHz your antenna factor 
> will be on the order of 20 dB or worse (assuming the mutual coupling length 
> to be 1 m).  At the high end (near 1 GHz) you could be in the far field in 
> close and the field could scale up to a value of 92 dBuV/m, but the antenna 
> factor of a matched tuned dipole at 1 GHz is 26 dB so the potential from 
> that perfect antenna is 92 dBuV/m - 26 dB/m = 66 dBuV or 2 mV.  If you 
> consider that any signal with information content carried by 2 mV is 
> shielded, the issue becomes, once again, a non-p

Re: EMC-related safety issues

Dear John
Sorry to have taken so long to reply.

We were talking about safety-related systems. 

The general approach is to add additional back-ups to the safety related 
system to provide it with necessary reliability as far as safety is 
concerned, as I had hoped the examples in the full version of my original 
reply would help to make clear. 

Such reliability improvement exercises might have nothing to do with 
improving the EMC of a product or of making its functionality more reliable.

Safety engineers are not usually concerned about whether a product is 
reliable, merely that if it fails to function correctly (e.g. due to 
interference) then it should not become unsafe.  

Another example that does not involve a dual (or triple) electronic system 
with voting is a gas boiler control. These days, large commercial and 
industrial gas boilers are controlled by microprocessors taking inputs from a 
lot of sensors. 

We don't want to add to the cost by duplicating the electronic control 
systems and transducers using diverse technologies - as you so rightly 
pointed should be done to avoid what are known as 'common-cause failures'. 

So what we can do is use some good old fashioned engineering to ensure that 
if the controller goes haywire, the boiler shuts down safely. 

For instance, we can use a simple and well-understood type of gas valve that 
cuts the gas supply off if the flame goes out. No electronics, nothing to 
interfere with, but it stops the microprocessor from erroneously pumping out 
gas when the flame isn't lit because (for instance) someone is standing too 
near by talking on their cellphone.

If the microprocessor turns the flame up too high for too long and the boiler 
could overheat, our old friends the pressure relief valve and thermal trip 
come to the rescue. 

By using these additional components (and considering a few more failure 
scenarios) we can use an unreliable and cheap microprocessor with terrible 
EMC immunity performance and yet have great safety performance. The 
reliability of the system might be poor, and customers might be always 
complaining about their boilers cutting out, but as I said safety engineers 
(and safety test labs) don't care if you have a poor product that nobody will 
be pleased with, as long as it is safe.

The mistake that many people make is to confuse functional reliability 
(sometimes called availability or uptime, the reciprocal of downtime) with 
functional safety. A very unreliable and low-cost system can be a perfectly 
safe one, with appropriate design techniques.

Regards, Keith Armstrong
PS:  It will be another week before I can reply again to postings in this 
thread.

In a message dated 06/01/02 19:34:49 GMT Standard Time, j...@jmwa.demon.co.uk 
writes:

> Subj:Re: EMC-related safety issues
> Date:06/01/02 19:34:49 GMT Standard Time
> From:j...@jmwa.demon.co.uk (John Woodgate)
> Sender:owner-emc-p...@majordomo.ieee.org
> Reply-to: mailto:j...@jmwa.demon.co.uk";>j...@jmwa.demon.co.uk 
> (John Woodgate)
> To:emc-p...@majordomo.ieee.org
> 
> I read in !emc-pstc that cherryclo...@aol.com wrote (in <162.6b92ca5.296
> 9c...@aol.com>) about 'EMC-related safety issues', on Sun, 6 Jan 2002:
> >Yes, John, you are quite right in both your comments as far as you go: 
> >
> >1) You are not the only person who can dramatise an issue so as to 
> encourage 
> >people to debate it; 
> 
> I don't know what you are referring to. I have 146 articles already read
> in the thread: I don't see that the debate needs any encouragement.
> >
> >2) If you sold a single electronic safety-related circuit with a 
> failure 
> >probability of 10^ -9 to 100,000 customers the cumulative failure 
> >probability is indeed 10^ -4. As you correctly said, Olber's Paradox 
> does 
> >not apply in this area. 
> >
> >But nevertheless this does not mean we need to make electronic 
> circuits with 
> >failure rates equal to or better than 10^ -9. As you have said (and I 
> agree) 
> >this would be a very difficult task indeed and likely to be very 
> expensive, 
> >especially for any product using software. 
> >
> >So how do we square this particular circle? 
> >
> >Those members who are familiar with safety engineering techniques will 
> be 
> >familiar with the idea of building very reliable systems up using a 
> number 
> >of independent systems or devices each with lower reliability. These 
> have 
> >various names, such as 'redundant channels' or 'duplicate channels' or 
> >'safety back-ups' or 'fail-safe circuits' and many others. 
> >
> I don't see how this applies to the reduction of emissions or,
> practicably, to the improvement of immunity. Do you envisage three
> separate systems in every product, with majority voting? I suspect that
> in terms of improving immunity, it would be ineffective, because a
> disturbance that compromised one system would be very likely to
> compromise at least o

Re: EMC-related safety issues

Dear John
Sorry to have taken so long to reply.

We will have to disagree over the educational value of the EMC + Compliance 
Journal's "Banana Skins" column.

If you haven't seen anything that was CE marked but which was obviously not 
compliant, then I think you must be lucky. 

As I mentioned earlier, whenever EMC enforcers in the EU carry out random 
checks on products in the marketplace, they seem to find that around 30% are 
clearly not compliant (a broad-brush average, since it seems to depend on the 
type of product), and there have been some papers presented by such enforcers 
in recent years for which I will be pleased to provide such references as I 
have.

Your 'unfoggy' replacement statement was good, but only relevant to carefully 
limited circumstances. 
I notice you included the lines: "...are extremely unlikely to cause 
malfunction of other equipment having the degree of immunity afforded by 
normal design practices." – but could you please define exactly what you mean 
by "extremely unlikely", "malfunction" and "normal design practices". 

It seems to me that in the end, your improved alternative statement still 
needs to use foggy' language after all.

I am pleased that you agree with me that the debate in question –
(which I seem to remember concerned whether "unintentional emitters" that are 
compliant with emissions standards when measured at 10 metres can interfere 
with electronic circuits which are not intentional radio receivers) 
– cannot be answered with a definitive yes or no. 
Everyone other than a single correspondent to this thread seem to have 
difficulty in accepting this basic and scientifically correct statement.

As for the assertion that : "Doctors and surgeons kill people one at a time, 
but engineers do it by the thousand." - consider that in the EU in the 
mid-90's there were around 30,000 fires caused by failures in washing 
machines every year, a proportion of which resulted in property damage and a 
few end in deaths.

An engineer who designs a faulty consumer product or vehicle can put 
thousands of lives at risk. Ask Ford and Firestone about the deaths (and the 
cost to their companies) of their recent engineering error in fitting the 
Ford Explorer with Firestone Wilderness tyres (maybe that should  be tires). 
Maybe a more accurate statement (if a little foggier) would be "Doctors and 
surgeons kill people one at a time, but some engineers could do it by the 
thousand."

Regards, Keith Armstrong
PS:  It will be another week before I can reply again to postings in this 
thread.

In a message dated 06/01/02 19:34:57 GMT Standard Time, j...@jmwa.demon.co.uk 
writes:

> Subj:Re: EMC-related safety issues
> Date:06/01/02 19:34:57 GMT Standard Time
> From:j...@jmwa.demon.co.uk (John Woodgate)
> Sender:owner-emc-p...@majordomo.ieee.org
> Reply-to: mailto:j...@jmwa.demon.co.uk";>j...@jmwa.demon.co.uk 
> (John Woodgate)
> To:emc-p...@majordomo.ieee.org
> 
> I read in !emc-pstc that cherryclo...@aol.com wrote (in <14b.6d4a617.296
> 9c...@aol.com>) about 'EMC-related safety issues', on Sun, 6 Jan 2002:
> >Dear John 
> >The incubator I described was already on the EU market in the latter 
> half of 
> >the 1990s, when I helped to test and fix it. 
> >
> >And I'm sorry to disappoint 
> 
> Inappropriate word; I'm not interested in scoring debating points but
> exploring the approaches to 'EMC and Safety', which I think need to be
> explored.
> 
> >but I have already experienced several similar 
> >examples I could quote, such as the electric blanket that would change 
> its 
> >heat settings randomly when a bedside light was switched on or off, or 
> from 
> >other low-level mains transients. 
> >This is a potentially fatal issue for certain kinds of invalid, or 
> people 
> >who are blind drunk (surely no person reading this would ever be in 
> such a 
> >state)  and by the way, this is not me being emotive again, 
> 
> I agree; what you have written here is not emotive.
> >it was the 
> >expressed concern of the manufacturer and one of the reasons why they 
> called 
> >me in. They sacked their Technical Director over this incident. 
> >They also didn't do a product recall despite having an estimated 
> 100,000 
> >products with the problem already out in the field. Of course, as a 
> >responsible engineer (and to cover my ass) I wrote them a letter 
> >recommending that they did a product recall (while thinking of the 
> designers 
> >of the Challenger Space Shuttle's infamous O-ring seals). 
> >
> >I find that many independent EMC people have dozens of similar 
> examples, 
> >which they can't talk about very much because of commercial 
> confidentiality. 
> >This is one reason why the EMC + Compliance Journal 
> >(www.compliance-club.com) started its 'Banana Skins' column - to help 
> >educate practising engineers about real EMC engineering problems they 
> almost 
>

Re: EMC-related safety issues

Dear Ken and John
Sorry to have taken so long to reply to your emails about my 200MHz 
oscillating HCMOS example. I hope it is OK to reply to you both in one email, 
too.

Replying to Ken...
My example was not an urban myth, it was a real example (although I didn't 
measure its RF field or estimate its ERP so can't vouch for their accuracy).

It was an unlikely chain of events that caused the problem, and it was not 
the HCMOS device that was doing the actual radiating.

The large PCB on which the HCMOS hex inverter was located had a 0.5 inch wide 
ground and power trace running all around its perimeter, one on each side of 
the two-layer PCB. Thin traces ran from these 'power buses' to all the ICs on 
the PCB.
The dimensions of the perimeter traces were perfectly right for resonance at 
200MHz (and there were no decouplers between the traces) and they made a 
wonderful rectangular frame antenna at that frequency too. 

The HCMOS device that suffered the unterminated gate was in the centre of the 
PCB and got its +5V from the trace at the top of the PCB, its 0V from the 
trace at the bottom, thereby making an excellent driver for the resonant 
circuit. The end result was a high-Q resonant 'tank' circuit being driven by 
the hard-switching device, and setting the basic oscillation frequency. 
Because the device was hard switching, it didn't heat up. Because the tank 
circuit had such high-Q and was also a great antenna it radiated the 200MHz 
component but not the other harmonics of the hard switching device. 

The result was a very efficient 200MHz transmitter design that RF transmitter 
designers would understand. I don't find it unusual that it could create 
quite strong field strengths.

My point in making this example is that events can sometimes combine to catch 
designers out.

Replying to John
I'm sure I said in my original posting on this example, that the HCMOS was 
'hard switching' and not producing a sine wave. A hot device was, of course, 
the first thing I looked for, and didn't find any. See the additional 
information above.

Regards, Keith Armstrong
PS:  It will be another week before I can reply again to postings in this 
thread.

> Date: 07/01/02 06:35:46 GMT Standard Time 
> From:j...@jmwa.demon.co.uk (John Woodgate) 

> Indeed, and assuming a 5 V supply, the current would be around 400 mA.
> At 200 MHz, the dissipation would be several hundred milliwatts. 

> The absence of harmonics even suggests that this gate was producing a
> sine-wave, which makes the figures even higher and less credible.

In a message dated 07/01/02 02:37:12 GMT Standard Time, 
ken.ja...@emccompliance.com writes:

> Subj:Re: EMC-related safety issues
> Date:07/01/02 02:37:12 GMT Standard Time
> From:ken.ja...@emccompliance.com (Ken Javor)
> To:cherryclo...@aol.com
> CC:m...@california.com, ghery.pet...@intel.com, 
> james.col...@usa.alcatel.com, emc-p...@majordomo.ieee.org
> 
> Quote : "Who would have expected an unterminated HCMOS gate to be able to 
> emit 2W at 200MHz?"
> 
> Not me - 2 Watts of effective radiated power implies over 2.5 V/m at 3 m!  
> I guess I have a hard time believing that was transmitted from an HCMOS 
> gate.   I think a little common sense will go a long way towards retiring 
> some of these EMC-urban legends.
> 
> on 1/6/02 10:40 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote:
> 
> >> A.2) A portable computing device used in an automatic change machine on 
>> board transport was tested to be fully compliant with EN 55022 (approx = 
>> CISPR 22). 
>> I helped the manufacturer investigate complaints of interference and 
>> discovered that sub-fitted variant, which had not been tested for EMC 
>> compliance, left an HCMOS inverter IC with an unterminated inverter - 
>> which promptly decided to self-oscillate at 200MHz. (Many manufacturers of 
>> products with a number of build variants only test the fully-loaded one 
>> for EMCD compliance and assume the others are at least as good.) 
>> 
>> The very interesting thing about this example is that the power-ground 
>> structure of the PCB made a beautifully tuned antenna and resonant circuit 
>> at 200MHz, so although the inverter was hard-switching and did not run 
>> hot, the only emissions were at the 200MHz fundamental - no harmonics were 
>> emitted at all. 
>> 
>> Another very interesting thing is that some of the complainants had 
>> measured the equivalent radiated RF power from these devices as 2W. 
>> 
> Who would have expected an unterminated HCMOS gate to be able to emit 2W at 
> 200MHz?

Re: EMC-related safety issues

2002-01-08 Thread John Woodgate


I read in !emc-pstc that Wan Juang Foo  wrote (in
) about 'EMC-related
safety issues', on Tue, 8 Jan 2002:
>EMI from the ASMD (anti ship missile defence) radar had cause
>the communication equipment to be inoperable.  During this brief period, an
>Exocet missile was not seen homing in on HMS Sheffield

According to a TV documentary the other day, the two systems were on
nearly the same frequency, so this was really a case of a clash between
military and civilian spectrum usage rather than normal EMC. Note
'usage'; at that time the military had almost carte blanche on spectrum
usage, especially in a combat situation. 

Presumably the Commander (E) should have ditched the satellite link, but
the TV documentary said that the surveillance radar lost the echoes from
the Super-Etandards flying at zero altitude and the potential threat was
not passed on to Commander (E).

The moral here is that you ALWAYS give Jack-the-Operator the benefit of
the doubt if he says he saw or heard something, whether it's radar or
ASDIC.

These days, it is at least alleged that there is much better co-
ordination between the UK military and the civil authority on spectrum
usage.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
After swimming across the Hellespont, I felt like a Hero. 

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Re: EMC-related safety issues

2002-01-08 Thread Wan Juang Foo



Alas! at last, I am tempted to throw in a bit to stir the muddy waters
after what I have read on this thread that had hunderds of postings!:

I belive George Alspaugh's posting is  refering to USS Forrestal if it is
the US Navy and it is 1967.
 134 dead: (July 29, 1967), the carrier USS Forrestal was conducting combat
operations in the Gulf of Tonkin, Vietnam. A 'Zuni' missile was launched
from an F-4 Phantom aircraft and ripped into an A-4 Skyhawk's belly fuel
tank.  A fire soon raged, which caused seven additional explosions on the
flight deck.

Train your search engine on USS Forrestal

Black Hawk helicopters crash:
( mid 1980s) US Army experienced 29 crashes of its UH-60 Black Hawk
helicopters, at least five of which were believed to be due to RFI.  The
helicopter exhibited flashing indicator lights and other unintended
responses by the stabilizer when it was near radar and microwave towers.
The US Navy also flies UH-60s under the name of Sea Hawks, but experienced
no RFI incidents.  The Navy had the chopper's manufacturer use additional
shielding to meet greater electromagnetic ambient requirements.
Eventually, the Army retrofitted its helicopters with additional shielding.

If it is in the 80's then it is the British navy (HMS Shelfield their story
of defence contractors being granted a concession for their lack of EMC!)
HMS Sheffield
 20 dead:  During the Falklands war (May 4, 1980) between UK and Argentina,
the British frigate, HMS Sheffield, was hit by an Exocet missile and ...
subsquently sunk.  The ships' surveillance radar was shut off during a GPS
reading communication equipment to report to London via a passing overhead
satellite.  EMI from the ASMD (anti ship missile defence) radar had cause
the communication equipment to be inoperable.  During this brief period, an
Exocet missile was not seen homing in on HMS Sheffield
:-)

Tim Foo,
(or just call me 'Tim')


geor...@lexmark.com
Sent by: owner-emc-p...@majordomo.ieee.org


01/03/02 11:57 PM
To:emc-p...@ieee.org

Subject:: EMC-related safety issues


There can be, and have been, safety related consequences of EM
incompatibility.
In the 1980's (as I recall) a U.S. aircraft carrier suffered a major EMC
disaster.  The powerful on-board electronics, particularly the radar units,
triggered the launch of a missle from one of the on-deck planes.  The
missle
struck the bridge tower, resulting in a fire costing millions of dollars in
repairs and the loss of some lives.  I cannot find my copy of this event,
reported some years ago in one of the electronics magazines.

In general, Navies are far more sensitive to EMI due to the concentration
of on-
board electronics.  As a result, the U.S. Navy version of the Blackhawk
helicopter
had few EMI problems, while the Army version had several early crashes due
to
interference from nearby radio stations.

The moral, if there is one, is that emissions and susceptibility of
unregulated
devices is more often the problem than the emissions or susceptibility of a
regulated device.

George Alspaugh
Lexmark International






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Re: EMC-related safety issues

2002-01-07 Thread John Woodgate


I read in !emc-pstc that Crabb, John 
wrote (in ) about 'EMC-related safety issues', on Mon, 7 Jan 2002:
>Any suggestions how to overcome this ? My previous antique datalogger
>didn't have this problem, but it eventually had to be scrapped due to lack
>of spare parts - and the expectation that a more modern unit would be
>better !.
AS Gert Gremmen says, this problem is pretty fundamental. Maybe the only
solution is to use resistive temperature sensors instead, such as
precision thermistors.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
After swimming across the Hellespont, I felt like a Hero. 

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Re: EMC-related safety issues

2002-01-07 Thread John Woodgate


I read in !emc-pstc that richwo...@tycoint.com wrote (in <846BF526A205F8
4BA2B6045BBF7E9A6ABC4FEA@flbocexu05>) about 'EMC-related safety issues',
on Mon, 7 Jan 2002:
>John, I have to disagree with your statement, "As far as CENELEC is
>concerned, it was a conscious decision not to incorporate 'EMC and Safety'
>issues into EMC standards, but to treat it
>as a separate subject."

>
>If this is true, how do you explain the fact that the Alarm Systems immunity
>standard EN 50130-4 requires a higher immunity levels and that, per clause
>6, the acceptance criteria is per the requirements of a CENELEC performance
>standard if it is published - e.g. EN 50132-2-1 (CCTV cameras), EN50132-4-1
>(Access Control). This certainly appears to be safety related.

I was referring to the Generic and Basic Standards. But the cases you
cite are related to *false alarms* or the opposite, i.e. purely system
malfunction. Insofar as the standards apply to fire alarms and/or social
alarms, safety-of-life is a consequent issue. AFAIK, none of those more
stringent limits was determined according to the principles specified in
IEC61508.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
After swimming across the Hellespont, I felt like a Hero. 

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Re: EMC-related safety issues

Regarding the snip below.  The fact that it is a radio that is the victim is
still the salient factor here.  The emissions in close to the lamp are
higher than at three meters, but only enough higher to affect a radio,
nothing else.  Regarding the thermocouple based incubator issue (sensitivity
on the order of uV).  If the sensitivity is truly at the level of uV, then
yes this device could respond to lower level emissions, IF the pickup
mechanism were of the same efficiency as a radio antenna.  If it is not, and
they actually took some pains to shield the wiring, then it should have a
little more immunity.  But I said before, and I don't believe was rebutted
on this, that if the device was susceptible at or near CISPR22/FCC limits,
then it should never have worked from the get-go, as anyone who has ever
made measurements on an OATS would understand.


1/7/02 6:49 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote:

Secondly  maybe when you  wrote the above you weren't thinking of the
previous correspondence in this thread about the proximity of the low-energy
lamp to a bedside radio.

Yes, I know, this concerned a radio receiver, what I mean to draw your
attention to is the discussion about the intention and validity of the EMC
standards  they simply do not cover situations where devices are placed
close to each other  so they cannot be relied upon to provide compatibility
in such situations.
Military EMC standards are more thorough in this respect.

RE: EMC-related safety issues

2002-01-07 Thread richwoods


Yes, Gert, there is a fine line. The alarm systems standards are written
around performance. It would be highly unlikely that the failure of a CCTV
camera to comply with the increased immunity standards would create a
physical hazard from the camera itself. Rather, failure of the camera to
perform as intented might result in an hazard caused by external conditions
that occur undetected (e.g., fire, robbery, intrusion, etc).

Richard Woods
Sensormatic Electronics
Tyco International


-Original Message-
From: CE-TEST [mailto:cet...@cetest.nl]
Sent: Monday, January 07, 2002 9:13 AM
To: richwo...@tycoint.com; emc-p...@majordomo.ieee.org
Subject: RE: EMC-related safety issues


Hi Richard, Group


I agree that those requirements look safety related, but they
are strictly functional. The difference is subtle:
As this standard is concerned with equipment used
for safety purposes, the requirements are thus safety related in
THAT sense, but not in the sense of equipment's safety or
safety risks CAUSED by using the equipment. These are
not considered, althouigh testin according to EN 50130 may contribute
to increased product safety.

Most safety topics can be found in LVD related standards, such as
EN 60730 (not for EN 50130 equipment).
Many LVD standards are not very elaborate about EM Safety, and
directly point to a deviation of the Generic standards.

I might say that "EM and safety of equipment"
 is an area that is completely unexplored.

(i do not use the abbreviation EMC as this topic is not about compatibility.
I should
use EMS (afety) but this abbreviation has  already been taken...)


Gert Gremmen




-Original Message-
From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of
richwo...@tycoint.com
Sent: maandag 7 januari 2002 14:13
To: emc-p...@majordomo.ieee.org
Subject: RE: EMC-related safety issues



John, I have to disagree with your statement, "As far as CENELEC is
concerned, it was a conscious decision not to incorporate 'EMC and Safety'
issues into EMC standards, but to treat it
as a separate subject."

If this is true, how do you explain the fact that the Alarm Systems immunity
standard EN 50130-4 requires a higher immunity levels and that, per clause
6, the acceptance criteria is per the requirements of a CENELEC performance
standard if it is published - e.g. EN 50132-2-1 (CCTV cameras), EN50132-4-1
(Access Control). This certainly appears to be safety related.

Richard Woods
Sensormatic Electronics
Tyco International


-Original Message-
From: John Woodgate [mailto:j...@jmwa.demon.co.uk]
Sent: Friday, January 04, 2002 11:49 AM
To: emc-p...@majordomo.ieee.org
Subject: Re: EMC-related safety issues



I read in !emc-pstc that cherryclo...@aol.com wrote (in <167.698dddc.296
70...@aol.com>) about 'EMC-related safety issues', on Fri, 4 Jan 2002:
>As my paper at the IEEE's EMC Symposium in Montreal and my recent
article in
>ITEM UPDATE 2001 show - at present EMC standards don't address safety
>issues, and most safety standards don't address EMC-related functional
>safety issues.

As far as CENELEC is concerned, it was a conscious decision not to
incorporate 'EMC and Safety' issues into EMC standards, but to treat it
as a separate subject.

Some people may find a clarification helpful. We have EMC matters,
concerned with compatibility between items of equipment, ensuring that
they continue to work (Criterion A in the Generic Standards) or fail
gracefully (Criteria B and C). These criteria do not address safety
issues, as indicated in paragraph 1 above. However, the Generic
Standards do have a limited 'blanket' requirement, that equipment must
not become unsafe *during testing*.

We also have safety matters per se, which don't involve EMC.

We ALSO have the separate subject, called 'EMC and Safety' or reasonable
variants thereof. This addresses the matter of equipment becoming unsafe
*in service* due to excessive emission levels in the environment, or
lack of sufficient immunity to acceptable emission levels. So far, this
seems perfectly reasonable.

BUT it stops seeming reasonable when the question 'What could go wrong?'
is asked and statistical data is used to attempt to answer it. To take a
very simple example (maybe over-simplified), we might say that the
probability of an unsafe occurrence should be less than 10^-9. That
immediately means that the designer of the equipment has to look at ALL
risk scenarios down to the billion-to-one against level of probability.
To say that that is difficult is surely a great understatement.

But some experts in the field seem to ignore that great difficulty, and
simply (or maybe not so simply) state that if the designer fails to take
into account ANY scenario that subsequently results in an unsafe
condition, the designer has failed in his professional responsi

RE: EMC-related safety issues

2002-01-07 Thread CE-TEST

In addition, the junction of any thermocouple is an inherent AC rectifier
that is out of control by the designer. Any impedance
unbalance between the two thermocouple wires (including the PCB and OPAMP)
will cause current to flow in the thermocouple junction and give rise to (large 
errors)
I personally found error from 120 degrees Kelvin at room temperature
using thermocouple meters for the process industry.
This inherent sensitivity of thermocouples disqualifies most designs for
reliability purposes.

Gert Gremmen

ce-test, qualified testing


http://www.cetest.nl

  -Original Message-
  From: owner-emc-p...@majordomo.ieee.org 
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of cherryclo...@aol.com
  Sent: maandag 7 januari 2002 12:49
  To: ken.ja...@emccompliance.com
  Cc: emc-p...@majordomo.ieee.org
  Subject: Re: EMC-related safety issues


  Sorry everyone! 
  When I replied yesterday to Ken's posting I didn't spot an error he had made. 

  He had assumed an incubator compliant to 1V/m close to a laptop, whereas the 
question I originally posed concerned an incubator such as the one I had tested 
that had full-scale temperature errors at 1V/m from 30 to 1000MHz. 

  So I hope you'll all forgive me if I redo part of my reply. Here goes... 

  Ken said (06/01/02 06:56:46 GMT Standard Time)... 

Would I feel comfortable placing a CISPR compliant PC next to a medical 
device qualified to 1 V/m?  There is an inherent (not planned) margin of safety 
here that is many orders of magnitude.   The answer is absolutely yes.  If 
there were a problem, I would expect it more to occur below 30 MHz, at the 
power supply switching frequency, IF the medical device processed extremely low 
levels of electrical signals and was poorly shielded.  But I believe there are 
separate immunity requirements which cover this eventuality as well. 


  Firstly – my original question concerned how close one would be prepared to 
place a fully-compliant laptop to the unmodified incubator, which as you will 
recall I found to give full-scale temperature errors at 1V/m field strengths 
from 30 to 1000MHz. 

  An incubator that was qualified to 1V/m (as per Ken's reply above) would be 
at least 28dB less sensitive to RF fields (assuming a square-law relationship 
for error voltage versus field strength) and would be much more robust. 

  In the EU such medical devices are expected to work properly in fields of at 
least 3V/m (you can't rely on the CE mark as any guarantee), but I posed the 
question about the unmodified incubator because I understand that outside of 
the EU few countries have mandatory immunity regulations. 

  Note that thermocouples have an output of between 3 and 50 uV/degreeC, so if 
you want to achieve ±0.1C accuracy you are looking to keep error voltages below 
0.3 to 5uV. It doesn't take much RF ingress to cause that level of error. 

  Note also that traditional thermocouple amplifier design (such as commonly 
seen in the 1960s and 1970s, and still lingering on in some products) brings 
the thermocouple wires straight into an opamp. No shielding, no filtering, and 
no CMR in the opamp at RF. Worst-case RF demodulation performance is almost a 
certainty with such a design. 

  Many other 'traditional' transducers using microvolt signal levels  used to 
use amplifiers designed just as badly for EMC, and I sincerely hope there are 
none of them left any more. 

  Aside: A typical comment from a UK EMC test lab manager (this one from a 
personal communication in 1998): "I was testing a temperature control system 
for immunity yesterday. As usual, I found that I could get any temperature I 
wanted simply by varying the RF frequency." 
  Just so you don't think my incubator example was a one-off. 

  Secondly – maybe when you  wrote the above you weren't thinking of the 
previous correspondence in this thread about the proximity of the low-energy 
lamp to a bedside radio. 

  Yes, I know, this concerned a radio receiver, what I mean to draw your 
attention to is the discussion about the intention and validity of the EMC 
standards – they simply do not cover situations where devices are placed close 
to each other – so they cannot be relied upon to provide compatibility in such 
situations. 
  Military EMC standards are more thorough in this respect. 

  And as I have already said, commercial EMC standards were not written with 
safety issues in mind, and most safety standards have not been written with 
EMC-related issues in mind (see my IEEE 2001 EMC Symposium paper and my longer 
article in ITEM UPDATE 2001 for details). 

  Regards again, Keith Armstrong 

  In a message dated 06/01/02 15:51:27 GMT Standard Time, cherryclo...@aol.com 
writes: 


Subj:Re: EMC-related safety issues 
Date:06/01/02 15:51:27 GMT Standard Time 
From:cherryclo...@aol.com 
Sender:owner-emc-p...@majordomo.ieee.org 
Reply-to: cherrycl

RE: EMC-related safety issues

2002-01-07 Thread CE-TEST


Hi Richard, Group


I agree that those requirements look safety related, but they
are strictly functional. The difference is subtle:
As this standard is concerned with equipment used
for safety purposes, the requirements are thus safety related in
THAT sense, but not in the sense of equipment's safety or
safety risks CAUSED by using the equipment. These are
not considered, althouigh testin according to EN 50130 may contribute
to increased product safety.

Most safety topics can be found in LVD related standards, such as
EN 60730 (not for EN 50130 equipment).
Many LVD standards are not very elaborate about EM Safety, and
directly point to a deviation of the Generic standards.

I might say that "EM and safety of equipment"
 is an area that is completely unexplored.

(i do not use the abbreviation EMC as this topic is not about compatibility.
I should
use EMS (afety) but this abbreviation has  already been taken...)


Gert Gremmen




-Original Message-
From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of
richwo...@tycoint.com
Sent: maandag 7 januari 2002 14:13
To: emc-p...@majordomo.ieee.org
Subject: RE: EMC-related safety issues



John, I have to disagree with your statement, "As far as CENELEC is
concerned, it was a conscious decision not to incorporate 'EMC and Safety'
issues into EMC standards, but to treat it
as a separate subject."

If this is true, how do you explain the fact that the Alarm Systems immunity
standard EN 50130-4 requires a higher immunity levels and that, per clause
6, the acceptance criteria is per the requirements of a CENELEC performance
standard if it is published - e.g. EN 50132-2-1 (CCTV cameras), EN50132-4-1
(Access Control). This certainly appears to be safety related.

Richard Woods
Sensormatic Electronics
Tyco International


-Original Message-
From: John Woodgate [mailto:j...@jmwa.demon.co.uk]
Sent: Friday, January 04, 2002 11:49 AM
To: emc-p...@majordomo.ieee.org
Subject: Re: EMC-related safety issues



I read in !emc-pstc that cherryclo...@aol.com wrote (in <167.698dddc.296
70...@aol.com>) about 'EMC-related safety issues', on Fri, 4 Jan 2002:
>As my paper at the IEEE's EMC Symposium in Montreal and my recent
article in
>ITEM UPDATE 2001 show - at present EMC standards don't address safety
>issues, and most safety standards don't address EMC-related functional
>safety issues.

As far as CENELEC is concerned, it was a conscious decision not to
incorporate 'EMC and Safety' issues into EMC standards, but to treat it
as a separate subject.

Some people may find a clarification helpful. We have EMC matters,
concerned with compatibility between items of equipment, ensuring that
they continue to work (Criterion A in the Generic Standards) or fail
gracefully (Criteria B and C). These criteria do not address safety
issues, as indicated in paragraph 1 above. However, the Generic
Standards do have a limited 'blanket' requirement, that equipment must
not become unsafe *during testing*.

We also have safety matters per se, which don't involve EMC.

We ALSO have the separate subject, called 'EMC and Safety' or reasonable
variants thereof. This addresses the matter of equipment becoming unsafe
*in service* due to excessive emission levels in the environment, or
lack of sufficient immunity to acceptable emission levels. So far, this
seems perfectly reasonable.

BUT it stops seeming reasonable when the question 'What could go wrong?'
is asked and statistical data is used to attempt to answer it. To take a
very simple example (maybe over-simplified), we might say that the
probability of an unsafe occurrence should be less than 10^-9. That
immediately means that the designer of the equipment has to look at ALL
risk scenarios down to the billion-to-one against level of probability.
To say that that is difficult is surely a great understatement.

But some experts in the field seem to ignore that great difficulty, and
simply (or maybe not so simply) state that if the designer fails to take
into account ANY scenario that subsequently results in an unsafe
condition, the designer has failed in his professional responsibility,
and may be held criminally responsible for negligence.

Well, let us be very circumspect designers and look at what immunity
levels we might need to get down to that 10^-9 probability. For radiated
emissions, the necessary test levels seem to be of the order of 100 V/m.
Test levels for other disturbances seem to be equally distantly related
to the levels normally experienced and to the test levels in pure EMC
standards.

We might conclude that assessment of EMC immunity per se is completely
unnecessary, because testing for 'EMC and Safety' requires test levels
of the order of 30 dB higher!

One could go, with the sort of reasoning advocated by some experts,
further into

RE: EMC-related safety issues

2002-01-07 Thread Crabb, John

Seeing that we have got round to the subject of thermocouples, etc, I often
use a Solartron SI3535D datalogger with thermocouples for measuring 
component temperatures, and find quite often that it does not give "correct"
readings when thermocouples are placed on transformers in switching
power supplies, high voltage transformers in monitors, etc.  I can get a 
"correct" reading by switching off the EUT momentarily, obviously 
removing the source of the problem. Note that the problem can occur 
even if the thermocouple is not making an electrical connection to the
component winding involved.
 
Any suggestions how to overcome this ? My previous antique datalogger
didn't have this problem, but it eventually had to be scrapped due to lack
of spare parts - and the expectation that a more modern unit would be
better !.
 
Regards,
John Crabb, Development Excellence (Product Safety) , 
NCR  Financial Solutions Group Ltd.,  Kingsway West, Dundee, Scotland. DD2
3XX 
E-Mail :john.cr...@scotland.ncr.com 
Tel: +44 (0)1382-592289  (direct ). Fax +44 (0)1382-622243.   VoicePlus
6-341-2289.

RE: EMC-related safety issues

2002-01-07 Thread richwoods


John, I have to disagree with your statement, "As far as CENELEC is
concerned, it was a conscious decision not to incorporate 'EMC and Safety'
issues into EMC standards, but to treat it
as a separate subject."

If this is true, how do you explain the fact that the Alarm Systems immunity
standard EN 50130-4 requires a higher immunity levels and that, per clause
6, the acceptance criteria is per the requirements of a CENELEC performance
standard if it is published - e.g. EN 50132-2-1 (CCTV cameras), EN50132-4-1
(Access Control). This certainly appears to be safety related.

Richard Woods
Sensormatic Electronics
Tyco International


-Original Message-
From: John Woodgate [mailto:j...@jmwa.demon.co.uk]
Sent: Friday, January 04, 2002 11:49 AM
To: emc-p...@majordomo.ieee.org
Subject: Re: EMC-related safety issues



I read in !emc-pstc that cherryclo...@aol.com wrote (in <167.698dddc.296
70...@aol.com>) about 'EMC-related safety issues', on Fri, 4 Jan 2002:
>As my paper at the IEEE's EMC Symposium in Montreal and my recent
article in 
>ITEM UPDATE 2001 show - at present EMC standards don't address safety 
>issues, and most safety standards don't address EMC-related functional 
>safety issues. 

As far as CENELEC is concerned, it was a conscious decision not to
incorporate 'EMC and Safety' issues into EMC standards, but to treat it
as a separate subject.

Some people may find a clarification helpful. We have EMC matters,
concerned with compatibility between items of equipment, ensuring that
they continue to work (Criterion A in the Generic Standards) or fail
gracefully (Criteria B and C). These criteria do not address safety
issues, as indicated in paragraph 1 above. However, the Generic
Standards do have a limited 'blanket' requirement, that equipment must
not become unsafe *during testing*.

We also have safety matters per se, which don't involve EMC.

We ALSO have the separate subject, called 'EMC and Safety' or reasonable
variants thereof. This addresses the matter of equipment becoming unsafe
*in service* due to excessive emission levels in the environment, or
lack of sufficient immunity to acceptable emission levels. So far, this
seems perfectly reasonable. 

BUT it stops seeming reasonable when the question 'What could go wrong?'
is asked and statistical data is used to attempt to answer it. To take a
very simple example (maybe over-simplified), we might say that the
probability of an unsafe occurrence should be less than 10^-9. That
immediately means that the designer of the equipment has to look at ALL
risk scenarios down to the billion-to-one against level of probability.
To say that that is difficult is surely a great understatement. 

But some experts in the field seem to ignore that great difficulty, and
simply (or maybe not so simply) state that if the designer fails to take
into account ANY scenario that subsequently results in an unsafe
condition, the designer has failed in his professional responsibility,
and may be held criminally responsible for negligence.

Well, let us be very circumspect designers and look at what immunity
levels we might need to get down to that 10^-9 probability. For radiated
emissions, the necessary test levels seem to be of the order of 100 V/m.
Test levels for other disturbances seem to be equally distantly related
to the levels normally experienced and to the test levels in pure EMC
standards. 

We might conclude that assessment of EMC immunity per se is completely
unnecessary, because testing for 'EMC and Safety' requires test levels
of the order of 30 dB higher!

One could go, with the sort of reasoning advocated by some experts,
further into the realms of fantasy. Suppose, for a particular piece of
equipment, the designer, with great diligence, identifies a million
threat scenarios, each of which has a probability of 10^-9. The
cumulative probability of ANY ONE of them occurring is only 10^-3. Bit
risky, that!

If the above reasoning seems flawed, consider a specific case, a lottery
with 2000 tickets, numbered  to 1999. One person can buy up to 5
tickets, and all tickets are sold. Consider the probability of a
'remarkable occurrence'. This might be the drawing of the number ''
or '' or '1234' or even '1010', depending on what you think is
'remarkable'. OK, we already have a cumulative probability down from 1
in 2000 to 1 in 667 or 1 in 500. Now add in the probability that a
participant in the lottery is chosen at random to draw the winning
number, and draws (one of) his or her own numbers .. 

You shouldn't be able to get very long odds on a 'remarkable
occurrence'! 
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk

After swimming across the Hellespont, I felt like a Hero.

Re: EMC-related safety issues

2002-01-07 Thread CherryClough

Dear all
I have to retire from this correspondence for a few days.
I look forward to reading what you have all decided by the end of the week.
Regards, Keith Armstrong

Re: EMC-related safety issues

2002-01-07 Thread CherryClough

Sorry everyone!
When I replied yesterday to Ken's posting I didn't spot an error he had made.

He had assumed an incubator compliant to 1V/m close to a laptop, whereas the 
question I originally posed concerned an incubator such as the one I had 
tested that had full-scale temperature errors at 1V/m from 30 to 1000MHz.

So I hope you'll all forgive me if I redo part of my reply. Here goes...

Ken said (06/01/02 06:56:46 GMT Standard Time)...
> Would I feel comfortable placing a CISPR compliant PC next to a medical 
> device qualified to 1 V/m?  There is an inherent (not planned) margin of 
> safety here that is many orders of magnitude.   The answer is absolutely 
> yes.  If there were a problem, I would expect it more to occur below 30 
> MHz, at the power supply switching frequency, IF the medical device 
> processed extremely low levels of electrical signals and was poorly 
> shielded.  But I believe there are separate immunity requirements which 
> cover this eventuality as well. 
> 
Firstly – my original question concerned how close one would be prepared to 
place a fully-compliant laptop to the unmodified incubator, which as you will 
recall I found to give full-scale temperature errors at 1V/m field strengths 
from 30 to 1000MHz. 

An incubator that was qualified to 1V/m (as per Ken's reply above) would be 
at least 28dB less sensitive to RF fields (assuming a square-law relationship 
for error voltage versus field strength) and would be much more robust. 

In the EU such medical devices are expected to work properly in fields of at 
least 3V/m (you can't rely on the CE mark as any guarantee), but I posed the 
question about the unmodified incubator because I understand that outside of 
the EU few countries have mandatory immunity regulations.

Note that thermocouples have an output of between 3 and 50 uV/degreeC, so if 
you want to achieve ±0.1C accuracy you are looking to keep error voltages 
below 0.3 to 5uV. It doesn't take much RF ingress to cause that level of 
error.

Note also that traditional thermocouple amplifier design (such as commonly 
seen in the 1960s and 1970s, and still lingering on in some products) brings 
the thermocouple wires straight into an opamp. No shielding, no filtering, 
and no CMR in the opamp at RF. Worst-case RF demodulation performance is 
almost a certainty with such a design. 

Many other 'traditional' transducers using microvolt signal levels  used to 
use amplifiers designed just as badly for EMC, and I sincerely hope there are 
none of them left any more.

Aside: A typical comment from a UK EMC test lab manager (this one from a 
personal communication in 1998): "I was testing a temperature control system 
for immunity yesterday. As usual, I found that I could get any temperature I 
wanted simply by varying the RF frequency." 
Just so you don't think my incubator example was a one-off.

Secondly – maybe when you  wrote the above you weren't thinking of the 
previous correspondence in this thread about the proximity of the low-energy 
lamp to a bedside radio. 

Yes, I know, this concerned a radio receiver, what I mean to draw your 
attention to is the discussion about the intention and validity of the EMC 
standards – they simply do not cover situations where devices are placed 
close to each other – so they cannot be relied upon to provide compatibility 
in such situations. 
Military EMC standards are more thorough in this respect. 

And as I have already said, commercial EMC standards were not written with 
safety issues in mind, and most safety standards have not been written with 
EMC-related issues in mind (see my IEEE 2001 EMC Symposium paper and my 
longer article in ITEM UPDATE 2001 for details). 

Regards again, Keith Armstrong 

In a message dated 06/01/02 15:51:27 GMT Standard Time, cherryclo...@aol.com 
writes:

> Subj:Re: EMC-related safety issues
> Date:06/01/02 15:51:27 GMT Standard Time
> From:cherryclo...@aol.com
> Sender:owner-emc-p...@majordomo.ieee.org
> Reply-to: mailto:cherryclo...@aol.com";>cherryclo...@aol.com
> To:ken.ja...@emccompliance.com
> CC:emc-p...@majordomo.ieee.org
> 
> Ken, replies below. 
> Regards, Keith Armstrong 
> 
> In a message dated 06/01/02 06:56:46 GMT Standard Time, 
> ken.ja...@emccompliance.com writes: 
> 
> >> Subj:Re: EMC-related safety issues 
>> Date:06/01/02 06:56:46 GMT Standard Time 
>> From:ken.ja...@emccompliance.com (Ken Javor) 
>> To:cherryclo...@aol.com, cortland.richm...@alcatel.com 
>> CC:emc-p...@majordomo.ieee.org 
>> 
>> What an EMC engineer who understands the physics of field-to-wire coupling 
>> would say is that the operation of non-antenna connected electronics 
>> associated with one subsystem will not be degraded by close proximity with 
>> the non-antenna connected electronics of another subsystem.  Forget 10 
>> meters.  Are the PCs in your office separated by 10 m?  Would you expect 
>> two PCs stacked side-by-side or one on top of the other to interact in any

Re: EMC-related safety issues

2002-01-07 Thread John Woodgate


I read in !emc-pstc that Ken Javor  wrote
(in ) about 'EMC-related
safety issues', on Sun, 6 Jan 2002:
>Quote : "Who would have expected an unterminated HCMOS gate to be 
>able to emit 2W at 200MHz?"
>
>Not me - 2 Watts of effective radiated power implies over 2.5 V/m 
>at 3 m!  I guess I have a hard time believing that was transmitted 
>from an HCMOS gate.   I think a little common sense will go a long 
>way towards retiring some of these EMC-urban legends.
>
>on 1/6/02 10:40 AM, cherryclo...@aol.com at cherryclo...@aol.com 
>wrote:
>
>>   A.2) A portable computing device used in an automatic change machine 
>> on 
>>   board transport was tested to be fully compliant with EN 55022 (approx 
>> = 
>>   CISPR 22). 
>>   I helped the manufacturer investigate complaints of interference and 
>>   discovered that sub-fitted variant, which had not been tested for EMC 
>>   compliance, left an HCMOS inverter IC with an unterminated inverter - 
>>   which promptly decided to self-oscillate at 200MHz. (Many 
>> manufacturers 
>>   of products with a number of build variants only test the fully-loaded 
>>   one for EMCD compliance and assume the others are at least as good.) 
>
>>   The very interesting thing about this example is that the power-ground 
>>   structure of the PCB made a beautifully tuned antenna and resonant 
>>   circuit at 200MHz, so although the inverter was hard-switching and did 
>>   not run hot, the only emissions were at the 200MHz fundamental - no 
>>   harmonics were emitted at all. 
>
>>   Another very interesting thing is that some of the complainants had 
>>   measured the equivalent radiated RF power from these devices as 2W. 
>Who would have expected an unterminated HCMOS gate to be able to emit 2W 
> at 
>200MHz? 

Indeed, and assuming a 5 V supply, the current would be around 400 mA.
At 200 MHz, the dissipation would be several hundred milliwatts. 

The absence of harmonics even suggests that this gate was producing a
sine-wave, which makes the figures even higher and less credible.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
After swimming across the Hellespont, I felt like a Hero. 

---
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Re: EMC-related safety issues

The question of ethics or morality is at the heart of this discussion which
makes it much more important than technical discussions about
electromagnetism, which is the ONLY reason I have pursued this so far.  I
was critical of the IEE safety guide on MORAL grounds.  It is part of the
morality which says that businessmen or producers are considered guilty
until proven innocent because of what they are - profit-making producers.
That it is immoral to make a profit and anyone doing so is taking advantage
of someone else.  This is not the morality which built the USA into the
world's wealthiest nation, but it is the morality which will reduce us to
the most impecunious.  The strict Muslim countries that have been in the
news of late forbid loaning of money at interest, because the Koran forbids
usury.  It is no accident that these countries all belong to the third
world.  Progress depends on the ability to raise capital.  The most
efficient way to do that is for people who have profited from past ventures
to invest those profits in new ventures.  That is what banks facilitate.  If
there are no profits, then there is no money to borrow and to start a
venture and progress stops or becomes agonizingly slow.   A policy which
says that producers are liable for unlimited damages without needing to show
defect or negligence is on a moral level with the prohibition of lending
money at interest.  We have to decide if we wish to live in a civilized
world or not.  That is a question of moral significance.

The idea that businessmen are immoral greedy people who give no thought to
the quality of their products is an ugly lie spread by enemies of
capitalism.  A little thought will show that businessmen who operate like
this do not stay in business long because their products get a bad
reputation.  Certainly you can find examples of bad or ignorant behavior.
Does this justify policies which assume all businessmen are evil and that
they must be reined in by pure-hearted regulators?  What makes the
regulators pure-hearted?  That they don't make profit, but siphon profits
away?  What is the cost of the regulation relative to the benefit?  What
marvelous inventions didn't occur because the seed money necessary to
initiate a development wasn't there?

When engineers make false claims that unintentional RE from ITE can cause
safety-critical circuits to fail catastrophically, we engage in another
moral transgression.  We attempt to get a short term gain at the cost of
long  term loss.  The short term gain is to make ourselves and our
profession look more important.  But the long term loss is that of the
little boy who cried wolf.  After a long enough period of false alarms, we
will lose the respect and ear of management and if we must raise a REAL
issue, it will fall on deaf ears.  I have no way of knowing, but I wonder
how many unfulfilled warnings the managers who OK'd the launch of 51L
(Challenger) had listened to prior to making their fateful decision.

on 1/6/02 10:24 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote:

Dear John 
The incubator I described was already on the EU market in the latter half of
the 1990s, when I helped to test and fix it.

And I'm sorry to disappoint but I have already experienced several similar
examples I could quote, such as the electric blanket that would change its
heat settings randomly when a bedside light was switched on or off, or from
other low-level mains transients.
This is a potentially fatal issue for certain kinds of invalid, or people
who are blind drunk (surely no person reading this would ever be in such a
state)  and by the way, this is not me being emotive again, it was the
expressed concern of the manufacturer and one of the reasons why they called
me in. They sacked their Technical Director over this incident.
They also didn't do a product recall despite having an estimated 100,000
products with the problem already out in the field. Of course, as a
responsible engineer (and to cover my ass) I wrote them a letter
recommending that they did a product recall (while thinking of the designers
of the Challenger Space Shuttle's infamous O-ring seals).

I find that many independent EMC people have dozens of similar examples,
which they can't talk about very much because of commercial
confidentiality.. This is one reason why the EMC + Compliance Journal
(www.compliance-club.com) started its 'Banana Skins' column - to help
educate practising engineers about real EMC engineering problems they almost
certainly weren't taught about at college and may not (yet) have experienced
for themselves. 

I also have personal experience of a UK company that in the late 90's was
selling a range of over 110 CE-marked products (such as incubators) intended
for medical and chemical laboratories although less than 10% of their
products met both the EMCD and the LVD. The company in question had just
been purchased by another, which is why I was involved.

Interestingly, the new owners continued to s

Re: EMC-related safety issues

I do not recall a single example or argument to show what you claim.  On the
other hand, I have given physical and numerical arguments to back up my
common sense position.

on 1/6/02 10:51 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote:

Ken, I believe other postings on this topic this weekend clearly show that
electronic circuits which were not designed as radio receivers can possibly
be interfered with by the emissions from products which meet FCC/CISPR 22
limits, for a number of possible reasons, especially when the product is
closer than 10 metres to the source of the emissions.

Certain kinds of transducers and their amplifiers appear to be particularly
at risk because of the low levels of their transducer signals.

Regards, Keith Armstrong

In a message dated 06/01/02 06:56:28 GMT Standard Time,
ken.ja...@emccompliance.com writes:

Subj:Re: EMC-related safety issues
List-Post: emc-pstc@listserv.ieee.org
Date:06/01/02 06:56:28 GMT Standard Time
From:ken.ja...@emccompliance.com (Ken Javor)
To:cherryclo...@aol.com
CC:emc-p...@majordomo.ieee.org

My point was that only radios are sensitive to rf fields at the levels
controlled by FCC/CISPR22 and indeed, as Ing. Gremen pointed out, levels
well above the limits.  Which means that the only rationale behind
FCC/CISPR22 is protection of radio broadcast reception.  Period.

on 1/5/02 12:10 PM, cherryclo...@aol.com at cherryclo...@aol.com wrote:

Dear Ken 
I am truly sorry if I irritated you by misunderstanding your words, but I
took your posting to imply that electronic circuits which are not designed
as RF receivers would not respond very well to radio frequencies.

My example was not intended to be a full answer to your example (there are
other postings which are dealing with that) just to indicate that the
frequency response of slow and commonplace ICs can be very high indeed.

I am sensitive to this issue because I keep on running across electronics
designers who say things like: "I don't need to worry about the RF immunity
of my audio amplifier/motor
controller/temperature/pressure/flow/weight/velocity measurement and control
system (please delete where applicable) because the opamps I use have a GBW
of under 1MHz so they won't see the RF"  which is of course complete
bollocks (a UK phrase that I hope translates well enough for all emc-pstc
subscribers). 

And no, I still don't agree with you that only radio receivers are sensitive
enough to RF to have a problem with what you are still calling
'unintentional emissions' (even though this term means very little in an
international forum unless you define the relevant standards or laws).

I think the problem you are concerned with is application dependant and we
cannot make such broad assumptions. As I said earlier, most interference
problems are caused by radio transmitters or radio receivers, but not all.

Regards, Keith Armstrong

In a message dated 05/01/02 01:20:27 GMT Standard Time,
ken.ja...@emccompliance.com writes:

Subj:Re: EMC-related safety issues
List-Post: emc-pstc@listserv.ieee.org
Date:05/01/02 01:20:27 GMT Standard Time
From:ken.ja...@emccompliance.com (Ken Javor)
To:cherryclo...@aol.com, emc-p...@majordomo.ieee.org

One sure way to REALLY irritate me is to twist my words and try to make me
look stupid (I do a fine job by myself on occasion and don't appreciate any
outside help).  I did not say that pn junctions don't detect and rectify rf,
I said that the field intensities associated with unintentional emissions
from ITE are too low to cause susceptibility in circuits other than radios.
Your example here is 10 V/m, and you are talking about an op-amp (gain
unspecified) and that it was susceptible at that level should be no surprise
to anyone. 

on 1/4/02 7:34 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote:

Does anyone else think that ordinary semiconductors doesn't respond to RF?

I have tested a product which was little more than an LM324 quad op-amp for
RF immunity using IEC 61000-4-3. This op-amp has a slew rate of
1V/micro-second on a good day with the wind in its favour. It was housed in
an unshielded plastic enclosure.

Demodulated noise that exceeded the (not very tough) product specification
were seen all the way up to 500MHz at a number of spot frequencies that
appeared to be due to the natural resonances of the input and output cables.

Above 500MHz this resonant behaviour vanished to be replaced by a steadily
rising level of demodulated 1kHz tone as the frequency increased. I stopped
testing at 1GHz, where the output error from the product was about 10% and
still rising with increased frequency.

OK, the field strength for the test was 10V/m (unmodulated) but the real
surprise was how well this very cheap and very slow opamp demodulated the
RF, and that it demodulated better at 1GHz than at 500MHz.

I have done many many immunity tests using IEC 61000-4-3 on audio equipment
and found much the same effects with every product I've ever tested.

Re: EMC-related safety issues

Quote : "Who would have expected an unterminated HCMOS gate to be able to
emit 2W at 200MHz?"

Not me - 2 Watts of effective radiated power implies over 2.5 V/m at 3 m!  I
guess I have a hard time believing that was transmitted from an HCMOS gate.
I think a little common sense will go a long way towards retiring some of
these EMC-urban legends.

on 1/6/02 10:40 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote:

A.2) A portable computing device used in an automatic change machine on
board transport was tested to be fully compliant with EN 55022 (approx =
CISPR 22). 
I helped the manufacturer investigate complaints of interference and
discovered that sub-fitted variant, which had not been tested for EMC
compliance, left an HCMOS inverter IC with an unterminated inverter - which
promptly decided to self-oscillate at 200MHz. (Many manufacturers of
products with a number of build variants only test the fully-loaded one for
EMCD compliance and assume the others are at least as good.)

The very interesting thing about this example is that the power-ground
structure of the PCB made a beautifully tuned antenna and resonant circuit
at 200MHz, so although the inverter was hard-switching and did not run hot,
the only emissions were at the 200MHz fundamental - no harmonics were
emitted at all. 

Another very interesting thing is that some of the complainants had measured
the equivalent radiated RF power from these devices as 2W.
Who would have expected an unterminated HCMOS gate to be able to emit 2W at
200MHz?

Re: EMC-related safety issues

QUOTE: "And I don't think that 92dBuV/m is a high field strength to be
emitted by a PC placed nearby, or for a non-compliant laptop at 10 metres."

You may not think so, but I am sorry, the numbers just don't add up.  92
dBuV/m at 10 meters implies an effective radiated power of 5.3 mW.  Consider
that the source is not an intentional antenna.  It will have no more
directivity than a dipole and its efficiency will be much less since it
isn't matched to the source.  If we simply assume no gain (meaning matching
losses just offset directivity) , that means 5.3 mW of rf power are emitted
from the EUT or its attached cables.  If one makes the reasonable assumption
that it is common mode rf current which is radiating, then the potential
associated with rf power will be a small number of millivolts (in the
frequency domain).  This in turn implies a significant fraction of an Ampere
of common mode rf current.  A highly unlikely situation!  Once again, with
an impossible conclusion, either the assumption or the logic must be wrong.
You can choose to disbelieve, but please point out where the logic has gone
awry.  You have several times cited Mr. Woodgate for non-constructive
criticism.  Now I am asking you, don't give more hearsay: explain where my
physics is incorrect.  We are engineers here, not pollsters.

And if you are saying that specification level compliance at 10 meters can
scale up to 92 dBuV/m nearby, that is either false or misleading depending
on the frequency range.  At the low end, say 30 MHz, the area subtended by
position near the offending PC isn't large enough to efficiently radiate or
couple the field (the wavelength is 10 meters, and the other gentleman's
antenna factor calculation assumed a tuned dipole antenna in order to get a
small antenna factor).  So the field will not scale up  as per your
prediction, and the pickup mechanism will be nowhere near the antenna factor
that gentleman calculated.  In fact at 30 MHz your antenna factor will be on
the order of 20 dB or worse (assuming the mutual coupling length to be 1 m).
At the high end (near 1 GHz) you could be in the far field in close and the
field could scale up to a value of 92 dBuV/m, but the antenna factor of a
matched tuned dipole at 1 GHz is 26 dB so the potential from that perfect
antenna is 92 dBuV/m - 26 dB/m = 66 dBuV or 2 mV.  If you consider that any
signal with information content carried by 2 mV is shielded, the issue
becomes, once again, a non-problem.



on 1/6/02 10:43 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote:

Snip:  And I don't think that 92dBuV/m is a high field strength to be
emitted by a PC placed nearby, or for a non-compliant laptop at 10 metres.

Re: EMC-related safety issues

I abstracted the physical process and did not attach numbers.  80 dBuV/m is
orders of magnitude above RE limits.  That is 10 mV/m.If you use the
worst case assumptions of IEC 1000-4-6 and associate an open circuit drive
potential numerically equivalent to the field intensity, but with a 150 Ohm
source impedance, then you would have 10 mV driving current from a 150 Ohm
source.  If you assume the impedance (not transfer impedance) of the shield
to be a dead short, then 10 mV will cause 67 uA to flow on the shield.  If
shield transfer impedance were 100 milliohms (pretty high, especially at
frequencies where an op-amp might respond) you would get 6.7 uV induced
common mode on the circuit.  Assuming no CMR, this is the potential that is
added to the intentional signal.  That can affect a radio front-end, but not
an op-amp.

Once again, unintentional RE from ITE, even at unsuppressed levels, do not
cause interference to other non-antenna connected electronics.

on 1/6/02 10:28 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote:

Ken, can we take it that in the posting below you are agreeing that
interference with non radio-receiving circuits from what you meant by
"unintentional emitters" is a possibility, albeit a worst-case one?

If my reading above is correct, how can you then go on to say that
"...unintentional emissions from ITE can only upset a radio receiver tuned
to the emission frequency."

It seems to me that the words "can only" in the your quote above should be
replaced by "are most likely to", which I would agree with.

Regards, Keith Armstrong

In a message dated 06/01/02 06:56:07 GMT Standard Time,
ken.ja...@emccompliance.com writes:

Subj:Re: EMC-related safety issues
List-Post: emc-pstc@listserv.ieee.org
Date:06/01/02 06:56:07 GMT Standard Time
From:ken.ja...@emccompliance.com (Ken Javor)
To:t...@tncokenias.org (Tom Cokenias), cherryclo...@aol.com,
emc-p...@majordomo.ieee.org

The analytical portion of this post is, as the author stated, worst case.  A
cable attached to a susceptible circuit picks up a common-mode potential,
which most likely drives a current on a shield if the the circuit is
sensitive.  Then only the current multiplied by shield transfer impedance
actually gets into the victim, assuming no CMR.  Which just makes my
original point - unintentional emissions from ITE can only upset a radio
receiver tuned to the emission frequency.  That is why, as another
contributor posted, we use EMI receivers and spectrum analyzers with preamps
to make OATS measurements.

on 1/4/02 12:51 PM, Tom Cokenias at t...@tncokenias.org wrote:

> At 8:34 AM -0500 1/4/2002, Keith Armstrong wrote:
> 
>> Does anyone else think that ordinary semiconductors doesn't respond to RF?
> 
> 
> 
> I agree that commonly used semiconductors have responses well into
> the 100's of MHz.
> 
> How much of a problem this is will depend on the nature and function
> of the circuitry using these components.
> 
> The EUT wires, cables, pcb traces etc. act like antennae,  on which
> the incident field voltages and currents.  An antenna factor can be
> thought of as ratio of the field strength  to the voltage induced on
> the terminated cable connected to the antenna.
> 
> In an impedance matched system,
> 
> 
> AF=9.734/lamda*(G)^0.5,   lamda being wavelength in meters, G being
> antenna gain over isotropic,
> 
> or in dB 
> 
> AF dB =  -  G dBi  -29.7 dB + 20logFMHz
> 
> Assuming G is 1 (isotropic antenna), AF is 1  (= 0 dB) at about 30.8
> MHz, and AF get larger  as frequency increases, to  a factor of 32.7
> (= 30.3 dB) at 1 GHz .  Since AF is  field strength divided by
> induced voltage, the voltage induced on the trace goes down as
> frequency goes up for the same incident field strength.
> 
> An effective receive antenna needs to be on the order of 1/2
> wavelength or so; for 30 MHz this is 15m, for 1000 MHz this is 15 cm.
> 
> So if a victim EUT circuit has a pretty effective receive  antenna,
> and does not have any filtering and is equally sensitive across the
> frequency range under consideration (all taken together, a worst case
> scenario for susceptibility),
> 
> (1)  A 10 V/m field will  theoretically induce a voltage  0.33V  to
> 10V, depending on frequency
> 
> (2) A 5000 uV/m field (10x the FCC class B limit above 960 MHz) will
> theoretically induce a voltage from 152 uV to 5 mV, depending on
> frequency. 
> 
> (3) A 500 uV/m field will  theoretically induce a voltage from 15 uV
> to 500 uV depending on frequency.
> 
> These are first order approximations, but they are useful in
> determining the level of the potential EMI  threat.   For instance a
> 4-30 mA sensor circuit using high gain operational amps will most
> likely  be interfered with  in scenario (1),  there may be some
> susceptibility detected in scenario (2), and most likely no problem
> encountered with scenario (3).
> 
> A sensitive all - band  AM communications receiver will have problems
> with all three, a broadcast TV opera

Re: EMC-related safety issues

2002-01-06 Thread John Woodgate


I read in !emc-pstc that cherryclo...@aol.com wrote (in <14b.6d4a617.296
9c...@aol.com>) about 'EMC-related safety issues', on Sun, 6 Jan 2002:
>Dear John 
>The incubator I described was already on the EU market in the latter half 
> of 
>the 1990s, when I helped to test and fix it. 
>
>And I'm sorry to disappoint 

Inappropriate word; I'm not interested in scoring debating points but
exploring the approaches to 'EMC and Safety', which I think need to be
explored.

>but I have already experienced several similar 
>examples I could quote, such as the electric blanket that would change its 
>heat settings randomly when a bedside light was switched on or off, or 
> from 
>other low-level mains transients. 
>This is a potentially fatal issue for certain kinds of invalid, or people 
>who are blind drunk (surely no person reading this would ever be in such a 
>state)  and by the way, this is not me being emotive again, 

I agree; what you have written here is not emotive.
>it was the 
>expressed concern of the manufacturer and one of the reasons why they 
> called 
>me in. They sacked their Technical Director over this incident. 
>They also didn't do a product recall despite having an estimated 100,000 
>products with the problem already out in the field. Of course, as a 
>responsible engineer (and to cover my ass) I wrote them a letter 
>recommending that they did a product recall (while thinking of the 
> designers 
>of the Challenger Space Shuttle's infamous O-ring seals). 
>
>I find that many independent EMC people have dozens of similar examples, 
>which they can't talk about very much because of commercial 
> confidentiality. 
>This is one reason why the EMC + Compliance Journal 
>(www.compliance-club.com) started its 'Banana Skins' column - to help 
>educate practising engineers about real EMC engineering problems they 
> almost 
>certainly weren't taught about at college and may not (yet) have 
> experienced 
>for themselves. 

But, by its nature, it tends to report very low-probability occurrences
and/or anecdotes, which are probably not very effective as training
examples.
>
>I also have personal experience of a UK company that in the late 90's was 
>selling a range of over 110 CE-marked products (such as incubators) 
> intended 
>for medical and chemical laboratories although less than 10% of their 
>products met both the EMCD and the LVD. The company in question had just 
>been purchased by another, which is why I was involved. 
>
>Interestingly, the new owners continued to sell the non-compliant products 
>while they re-engineered them one at a time to be compliant (which took 
>several years). 
>
>My simple investigations over a number of years into a number of 
> companies' 
>CE marked products have led me to be very cynical. As a rule of thumb I 
>guess that around 30% of CE marked products are non-compliant with EMC or 
>LVD, with another 30% being borderline cases. This seems to be borne out 
> by 
>recent enforcement surveys in Finland and in the UK and published articles 
>from some test labs. 

You experiences are certainly a great deal worse than mine. I do find
quite a few 'compliance failures' i.e. things like incorrect labelling
or items omitted from instruction books, but few real hazards. I have
found many products that were submitted for pre-compliance EMC
assessment that would never pass unless completely redesigned, but I
haven't (yet) seen anything CE marked that obviously fails.
>
>Changing to another of your criticisms below... 
>If you think my proposed statement is fog-filled, what do you propose 
>instead? 
>Lets have constructive criticism instead of merely criticism. 

There are many possible statements that could be made on the subject,
but here is one:

'Conducted and radiated emissions from equipment which does not include
any one of:

- switching of voltages above 10 V and currents above 100 mA;

- generation of radio-frequency (150 kHz to 400 GHz) voltages above 100
mV;

- power consumption greater than 75 W

are extremely unlikely to cause malfunction of other equipment having
the degree of immunity afforded by normal design practices.'

This is the sort of statement/guideline that can be used by a designer
or compliance engineer to determine what testing, if any, is necessary.

>
>In fact, in most scientific or engineering activities, one can only make 
>public statements using foggy words like 'generally'. 

See above.

>Remember the UK government's teams of scientific advisors and their 
>pronouncements on BSE and the foot and mouth epidemic? Would you have 
>expected them to produce precise and accurate predictions? 
>I am of the opinion that the outbreak of foot and mouth disease in the UK 
>was better understood, had fewer variables, and could be better controlled 
>

Re: EMC-related safety issues

2002-01-06 Thread John Woodgate


I read in !emc-pstc that cherryclo...@aol.com wrote (in <162.6b92ca5.296
9c...@aol.com>) about 'EMC-related safety issues', on Sun, 6 Jan 2002:
>Yes, John, you are quite right in both your comments as far as you go: 
>
>1) You are not the only person who can dramatise an issue so as to 
> encourage 
>people to debate it; 

I don't know what you are referring to. I have 146 articles already read
in the thread: I don't see that the debate needs any encouragement.
>
>2) If you sold a single electronic safety-related circuit with a failure 
>probability of 10^ -9 to 100,000 customers the cumulative failure 
>probability is indeed 10^ -4. As you correctly said, Olber's Paradox does 
>not apply in this area. 
>
>But nevertheless this does not mean we need to make electronic circuits 
> with 
>failure rates equal to or better than 10^ -9. As you have said (and I 
> agree) 
>this would be a very difficult task indeed and likely to be very 
> expensive, 
>especially for any product using software. 
>
>So how do we square this particular circle? 
>
>Those members who are familiar with safety engineering techniques will be 
>familiar with the idea of building very reliable systems up using a number 
>of independent systems or devices each with lower reliability. These have 
>various names, such as 'redundant channels' or 'duplicate channels' or 
>'safety back-ups' or 'fail-safe circuits' and many others. 
>
I don't see how this applies to the reduction of emissions or,
practicably, to the improvement of immunity. Do you envisage three
separate systems in every product, with majority voting? I suspect that
in terms of improving immunity, it would be ineffective, because a
disturbance that compromised one system would be very likely to
compromise at least one other. Consider you incubator, for example.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
After swimming across the Hellespont, I felt like a Hero. 

---
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Re: EMC-related safety issues

Ken, I believe other postings on this topic this weekend clearly show that 
electronic circuits which were not designed as radio receivers can possibly 
be interfered with by the emissions from products which meet FCC/CISPR 22 
limits, for a number of possible reasons, especially when the product is 
closer than 10 metres to the source of the emissions.

Certain kinds of transducers and their amplifiers appear to be particularly 
at risk because of the low levels of their transducer signals.

Regards, Keith Armstrong

In a message dated 06/01/02 06:56:28 GMT Standard Time, 
ken.ja...@emccompliance.com writes:

> Subj:Re: EMC-related safety issues
> Date:06/01/02 06:56:28 GMT Standard Time
> From:ken.ja...@emccompliance.com (Ken Javor)
> To:cherryclo...@aol.com
> CC:emc-p...@majordomo.ieee.org
> 
> My point was that only radios are sensitive to rf fields at the levels 
> controlled by FCC/CISPR22 and indeed, as Ing. Gremen pointed out, levels 
> well above the limits.  Which means that the only rationale behind 
> FCC/CISPR22 is protection of radio broadcast reception.  Period.
> 
> on 1/5/02 12:10 PM, cherryclo...@aol.com at cherryclo...@aol.com wrote:
> 
> >> Dear Ken 
>> I am truly sorry if I irritated you by misunderstanding your words, but I 
>> took your posting to imply that electronic circuits which are not designed 
>> as RF receivers would not respond very well to radio frequencies. 
>> 
>> My example was not intended to be a full answer to your example (there are 
>> other postings which are dealing with that) just to indicate that the 
>> frequency response of slow and commonplace ICs can be very high indeed. 
>> 
>> I am sensitive to this issue because I keep on running across electronics 
>> designers who say things like: "I don't need to worry about the RF 
>> immunity of my audio amplifier/motor 
>> controller/temperature/pressure/flow/weight/velocity measurement and 
>> control system (please delete where applicable) because the opamps I use 
>> have a GBW of under 1MHz so they won't see the RF"  which is of 
>> course complete bollocks (a UK phrase that I hope translates well enough 
>> for all emc-pstc subscribers). 
>> 
>> And no, I still don't agree with you that only radio receivers are 
>> sensitive enough to RF to have a problem with what you are still calling 
>> 'unintentional emissions' (even though this term means very little in an 
>> international forum unless you define the relevant standards or laws). 
>> 
>> I think the problem you are concerned with is application dependant and we 
>> cannot make such broad assumptions. As I said earlier, most interference 
>> problems are caused by radio transmitters or radio receivers, but not all. 
>> 
>> Regards, Keith Armstrong 
>> 
>> In a message dated 05/01/02 01:20:27 GMT Standard Time, 
>> ken.ja...@emccompliance.com writes: 
>> 
>> >>> Subj:Re: EMC-related safety issues 
>>> Date:05/01/02 01:20:27 GMT Standard Time 
>>> From:ken.ja...@emccompliance.com (Ken Javor) 
>>> To:cherryclo...@aol.com, emc-p...@majordomo.ieee.org 
>>> 
>>> One sure way to REALLY irritate me is to twist my words and try to make 
>>> me look stupid (I do a fine job by myself on occasion and don't 
>>> appreciate any outside help).  I did not say that pn junctions don't 
>>> detect and rectify rf, I said that the field intensities associated with 
>>> unintentional emissions from ITE are too low to cause susceptibility in 
>>> circuits other than radios.  Your example here is 10 V/m, and you are 
>>> talking about an op-amp (gain unspecified) and that it was susceptible at 
>>> that level should be no surprise to anyone. 
>>> 
>>> on 1/4/02 7:34 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote: 
>>> 
>>>  Does anyone else think that ordinary semiconductors doesn't respond 
 to RF? 

 I have tested a product which was little more than an LM324 quad op-amp 
 for RF immunity using IEC 61000-4-3. This op-amp has a slew rate of 
 1V/micro-second on a good day with the wind in its favour. It was housed 
 in an unshielded plastic enclosure. 

 Demodulated noise that exceeded the (not very tough) product 
 specification were seen all the way up to 500MHz at a number of spot 
 frequencies that appeared to be due to the natural resonances of the 
 input and output cables. 

 Above 500MHz this resonant behaviour vanished to be replaced by a 
 steadily rising level of demodulated 1kHz tone as the frequency 
 increased. I stopped testing at 1GHz, where the output error from the 
 product was about 10% and still rising with increased frequency. 

 OK, the field strength for the test was 10V/m (unmodulated) but the real 
 surprise was how well this very cheap and very slow opamp demodulated 
 the RF, and that it demodulated better at 1GHz than at 500MHz. 

 I have done many many immunity tests using IEC 61000-4-3 on audio 
 equipment and found muc

Re: EMC-related safety issues

Taking Toms' calculations a little further

Typical thermocouple sensors have output voltages in the range 3 - 50 
microvolts per degree C. So to create a 60C error in a thermocouple-based 
temperature control system (see my recent posting about the RF immunity of a 
blood sample incubator) all we need is an error voltage in the range 180 
microvolts to 3 millivolts.

According to Toms' calculations below: 
"(3) A 500 uV/m field will  theoretically induce a voltage from 15 uV to 500 
uV depending on frequency." 

Now, 500 microvolts per meter = 54dBmicrovolts/meter which is only 7dB above 
the CISPR 22 10 metre Class A limit and 17dB above the Class B limit, between 
230 and 1000MHz.

This implies a fully CISPR 22 compliant laptop PC is capable of generating 
significant errors (10s of degrees C) in certain kinds of thermocouple 
measuring and control systems even when the laptop is 10 metres away.

If the laptop was closer to the thermocouple system than 10 metres the field 
strength of its RF emissions will obviously increase. But when it is in the 
laptop's near field we would expect the 10 metre measurements to be 
meaningless because there are components of near field emissions which fall 
off with the cube of the distance and are not detected by 10 metre tests. 

For example, many products seem to have very quite strong frequency magnetic 
fields nearby, at audio frequencies and lower, caused by variations in the 
loading on their DC power supplies.

For this and several other reasons I can't agree with the idea that emissions 
from what are known under some US laws as "unintentional radiators" cannot 
possibly cause interference in circuits which are not intentional radio 
receivers. 
It seems to me that many types of transducer systems (maybe even the fluxgate 
magnetometers used in some types of compasses) can be vulnerable.

Regards, Keith Armstrong

In a message dated 04/01/02 19:03:15 GMT Standard Time, t...@tncokenias.org 
writes:

> Subj:Re: EMC-related safety issues
> Date:04/01/02 19:03:15 GMT Standard Time
> From:t...@tncokenias.org (Tom Cokenias)
> Sender:owner-emc-p...@majordomo.ieee.org
> Reply-to: mailto:t...@tncokenias.org";>t...@tncokenias.org (Tom 
> Cokenias)
> To:cherryclo...@aol.com, emc-p...@majordomo.ieee.org
> 
> At 8:34 AM -0500 1/4/2002, Keith Armstrong wrote:
> 
> >Does anyone else think that ordinary semiconductors doesn't respond to RF?
> 
> 
> 
> I agree that commonly used semiconductors have responses well into 
> the 100's of MHz.
> 
> How much of a problem this is will depend on the nature and function 
> of the circuitry using these components.
> 
> The EUT wires, cables, pcb traces etc. act like antennae,  on which 
> the incident field voltages and currents.  An antenna factor can be 
> thought of as ratio of the field strength  to the voltage induced on 
> the terminated cable connected to the antenna.
> 
> In an impedance matched system,
> 
> 
> AF=9.734/lamda*(G)^0.5,   lamda being wavelength in meters, G being 
> antenna gain over isotropic,
> 
> or in dB
> 
> AF dB =  -  G dBi  -29.7 dB + 20logFMHz
> 
> Assuming G is 1 (isotropic antenna), AF is 1  (= 0 dB) at about 30.8 
> MHz, and AF get larger  as frequency increases, to  a factor of 32.7 
> (= 30.3 dB) at 1 GHz .  Since AF is  field strength divided by 
> induced voltage, the voltage induced on the trace goes down as 
> frequency goes up for the same incident field strength.
> 
> An effective receive antenna needs to be on the order of 1/2 
> wavelength or so; for 30 MHz this is 15m, for 1000 MHz this is 15 cm.
> 
> So if a victim EUT circuit has a pretty effective receive  antenna, 
> and does not have any filtering and is equally sensitive across the 
> frequency range under consideration (all taken together, a worst case 
> scenario for susceptibility),
> 
> (1)  A 10 V/m field will  theoretically induce a voltage  0.33V  to 
> 10V, depending on frequency
> 
> (2) A 5000 uV/m field (10x the FCC class B limit above 960 MHz) will 
> theoretically induce a voltage from 152 uV to 5 mV, depending on 
> frequency.
> 
> (3) A 500 uV/m field will  theoretically induce a voltage from 15 uV 
> to 500 uV depending on frequency.
> 
> These are first order approximations, but they are useful in 
> determining the level of the potential EMI  threat.   For instance a 
> 4-30 mA sensor circuit using high gain operational amps will most 
> likely  be interfered with  in scenario (1),  there may be some 
> susceptibility detected in scenario (2), and most likely no problem 
> encountered with scenario (3).
> 
> A sensitive all - band  AM communications receiver will have problems 
> with all three, a broadcast TV operating in a strong signal area will 
> probably be OK  with scenario 3 but not with 1 or 2.
> 
> I guess what I'm really trying to say with all this is that EMC is a 
> systems thing, taking into account the nature of the culprit EMI 
> generator, the nature of the victim EMI receiver,  and th

Re: EMC-related safety issues

Yes, John, you are quite right in both your comments as far as you go:

1) You are not the only person who can dramatise an issue so as to encourage 
people to debate it;

2) If you sold a single electronic safety-related circuit with a failure 
probability of 10^ -9 to 100,000 customers the cumulative failure probability 
is indeed 10^ -4. As you correctly said, Olber's Paradox does not apply in 
this area.

But nevertheless this does not mean we need to make electronic circuits with 
failure rates equal to or better than 10^ -9. As you have said (and I agree) 
this would be a very difficult task indeed and likely to be very expensive, 
especially for any product using software.

So how do we square this particular circle?

Those members who are familiar with safety engineering techniques will be 
familiar with the idea of building very reliable systems up using a number of 
independent systems or devices each with lower reliability. These have 
various names, such as 'redundant channels' or 'duplicate channels' or 
'safety back-ups' or 'fail-safe circuits' and many others.

Some examples...
I understand that car braking systems have (by law in Europe and North 
America at least) an independent hydraulic back-up system in case the primary 
system fails - because it is practically impossible to make the primary 
system reliable enough at a cost anyone would want to pay.

The electronic flight-control systems in modern aircraft have two or three 
independent hardware 'channels'. Where software is involved they sometimes 
use three sets of independently-coded software each using 
architecturally-different operating systems and each running on an 
architecturally different hardware processor voting 2 out of 3 on every 
decision/output). 

I understand that the Space Shuttle launch control system uses 5 independent 
computers voting on each decision/output.

The pressure relief valve on most pressure systems does not have a very high 
reliability, but when combined with the statistical probability of the system 
pressure going out of control the whole system is considered to be reliable 
enough. 
(Of course, pressure system designers must remember to site the pressure 
relief valve so that if it operates it doesn't cause a hazard of its own.)

Three cheap and cheerful independent circuits, each achieving merely 10^ -3 
reliability, can easily be combined together to create a system with 10^ -9 
reliability – achieving very high levels of safety at low cost without any 
heartache in design or heart attacks from management. 

This is the way that high reliability is normally achieved at reasonable cost 
in practice (and has been achieved for many many years). 
IEC 61508 describes (or refers to) the necessary techniques.

(PS: My statistical maths is rusty, so don't rely on the above simple 
calculation for any designs. Refer to IEC 61508 for more detail).

Regards, Keith Armstrong

In a message dated 05/01/02 21:01:18 GMT Standard Time, j...@jmwa.demon.co.uk 
writes:

> Subj:Re: EMC-related safety issues
> Date:05/01/02 21:01:18 GMT Standard Time
> From:j...@jmwa.demon.co.uk (John Woodgate)
> Sender:owner-emc-p...@majordomo.ieee.org
> Reply-to: mailto:j...@jmwa.demon.co.uk";>j...@jmwa.demon.co.uk 
> (John Woodgate)
> To:emc-p...@majordomo.ieee.org
> 
> I read in !emc-pstc that cherryclo...@aol.com wrote (in
> <43.47bb025.29689...@aol.com>) about 'EMC-related safety issues', on
> Sat, 5 Jan 2002:
> >The "one in a billion" John refers to sounds very dramatic and 
> difficult. 
> 
> More dramatic than you 'infant daughter' and '40 mph past a school'?
> 
> I explained in VERY GREAT DETAIL the effect of cumulative probability in
> requiring very low probability events to be taken into account. In
> principle, as the probability goes down, the  number of risk scenarios
> increases *combinatorially*. There is no Olber's Paradox in this area,
> the 'night sky is infinitely brighter than the Sun'!
> >
> >So it may be helpful to refer to IEC 61508 which is a 
> recently-published 
> >'basic safety publication' covering "The functional safety of 
> electrical / 
> >electronic / programmable safety-related systems" 
> >
> >IEC 61508 uses the concept of the Safety Integrity Level (or SIL) to 
> help 
> >design safety-related systems which have quantified failure 
> probabilities. 
> >
> >The SILs for average probability of failure to perform design 
> function on 
> >demand are: 
> >SIL level 1: up to 10^ -2 
> >SIL level 2: 10^ -2 to 10^ -3 
> >SIL level 3: 10^ -3 to 10^ -4 
> >SIL level 4:  10^ -4 to 10^ -5 or even lower levels 
> >
> >The SILs for average probability of dangerous failure per hour of 
> operation 
> >are: 
> >SIL level 1: up to 10^ -6 
> >SIL level 2: 10^ -6 to 10^ -7 
> >SIL level 3: 10^ -7 to 10^ -8 
> >SIL level 4:  10^ -8 to 10^ -9 or even lower levels 
> >
> >The standard describes how to select the SIL level

Re: EMC-related safety issues

Ken, replies below.
Regards, Keith Armstrong

In a message dated 06/01/02 06:56:46 GMT Standard Time, 
ken.ja...@emccompliance.com writes:

> Subj:Re: EMC-related safety issues
> Date:06/01/02 06:56:46 GMT Standard Time
> From:ken.ja...@emccompliance.com (Ken Javor)
> To:cherryclo...@aol.com, cortland.richm...@alcatel.com
> CC:emc-p...@majordomo.ieee.org
> 
> What an EMC engineer who understands the physics of field-to-wire coupling 
> would say is that the operation of non-antenna connected electronics 
> associated with one subsystem will not be degraded by close proximity with 
> the non-antenna connected electronics of another subsystem.  Forget 10 
> meters.  Are the PCs in your office separated by 10 m?  Would you expect 
> two PCs stacked side-by-side or one on top of the other to interact in any 
> manner?  These are rhetorical questions.
> 

I don't see the relevance of this paragraph to my example. This might be 
because 
I am a little slow. I would appreciate more explanation.

> About the blood pressure monitor example.  Not enough info here to back out 
> what is wrong, but basic logic theory says when the conclusion is 
> impossible, you must re-examine your assumptions.  If 92 dBuV/m were enough 
> to make the device malfunction, it would malfunction a lot and there would 
> have been enough trouble reports to get it fixed or withdrawn. And 92 
> dBuV/m at 10 meters is SCREAMING!!!  I am on location and don't have FCC 
> regs easily available, but the limits stair-step around 40 dBuV/m at 3 m, 
> per my recollection.

This is exactly why I emphasised that the front-panel display of the blood 
sample incubator (not a blood pressure monitor) continued to read the 
set-point temperature (37.1C) even though the actual temperature could be way 
off. 
I am confident that in actual operation the incubator temperature was quite 
often at least a few degrees C different from what was displayed on its front 
panel, probably affecting the performance of the reagents.

And I don't think that 92dBuV/m is a high field strength to be emitted by a 
PC placed nearby, or for a non-compliant laptop at 10 metres.

> Would I feel comfortable placing a CISPR compliant PC next to a medical 
> device qualified to 1 V/m?  There is an inherent (not planned) margin of 
> safety here that is many orders of magnitude.   The answer is absolutely 
> yes.  If there were a problem, I would expect it more to occur below 30 
> MHz, at the power supply switching frequency, IF the medical device 
> processed extremely low levels of electrical signals and was poorly 
> shielded.  But I believe there are separate immunity requirements which 
> cover this eventuality as well.
> 
Maybe when you  wrote the above you weren't thinking of the previous 
correspondence in this thread about the proximity of the low-energy lamp to a 
bedside radio. 

Yes, I know, this concerned a radio receiver, what I mean to draw your 
attention to is the discussion about the intention and validity of the EMC 
standards – they simply do not cover situations where devices are placed 
close to each other – so they cannot be relied upon to provide compatibility 
in such situations. 
Military EMC standards are more thorough in this respect.

And as I have already said, commercial EMC standards were not written with 
safety issues in mind, and most safety standards have not been written with 
EMC-related issues in mind (see my IEEE 2001 EMC Symposium paper and my 
longer article in ITEM UPDATE 2001 for details).

So I cannot see that there is any 'inherent' margin of safety in the above 
situation, as you claim there "absolutely is".

(And may I suggest that anyone who thinks that the statement in all (or most) 
IEC EMC immunity standards: "Products shall not become unsafe as a result of 
these tests." means that that products which pass those immunity tests are 
necessarily free from EMC-related safety problems, needs to think a little 
bit harder about the subject?)

Regards again, Keith Armstrong

> on 1/5/02 12:23 PM, cherryclo...@aol.com at cherryclo...@aol.com wrote:
> 
> >> Dear Cortland 
>> People can't simply say: "ordinary semiconductors won't demodulate RF 
>> levels produced by an unintentional radiator"  even the smallest 
>> amount of RF can be demodulated  there are no hysteresis or threshold 
>> effects in a PN semiconductor junction or FET that is biased into its 
>> conduction region (at least not until you get below signal levels 
>> equivalent to less than a single electron). 
>> 
>> What I am sure most engineers would really mean to say is: 
>> "ordinary semiconductors exposed to RF levels from an information 
>> technology product which is fully compliant with all relevant EMC 
>> emissions standards and is at 10 metres distance will generally not 
>> demodulate a sufficient level of interference to make an appreciable 
>> difference to most electronic systems." 
>> 
>> Now we have a statement which has some scientific ri

Re: EMC-related safety issues

A) I don't agree with Ken that: "Emissions from a laptop are naturally 
(without suppression) on the order of 10 uV/m to 100s of uV/m."

Maybe IBM PC clone laptops use similar enough architecture and chipsets and 
design techniques to be this consistent (I don't know) but I have seen the 
following emissions in portable computing products that would come under the 
same FCC/EMCD emissions standards as a laptop...

A.1) A portable computing device with a large additional RAM array for use by 
people who had lost the power of speech. They would type the word they wanted 
to say and it would speak it for them using loudspeakers.

This was a product that was sold in the UK without a CE mark at around the 
time the EMC directive came into force (1996). I only measured its with a 1cm 
diameter unshielded shorted-turn probe. I am used to seeing levels of around 
60 to 100 dBmicrovolts from this probe when it is closer than one inch to 
typical laptop PCBs, with less than 20 dBmicrovolts at a distance of more 
than one foot. 

But with this product I saw over 50 dBmicrovolts at frequencies from 30 to 
300MHz when my 1cm loop probe was 4 feet away!  Maybe some less 
mathematically-challenged member of the group would like to work out what the 
electric field strength could have been measured at 10 metres.

I've never seen anything quite as bad as that before or since, but it shows 
what poor EMC design can achieve in the hands of some designers of 
computing-related products.

(Incidentally, they sold it with a clamp for fixing to wheelchairs - some 
models of which have already been mentioned in this thread as being known to 
run amok under certain conditions of RF field.)

A.2) A portable computing device used in an automatic change machine on board 
transport was tested to be fully compliant with EN 55022 (approx = CISPR 22). 
I helped the manufacturer investigate complaints of interference and 
discovered that sub-fitted variant, which had not been tested for EMC 
compliance, left an HCMOS inverter IC with an unterminated inverter - which 
promptly decided to self-oscillate at 200MHz. (Many manufacturers of products 
with a number of build variants only test the fully-loaded one for EMCD 
compliance and assume the others are at least as good.)

The very interesting thing about this example is that the power-ground 
structure of the PCB made a beautifully tuned antenna and resonant circuit at 
200MHz, so although the inverter was hard-switching and did not run hot, the 
only emissions were at the 200MHz fundamental - no harmonics were emitted at 
all.

Another very interesting thing is that some of the complainants had measured 
the equivalent radiated RF power from these devices as 2W.
Who would have expected an unterminated HCMOS gate to be able to emit 2W at 
200MHz?

Well, now you know that it is possible (if not probable) it becomes something 
you should think about when designing safety-related systems.

A.3) Laptops which are fully compliant with CISPR 22 or the equivalent US 
regs will have higher field strengths when they are less than 10 metres away. 
How many of us can guarantee that there is always at least 10 metres between 
each item of electronic equipment? 

Another thread to this discussion has discussed the problems of low-energy 
lamps interfering with bedside radios, and this shows up the difficulties of 
confusing compliance with standards intended for legal market entry and 
protection of the radio spectrum with the actual EMC engineering to prevent 
interference in real applications. 

Another problem is that when we are in the near field of a product its 10 
metre emissions measurements are meaningless. There are components of near 
field emissions which fall off with the cube of the distance and are not 
usually detected at all by 10 metre tests. 

For example I understand that many products have very quite strong frequency 
magnetic fields nearby, at audio frequencies and lower, caused by variations 
in the loading on their DC power supplies.

A.4) The standard commercial and industrial tests for emissions do not test 
the full range of possible emissions, since they were only ever intended to 
protect the radio communication and broadcasting spectrum. Actual electronic 
devices, especially certain kinds of transducers and their amplifiers, can be 
very sensitive to frequencies outside said spectrum. Military EMC standards 
recognise this real-life problem and typically test for emissions down to 100 
or even 20Hz.

B) I don't agree with Ken that "1000 uV/m would represent at least a 20 dB 
outage
at frequencies that could possibly interfere with sensor electronics."

See my other posting today adding to Tom Cokenias's calculations to show that 
RF field strengths of 500uV/m can easily cause severe errors (tens of degrees 
C) in some thermocouple temperature measuring systems.

Also refer to my recent posting about the significant RF immunity problems 
experienced with a blood sample in

Re: EMC-related safety issues

Dear John
In previous postings from Ken Javor and myself, I believe that Ken (who I was 
replying to in the fragment below) has made it clear that what he is really 
concerned with is  "the kinds of emissions controlled by CISPR 22 and Title 
47, part 15B of the US Code of Federal Regulations" (I hope I have got this 
right, Ken!).

In earlier postings I believe that Ken complained that I was widening the 
definition to include such things as the unintentional emissions from welding 
apparatus (I didn't think of your electric fence example).

I think John's comments emphasise a point I made earlier in this 
correspondence, which is that we need to be very careful in an international 
forum when using terms like "unintentional emitter". Such terms can have 
specific definitions in some EMC standards or Regulations in some countries, 
but they can also have a wider EMC engineering usage, such as that mentioned 
by John below. 
Confusion is possible unless we are more precise.

Regards, Keith Armstrong

In a message dated 05/01/02 21:01:28 GMT Standard Time, j...@jmwa.demon.co.uk 
writes:

> >And no, I still don't agree with you that only radio receivers are 
> sensitive 
> >enough to RF to have a problem with what you are still calling 
> >'unintentional emissions' (even though this term means very little in 
> an 
> >international forum unless you define the relevant standards or laws). 
> 
> I think this term is quite legitimate and well-understood. If the
> equipment requires to emit in order to perform its intended function, it
> is an 'intentional emitter'. If it does not need to do so, but emits
> anyway, it is an 'unintentional emitter'. It is difficult to see how
> there could be any confusion or ambiguity about this.

Re: EMC-related safety issues

Dear John
The incubator I described was already on the EU market in the latter half of 
the 1990s, when I helped to test and fix it. 

And I'm sorry to disappoint but I have already experienced several similar 
examples I could quote, such as the electric blanket that would change its 
heat settings randomly when a bedside light was switched on or off, or from 
other low-level mains transients. 
This is a potentially fatal issue for certain kinds of invalid, or people who 
are blind drunk (surely no person reading this would ever be in such a state) 
– and by the way, this is not me being emotive again, it was the expressed 
concern of the manufacturer and one of the reasons why they called me in. 
They sacked their Technical Director over this incident. 
They also didn't do a product recall despite having an estimated 100,000 
products with the problem already out in the field. Of course, as a 
responsible engineer (and to cover my ass) I wrote them a letter recommending 
that they did a product recall (while thinking of the designers of the 
Challenger Space Shuttle's infamous O-ring seals).

I find that many independent EMC people have dozens of similar examples, 
which they can't talk about very much because of commercial confidentiality. 
This is one reason why the EMC + Compliance Journal (www.compliance-club.com) 
started its 'Banana Skins' column - to help educate practising engineers 
about real EMC engineering problems they almost certainly weren't taught 
about at college and may not (yet) have experienced for themselves. 

I also have personal experience of a UK company that in the late 90's was 
selling a range of over 110 CE-marked products (such as incubators) intended 
for medical and chemical laboratories although less than 10% of their 
products met both the EMCD and the LVD. The company in question had just been 
purchased by another, which is why I was involved. 

Interestingly, the new owners continued to sell the non-compliant products 
while they re-engineered them one at a time to be compliant (which took 
several years).

My simple investigations over a number of years into a number of companies' 
CE marked products have led me to be very cynical. As a rule of thumb I guess 
that around 30% of CE marked products are non-compliant with EMC or LVD, with 
another 30% being borderline cases. This seems to be borne out by recent 
enforcement surveys in Finland and in the UK and published articles from some 
test labs.

Changing to another of your criticisms below...
If you think my proposed statement is fog-filled, what do you propose 
instead? 
Lets have constructive criticism instead of merely criticism.

In fact, in most scientific or engineering activities, one can only make 
public statements using foggy words like 'generally'. 
Remember the UK government's teams of scientific advisors and their 
pronouncements on BSE and the foot and mouth epidemic? Would you have 
expected them to produce precise and accurate predictions? 
I am of the opinion that the outbreak of foot and mouth disease in the UK was 
better understood, had fewer variables, and could be better controlled than 
many real-life EMC-related safety engineering problems.

I believe the debate in question (whether "unintentional emitters" can 
interfere with electronic circuits which are not intentional radio receivers) 
cannot be answered with a definitive yes or no.  
I believe that each safety-related application needs to be investigated and 
firm engineering conclusions drawn. Even then, when one actually does such 
exercises in real life (and I have) one still finds statements concerning 
personal estimates of probability are necessary. 
You can deride these as being 'foggy' if you like but I don't think even you 
could be more precise in such circumstances.

Absolute certainty just does not exist in the real engineering world of 
interactions between complex systems and I am sure you understand this well.

As for the rest of your comments, I plead guilty to raising the emotional 
stakes.

I deliberately used emotive arguments because I find that most designers (and 
test lab engineers) prefer to keep their heads down doing the engineering 
work they believe they are paid to do. 

Where people could be injured or killed by their products I generally find 
that designers are uncomfortable even thinking about this. Maybe this is 
because it would mean them fighting with their management to get more 
resources allocated. 

I also find that most designers (and their managers) - if they think about 
their potential 'victims' at all - also tend to think of them as 'other 
people'. 
They don't seem to think of their customers ands third parties as if they 
were members of their own family (as if other people's families were less 
important).
So this is an emotive litmus test I often use to test designers' and managers 
ethics.

Yes, ETHICS. 
Now that the word has been mentioned no doubt there will be a new thread 
begun, f

Re: EMC-related safety issues

Ken, can we take it that in the posting below you are agreeing that 
interference with non radio-receiving circuits from what you meant by 
"unintentional emitters" is a possibility, albeit a worst-case one?

If my reading above is correct, how can you then go on to say that 
"...unintentional emissions from ITE can only upset a radio receiver tuned to 
the emission frequency."

It seems to me that the words "can only" in the your quote above should be 
replaced by "are most likely to", which I would agree with.

Regards, Keith Armstrong

In a message dated 06/01/02 06:56:07 GMT Standard Time, 
ken.ja...@emccompliance.com writes:

> Subj:Re: EMC-related safety issues
> Date:06/01/02 06:56:07 GMT Standard Time
> From:ken.ja...@emccompliance.com (Ken Javor)
> To:t...@tncokenias.org (Tom Cokenias), cherryclo...@aol.com, 
> emc-p...@majordomo.ieee.org
> 
> The analytical portion of this post is, as the author stated, worst case.  A
> cable attached to a susceptible circuit picks up a common-mode potential,
> which most likely drives a current on a shield if the the circuit is
> sensitive.  Then only the current multiplied by shield transfer impedance
> actually gets into the victim, assuming no CMR.  Which just makes my
> original point - unintentional emissions from ITE can only upset a radio
> receiver tuned to the emission frequency.  That is why, as another
> contributor posted, we use EMI receivers and spectrum analyzers with preamps
> to make OATS measurements.
> 
> on 1/4/02 12:51 PM, Tom Cokenias at t...@tncokenias.org wrote:
> 
> > At 8:34 AM -0500 1/4/2002, Keith Armstrong wrote:
> > 
> >> Does anyone else think that ordinary semiconductors doesn't respond to 
> RF?
> > 
> > 
> > 
> > I agree that commonly used semiconductors have responses well into
> > the 100's of MHz.
> > 
> > How much of a problem this is will depend on the nature and function
> > of the circuitry using these components.
> > 
> > The EUT wires, cables, pcb traces etc. act like antennae,  on which
> > the incident field voltages and currents.  An antenna factor can be
> > thought of as ratio of the field strength  to the voltage induced on
> > the terminated cable connected to the antenna.
> > 
> > In an impedance matched system,
> > 
> > 
> > AF=9.734/lamda*(G)^0.5,   lamda being wavelength in meters, G being
> > antenna gain over isotropic,
> > 
> > or in dB
> > 
> > AF dB =  -  G dBi  -29.7 dB + 20logFMHz
> > 
> > Assuming G is 1 (isotropic antenna), AF is 1  (= 0 dB) at about 30.8
> > MHz, and AF get larger  as frequency increases, to  a factor of 32.7
> > (= 30.3 dB) at 1 GHz .  Since AF is  field strength divided by
> > induced voltage, the voltage induced on the trace goes down as
> > frequency goes up for the same incident field strength.
> > 
> > An effective receive antenna needs to be on the order of 1/2
> > wavelength or so; for 30 MHz this is 15m, for 1000 MHz this is 15 cm.
> > 
> > So if a victim EUT circuit has a pretty effective receive  antenna,
> > and does not have any filtering and is equally sensitive across the
> > frequency range under consideration (all taken together, a worst case
> > scenario for susceptibility),
> > 
> > (1)  A 10 V/m field will  theoretically induce a voltage  0.33V  to
> > 10V, depending on frequency
> > 
> > (2) A 5000 uV/m field (10x the FCC class B limit above 960 MHz) will
> > theoretically induce a voltage from 152 uV to 5 mV, depending on
> > frequency.
> > 
> > (3) A 500 uV/m field will  theoretically induce a voltage from 15 uV
> > to 500 uV depending on frequency.
> > 
> > These are first order approximations, but they are useful in
> > determining the level of the potential EMI  threat.   For instance a
> > 4-30 mA sensor circuit using high gain operational amps will most
> > likely  be interfered with  in scenario (1),  there may be some
> > susceptibility detected in scenario (2), and most likely no problem
> > encountered with scenario (3).
> > 
> > A sensitive all - band  AM communications receiver will have problems
> > with all three, a broadcast TV operating in a strong signal area will
> > probably be OK  with scenario 3 but not with 1 or 2.
> > 
> > I guess what I'm really trying to say with all this is that EMC is a
> > systems thing, taking into account the nature of the culprit EMI
> > generator, the nature of the victim EMI receiver,  and the path
> > between them.  Then we have the economics of operating different
> > devices in the same vicinity, the politics of who gets how much of
> > what kind of protection, etc., etc.  All things considered, we should
> > have jobs for life!
> > 
> > best regards and a Happy New Year to all.
> > 
> > Tom Cokenias
> > 
> > T.N. Cokenias Consulting
> > P.O. Box 1086
> > El Granada CA 94018
> > 
> > tel   650 726 1263
> > cell 650 302 0887
> > fax  650 726 1252
>

Re: EMC-related safety issues

Thanks for the correction.  Medicine is not something I know much about.
The point remains that a huge benefit was derived from these vaccines which
were discontinued due to a very small fraction of bad reactions.  Forum
members:  when it turned out that a small number of people were killed or
hurt by airbags, there was no general hue and cry to remove them or sue the
automobile manufacturers.  Why?

Diphtheria and whooping cough are not mere viruses.  They are life
threatening illnesses that in former centuries contributed greatly to infant
morality.  And tetanus is potentially deadly at any age.

on 1/4/02 11:31 PM, Jim Freeman at free...@chelsio.com wrote:

Hi Ken, 
   The reason that those companies stopped was because it was found that
there was mercury in the formulation of the vaccine. The mercury had no
other use other than stabilization.  The mercury is known to cause brain
damage. Prior to around 1980, DPT was not given to infants. The rise in
autism has correlated with the increased use of the infant vaccines.Those
companies were also found to have poor process control that allowed too much
of a live virus in their vaccines causing a so-called 'hot batch'. The
company that is left doesn't have mercury in their formulation and has
superior process control. I would much rather see my child suffer through a
virus than be permanently brain damaged(usually undetectably)
   BTW, whooping cough and pertusis are the same thing. the D stands for
Diptheria. 

Jim Freeman 


Ken Javor wrote: 
My take on it is that rather than appease ridiculous demands, a company
ought to look at the profit vs. risk vs. cost to consumer and decide, heck,
it ain't worth it.  Case in point on the news today I heard that DPT shots
are in short supply, because two companies quit making it.  They quit making
it because there were a very small number of bad reactions to it and there
were lawsuits or gov't action.  Well, my kids are beyond that stage but I
sure feel sorry for the people out there whose infants are at risk for
whooping cough, diphtheria and pertussis.  The only thing worse than
watching your child become seriously ill is knowing it was easily
preventable. 


S on 1/4/02 7:37 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote:

Hey, Ken, let's try to be realistic here!

Sure - we should try to get laws we don't like changed, but that isn't going
to happen overnight and in the meantime we have to operate within the law as
it stands. 

Or are you suggesting immediate insurrection by product manufacturers?
(Outlaw manufacturers roaming the wild wild west - an interesting concept!)

The IEE's guide on EMC and Functional Safety is concerned with such legal
aspects, but is also concerned with saving lives in a world where electronic
control of safety-related functions is proliferating madly.

As my paper at the IEEE's EMC Symposium in Montreal and my recent article in
ITEM UPDATE 2001 show - at present EMC standards don't address safety
issues, and most safety standards don't address EMC-related functional
safety issues. 

Regards, Keith Armstrong

In a message dated 03/01/02 17:24:42 GMT Standard Time,
ken.ja...@emccompliance.com writes:

Subj:Re: EMC-related safety issues
List-Post: emc-pstc@listserv.ieee.org
Date:03/01/02 17:24:42 GMT Standard Time
From:ken.ja...@emccompliance.com (Ken Javor)
Sender:owner-emc-p...@majordomo.ieee.org
Reply-to: ken.ja...@emccompliance.com (Ken Javor)
To:c...@dolby.co.uk (James, Chris), acar...@uk.xyratex.com
('acar...@uk.xyratex.com'), emc-p...@majordomo.ieee.org



There is an inherent contradiction in this anti-profit, anti-technology
point-of-view that I cannot and will not defend.  All I am saying is that
people who feel this is wrong should stand up and say so, not write guides
for how to go along with it.

Re: EMC-related safety issues

What an EMC engineer who understands the physics of field-to-wire coupling
would say is that the operation of non-antenna connected electronics
associated with one subsystem will not be degraded by close proximity with
the non-antenna connected electronics of another subsystem.  Forget 10
meters.  Are the PCs in your office separated by 10 m?  Would you expect two
PCs stacked side-by-side or one on top of the other to interact in any
manner?  These are rhetorical questions.

About the blood pressure monitor example.  Not enough info here to back out
what is wrong, but basic logic theory says when the conclusion is
impossible, you must re-examine your assumptions.  If 92 dBuV/m were enough
to make the device malfunction, it would malfunction a lot and there would
have been enough trouble reports to get it fixed or withdrawn. And 92 dBuV/m
at 10 meters is SCREAMING!!!  I am on location and don't have FCC regs
easily available, but the limits stair-step around 40 dBuV/m at 3 m, per my
recollection.

Would I feel comfortable placing a CISPR compliant PC next to a medical
device qualified to 1 V/m?  There is an inherent (not planned) margin of
safety here that is many orders of magnitude.   The answer is absolutely
yes.  If there were a problem, I would expect it more to occur below 30 MHz,
at the power supply switching frequency, IF the medical device processed
extremely low levels of electrical signals and was poorly shielded.  But I
believe there are separate immunity requirements which cover this
eventuality as well.




on 1/5/02 12:23 PM, cherryclo...@aol.com at cherryclo...@aol.com wrote:

Dear Cortland 
People can't simply say: "ordinary semiconductors won't demodulate RF levels
produced by an unintentional radiator"  even the smallest amount of RF can
be demodulated  there are no hysteresis or threshold effects in a PN
semiconductor junction or FET that is biased into its conduction region (at
least not until you get below signal levels equivalent to less than a single
electron). 

What I am sure most engineers would really mean to say is:
"ordinary semiconductors exposed to RF levels from an information technology
product which is fully compliant with all relevant EMC emissions standards
and is at 10 metres distance will generally not demodulate a sufficient
level of interference to make an appreciable difference to most electronic
systems." 

Now we have a statement which has some scientific rigor and some engineering
validity to it. 
(Although I do worry that in Europe our harmonised EMC standards only test
emissions up to 1GHz, so what does that say about the possible emitted
fields strengths from a PC with a 1.2GHz clock frequency?)

Let's see if we can put some meat into this discussion with a real-life
example... 

I once tested a blood sample incubator for RF field immunity. The incubator
was used during screening programs (for cancer and other diseases) and kept
about 100 test tubes at 37.1C (normal blood temperature), while the reagents
in the test tubes changed colour. After 24 hours of incubation medical staff
would inspect the test tubes and write letters to people telling them they
were sick, or that they were clear of the disease. I don't know what
temperature tolerance the reagents had to give an accurate medical
diagnosis, so assume ±0.1C.

On the front panel of the incubator was a display of its temperature, which
was of course 37.1C. We found that field strengths as low as 1V/m would
cause the incubation temperature to range over full scale, from heaters
fully off (in which case the temperature would decline to ambient) to
maximum (in which case the water used to incubate the test tubes would
boil). 
We could use the RF test frequency to control the temperature between plus
and minus full scale over the frequency range 80 to 1000MHz at 1V/m (and did
not test beyond 1GHz).

Most worryingly, the front panel display would only show temporary
variations from its 37.1C when the RF field was turned off or on, and would
continue to show 37.1C even when the water in the incubator was stone cold
or actually boiling.

Most demodulation effects in bipolar and FET devices approximate to a square
law - for example a 1dB fall in the field strength (keeping everything else
constant) would typically result in a 2dB fall in the demodulated
'interference' error signal, as John Woodgate has recently pointed out.

If we assume that the 1V/m field strength was causing a 60C temperature
error, how low would we need to make the RF field to get down to the 0.1C
accuracy of the front panel display?

Assuming square-law characteristics for the device doing the demodulation I
calculate a field strength of around 40mV/m or 92dBmicrovolts/metre.

You will notice that I have been generous to the incubator and assumed that
the 1V/m field just about caused its temperature error to increase by 60C to
boil the water, whereas it could have been overdriving the internal circuits
by a considerable margin and still suf

Re: EMC-related safety issues


The analytical portion of this post is, as the author stated, worst case.  A
cable attached to a susceptible circuit picks up a common-mode potential,
which most likely drives a current on a shield if the the circuit is
sensitive.  Then only the current multiplied by shield transfer impedance
actually gets into the victim, assuming no CMR.  Which just makes my
original point - unintentional emissions from ITE can only upset a radio
receiver tuned to the emission frequency.  That is why, as another
contributor posted, we use EMI receivers and spectrum analyzers with preamps
to make OATS measurements.

 on 1/4/02 12:51 PM, Tom Cokenias at t...@tncokenias.org wrote:

> At 8:34 AM -0500 1/4/2002, Keith Armstrong wrote:
> 
>> Does anyone else think that ordinary semiconductors doesn't respond to RF?
> 
> 
> 
> I agree that commonly used semiconductors have responses well into
> the 100's of MHz.
> 
> How much of a problem this is will depend on the nature and function
> of the circuitry using these components.
> 
> The EUT wires, cables, pcb traces etc. act like antennae,  on which
> the incident field voltages and currents.  An antenna factor can be
> thought of as ratio of the field strength  to the voltage induced on
> the terminated cable connected to the antenna.
> 
> In an impedance matched system,
> 
> 
> AF=9.734/lamda*(G)^0.5,   lamda being wavelength in meters, G being
> antenna gain over isotropic,
> 
> or in dB
> 
> AF dB =  -  G dBi  -29.7 dB + 20logFMHz
> 
> Assuming G is 1 (isotropic antenna), AF is 1  (= 0 dB) at about 30.8
> MHz, and AF get larger  as frequency increases, to  a factor of 32.7
> (= 30.3 dB) at 1 GHz .  Since AF is  field strength divided by
> induced voltage, the voltage induced on the trace goes down as
> frequency goes up for the same incident field strength.
> 
> An effective receive antenna needs to be on the order of 1/2
> wavelength or so; for 30 MHz this is 15m, for 1000 MHz this is 15 cm.
> 
> So if a victim EUT circuit has a pretty effective receive  antenna,
> and does not have any filtering and is equally sensitive across the
> frequency range under consideration (all taken together, a worst case
> scenario for susceptibility),
> 
> (1)  A 10 V/m field will  theoretically induce a voltage  0.33V  to
> 10V, depending on frequency
> 
> (2) A 5000 uV/m field (10x the FCC class B limit above 960 MHz) will
> theoretically induce a voltage from 152 uV to 5 mV, depending on
> frequency.
> 
> (3) A 500 uV/m field will  theoretically induce a voltage from 15 uV
> to 500 uV depending on frequency.
> 
> These are first order approximations, but they are useful in
> determining the level of the potential EMI  threat.   For instance a
> 4-30 mA sensor circuit using high gain operational amps will most
> likely  be interfered with  in scenario (1),  there may be some
> susceptibility detected in scenario (2), and most likely no problem
> encountered with scenario (3).
> 
> A sensitive all - band  AM communications receiver will have problems
> with all three, a broadcast TV operating in a strong signal area will
> probably be OK  with scenario 3 but not with 1 or 2.
> 
> I guess what I'm really trying to say with all this is that EMC is a
> systems thing, taking into account the nature of the culprit EMI
> generator, the nature of the victim EMI receiver,  and the path
> between them.  Then we have the economics of operating different
> devices in the same vicinity, the politics of who gets how much of
> what kind of protection, etc., etc.  All things considered, we should
> have jobs for life!
> 
> best regards and a Happy New Year to all.
> 
> Tom Cokenias
> 
> T.N. Cokenias Consulting
> P.O. Box 1086
> El Granada CA 94018
> 
> tel   650 726 1263
> cell 650 302 0887
> fax  650 726 1252
> 
> 
> 
> 
> 
> 
> 
> 


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Re: EMC-related safety issues

My point was that only radios are sensitive to rf fields at the levels
controlled by FCC/CISPR22 and indeed, as Ing. Gremen pointed out, levels
well above the limits.  Which means that the only rationale behind
FCC/CISPR22 is protection of radio broadcast reception.  Period.

on 1/5/02 12:10 PM, cherryclo...@aol.com at cherryclo...@aol.com wrote:

Dear Ken 
I am truly sorry if I irritated you by misunderstanding your words, but I
took your posting to imply that electronic circuits which are not designed
as RF receivers would not respond very well to radio frequencies.

My example was not intended to be a full answer to your example (there are
other postings which are dealing with that) just to indicate that the
frequency response of slow and commonplace ICs can be very high indeed.

I am sensitive to this issue because I keep on running across electronics
designers who say things like: "I don't need to worry about the RF immunity
of my audio amplifier/motor
controller/temperature/pressure/flow/weight/velocity measurement and control
system (please delete where applicable) because the opamps I use have a GBW
of under 1MHz so they won't see the RF"  which is of course complete
bollocks (a UK phrase that I hope translates well enough for all emc-pstc
subscribers). 

And no, I still don't agree with you that only radio receivers are sensitive
enough to RF to have a problem with what you are still calling
'unintentional emissions' (even though this term means very little in an
international forum unless you define the relevant standards or laws).

I think the problem you are concerned with is application dependant and we
cannot make such broad assumptions. As I said earlier, most interference
problems are caused by radio transmitters or radio receivers, but not all.

Regards, Keith Armstrong

In a message dated 05/01/02 01:20:27 GMT Standard Time,
ken.ja...@emccompliance.com writes:

Subj:Re: EMC-related safety issues
List-Post: emc-pstc@listserv.ieee.org
Date:05/01/02 01:20:27 GMT Standard Time
From:ken.ja...@emccompliance.com (Ken Javor)
To:cherryclo...@aol.com, emc-p...@majordomo.ieee.org

One sure way to REALLY irritate me is to twist my words and try to make me
look stupid (I do a fine job by myself on occasion and don't appreciate any
outside help).  I did not say that pn junctions don't detect and rectify rf,
I said that the field intensities associated with unintentional emissions
from ITE are too low to cause susceptibility in circuits other than radios.
Your example here is 10 V/m, and you are talking about an op-amp (gain
unspecified) and that it was susceptible at that level should be no surprise
to anyone. 

on 1/4/02 7:34 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote:

Does anyone else think that ordinary semiconductors doesn't respond to RF?

I have tested a product which was little more than an LM324 quad op-amp for
RF immunity using IEC 61000-4-3. This op-amp has a slew rate of
1V/micro-second on a good day with the wind in its favour. It was housed in
an unshielded plastic enclosure.

Demodulated noise that exceeded the (not very tough) product specification
were seen all the way up to 500MHz at a number of spot frequencies that
appeared to be due to the natural resonances of the input and output cables.

Above 500MHz this resonant behaviour vanished to be replaced by a steadily
rising level of demodulated 1kHz tone as the frequency increased. I stopped
testing at 1GHz, where the output error from the product was about 10% and
still rising with increased frequency.

OK, the field strength for the test was 10V/m (unmodulated) but the real
surprise was how well this very cheap and very slow opamp demodulated the
RF, and that it demodulated better at 1GHz than at 500MHz.

I have done many many immunity tests using IEC 61000-4-3 on audio equipment
and found much the same effects with every product I've ever tested.
With most larger products there is usually a roll-off in the demodulation
above 500MHz - not because the semiconductors in the ICs can't respond (they
can) but apparently because larger products have higher losses above 500MHz
or so between the cable ports and the semiconductors, plus a denser
structure that might provide more self-screening.

The transistors and diodes in all modern ICs (analog or digital) are so tiny
that they make excellent detectors at UHF and beyond. As they get smaller
(and they are) their frequency response increases (and their vulnerability
to upset and damage decreases).

Regards, Keith Armstrong

Re: EMC-related safety issues


I read in !emc-pstc that cherryclo...@aol.com wrote (in <132.6f59d2b.296
89...@aol.com>) about 'EMC-related safety issues', on Sat, 5 Jan 2002:
>Dear Cortland 
>People can't simply say: "ordinary semiconductors won't demodulate RF 
> levels 
>produced by an unintentional radiator"  even the smallest amount of RF 
> can 
>be demodulated  there are no hysteresis or threshold effects in a PN 
>semiconductor junction or FET that is biased into its conduction region 
> (at 
>least not until you get below signal levels equivalent to less than a 
> single 
>electron). 

The question is not whether demodulation occurs, but whether the
recovered modulation is at a level to cause a problem. 1 mV of r.f.
can't produce even 1 mV of recovered modulation.
>
>What I am sure most engineers would really mean to say is: 
>"ordinary semiconductors exposed to RF levels from an information 
> technology 
>product which is fully compliant with all relevant EMC emissions standards 
>and is at 10 metres distance will generally not demodulate a sufficient 
>level of interference to make an appreciable difference to most electronic 
>systems." 

I don't think most engineers would go along with a statement with such a
high fog-factor. That is one of the points of contention; this subject
seems to attract fog-factor like a superconducting magnet.
>
>Now we have a statement which has some scientific rigor and some 
> engineering 
>validity to it. 

Are you seriously putting that forward? It's so vague, IMO, as to be not
useful; it does not help in any way to realise solutions.

>(Although I do worry that in Europe our harmonised EMC standards only test 
>emissions up to 1GHz, so what does that say about the possible emitted 
>fields strengths from a PC with a 1.2GHz clock frequency?) 

Extension up to 3 GHz (much higher in some cases) is being studied
intensively. One major problem is that repeatable measurements above 1
GHz are very difficult to achieve.
>
>Let's see if we can put some meat into this discussion with a real-life 
>example... 

Well, it's a very extreme case of real life! I doubt that you'll come
across another one before you retire!
>
>I once tested a blood sample incubator for RF field immunity. 

When was this? Before or after 1976, when EMC of medical equipment first
(AFAIK) surfaced as a matter to be studied intensively.

[Big snip]
>
>How many people reading this would be now be quite happy to place even a 
>fully-compliant PC (compliant at 10 metres distance, that is) right next 
> to 
>the unmodified incubator? 
>
>If it helps, imagine that it is your young daughter whose blood sample is 
> in 
>the incubator to discover which drugs she needs to survive. 
>
>Shall we have a vote on how close we would be prepared to place the PC? 
>Might be interesting. 

This appeal to emotion is out of place. 
>
>Let's not even think about the problems of proximity to cellphones and 
> other 
>intentional radiators. 
>
>I didn't mention that the incubator was a small model used for mobile 
>screening, for installation in a truck adapted for medical screening 
>purposes which travels to various communities and parks there for a few 
> days 
>while it tests the local people for disease - hardly a very well 
> controlled 
>electromagnetic environment. 
>
>What does the above imply for similar incubators in countries that do not 
>have mandatory EMC immunity standards? Or for older incubators in the EU 
>that have never had to meet the EMC directive? 
>
>(Please don't reply with the old chestnut that "we haven't heard of any 
>problems so far, so everything must be OK" - people who should have known 
>better were using that phrase before September 11th. It is just not an 
>acceptable argument where safety issues are involved, as any expert in 
>safety law will tell you. Try: "I've been driving past that school at 
> 40mph 
>for ten years and haven't hit a kid yet, so it must be safe mustn't it?" 
> as 
>a test of the concept.) 

More emotion. This is another point of contention: as soon as any
critique is offered to some pronouncement, these emotional arguments are
trotted out. I had a similar experience with a militant carer of
disabled people. Anything that suggested that her views were perhaps
just a *little* extreme (like scrapping all London's black cabs
overnight because they won't accommodate a wheelchair with the user in
it) was greeted with 'Oh, so you are prejudiced against disabled people,
are you?'

IMO, your reasoning is utterly unreasonable. Designers are not
omniscient, or had better assume they are not. So they must assume that
they have not thought of every possible scenario down to that 10^-9
probability. How, then, can the designer be reasonably assured that his
design is satisfactory, if he cannot rely on the absence of reports of

Re: EMC-related safety issues


I read in !emc-pstc that cherryclo...@aol.com wrote (in <92.1f676722.296
88...@aol.com>) about 'EMC-related safety issues', on Sat, 5 Jan 2002:
>I am truly sorry if I irritated you by misunderstanding your words, but I 
>took your posting to imply that electronic circuits which are not designed 
>as RF receivers would not respond very well to radio frequencies. 

They DON'T respond very well, if compared with a receiver.
>
>My example was not intended to be a full answer to your example (there are 
>other postings which are dealing with that) just to indicate that the 
>frequency response of slow and commonplace ICs can be very high indeed. 

Well, that is not really correct. The r.f is demodulated at the first
junction (usually) and beyond that point the device is only handling the
modulation, at much lower frequencies.
>
>I am sensitive to this issue because I keep on running across electronics 
>designers who say things like: "I don't need to worry about the RF 
> immunity 
>of my audio amplifier/motor 
>controller/temperature/pressure/flow/weight/velocity measurement and 
> control 
>system (please delete where applicable) because the opamps I use have a 
> GBW 
>of under 1MHz so they won't see the RF"  which is of course complete 
>bollocks (a UK phrase that I hope translates well enough for all emc-pstc 
>subscribers). 

There are always some!
>
>And no, I still don't agree with you that only radio receivers are 
> sensitive 
>enough to RF to have a problem with what you are still calling 
>'unintentional emissions' (even though this term means very little in an 
>international forum unless you define the relevant standards or laws). 

I think this term is quite legitimate and well-understood. If the
equipment requires to emit in order to perform its intended function, it
is an 'intentional emitter'. If it does not need to do so, but emits
anyway, it is an 'unintentional emitter'. It is difficult to see how
there could be any confusion or ambiguity about this.
>
>I think the problem you are concerned with is application dependant and we 
>cannot make such broad assumptions. As I said earlier, most interference 
>problems are caused by radio transmitters or radio receivers, but not all. 
>
Well, electric fences
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
After swimming across the Hellespont, I felt like a Hero. 

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Re: EMC-related safety issues


I read in !emc-pstc that cherryclo...@aol.com wrote (in
<43.47bb025.29689...@aol.com>) about 'EMC-related safety issues', on
Sat, 5 Jan 2002:
>The "one in a billion" John refers to sounds very dramatic and difficult. 

More dramatic than you 'infant daughter' and '40 mph past a school'?

I explained in VERY GREAT DETAIL the effect of cumulative probability in
requiring very low probability events to be taken into account. In
principle, as the probability goes down, the  number of risk scenarios
increases *combinatorially*. There is no Olber's Paradox in this area,
the 'night sky is infinitely brighter than the Sun'!
>
>So it may be helpful to refer to IEC 61508 which is a recently-published 
>'basic safety publication' covering "The functional safety of electrical / 
>electronic / programmable safety-related systems" 
>
>IEC 61508 uses the concept of the Safety Integrity Level (or SIL) to help 
>design safety-related systems which have quantified failure probabilities. 
>
>The SILs for average probability of failure to perform design function on 
>demand are: 
>SIL level 1: up to 10^ -2 
>SIL level 2: 10^ -2 to 10^ -3 
>SIL level 3: 10^ -3 to 10^ -4 
>SIL level 4:  10^ -4 to 10^ -5 or even lower levels 
>
>The SILs for average probability of dangerous failure per hour of 
> operation 
>are: 
>SIL level 1: up to 10^ -6 
>SIL level 2: 10^ -6 to 10^ -7 
>SIL level 3: 10^ -7 to 10^ -8 
>SIL level 4:  10^ -8 to 10^ -9 or even lower levels 
>
>The standard describes how to select the SIL level for a particular 
>safety-related application, and we find that SIL4 is required where a 
>failure of the safety system could result in the deaths or serious 
> injuries 
>of large numbers of people. 

Yes, my 10^-9 figure was in the context of your 'relatives sobbing all
over the courtroom'. 
>
>Most safety-related applications that most practising engineers will be 
>involved in will be SIL1 or 2, maybe even SIL3, and hence require very 
> much 
>lower reliability than one in a billion. 

You are neglecting cumulative probability, in spite of quoting my whole
text on it! SIL2, if it is applied to individual risk scenarios, is a
recipe for disaster if you are putting many thousands of units, such as
PCs or TVs, into the field. If is it applied, as it should be, to the
cumulative probability of ALL risk scenarios, then *each one* needs to
be constrained to that 10^-9 probability, preferably well below it. 100
scenarios at 10^-9 each gives a cumulative of 10^-7, after all. 
>

-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
After swimming across the Hellespont, I felt like a Hero. 

---
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Re: EMC-related safety issues

The "one in a billion" John refers to sounds very dramatic and difficult. 

So it may be helpful to refer to IEC 61508 which is a recently-published 
'basic safety publication' covering "The functional safety of electrical / 
electronic / programmable safety-related systems"

IEC 61508 uses the concept of the Safety Integrity Level (or SIL) to help 
design safety-related systems which have quantified failure probabilities. 

The SILs for “average probability of failure to perform design function on 
demand” are:
SIL level 1: up to 10^ -2
SIL level 2: 10^ -2 to 10^ -3
SIL level 3: 10^ -3 to 10^ -4
SIL level 4:  10^ -4 to 10^ -5 or even lower levels

The SILs for ““average probability of dangerous failure per hour of 
operation” are:
SIL level 1: up to 10^ -6
SIL level 2: 10^ -6 to 10^ -7
SIL level 3: 10^ -7 to 10^ -8
SIL level 4:  10^ -8 to 10^ -9 or even lower levels

The standard describes how to select the SIL level for a particular 
safety-related application, and we find that SIL4 is required where a failure 
of the safety system could result in the deaths or serious injuries of large 
numbers of people.

Most safety-related applications that most practising engineers will be 
involved in will be SIL1 or 2, maybe even SIL3, and hence require very much 
lower reliability than one in a billion.

'm sure that when we are driving our cars, or living near a nuclear plant, we 
would like to think that the designers of the braking system or control rod 
control systems (respectively) had looked at 'ALL risk scenarios down to the 
billion-to-one against level of probability' - to use John's words.

Regards, Keith Armstrong

In a message dated 04/01/02 19:31:57 GMT Standard Time, j...@jmwa.demon.co.uk 
writes:

> Subj:Re: EMC-related safety issues
> Date:04/01/02 19:31:57 GMT Standard Time
> From:j...@jmwa.demon.co.uk (John Woodgate)
> 
> I read in !emc-pstc that cherryclo...@aol.com wrote (in <167.698dddc.296
> 70...@aol.com>) about 'EMC-related safety issues', on Fri, 4 Jan 2002:
> >As my paper at the IEEE's EMC Symposium in Montreal and my recent 
> article in 
> >ITEM UPDATE 2001 show - at present EMC standards don't address safety 
> >issues, and most safety standards don't address EMC-related functional 
> >safety issues. 
> 
> As far as CENELEC is concerned, it was a conscious decision not to
> incorporate 'EMC and Safety' issues into EMC standards, but to treat it
> as a separate subject.
> 
> Some people may find a clarification helpful. We have EMC matters,
> concerned with compatibility between items of equipment, ensuring that
> they continue to work (Criterion A in the Generic Standards) or fail
> gracefully (Criteria B and C). These criteria do not address safety
> issues, as indicated in paragraph 1 above. However, the Generic
> Standards do have a limited 'blanket' requirement, that equipment must
> not become unsafe *during testing*.
> 
> We also have safety matters per se, which don't involve EMC.
> 
> We ALSO have the separate subject, called 'EMC and Safety' or reasonable
> variants thereof. This addresses the matter of equipment becoming unsafe
> *in service* due to excessive emission levels in the environment, or
> lack of sufficient immunity to acceptable emission levels. So far, this
> seems perfectly reasonable. 
> 
> BUT it stops seeming reasonable when the question 'What could go wrong?'
> is asked and statistical data is used to attempt to answer it. To take a
> very simple example (maybe over-simplified), we might say that the
> probability of an unsafe occurrence should be less than 10^-9. That
> immediately means that the designer of the equipment has to look at ALL
> risk scenarios down to the billion-to-one against level of probability.
> To say that that is difficult is surely a great understatement. 
> 
> But some experts in the field seem to ignore that great difficulty, and
> simply (or maybe not so simply) state that if the designer fails to take
> into account ANY scenario that subsequently results in an unsafe
> condition, the designer has failed in his professional responsibility,
> and may be held criminally responsible for negligence.
> 
> Well, let us be very circumspect designers and look at what immunity
> levels we might need to get down to that 10^-9 probability. For radiated
> emissions, the necessary test levels seem to be of the order of 100 V/m.
> Test levels for other disturbances seem to be equally distantly related
> to the levels normally experienced and to the test levels in pure EMC
> standards. 
> 
> We might conclude that assessment of EMC immunity per se is completely
> unnecessary, because testing for 'EMC and Safety' requires test levels
> of the order of 30 dB higher!
> 
> One could go, with the sort of reasoning advocated by some experts,
> further into the realms of fantasy. Suppose, for a particular piece of
> equipment, the designer, with great diligence, identifies a million
> threat scenarios, each of which has a probabili

Re: EMC-related safety issues

In a message dated 04/01/02 19:31:51 GMT Standard Time, j...@jmwa.demon.co.uk 
writes:

> >The trick, I believe, is not to be in that position in the first place. 
> >Design your products using the latest safety knowledge and test them well 
> to 
> >discover if they have any weaknesses you did not address. 
> 
> How do you decide what tests to do **for weaknesses you don't suspect**?
> Isn't that fundamentally impossible?

I actually said "for weaknesses you did not address" not "for weaknesses you 
did not suspect" - quite a different matter. 

Mind you, if a designer is not very competent in safety matters there might 
be quite a number of things that he/she did not suspect, much less address, 
that he/she should have done.

But I was thinking of tests such as bump and vibration, thermal extremes, 
etc, that reputable companies do to test the reliability of their products. 
Also safety tests such as simulating faults in components (such as shorting 
or opening power transistors and capacitors, disconnecting connections to 
resistors and ICs, etc.). 

These tests tend to reveal many safety issues that were overlooked in the 
heat of the design process, or through lack of knowledge of the design staff, 
and sometimes even reveal things that safety experts familiar with the 
product type would not have expected.

Because such tests can be done and are available from many suppliers (if you 
don't do them yourself) I understand from UK safety enforcers (Trading 
Standards) that a manufacturer would have a hard time proving compliance with 
the LVD or PLD directives if using them would have revealed a safety problem 
that contributed to an actual safety incident. 

Regards, Keith Armstrong

Re: EMC-related safety issues

Dear Cortland
People can't simply say: "ordinary semiconductors won't demodulate RF levels 
produced by an unintentional radiator" – even the smallest amount of RF can 
be demodulated – there are no hysteresis or threshold effects in a PN 
semiconductor junction or FET that is biased into its conduction region (at 
least not until you get below signal levels equivalent to less than a single 
electron).

What I am sure most engineers would really mean to say is: 
"ordinary semiconductors exposed to RF levels from an information technology 
product which is fully compliant with all relevant EMC emissions standards 
and is at 10 metres distance will generally not demodulate a sufficient level 
of interference to make an appreciable difference to most electronic systems."

Now we have a statement which has some scientific rigor and some engineering 
validity to it. 
(Although I do worry that in Europe our harmonised EMC standards only test 
emissions up to 1GHz, so what does that say about the possible emitted fields 
strengths from a PC with a 1.2GHz clock frequency?)

Let's see if we can put some meat into this discussion with a real-life 
example...

I once tested a blood sample incubator for RF field immunity. The incubator 
was used during screening programs (for cancer and other diseases) and kept 
about 100 test tubes at 37.1C (normal blood temperature), while the reagents 
in the test tubes changed colour. After 24 hours of incubation medical staff 
would inspect the test tubes and write letters to people telling them they 
were sick, or that they were clear of the disease. I don't know what 
temperature tolerance the reagents had to give an accurate medical diagnosis, 
so assume ±0.1C.

On the front panel of the incubator was a display of its temperature, which 
was of course 37.1C. We found that field strengths as low as 1V/m would cause 
the incubation temperature to range over full scale, from heaters fully off 
(in which case the temperature would decline to ambient) to maximum (in which 
case the water used to incubate the test tubes would boil). 
We could use the RF test frequency to control the temperature between plus 
and minus full scale over the frequency range 80 to 1000MHz at 1V/m (and did 
not test beyond 1GHz). 

Most worryingly, the front panel display would only show temporary variations 
from its 37.1C when the RF field was turned off or on, and would continue to 
show 37.1C even when the water in the incubator was stone cold or actually 
boiling.

Most demodulation effects in bipolar and FET devices approximate to a square 
law - for example a 1dB fall in the field strength (keeping everything else 
constant) would typically result in a 2dB fall in the demodulated 
'interference' error signal, as John Woodgate has recently pointed out.

If we assume that the 1V/m field strength was causing a 60C temperature 
error, how low would we need to make the RF field to get down to the 0.1C 
accuracy of the front panel display? 

Assuming square-law characteristics for the device doing the demodulation I 
calculate a field strength of around 40mV/m or 92dBmicrovolts/metre.

You will notice that I have been generous to the incubator and assumed that 
the 1V/m field just about caused its temperature error to increase by 60C to 
boil the water, whereas it could have been overdriving the internal circuits 
by a considerable margin and still suffered a 60C error at 0.1V/m. We didn't 
test this possibility as our focus was (as in most of these cases) on quickly 
modifying the product so it passed the immunity test - which we did.

92dBmicrovolts/metre is not a very high RF field level for a PC without any 
EMC precautions at a distance of 10 metres. 

How many people reading this would be now be quite happy to place even a 
fully-compliant PC (compliant at 10 metres distance, that is) right next to 
the unmodified incubator? 

If it helps, imagine that it is your young daughter whose blood sample is in 
the incubator to discover which drugs she needs to survive.

Shall we have a vote on how close we would be prepared to place the PC? 
Might be interesting.

Let's not even think about the problems of proximity to cellphones and other 
intentional radiators. 

I didn't mention that the incubator was a small model used for mobile 
screening, for installation in a truck adapted for medical screening purposes 
which travels to various communities and parks there for a few days while it 
tests the local people for disease - hardly a very well controlled 
electromagnetic environment.

What does the above imply for similar incubators in countries that do not 
have mandatory EMC immunity standards? Or for older incubators in the EU that 
have never had to meet the EMC directive?

(Please don't reply with the old chestnut that "we haven't heard of any 
problems so far, so everything must be OK" - people who should have known 
better were using that phrase before September 11th. It is just not an 
acceptable

Re: EMC-related safety issues

Dear Ken
That is exactly what I am saying:  under the EU's Product Liability Directive 
a company can be held liable for unlimited damages with no proof of 
negligence on the manufacturer's part.

It is of course a valid management decision to ignore a market that is almost 
as large as USA/Canada because of financial risk issues – but you'll notice 
that a lot of manufacturers are still making lots of money selling goods in 
the EU.

Regards, Keith Armstrong

In a message dated 05/01/02 01:31:03 GMT Standard Time, 
ken.ja...@emccompliance.com writes:

> Subj:Re: EMC-related safety issues
> Date:05/01/02 01:31:03 GMT Standard Time
> From:ken.ja...@emccompliance.com (Ken Javor)
> To:cherryclo...@aol.com, emc-p...@majordomo.ieee.org
> 
> Interesting to note that this country (USA) got started in part because of 
> a tax on tea.  I think you are saying here that a company can be held 
> liable for unlimited damages with no proof of negligence on the 
> manufacturer's part.  If I were a manufacturer I would simply not market to 
> the EU.
>

Re: EMC-related safety issues

Dear Ken
That is precisely the point I was trying to make: all companies (and people) 
always weigh up all the costs and risks that they know about and act 
accordingly.

The problem arises when certain risks are unknown or ignored, for whatever 
reasons.

I see it as part of every engineer's job to inform the people who make the 
cost/risk decisions about all the costs and risks associated with a certain 
course of action. 

What I find in practice is that most engineers are aware of the costs but as 
it is so hard to quantify the risks they often don't bother. Also, many 
engineers are uncomfortable with quoting numbers that they can't accurately 
calculate to five decimal places.

Hands up all those whose formal (or in-company) engineering education 
included risk analysis and estimation and how to present the data to 
management

So in many cases management don't have the full information on which to base 
their cost/risk decisions.

Regards, Keith Armstrong

In a message dated 05/01/02 01:27:34 GMT Standard Time, 
ken.ja...@emccompliance.com writes:

> Subj:Re: EMC-related safety issues
> Date:05/01/02 01:27:34 GMT Standard Time
> From:ken.ja...@emccompliance.com (Ken Javor)
> To:cherryclo...@aol.com, emc-p...@majordomo.ieee.org
> 
> My take on it is that rather than appease ridiculous demands, a company 
> ought to look at the profit vs. risk vs. cost to consumer and decide, heck, 
> it ain't worth it.  Case in point on the news today I heard that DPT shots 
> are in short supply, because two companies quit making it.  They quit 
> making it because there were a very small number of bad reactions to it and 
> there were lawsuits or gov't action.  Well, my kids are beyond that stage 
> but I sure feel sorry for the people out there whose infants are at risk 
> for whooping cough, diphtheria and pertussis.   The only thing worse than 
> watching your child become seriously ill is knowing it was easily 
> preventable.
> 
> 
> S on 1/4/02 7:37 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote:
> 
> >> Hey, Ken, let's try to be realistic here! 
>> 
>> Sure - we should try to get laws we don't like changed, but that isn't 
>> going to happen overnight and in the meantime we have to operate within 
>> the law as it stands. 
>> 
>> Or are you suggesting immediate insurrection by product manufacturers? 
>> (Outlaw manufacturers roaming the wild wild west - an interesting 
>> concept!) 
>> 
>> The IEE's guide on EMC and Functional Safety is concerned with such legal 
>> aspects, but is also concerned with saving lives in a world where 
>> electronic control of safety-related functions is proliferating madly. 
>> 
>> As my paper at the IEEE's EMC Symposium in Montreal and my recent article 
>> in ITEM UPDATE 2001 show - at present EMC standards don't address safety 
>> issues, and most safety standards don't address EMC-related functional 
>> safety issues. 
>> 
>> Regards, Keith Armstrong 
>> 
>> In a message dated 03/01/02 17:24:42 GMT Standard Time, 
>> ken.ja...@emccompliance.com writes: 
>> 
>> >>> Subj:Re: EMC-related safety issues 
>>> Date:03/01/02 17:24:42 GMT Standard Time 
>>> From:ken.ja...@emccompliance.com (Ken Javor) 
>>> Sender:owner-emc-p...@majordomo.ieee.org 
>>> Reply-to: ken.ja...@emccompliance.com (Ken Javor) 
>>> 
>> To:c...@dolby.co.uk (James, Chris), acar...@uk.xyratex.com 
>> ('acar...@uk.xyratex.com'), emc-p...@majordomo.ieee.org
>> 
>> 
>> >>> There is an inherent contradiction in this anti-profit, anti-technology 
>>> point-of-view that I cannot and will not defend.  All I am saying is that 
>>> people who feel this is wrong should stand up and say so, not write 
>>> guides for how to go along with it. 
>>> 
>>

Re: EMC-related safety issues

Dear Ken
I am truly sorry if I irritated you by misunderstanding your words, but I 
took your posting to imply that electronic circuits which are not designed as 
RF receivers would not respond very well to radio frequencies.

My example was not intended to be a full answer to your example (there are 
other postings which are dealing with that) just to indicate that the 
frequency response of slow and commonplace ICs can be very high indeed. 

I am sensitive to this issue because I keep on running across electronics 
designers who say things like: "I don't need to worry about the RF immunity 
of my audio amplifier/motor 
controller/temperature/pressure/flow/weight/velocity measurement and control 
system (please delete where applicable) because the opamps I use have a GBW 
of under 1MHz so they won't see the RF" – which is of course complete 
bollocks (a UK phrase that I hope translates well enough for all emc-pstc 
subscribers).

And no, I still don't agree with you that only radio receivers are sensitive 
enough to RF to have a problem with what you are still calling 'unintentional 
emissions' (even though this term means very little in an international forum 
unless you define the relevant standards or laws). 

I think the problem you are concerned with is application dependant and we 
cannot make such broad assumptions. As I said earlier, most interference 
problems are caused by radio transmitters or radio receivers, but not all.

Regards, Keith Armstrong

In a message dated 05/01/02 01:20:27 GMT Standard Time, 
ken.ja...@emccompliance.com writes:

> Subj:Re: EMC-related safety issues
> Date:05/01/02 01:20:27 GMT Standard Time
> From:ken.ja...@emccompliance.com (Ken Javor)
> To:cherryclo...@aol.com, emc-p...@majordomo.ieee.org
> 
> One sure way to REALLY irritate me is to twist my words and try to make me 
> look stupid (I do a fine job by myself on occasion and don't appreciate any 
> outside help).  I did not say that pn junctions don't detect and rectify 
> rf, I said that the field intensities associated with unintentional 
> emissions from ITE are too low to cause susceptibility in circuits other 
> than radios.  Your example here is 10 V/m, and you are talking about an 
> op-amp (gain unspecified) and that it was susceptible at that level should 
> be no surprise to anyone.
> 
> on 1/4/02 7:34 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote:
> 
> >> Does anyone else think that ordinary semiconductors doesn't respond to 
>> RF? 
>> 
>> I have tested a product which was little more than an LM324 quad op-amp 
>> for RF immunity using IEC 61000-4-3. This op-amp has a slew rate of 
>> 1V/micro-second on a good day with the wind in its favour. It was housed 
>> in an unshielded plastic enclosure. 
>> 
>> Demodulated noise that exceeded the (not very tough) product specification 
>> were seen all the way up to 500MHz at a number of spot frequencies that 
>> appeared to be due to the natural resonances of the input and output 
>> cables. 
>> 
>> Above 500MHz this resonant behaviour vanished to be replaced by a steadily 
>> rising level of demodulated 1kHz tone as the frequency increased. I 
>> stopped testing at 1GHz, where the output error from the product was about 
>> 10% and still rising with increased frequency. 
>> 
>> OK, the field strength for the test was 10V/m (unmodulated) but the real 
>> surprise was how well this very cheap and very slow opamp demodulated the 
>> RF, and that it demodulated better at 1GHz than at 500MHz. 
>> 
>> I have done many many immunity tests using IEC 61000-4-3 on audio 
>> equipment and found much the same effects with every product I've ever 
>> tested. 
>> With most larger products there is usually a roll-off in the demodulation 
>> above 500MHz - not because the semiconductors in the ICs can't respond 
>> (they can) but apparently because larger products have higher losses above 
>> 500MHz or so between the cable ports and the semiconductors, plus a denser 
>> structure that might provide more self-screening. 
>> 
>> The transistors and diodes in all modern ICs (analog or digital) are so 
>> tiny that they make excellent detectors at UHF and beyond. As they get 
>> smaller (and they are) their frequency response increases (and their 
>> vulnerability to upset and damage decreases). 
>> 
>> Regards, Keith Armstrong 
>>

Re: EMC-related safety issues


I read in !emc-pstc that Ken Javor  wrote
(in ) about 'EMC-related
safety issues', on Fri, 4 Jan 2002:
>My take on it is that rather than appease ridiculous demands, a 
>company ought to look at the profit vs. risk vs. cost to consumer 
>and decide, heck, it ain't worth it. Case in point on the news 
>today I heard that DPT shots are in short supply, because two 
>companies quit making it. They quit making it because there were a 
>very small number of bad reactions to it and there were lawsuits or 
>gov't action.  Well, my kids are beyond that stage but I sure feel 
>sorry for the people out there whose infants are at risk for 
>whooping cough, diphtheria and pertussis.

Ahem, whooping cough IS pertussis. 'DPT' = Diphtheria, pertussis and
tetanus.

>   The only thing worse 
>than watching your child become seriously ill is knowing it was 
>easily preventable.
>
This is wildly OT, but there is a big issue in Britain in this area,
because what we call the 'triple vaccine' or 'MMR' (measles, mumps and
rubella) is alleged to be implicated in autism and serious bowel
disorders. The connection is, AIUI, considered by a *small* number of
qualified medical people, to be proved, or very probable. This is
another case of (alleged) dire results of a very low probability, but
much higher that my suggested 'generic' 10^-9 level. The government has,
if anything, made matters worse, by denying parents the right to choose,
on the National Health (free) Service, three separate vaccinations
instead of the triple, so it's the triple or none and it seems about 20%
of parents are choosing 'none', in addition to the 10% or so who reject
or do not bother about vaccination per se. With only 70% of infants
vaccinated, there is a real risk of an epidemic.

Matters were made even worse by the indignant reaction of the Prime
Minister, who refused to answer in Parliament when asked if his infant
son has had the triple vaccine! The implication is that the PM has paid
for three separate vaccinations instead. 

I believe also that the DPT vaccine  is not licensed in Europe because
of the (alleged) incidence of serious side-effects.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
After swimming across the Hellespont, I felt like a Hero. 

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Re: EMC-related safety issues


I read in !emc-pstc that John Shinn  wrote
(in <002401c19584$35f73660$0b3d1...@hadco.comsanmina.com>) about 'EMC-
related safety issues', on Fri, 4 Jan 2002:
>So where do I drill the hole in my fuel injection system?

You don't. You put a pint of water in the tank and a spoonful of liquid
detergent to make it mix with the fuel. Don't forget to replace the
whole engine after you've passed the emission test. (;-)
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
After swimming across the Hellespont, I felt like a Hero. 

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Re: EMC-related safety issues

2002-01-05 Thread Jim Freeman

Hi Ken,
The reason that those companies stopped was because it was found
that there was mercury in the formulation of the vaccine. The mercury
had no other use other than stabilization.  The mercury is known to
cause brain damage. Prior to around 1980, DPT was not given to infants.
The rise in autism has correlated with the increased  use of the infant
vaccines.Those companies were also found to have poor process control
that allowed too much of a live virus in their vaccines causing a
so-called 'hot batch'. The company that is left doesn't have mercury in
their formulation and has superior process control. I would much rather
see my child suffer through a virus than be permanently brain
damaged(usually undetectably)
BTW, whooping cough and pertusis are the same thing. the D stands
for Diptheria.

Jim Freeman


Ken Javor wrote:

> My take on it is that rather than appease ridiculous demands, a
> company ought to look at the profit vs. risk vs. cost to consumer and
> decide, heck, it ain't worth it.  Case in point on the news today I
> heard that DPT shots are in short supply, because two companies quit
> making it.  They quit making it because there were a very small number
> of bad reactions to it and there were lawsuits or gov't action.  Well,
> my kids are beyond that stage but I sure feel sorry for the people out
> there whose infants are at risk for whooping cough, diphtheria and
> pertussis.   The only thing worse than watching your child become
> seriously ill is knowing it was easily preventable.
>
>
> S on 1/4/02 7:37 AM, cherryclo...@aol.com at cherryclo...@aol.com
> wrote:
>
>
>  Hey, Ken, let's try to be realistic here!
>
>  Sure - we should try to get laws we don't like changed, but
>  that isn't going to happen overnight and in the meantime we
>  have to operate within the law as it stands.
>
>  Or are you suggesting immediate insurrection by product
>  manufacturers?
>  (Outlaw manufacturers roaming the wild wild west - an
>  interesting concept!)
>
>  The IEE's guide on EMC and Functional Safety is concerned
>  with such legal aspects, but is also concerned with saving
>  lives in a world where electronic control of safety-related
>  functions is proliferating madly.
>
>  As my paper at the IEEE's EMC Symposium in Montreal and my
>  recent article in ITEM UPDATE 2001 show - at present EMC
>  standards don't address safety issues, and most safety
>  standards don't address EMC-related functional safety
>  issues.
>
>  Regards, Keith Armstrong
>
>  In a message dated 03/01/02 17:24:42 GMT Standard Time,
>  ken.ja...@emccompliance.com writes:
>
>
>   Subj:Re: EMC-related safety issues
>   Date:03/01/02 17:24:42 GMT Standard Time
>   From:ken.ja...@emccompliance.com (Ken Javor)
>   Sender:owner-emc-p...@majordomo.ieee.org
>   Reply-to: ken.ja...@emccompliance.com (Ken Javor)
>
>  To:c...@dolby.co.uk (James, Chris),
>  acar...@uk.xyratex.com ('acar...@uk.xyratex.com'),
>  emc-p...@majordomo.ieee.org
>
>
>
>
>   There is an inherent contradiction in this
>   anti-profit, anti-technology point-of-view that I
>   cannot and will not defend.  All I am saying is
>   that people who feel this is wrong should stand up
>   and say so, not write guides for how to go along
>   with it.
>

Re: EMC-related safety issues

2002-01-05 Thread Ken Javor

Interesting to note that this country (USA) got started in part because of a
tax on tea. I think you are saying here that a company can be held liable
for unlimited damages with no proof of negligence on the manufacturer's
part. If I were a manufacturer I would simply not market to the EU.

on 1/4/02 7:39 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote:

As I understand the way the civil law section of the EU's Product Liability
Directive operates (I am not a lawyer) it does in fact place the burden of
proof on the manufacturer, who is effectively considered 'guilty until
proved innocent'.

I also understand that any number of manufacturers can be sued in the civil
courts under one safety incident, and the liabilities of each awarded 'on
the balance of probabilities' that their product caused the damage, injury
or death being complained about.

Also...nobody has to prove negligence on the part of the manufacturer, this
is sometimes called 'no-fault liability' - you can be held to be liable
under the law even though nobody has proved that your product was actually
the cause of the safety incident.

Another interesting fact about EU Product Liability is that in the civil
courts in most EU member states there is no financial upper limit to the
damages that can be awarded against a manufacturer.

We may not like it, but that's how the world appears to be at the moment.
Regards, Keith Armstrong

In a message dated 03/01/02 19:52:20 GMT Standard Time, j...@jmwa.demon.co.uk
writes:

Subj:Re: EMC-related safety issues
List-Post: emc-pstc@listserv.ieee.org
Date:03/01/02 19:52:20 GMT Standard Time
From:j...@jmwa.demon.co.uk (John Woodgate)
Sender:owner-emc-p...@majordomo.ieee.org
Reply-to: j...@jmwa.demon.co.uk (John Woodgate)
To:emc-p...@majordomo.ieee.org

I read in !emc-pstc that Gary McInturff wrote (in <917063bab0ddb043af5faa73c7a835d40ac...@windlord.wwp.com
>) about 'EMC-related safety issues', on Thu, 3 Jan 2002:

> While I take your point - I'll challenge with the equally valid argument
>that says show me the data that they do cause SIDS!

Out of order! That's the whole point! Manufacturers are being required
to prepare to prove a negative, which is inherently impossible in most
cases. No-one is required to prove a positive, which is easy if it is
true.

Re: EMC-related safety issues

2002-01-05 Thread Ken Javor

My take on it is that rather than appease ridiculous demands, a company
ought to look at the profit vs. risk vs. cost to consumer and decide, heck,
it ain't worth it.  Case in point on the news today I heard that DPT shots
are in short supply, because two companies quit making it.  They quit making
it because there were a very small number of bad reactions to it and there
were lawsuits or gov't action.  Well, my kids are beyond that stage but I
sure feel sorry for the people out there whose infants are at risk for
whooping cough, diphtheria and pertussis.   The only thing worse than
watching your child become seriously ill is knowing it was easily
preventable.


S on 1/4/02 7:37 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote:

Hey, Ken, let's try to be realistic here!

Sure - we should try to get laws we don't like changed, but that isn't going
to happen overnight and in the meantime we have to operate within the law as
it stands. 

Or are you suggesting immediate insurrection by product manufacturers?
(Outlaw manufacturers roaming the wild wild west - an interesting concept!)

The IEE's guide on EMC and Functional Safety is concerned with such legal
aspects, but is also concerned with saving lives in a world where electronic
control of safety-related functions is proliferating madly.

As my paper at the IEEE's EMC Symposium in Montreal and my recent article in
ITEM UPDATE 2001 show - at present EMC standards don't address safety
issues, and most safety standards don't address EMC-related functional
safety issues. 

Regards, Keith Armstrong

In a message dated 03/01/02 17:24:42 GMT Standard Time,
ken.ja...@emccompliance.com writes:

Subj:Re: EMC-related safety issues
List-Post: emc-pstc@listserv.ieee.org
Date:03/01/02 17:24:42 GMT Standard Time
From:ken.ja...@emccompliance.com (Ken Javor)
Sender:owner-emc-p...@majordomo.ieee.org
Reply-to: ken.ja...@emccompliance.com (Ken Javor)
To:c...@dolby.co.uk (James, Chris), acar...@uk.xyratex.com
('acar...@uk.xyratex.com'), emc-p...@majordomo.ieee.org



There is an inherent contradiction in this anti-profit, anti-technology
point-of-view that I cannot and will not defend.  All I am saying is that
people who feel this is wrong should stand up and say so, not write guides
for how to go along with it.

Re: EMC-related safety issues

2002-01-05 Thread Ken Javor

One sure way to REALLY irritate me is to twist my words and try to make me
look stupid (I do a fine job by myself on occasion and don't appreciate any
outside help).  I did not say that pn junctions don't detect and rectify rf,
I said that the field intensities associated with unintentional emissions
from ITE are too low to cause susceptibility in circuits other than radios.
Your example here is 10 V/m, and you are talking about an op-amp (gain
unspecified) and that it was susceptible at that level should be no surprise
to anyone.

on 1/4/02 7:34 AM, cherryclo...@aol.com at cherryclo...@aol.com wrote:

Does anyone else think that ordinary semiconductors doesn't respond to RF?

I have tested a product which was little more than an LM324 quad op-amp for
RF immunity using IEC 61000-4-3. This op-amp has a slew rate of
1V/micro-second on a good day with the wind in its favour. It was housed in
an unshielded plastic enclosure.

Demodulated noise that exceeded the (not very tough) product specification
were seen all the way up to 500MHz at a number of spot frequencies that
appeared to be due to the natural resonances of the input and output cables.

Above 500MHz this resonant behaviour vanished to be replaced by a steadily
rising level of demodulated 1kHz tone as the frequency increased. I stopped
testing at 1GHz, where the output error from the product was about 10% and
still rising with increased frequency.

OK, the field strength for the test was 10V/m (unmodulated) but the real
surprise was how well this very cheap and very slow opamp demodulated the
RF, and that it demodulated better at 1GHz than at 500MHz.

I have done many many immunity tests using IEC 61000-4-3 on audio equipment
and found much the same effects with every product I've ever tested.
With most larger products there is usually a roll-off in the demodulation
above 500MHz - not because the semiconductors in the ICs can't respond (they
can) but apparently because larger products have higher losses above 500MHz
or so between the cable ports and the semiconductors, plus a denser
structure that might provide more self-screening.

The transistors and diodes in all modern ICs (analog or digital) are so tiny
that they make excellent detectors at UHF and beyond. As they get smaller
(and they are) their frequency response increases (and their vulnerability
to upset and damage decreases).

Regards, Keith Armstrong

In a message dated 03/01/02 23:27:19 GMT Standard Time,
ken.ja...@emccompliance.com writes:

Subj:Re: EMC-related safety issues
List-Post: emc-pstc@listserv.ieee.org
Date:03/01/02 23:27:19 GMT Standard Time
From:ken.ja...@emccompliance.com (Ken Javor)
Sender:owner-emc-p...@majordomo.ieee.org
Reply-to: ken.ja...@emccompliance.com (Ken Javor)
To:m...@california.com (Robert Macy), ghery.pet...@intel.com (Pettit,
Ghery), james.col...@usa.alcatel.com ('James Collum'),
emc-p...@majordomo.ieee.org

Emissions from a laptop are naturally (without suppression) on the order of
10 uV/m to 100s of uV/m.  1000 uV/m would represent at least a 20 dB outage
at frequencies that could possibly interfere with sensor electronics.  The
coupling is lossy: 1 mV/m will generate far less than 1 mV signal in the
electronics, and this at rf.  Does anyone really see this as a remotely
possible mechanism?  I don't.

-- 
>From: "Robert Macy" 
>To: "Pettit, Ghery" , "'James Collum'"
, 
>Subject: Re: EMC-related safety issues
>Date: Thu, Jan 3, 2002, 3:25 PM
> 

> 
> Perhaps, it merely interfered with the "sensor" electronics, not the true
> magnetic field that was being sensed.
> 
>  - Robert -
> 
>Robert A. Macy, PEm...@california.com
>408 286 3985  fx 408 297 9121
>AJM International Electronics Consultants
>619 North First St,   San Jose, CA  95112
> 
> -Original Message-
>     From: Pettit, Ghery 
>     To: 'James Collum' ;
> emc-p...@majordomo.ieee.org 
> Date: Thursday, January 03, 2002 11:46 AM
> Subject: RE: EMC-related safety issues
> 
> 
> I still have a hard time believing it was a compass that was affected by
> a laptop computer.  ADF indication, could be.  VOR, maybe.  Magnetic
> compass?  I wouldn't want a magnetic source that strong in my lap!  My belt
> buckle would be stuck to it.  There is quite a distance between a magnetic
> compass in the cockpit of an airliner and anything a passenger is carrying.
> Not so in a Cessna 172, but in a DC-10?
> 
> Ghery Pettit 
> 
> -Original Message-
> From: James Collum [mailto:james.col...@usa.alcatel.com]
> Sent: Thursday, January 03, 2002 10:47 AM
> To: emc-p...@majordomo.ieee.org
> Subject: Re: EMC-related safety issues
> 
> 
> 
> 
> *

Re: EMC-related safety issues

2002-01-05 Thread Cortland Richmond

We need to separate specific regulation from general. The FCC does not care if 
a radio front end is wide open,  though
it now requires scanning receivers to have 38 dB image rejection.  This does 
not mean they have narrow front ends,
however.  A SW receiver with a 75 MHz If may well have nothing but a low-pass 
filter in front of it.

Cortland
(What I write here is mine alone.
My employer does not
Concur, agree or else endorse
These words, their tone, or thought.)

John Shinn wrote:

> Actually, if you consider that there are two issues here.  First, the TV and
> Radio manufacturers are required to no longer have a wide-open front end ...

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RE: EMC-related safety issues

2002-01-05 Thread John Shinn

So where do I drill the hole in my fuel injection system?

John

-Original Message-
From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Doug McKean
Sent: Friday, January 04, 2002 2:37 PM
To: EMC-PSTC Discussion Group
Subject: Re: EMC-related safety issues

RE: EMC-related safety issuesKyle Ehler wrote:
>
> Another point of trivia is that a fresh oil change and new air
filter
> prior to having your vehicle smog tested will improve the emissions
> results.  At one time there was available OTC a fuel additive that
one
> could deploy to further skew the results in your favor.

I knew a guy who drilled a small hole in the side of his carborator,
attatched a hose setup that you would use for an acquirium the
other end of which was put into a water bottle.  While the car
was in idle, he'd adjust a valve on the hose to a slow drip of
water into the carborator.  This setup was on an old truck of
his and he always got terrifically low emissions readings.

- Doug McKean

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RE: EMC-related safety issues

2002-01-05 Thread George Stults

As I recall,  a tank of gasohol and a long trip down the freeway beforehand
was another method.  
Of course it didn't work as well if you then got in a long waiting line for
the test.

-George S.

 -Original Message-
From:   Doug McKean [mailto:dmck...@auspex.com] 
Sent:   Friday, January 04, 2002 2:37 PM
To: EMC-PSTC Discussion Group
Subject:        Re: EMC-related safety issues

RE: EMC-related safety issuesKyle Ehler wrote:
>
> Another point of trivia is that a fresh oil change and new air
filter
> prior to having your vehicle smog tested will improve the emissions
> results.  At one time there was available OTC a fuel additive that
one
> could deploy to further skew the results in your favor.

I knew a guy who drilled a small hole in the side of his carborator,
attatched a hose setup that you would use for an acquirium the
other end of which was put into a water bottle.  While the car
was in idle, he'd adjust a valve on the hose to a slow drip of
water into the carborator.  This setup was on an old truck of
his and he always got terrifically low emissions readings.

- Doug McKean

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Re: EMC-related safety issues

"Cortland Richmond" wrote:
>
> AIrbag testing? Well, since it costs about $US 1500 to replace them
(here),
> I suppose there WOULD be a price hike!

A couple of kids were caught by the police in a parking lot.
Seems the fun thing to do to people's cars was to walk
around the parking lot with baseball bats and bang on
the front bumper causing the air bags to activate.
Can't imagine what that all cost.

- Doug McKean

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Re: EMC-related safety issues

RE: EMC-related safety issuesKyle Ehler wrote:
>
> Another point of trivia is that a fresh oil change and new air
filter
> prior to having your vehicle smog tested will improve the emissions
> results.  At one time there was available OTC a fuel additive that
one
> could deploy to further skew the results in your favor.

I knew a guy who drilled a small hole in the side of his carborator,
attatched a hose setup that you would use for an acquirium the
other end of which was put into a water bottle.  While the car
was in idle, he'd adjust a valve on the hose to a slow drip of
water into the carborator.  This setup was on an old truck of
his and he always got terrifically low emissions readings.

- Doug McKean

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Re: EMC-related safety issues

2002-01-04 Thread CE-test - Ing. Gert Gremmen - ce-marking and more...


I read in !emc-pstc that Gregg Kervill  wrote (in
<004801c1955f$fe610f10$7e00a8c0@MENHADEN>) about 'EMC-related safety
issues', on Fri, 4 Jan 2002:
>The semiconductor may switch the relay due to external EMC - but it is 
> more 
>likely that the semiconductor or the relay will fail and produce an 
> 'unsafe' 
>output.

What disturbance levels do you have in mind? Nearby lightning? I don't
see what else will pop a transistor, still less a relay.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
After swimming across the Hellespont, I felt like a Hero. 

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RE: EMC-related safety issues

Sorry Rich,

I support John's statement about the 3 meters separation
distance. After all, you're in control in your own sleeping
room.  BTW listening radio in the dark is an enlightening experience.
If it were your neighbour sleeping that close to your lamp
this would have given rise to discussion between you or worse .
(if he understood the cause of the interference)

Govenrment regulations were not there to prevent
interference under all circumstances, just to regulate
the number of complaints that might give rise to legal issues.

Or would you sue yourself for operating your bedlamp so close to your AM
radio ;<)))

I suggest you reinsert your old filament bulb or buy a receiver
with external antenna (but keep it away from your neighnours bedlamp ;<))

Regards,

Gert Gremmen, (Ing)

ce-test, qualified testing

===
Web presence  http://www.cetest.nl
CE-shop http://www.cetest.nl/ce_shop.htm
/-/ Compliance testing is our core business /-/
===


>>-Original Message-
>>From: owner-emc-p...@majordomo.ieee.org
>>[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Rich Nute
>>Sent: Thursday, January 03, 2002 10:09 PM
>>To: j...@jmwa.demon.co.uk
>>Cc: emc-p...@majordomo.ieee.org
>>Subject: Re: EMC-related safety issues
>>
>>
>>
>>
>>
>>
>>Hi John:
>>
>>
>>>   >I've replaced the incandescent lamp on my bedside
>>>   >table with a new energy-saving compact flourescent
>>>   >lamp.  With the lamp on, I cannot listen to even
>>>   >the strongest AM radio station on my clock radio
>>>   >(on the same bedside table) due to the lamp
>>>   >interference.  This must not be the usage
>>>   >contemplated by EMC requirements.
>>>
>>>   Limits in the household environment are based on a 3 m separation
>>>   between source and receiver.
>>
>>Wonderful!
>>
>>Either the lamp or the radio must be on the opposite
>>side of the room from my bedside table.  When I am in
>>bed, one or the other is not controllable, and is
>>therefore useless to me.
>>
>>Whine mode on:  I want both on my bedside table, and
>>I want both to do all of their functions.  This IS
>>not the usage contemplated by 3 m separation EMC
>>requirements.
>>
>>:-)
>>
>>
>>Best wishes for the New Year,
>>Rich
>>
>>
>>
>>
>>---
>>This message is from the IEEE EMC Society Product Safety
>>Technical Committee emc-pstc discussion list.
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<>

Re: EMC-related safety issues


I read in !emc-pstc that Cortland Richmond  wrote (in <3c35ec35.5d1a...@alcatel.com>) about 'EMC-related safety
issues', on Fri, 4 Jan 2002:
>I don't believe this is what people are saying here. What they are 
>saying is, ordinary semiconductors won't demodulate RF levels 
>produced by an unintentional radiator. 
>
Oh, is THAT what the message meant? There's not much comparison between
10 V/m or even 3 V/m and the permitted emission levels of around 1 mV/m!
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
After swimming across the Hellespont, I felt like a Hero. 

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Re: EMC-related safety issues


I read in !emc-pstc that Rich Nute  wrote (in
<200201041623.iaa13...@epgc264.sdd.hp.com>) about 'EMC-related safety
issues', on Fri, 4 Jan 2002:

>So, I am acting unreasonably by using a
>CFL and a radio on my bedside table.

If we're being very meticulous, it is not unreasonable to use a CFL next
to a radio, but it IS unreasonable to complain about what happens!

Is there another solution? Further reducing the emissions  is simply too
costly, and is bad economics anyway, since all the mitigation
components, probably still in good working order, are thrown away when
the lamp fails (usually the filter capacitor in the d.c. supply dries
out).
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
After swimming across the Hellespont, I felt like a Hero. 

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RE: EMC-related safety issues

2002-01-04 Thread Gregg Kervill

I agree - ALL semiconductor demodulate.

If they did not then there would be NO distortion in amplifiers and most of
the HiFi industry would be out of business.





Demodulation is only part of the problem however.


Consider a semiconductor switching a relay.

The semiconductor may switch the relay due to external EMC - but it is more
likely that the semiconductor or the relay will fail and produce an 'unsafe'
output.

I spent 6 months designing a fail-safe synchronous gating circuit  and 3
months writing the patent so Please don't tell me that it is impossible to
design a safe circuit.


In my experience (20 years of R&D) spurious EMC/safety issues are mostly due
to poor design, in the first place, and then inadequate testing.


EXAMPLE from the last 10 years - when the 5Volt PSU for a safety circuit was
disconnected, the system was ARMED. This was discover just before the
product went into production and after "through"(sic) testing.


Best regards

Gregg

PLEASE NOTE NEW NUMBERS
P.O. Box 310, Reedville,
Virginia 22539  USA

Phone: (804) 453-3141
Fax: (804) 453-9039
Web: www.test4safety.com


  -Original Message-
  From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Cortland Richmond
  Sent: Friday, January 04, 2002 12:54 PM
  To: cherryclo...@aol.com
  Cc: emc-p...@majordomo.ieee.org
  Subject: Re: EMC-related safety issues


  I don't believe this is what people are saying here. What they are saying
is, ordinary semiconductors won't demodulate RF levels produced by an
unintentional radiator.
  Cortland
  (What I write here is mine alone.
  My employer does not
  Concur, agree or else endorse
  These words, their tone, or thought.)



  cherryclo...@aol.com wrote:

Does anyone else think that ordinary semiconductors doesn't respond to
RF?
I have tested a product which was little more than an LM324 quad op-amp
for RF immunity using IEC 61000-4-3. This op-amp has a slew rate of
1V/micro-second on a good day with the wind in its favour. It was housed in
an unshielded plastic enclosure.

Demodulated noise that exceeded the (not very tough) product
specification were seen all the way up to 500MHz at a number of spot
frequencies that appeared to be due to the natural resonances of the input
and output cables.


  --- This message is from the IEEE
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RE: EMC-related safety issues

2002-01-04 Thread Price, Ed


Ghery:


Every couple of years, I rise to the level of personal expert, as I endure
the local bi-annual vehicle smog inspection. Two days ago, I had my 1974
Chevy Nova tested. (It passed, as usual, with measured emissions at 3% to
10% of allowable limits, but I had to buy a new gas tank cap.)

They check the hydrocarbon, carbon monoxide and nitrogen oxide emission
levels. They look to be sure you still have all your Federally required
emission systems. They check the function of engine systems like the PC
valve, the exhaust gas valve and the ignition timing. Testing is performed
on a dynamometer, at low & high speed. They even take off your gas tank cap
and make sure it holds a vacuum.

The rules are a labyrinth. California does smog checks on 1974 and newer
models only. Unless your car is new, or up to a few (?) years old, and then
you are also exempt. Not every county in California requires the smog
checks. And in counties which do require the testing, some parts of counties
are exempt. I live in El Cajon in San Diego county, but if I had a legal
address in Julian (same county, just about 40 miles away) I would be exempt.
(It's interesting that Julian has a huge population that uses PO boxes and
never seems to be in town.)

When your car is from the 70's, you periodically are notified that you are a
"gross polluter" and have to get your smog check done at a special "test
only" station. (This type of test station is supposed to be more honest,
since they are prohibited from providing any repairs, or even advice on your
car's condition, other than handing you the computer print-out.)

The whole test takes about 30 minutes, with almost everything under computer
control. Newer cars, with on-board computers, are being tested by connecting
the station computer to the vehicle's data port. Makes you wonder how much
information about your driving habits and maintenance is being stored in
your car's computer. Maybe the DMV will soon be able to download speed and
acceleration data. Maybe you can get a moving violation from pulling too
many g's (higher gas consumption, higher emissions) or exceeding 65 MPH
(maybe billed like power, in increments of MPH-minutes). Maybe ignoring your
"check engine" idiot light will become a DMV felony.

The ultimate step will be to equip your on-board computer with a short-range
data link. Then, periodic roadway sensors can determine if you are allowed
to drive under current conditions. You might be given an option to slow to
42 MPH maximum, or pay a speed surcharge, or halt until 10 PM when smog
control limits relax.

I'm thinking about moving to Julian.

Ed
 

Ed Price
ed.pr...@cubic.com
Electromagnetic Compatibility Lab
Cubic Defense Systems
San Diego, CA  USA
858-505-2780  (Voice)
858-505-1583  (Fax)
Military & Avionics EMC Services Is Our Specialty
Shake-Bake-Shock - Metrology - Reliability Analysis


>-Original Message-
>From: Pettit, Ghery [mailto:ghery.pet...@intel.com]
>Sent: Friday, January 04, 2002 8:28 AM
>To: 'James, Chris'; 'Ken Javor'; Doug McKean; EMC-PSTC Discussion Group
>Subject: RE: EMC-related safety issues
>
>
>
>Chris,
>
>Annual inspections of motor vehicles are done on a state by 
>state basis,
>rather than as a national requirement in the U.S.  Automobiles are
>registered at the state level, so the federal government doesn't get
>involved.  Some states have annual inspections, others don't.  
>Likewise,
>smog inspections are at a state or lower level.  California cars get
>smogged.  Here in Washington it depends on what county you 
>live in.  If air
>quality in your county is good enough, you don't have to have your car
>smogged.  If not, you get to pay more for the privilege of 
>having a car.  I
>live in a county where I don't have to deal with the fight.
>
>BTW, a trick I learned when I lived in California is that you 
>stand a much
>better chance of passing the smog test if the engine is well 
>warmed up when
>you arrive at the inspection station.  Take it for what it's worth.
>
>Be thankful that we don't have to have annual inspections on 
>our cars to the
>extent that one does on an airplane...  $$$
>
>Ghery Pettit
>Intel
>
>
>-Original Message-
>From: James, Chris [mailto:c...@dolby.co.uk]
>Sent: Friday, January 04, 2002 1:02 AM
>To: 'Ken Javor'; Doug McKean; EMC-PSTC Discussion Group
>Subject: RE: EMC-related safety issues
>
>
>
>Sorry disagree about turn and brake lights not being in the same class.
>Their very failure is often the reason for very serious 
>accidents. I have
>long wished that all car manufacturers had to by law fit bulb failure
>warning devices to cars (but what happens when that fails).
>
>In the UK it is an offence to drive a ve

Re: EMC-related safety issues


I read in !emc-pstc that cherryclo...@aol.com wrote (in <167.698dddc.296
70...@aol.com>) about 'EMC-related safety issues', on Fri, 4 Jan 2002:
>As my paper at the IEEE's EMC Symposium in Montreal and my recent article 
> in 
>ITEM UPDATE 2001 show - at present EMC standards don't address safety 
>issues, and most safety standards don't address EMC-related functional 
>safety issues. 

As far as CENELEC is concerned, it was a conscious decision not to
incorporate 'EMC and Safety' issues into EMC standards, but to treat it
as a separate subject.

Some people may find a clarification helpful. We have EMC matters,
concerned with compatibility between items of equipment, ensuring that
they continue to work (Criterion A in the Generic Standards) or fail
gracefully (Criteria B and C). These criteria do not address safety
issues, as indicated in paragraph 1 above. However, the Generic
Standards do have a limited 'blanket' requirement, that equipment must
not become unsafe *during testing*.

We also have safety matters per se, which don't involve EMC.

We ALSO have the separate subject, called 'EMC and Safety' or reasonable
variants thereof. This addresses the matter of equipment becoming unsafe
*in service* due to excessive emission levels in the environment, or
lack of sufficient immunity to acceptable emission levels. So far, this
seems perfectly reasonable. 

BUT it stops seeming reasonable when the question 'What could go wrong?'
is asked and statistical data is used to attempt to answer it. To take a
very simple example (maybe over-simplified), we might say that the
probability of an unsafe occurrence should be less than 10^-9. That
immediately means that the designer of the equipment has to look at ALL
risk scenarios down to the billion-to-one against level of probability.
To say that that is difficult is surely a great understatement. 

But some experts in the field seem to ignore that great difficulty, and
simply (or maybe not so simply) state that if the designer fails to take
into account ANY scenario that subsequently results in an unsafe
condition, the designer has failed in his professional responsibility,
and may be held criminally responsible for negligence.

Well, let us be very circumspect designers and look at what immunity
levels we might need to get down to that 10^-9 probability. For radiated
emissions, the necessary test levels seem to be of the order of 100 V/m.
Test levels for other disturbances seem to be equally distantly related
to the levels normally experienced and to the test levels in pure EMC
standards. 

We might conclude that assessment of EMC immunity per se is completely
unnecessary, because testing for 'EMC and Safety' requires test levels
of the order of 30 dB higher!

One could go, with the sort of reasoning advocated by some experts,
further into the realms of fantasy. Suppose, for a particular piece of
equipment, the designer, with great diligence, identifies a million
threat scenarios, each of which has a probability of 10^-9. The
cumulative probability of ANY ONE of them occurring is only 10^-3. Bit
risky, that!

If the above reasoning seems flawed, consider a specific case, a lottery
with 2000 tickets, numbered  to 1999. One person can buy up to 5
tickets, and all tickets are sold. Consider the probability of a
'remarkable occurrence'. This might be the drawing of the number ''
or '' or '1234' or even '1010', depending on what you think is
'remarkable'. OK, we already have a cumulative probability down from 1
in 2000 to 1 in 667 or 1 in 500. Now add in the probability that a
participant in the lottery is chosen at random to draw the winning
number, and draws (one of) his or her own numbers .. 

You shouldn't be able to get very long odds on a 'remarkable
occurrence'! 
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
After swimming across the Hellespont, I felt like a Hero. 

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Re: EMC-related safety issues


I read in !emc-pstc that cherryclo...@aol.com wrote (in <131.6a66623.296
70...@aol.com>) about 'EMC-related safety issues', on Fri, 4 Jan 2002:
>As I recall, the EU's Product Liability Directive (85/374/EEC amended by 
>99/34/EC) requires manufacturers to produce products that are: "as safe as 
>people generally have the right to expect".

I believe it does.
>
>Note that it does not require things to be 100% safe - that is impossible.

Indeed.
>
>The real problem is that whether a product really is  "as safe as people 
>generally have the right to expect" is usually tested in a court of law where 
>there are lots of photographs of a dead or maimed person or a burnt-down 
>building, or whatever. 
>
>It is difficult to argue that your product is safe enough when there are 
>relatives sobbing all over the courtroom. 

Indeed.
>
>The trick, I believe, is not to be in that position in the first place. 
>Design your products using the latest safety knowledge and test them well to 
>discover if they have any weaknesses you did not address. 

How do you decide what tests to do **for weaknesses you don't suspect**?
Isn't that fundamentally impossible?

>And yes, you must consider foreseeable misuse and stupid users too. (The 
>trouble with trying to make something foolproof is that fools are so 
>ingenious!)

Exactly! Is replacing the mains fuse in a product with a bit of fencing
wire 'foreseeable misuse'? I have put this question to an IEC safety
committee; it's not just a debating point!
>
>Then hopefully you won't ever find yourself trying to defend your design 
>decisions in a court of law. 

Hopefully! Will your CEO accept that 'hopefully' your design won't put
him in jail for corporate manslaughter? But can you ever give a better
assurance than 'hopefully', at the necessary 1 in a billion probability
level? I think not.

>Also, your company's exposure to significant financial and commercial risks 
>will be reduced - this is the key to justifying the expense of good safety 
>design to your employers.

But it seems that the expense of 'good safety design', as determined by
some safety experts, is going through the roof. 
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
After swimming across the Hellespont, I felt like a Hero. 

---
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Re: EMC-related safety issues


I read in !emc-pstc that cherryclo...@aol.com wrote (in <17d.1b28bc2.296
70...@aol.com>) about 'EMC-related safety issues', on Fri, 4 Jan 2002:

>Does anyone else think that ordinary semiconductors doesn't respond to RF?

Your experience has been shared by thousands. The demodulation normally
occurs at the first semiconductor junction that the r.f signal 'sees',
although at 10 V/m there may be propagation effects.

The faulty reasoning that makes this effect surprising is 'silicon
diodes and transistors need 0.6 V forward bias in order to conduct'. It
isn't TRUE! If you add 'more than a few microamps' it's less untrue. But
conduction occurs right down to minute signal voltages, resulting,
certainly, in even more minute currents, but current enough to cause
trouble. 'Underbiased' junctions act as excellent square-law detectors;
for every 1 dB increase in input signal level you get 2 dB increase in
level of recovered modulation.

You may well find that JFET-input op-amps are far less sensitive to r.f.
A test that I carried out a while back, on a very simple board with no
EMC counter-measures at all, indicated a 26 dB difference between an
LM324 and a TL072, the difference being substantially independent of
frequency from 150 kHz to 1 GHz.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
After swimming across the Hellespont, I felt like a Hero. 

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RE: EMC-related safety issues

2002-01-04 Thread Ehler, Kyle

In Kansas there are no emissions laws or annual inspections.
The entire state gets a full air change every 10 minutes -so why bother?
We also benefit from no mandated vehicle inspections -ever.  The only
thing that does get a check is the odometer and VIN, but only when a title
transfer occurs.  The state is more interested in indentity than safety
of the machines the public chooses to play caroms with. 

IIRC, California and many states have an amendment to their respective 
emissions law that states that once a car is more than XX years old, 
they are considered 'antique' and exempt from the law.
The threshold ranges from 20 to 30 years, depending on state/county.

Another point of trivia is that a fresh oil change and new air filter 
prior to having your vehicle smog tested will improve the emissions 
results.  At one time there was available OTC a fuel additive that one 
could deploy to further skew the results in your favor.

Kyle Ehler
'73 and
'76 914 2.0 'Euro' antiques

-Original Message-
From: Pettit, Ghery [mailto:ghery.pet...@intel.com]
Sent: Friday, January 04, 2002 10:28 AM
To: 'James, Chris'; 'Ken Javor'; Doug McKean; EMC-PSTC Discussion Group
Subject: RE: EMC-related safety issues



Chris,

Annual inspections of motor vehicles are done on a state by state basis,
rather than as a national requirement in the U.S.  Automobiles are
registered at the state level, so the federal government doesn't get
involved.  Some states have annual inspections, others don't.  Likewise,
smog inspections are at a state or lower level.  California cars get
smogged.  Here in Washington it depends on what county you live in.  If air
quality in your county is good enough, you don't have to have your car
smogged.  If not, you get to pay more for the privilege of having a car.  I
live in a county where I don't have to deal with the fight.

BTW, a trick I learned when I lived in California is that you stand a much
better chance of passing the smog test if the engine is well warmed up when
you arrive at the inspection station.  Take it for what it's worth.

Be thankful that we don't have to have annual inspections on our cars to the
extent that one does on an airplane...  $$$

Ghery Pettit
Intel


-Original Message-
From: James, Chris [mailto:c...@dolby.co.uk]
Sent: Friday, January 04, 2002 1:02 AM
To: 'Ken Javor'; Doug McKean; EMC-PSTC Discussion Group
Subject: RE: EMC-related safety issues



Sorry disagree about turn and brake lights not being in the same class.
Their very failure is often the reason for very serious accidents. I have
long wished that all car manufacturers had to by law fit bulb failure
warning devices to cars (but what happens when that fails).

In the UK it is an offence to drive a vehicle with defective lights,
(although many do). It is the driver's (not owner's) obligation to be
satisfied the vehicle they are driving is fit to be on the road irespective
of whether it passed it's MOT the previous day.

The UK mandatory annual vehicle inspection (MOT) for vehicles over 3 years
old, covers seat belts, brake efficiency on a rolling road, mirrors,
windshield cracks (a 20mm, 3/4inch crack in the wrong place will fail a
vehicle), tyres, wheel bearings, gaiters, steering components, structural
body condition, lights, smog emissions, etcI don't
believe airbags are tested but guess it will come, along with the inevitable
hike in price.

I'm surprised the US does not have a similar Federal requirement - with all
the vehicles this is a cash cow waiting to be milked.


Chris

-Original Message-
From: Ken Javor [mailto:ken.ja...@emccompliance.com]
Sent: 04 January 2002 02:40
To: Doug McKean; EMC-PSTC Discussion Group
Subject: Re: EMC-related safety issues



A signal light is easily replaceable in terms of time and money.  Most 
people don't use them (well, in good old Huntsville, AL, anyway, where a
favorite bumper sticker reads, "Turn signals, not just for smart people
anymore").  Failure of a light is not in the same class as an airbag
deploying at the wrong time or not deploying, or ditto for brakes.

--
>From: "Doug McKean" 
>To: "EMC-PSTC Discussion Group" 
>Subject: Re: EMC-related safety issues
>Date: Thu, Jan 3, 2002, 7:00 PM
>

>
> Point taken Ken, but consider signal lights.  They're
> essentially safety devices and they're supposed to
> be maintained on cars which have been transferred
> amongst several owners and are decades old.
> Same idea with windshields, I guess also.
>
> - Doug McKean
>
>
> ---
> This message is from the IEEE EMC Society Product Safety
> Technical Committee emc-pstc discussion list.
>
> Visit our web site at:  http://www.ewh.ieee.org/soc/emcs/pstc/
>
> To c

Re: EMC-related safety issues

2002-01-04 Thread Tom Cokenias


At 8:34 AM -0500 1/4/2002, Keith Armstrong wrote:


Does anyone else think that ordinary semiconductors doesn't respond to RF?




I agree that commonly used semiconductors have responses well into 
the 100's of MHz.


How much of a problem this is will depend on the nature and function 
of the circuitry using these components.


The EUT wires, cables, pcb traces etc. act like antennae,  on which 
the incident field voltages and currents.  An antenna factor can be 
thought of as ratio of the field strength  to the voltage induced on 
the terminated cable connected to the antenna.


In an impedance matched system,


AF=9.734/lamda*(G)^0.5,   lamda being wavelength in meters, G being 
antenna gain over isotropic,


or in dB

AF dB =  -  G dBi  -29.7 dB + 20logFMHz

Assuming G is 1 (isotropic antenna), AF is 1  (= 0 dB) at about 30.8 
MHz, and AF get larger  as frequency increases, to  a factor of 32.7 
(= 30.3 dB) at 1 GHz .  Since AF is  field strength divided by 
induced voltage, the voltage induced on the trace goes down as 
frequency goes up for the same incident field strength.


An effective receive antenna needs to be on the order of 1/2 
wavelength or so; for 30 MHz this is 15m, for 1000 MHz this is 15 cm.


So if a victim EUT circuit has a pretty effective receive  antenna, 
and does not have any filtering and is equally sensitive across the 
frequency range under consideration (all taken together, a worst case 
scenario for susceptibility),


(1)  A 10 V/m field will  theoretically induce a voltage  0.33V  to 
10V, depending on frequency


(2) A 5000 uV/m field (10x the FCC class B limit above 960 MHz) will 
theoretically induce a voltage from 152 uV to 5 mV, depending on 
frequency.


(3) A 500 uV/m field will  theoretically induce a voltage from 15 uV 
to 500 uV depending on frequency.


These are first order approximations, but they are useful in 
determining the level of the potential EMI  threat.   For instance a 
4-30 mA sensor circuit using high gain operational amps will most 
likely  be interfered with  in scenario (1),  there may be some 
susceptibility detected in scenario (2), and most likely no problem 
encountered with scenario (3).


A sensitive all - band  AM communications receiver will have problems 
with all three, a broadcast TV operating in a strong signal area will 
probably be OK  with scenario 3 but not with 1 or 2.


I guess what I'm really trying to say with all this is that EMC is a 
systems thing, taking into account the nature of the culprit EMI 
generator, the nature of the victim EMI receiver,  and the path 
between them.  Then we have the economics of operating different 
devices in the same vicinity, the politics of who gets how much of 
what kind of protection, etc., etc.  All things considered, we should 
have jobs for life!


best regards and a Happy New Year to all.

Tom Cokenias

T.N. Cokenias Consulting
P.O. Box 1086
El Granada CA 94018

tel   650 726 1263
cell 650 302 0887
fax  650 726 1252

Re: EMC-related safety issues

I don't believe this is what people are saying here. What they are saying
is, ordinary semiconductors won't demodulate RF levels produced by an unintentional
radiator.
Cortland
(What I write here is mine alone.
My employer does not
Concur, agree or else endorse
These words, their tone, or thought.)
cherryclo...@aol.com wrote:
Does anyone
else think that ordinary semiconductors doesn't respond to RF?
I have tested a product which
was little more than an LM324 quad op-amp for RF immunity using IEC 61000-4-3.
This op-amp has a slew rate of 1V/micro-second on a good day with the wind
in its favour. It was housed in an unshielded plastic enclosure.
Demodulated noise that exceeded
the (not very tough) product specification were seen all the way up to
500MHz at a number of spot frequencies that appeared to be due to the natural
resonances of the input and output cables.

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Re: EMC-related safety issues

There is a difference between extending a warranty and being liable for 
failure.  If your seat belts fail some time
after the warranty is up, the manufacturer won't pay for fixing them on your 
car.  But the manufacturer may well be
held liable for the failure.

Cortland

"Andrews, Kurt" wrote:

> From what I have found out it is not a requirement for safety related items
> to be warranted for the life of the car. I have recently been shopping for a

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Re: EMC-related safety issues

AIrbag testing? Well, since it costs about $US 1500 to replace them (here), I 
suppose there WOULD be a price hike!

One of the tests run  on a modern, computerized auto when the ignition is 
turned on is for airbag activation
circuitry.

Cortland

"James, Chris" wrote:

> I don't
> believe airbags are tested but guess it will come, along with the inevitable
> hike in price.

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Re: EMC-related safety issues


"Warranted" parts for a car is a whole other discussion. 
Warranties are simply for as long as the mfr/dealer want 
to do the contract.  I'm not sure if there's a law concerning 
minimum time of warranty or if it's simply driven by the 
free market.  

Supplying a parts inventory by the car mfr is I think is 
required for a maximum of up to 10 years.  The contract 
for making that part is then picked up by some other 
shop who thinks they can turn a profit. 

I can't imagine Moter Vehicles passing a car for inspection 
with a big gaping hole in the dash or steering column where 
the air bag used to be.  But I'll be the first to admit that I 
don't know any of the laws requiring parts such as selt 
belts and air bags being replaced years down the road. 
I did have an experience back in the early 80's in trying 
to replace a faulty seatbelt with a used one and I was 
prohibited from doing that.  I had to buy a new one.
That was back in CT so that may have been a state 
thing. 

I can only think of at least one or two modes of transportation 
that are covered by federal law for replacement parts being 
available for the entire life of the thing for as long as that 
may be - jet airliners and trains.  Elevators and escalators also 
come to mind as well. 

Anyone here work at Otis? 

- Doug McKean 



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RE: EMC-related safety issues

2002-01-04 Thread Pettit, Ghery


Chris,

Annual inspections of motor vehicles are done on a state by state basis,
rather than as a national requirement in the U.S.  Automobiles are
registered at the state level, so the federal government doesn't get
involved.  Some states have annual inspections, others don't.  Likewise,
smog inspections are at a state or lower level.  California cars get
smogged.  Here in Washington it depends on what county you live in.  If air
quality in your county is good enough, you don't have to have your car
smogged.  If not, you get to pay more for the privilege of having a car.  I
live in a county where I don't have to deal with the fight.

BTW, a trick I learned when I lived in California is that you stand a much
better chance of passing the smog test if the engine is well warmed up when
you arrive at the inspection station.  Take it for what it's worth.

Be thankful that we don't have to have annual inspections on our cars to the
extent that one does on an airplane...  $$$

Ghery Pettit
Intel


-Original Message-
From: James, Chris [mailto:c...@dolby.co.uk]
Sent: Friday, January 04, 2002 1:02 AM
To: 'Ken Javor'; Doug McKean; EMC-PSTC Discussion Group
Subject: RE: EMC-related safety issues



Sorry disagree about turn and brake lights not being in the same class.
Their very failure is often the reason for very serious accidents. I have
long wished that all car manufacturers had to by law fit bulb failure
warning devices to cars (but what happens when that fails).

In the UK it is an offence to drive a vehicle with defective lights,
(although many do). It is the driver's (not owner's) obligation to be
satisfied the vehicle they are driving is fit to be on the road irespective
of whether it passed it's MOT the previous day.

The UK mandatory annual vehicle inspection (MOT) for vehicles over 3 years
old, covers seat belts, brake efficiency on a rolling road, mirrors,
windshield cracks (a 20mm, 3/4inch crack in the wrong place will fail a
vehicle), tyres, wheel bearings, gaiters, steering components, structural
body condition, lights, smog emissions, etcI don't
believe airbags are tested but guess it will come, along with the inevitable
hike in price.

I'm surprised the US does not have a similar Federal requirement - with all
the vehicles this is a cash cow waiting to be milked.


Chris

-Original Message-
From: Ken Javor [mailto:ken.ja...@emccompliance.com]
Sent: 04 January 2002 02:40
To: Doug McKean; EMC-PSTC Discussion Group
Subject: Re: EMC-related safety issues



A signal light is easily replaceable in terms of time and money.  Most 
people don't use them (well, in good old Huntsville, AL, anyway, where a
favorite bumper sticker reads, "Turn signals, not just for smart people
anymore").  Failure of a light is not in the same class as an airbag
deploying at the wrong time or not deploying, or ditto for brakes.

------
>From: "Doug McKean" 
>To: "EMC-PSTC Discussion Group" 
>Subject: Re: EMC-related safety issues
>Date: Thu, Jan 3, 2002, 7:00 PM
>

>
> Point taken Ken, but consider signal lights.  They're
> essentially safety devices and they're supposed to
> be maintained on cars which have been transferred
> amongst several owners and are decades old.
> Same idea with windshields, I guess also.
>
> - Doug McKean
>
>
> ---
> This message is from the IEEE EMC Society Product Safety
> Technical Committee emc-pstc discussion list.
>
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All e

Re: EMC-related safety issues

2002-01-04 Thread Rich Nute





>   No, it's simply that it isn't considered reasonable to have a radio and
>   a CFL in close proximity. If you want a lamp and a radio close together,
>   use an incandescent lamp.

That's the bottom line, isn't it?  

Somebody has decided for me (in terms of
what is "reasonable") that if I use a CFL, 
then I must separate it from a radio by 
3 m or more.

So, I am acting unreasonably by using a
CFL and a radio on my bedside table.

:-(


Rich



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RE: EMC-related safety issues

2002-01-04 Thread Andrews, Kurt

>From what I have found out it is not a requirement for safety related items
to be warranted for the life of the car. I have recently been shopping for a
new car and one of the ones I looked at is the Toyota Celica. It states the
following in the brochure: The seat belts and air bags are covered under the
powertrain warranty which is for 5 years or 60,000 miles. The emission
control components are also not covered for the life of the car. The
brochure states that components covered under the Federal emission defect
warranty are covered for 3 years or 36,000 miles and specified major
emission control components are covered for 8 years or 80,000 miles. 

My current car, a 1990 Acura Integra, has the following coverage. The
anti-lock brakes are covered under the normal 3 year/36,000 mile coverage.
According to the owners manual the seat belts are covered for the life of
the car because Acura considers them vital to safety. The car does not have
airbags, it has those stupid mouse (automatic) seatbelts. So it appears that
the only reason that the seat belts are covered longer than the standard
warranty is because Acura chose to do so, not because they have to (and I
applaud them for that). I do not recall what the warranty is on the emission
control components. I would suspect it is the same as the Toyota if the
federal rules were the same in 1990 as they are now.

Kurt Andrews
Compliance Engineer

Tracewell Systems, Inc.
567 Enterprise Drive
Westerville, Ohio 43081
voice:  614.846.6175
toll free:  800.848.4525
fax: 614.846.7791

http://www.tracewellsystems.com/

 -Original Message-
From:   Doug McKean [mailto:dmck...@auspex.com] 
Sent:   Thursday, January 03, 2002 5:43 PM
To: EMC-PSTC Discussion Group
Subject:    Re: EMC-related safety issues

"Ken Javor" wrote: 
> 
> Curiosity.  How long must airbags work?  

As long as you have the car, supposedly.  Same with seat belts. 
They're all safety features.  Interestingly, if you have a cracked 
or broken windshield, a cop *can* write you up for the car 
being unsafe.  I've never heard of it, but a classmate of mine 
who became a statie told me when he saw a huge crack 
in my windshield. 

I'm also under the impression that manufacturers are responsible 
for maintaining a repair/replacement parts inventory to dealers 
for only 10 years.  Not sure about that one. 

- Doug McKean 

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Re: EMC-related safety issues

As I understand the way the civil law section of the EU's Product Liability 
Directive operates (I am not a lawyer) it does in fact place the burden of 
proof on the manufacturer, who is effectively considered 'guilty until proved 
innocent'.

I also understand that any number of manufacturers can be sued in the civil 
courts under one safety incident, and the liabilities of each awarded 'on the 
balance of probabilities' that their product caused the damage, injury or 
death being complained about. 

Also...nobody has to prove negligence on the part of the manufacturer, this 
is sometimes called 'no-fault liability' - you can be held to be liable under 
the law even though nobody has proved that your product was actually the 
cause of the safety incident.

Another interesting fact about EU Product Liability is that in the civil 
courts in  most EU member states there is no financial upper limit to the 
damages that can be awarded against a manufacturer.

We may not like it, but that's how the world appears to be at the moment.
Regards, Keith Armstrong

In a message dated 03/01/02 19:52:20 GMT Standard Time, j...@jmwa.demon.co.uk 
writes:

> Subj:Re: EMC-related safety issues
> Date:03/01/02 19:52:20 GMT Standard Time
> From:j...@jmwa.demon.co.uk (John Woodgate)
> Sender:owner-emc-p...@majordomo.ieee.org
> Reply-to: mailto:j...@jmwa.demon.co.uk";>j...@jmwa.demon.co.uk 
> (John Woodgate)
> To:emc-p...@majordomo.ieee.org
> 
> I read in !emc-pstc that Gary McInturff  .com> wrote (in <917063bab0ddb043af5faa73c7a835d40ac...@windlord.wwp.com
> >) about 'EMC-related safety issues', on Thu, 3 Jan 2002:
> 
> >   While I take your point - I'll challenge with the equally valid 
> argument 
> >that says show me the data that they do cause SIDS! 
> 
> Out of order! That's the whole point! Manufacturers are being required
> to prepare to prove a negative, which is inherently impossible in most
> cases. No-one is required to prove a positive, which is easy if it is
> true.
> -- 
> Regards, John Woodgate, OOO - Own Opinions Only. 
> http://www.jmwa.demon.co.uk 
>

Re: EMC-related safety issues

Hey, Ken, let's try to be realistic here!

Sure - we should try to get laws we don't like changed, but that isn't going 
to happen overnight and in the meantime we have to operate within the law as 
it stands.

Or are you suggesting immediate insurrection by product manufacturers?
(Outlaw manufacturers roaming the wild wild west - an interesting concept!)

The IEE's guide on EMC and Functional Safety is concerned with such legal 
aspects, but is also concerned with saving lives in a world where electronic 
control of safety-related functions is proliferating madly.

As my paper at the IEEE's EMC Symposium in Montreal and my recent article in 
ITEM UPDATE 2001 show - at present EMC standards don't address safety issues, 
and most safety standards don't address EMC-related functional safety issues.

Regards, Keith Armstrong

In a message dated 03/01/02 17:24:42 GMT Standard Time, 
ken.ja...@emccompliance.com writes:

> Subj:Re: EMC-related safety issues
> Date:03/01/02 17:24:42 GMT Standard Time
> From:ken.ja...@emccompliance.com (Ken Javor)
> Sender:owner-emc-p...@majordomo.ieee.org
> Reply-to:  HREF="mailto:ken.ja...@emccompliance.com";>ken.ja...@emccompliance.com 
> (Ken Javor)
> To:c...@dolby.co.uk (James, Chris), acar...@uk.xyratex.com 
> ('acar...@uk.xyratex.com'), emc-p...@majordomo.ieee.org

> There is an inherent contradiction in this anti-profit, anti-technology 
> point-of-view that I cannot and will not defend.  All I am saying is that 
> people who feel this is wrong should stand up and say so, not write guides 
> for how to go along with it.
>

Re: EMC-related safety issues

As I recall, the EU's Product Liability Directive (85/374/EEC amended by 
99/34/EC) requires manufacturers to produce products that are: "as safe as 
people generally have the right to expect".

Note that it does not require things to be 100% safe - that is impossible.

The real problem is that whether a product really is  "as safe as people 
generally have the right to expect" is usually tested in a court of law where 
there are lots of photographs of a dead or maimed person or a burnt-down 
building, or whatever. 

It is difficult to argue that your product is safe enough when there are 
relatives sobbing all over the courtroom. 

The trick, I believe, is not to be in that position in the first place. 
Design your products using the latest safety knowledge and test them well to 
discover if they have any weaknesses you did not address. 
And yes, you must consider foreseeable misuse and stupid users too. (The 
trouble with trying to make something foolproof is that fools are so 
ingenious!)

Then hopefully you won't ever find yourself trying to defend your design 
decisions in a court of law. 
Also, your company's exposure to significant financial and commercial risks 
will be reduced - this is the key to justifying the expense of good safety 
design to your employers.

Regards, Keith Armstrong

In a message dated 03/01/02 17:17:59 GMT Standard Time, c...@dolby.co.uk 
writes:

> Subj:RE: EMC-related safety issues
> Date:03/01/02 17:17:59 GMT Standard Time
> From:c...@dolby.co.uk (James, Chris)
> Sender:owner-emc-p...@majordomo.ieee.org
> Reply-to: mailto:c...@dolby.co.uk";>c...@dolby.co.uk (James, 
> Chris)
> To:ken.ja...@emccompliance.com ('Ken Javor'), acar...@uk.xyratex.com 
> ('acar...@uk.xyratex.com'), emc-p...@majordomo.ieee.org
> 
> So why ain't the US government chasing the knife manufacturer of the knives 
> used by the terrorists rather than Bin Laden I'm sorry but 
> stories like the below make me despair at the way society is headed. If 
> people want technology  they will have to accept some of the pitfalls that 
> come with it, within reason, else where will it end?
> 
> >> -Original Message-
>> From: Ken Javor [mailto:ken.ja...@emccompliance.com]
>> Sent: 03 January 2002 17:00
>> To: James, Chris; 'acar...@uk.xyratex.com'; emc-p...@majordomo.ieee.org
>> Subject: Re: EMC-related safety issues
>> 
>> 
>> I agree with what you say, but at least in this country the anti-business 
>> pendulum has swung farther than you imagine.  A couple examples.
>> 
>> Thurman Munson, a Yankee catcher in the '70s, was killed in his twin 
>> engine Cessna jet.  He crashed short of a runway.  His estate sued Cessna, 
>> not on the grounds that the jet was defective, but that Cessna had sold 
>> Munson more aircraft than he was capable of handling.  Cessna demonstrated 
>> that it had sold Munson the model he wanted, but the plaintiff claimed 
>> that it was Cessna' duty to assess Munson's skills as a pilot and tell 
>> him, the customer, what aircraft they would sell him.  I don't recall how 
>> the verdict was rendered, but I know Cessna paid something.
>> 
>> Another case involved the death of a child in an automobile accident 
>> involving a minivan.  The child was thrown from the vehicle, in part 
>> because the rear door sprang open on impact.  Plaintiff claimed the door 
>> was poorly designed and that the child would have remained in the vehicle 
>> and maybe not been killed had the doors remained closed.  Defendant 
>> pointed out that child was not restrained in vehicle, he was up and and 
>> about at the moment of impact.  Documentation supplied with vehicle 
>> clearly states all passengers should wear restraining belts.  Plaintiff 
>> countered that defendant should have known that if they built a vehicle as 
>> large as a minivan that kids would be up and about and vehicle should have 
>> been designed with that in mind.  Again do not recall verdict but I am 
>> sure plaintiff did not walk away empty-handed.
>> 
>> Agreed that a manufacturer is responsible for the safety of a product put 
>> into normal use.  That was established by case law as far back as the 
>> Babylonian Code of Hammurabi, wherein an architect who builds a house that 
>> collapses and kills the owner is liable to the same fate.  But the 
>> manufacturer today labors under a presumption of evil:  if he makes a 
>> profit from selling a product, he must have skimped somewhere, because 
>> profits are intrinsically evil.

Re: EMC-related safety issues

Does anyone else think that ordinary semiconductors doesn't respond to RF?

I have tested a product which was little more than an LM324 quad op-amp for 
RF immunity using IEC 61000-4-3. This op-amp has a slew rate of 
1V/micro-second on a good day with the wind in its favour. It was housed in 
an unshielded plastic enclosure.

Demodulated noise that exceeded the (not very tough) product specification 
were seen all the way up to 500MHz at a number of spot frequencies that 
appeared to be due to the natural resonances of the input and output cables. 

Above 500MHz this resonant behaviour vanished to be replaced by a steadily 
rising level of demodulated 1kHz tone as the frequency increased. I stopped 
testing at 1GHz, where the output error from the product was about 10% and 
still rising with increased frequency.

OK, the field strength for the test was 10V/m (unmodulated) but the real 
surprise was how well this very cheap and very slow opamp demodulated the RF, 
and that it demodulated better at 1GHz than at 500MHz.

I have done many many immunity tests using IEC 61000-4-3 on audio equipment 
and found much the same effects with every product I've ever tested. 
With most larger products there is usually a roll-off in the demodulation 
above 500MHz - not because the semiconductors in the ICs can't respond (they 
can) but apparently because larger products have higher losses above 500MHz 
or so between the cable ports and the semiconductors, plus a denser structure 
that might provide more self-screening.

The transistors and diodes in all modern ICs (analog or digital) are so tiny 
that they make excellent detectors at UHF and beyond. As they get smaller 
(and they are) their frequency response increases (and their vulnerability to 
upset and damage decreases).

Regards, Keith Armstrong

In a message dated 03/01/02 23:27:19 GMT Standard Time, 
ken.ja...@emccompliance.com writes:

> Subj:Re: EMC-related safety issues
> Date:03/01/02 23:27:19 GMT Standard Time
> From:ken.ja...@emccompliance.com (Ken Javor)
> Sender:owner-emc-p...@majordomo.ieee.org
> Reply-to:  HREF="mailto:ken.ja...@emccompliance.com";>ken.ja...@emccompliance.com 
> (Ken Javor)
> To:m...@california.com (Robert Macy), ghery.pet...@intel.com (Pettit, 
> Ghery), james.col...@usa.alcatel.com ('James Collum'), 
> emc-p...@majordomo.ieee.org
> 
> 
> Emissions from a laptop are naturally (without suppression) on the order of
> 10 uV/m to 100s of uV/m.  1000 uV/m would represent at least a 20 dB outage
> at frequencies that could possibly interfere with sensor electronics.  The
> coupling is lossy: 1 mV/m will generate far less than 1 mV signal in the
> electronics, and this at rf.  Does anyone really see this as a remotely
> possible mechanism?  I don't.
> 
> ------
> >From: "Robert Macy" 
> >To: "Pettit, Ghery" , "'James Collum'"
> , 
> >Subject: Re: EMC-related safety issues
> >Date: Thu, Jan 3, 2002, 3:25 PM
> >
> 
> >
> > Perhaps, it merely interfered with the "sensor" electronics, not the true
> > magnetic field that was being sensed.
> >
> >  - Robert -
> >
> >Robert A. Macy, PEm...@california.com
> >408 286 3985  fx 408 297 9121
> >AJM International Electronics Consultants
> >        619 North First St,   San Jose, CA  95112
> >
> > -Original Message-
> > From: Pettit, Ghery 
> > To: 'James Collum' ;
> > emc-p...@majordomo.ieee.org 
> > Date: Thursday, January 03, 2002 11:46 AM
> > Subject: RE: EMC-related safety issues
> >
> >
> > I still have a hard time believing it was a compass that was affected 
> by
> > a laptop computer.  ADF indication, could be.  VOR, maybe.  Magnetic
> > compass?  I wouldn't want a magnetic source that strong in my lap!  My 
> belt
> > buckle would be stuck to it.  There is quite a distance between a magnetic
> > compass in the cockpit of an airliner and anything a passenger is 
> carrying.
> > Not so in a Cessna 172, but in a DC-10?
> >
> > Ghery Pettit
> >
> > -Original Message-
> > From: James Collum [mailto:james.col...@usa.alcatel.com]
> > Sent: Thursday, January 03, 2002 10:47 AM
> > To: emc-p...@majordomo.ieee.org
> > Subject: Re: EMC-related safety issues
> >
> >
> >
> >
> > *
> > A routine flight over Dallas-Fort Worth was disrupted when one of
> > the compasses suddenly shifted 10 degrees to the right.  The pilot asked 
> if
> > any passenger was operating an electronic device,  and findin

Re: EMC-related safety issues

The IEE's guide on EMC and Functional Safety is concerned with helping 
engineers and managers avoid legal problems - but I don't call this 
appeasement, just good practice.
But the guide is also concerned with saving lives in a world where electronic 
control of safety-related functions is proliferating madly.

As my paper at the IEEE's EMC Symposium in Montreal and my recent article in 
ITEM UPDATE 2001 show - at present EMC standards don't address safety issues, 
and most safety standards don't address EMC-related functional safety issues.

Regards, Keith Armstrong

In a message dated 03/01/02 20:04:46 GMT Standard Time, 
ken.ja...@emccompliance.com writes:

> Subj:Re: EMC-related safety issues
> Date:03/01/02 20:04:46 GMT Standard Time
> From:ken.ja...@emccompliance.com (Ken Javor)
> Sender:owner-emc-p...@majordomo.ieee.org
> Reply-to:  HREF="mailto:ken.ja...@emccompliance.com";>ken.ja...@emccompliance.com 
> (Ken Javor)
> To:cortland.richm...@alcatel.com (Cortland Richmond), 
> acar...@uk.xyratex.com (Andrew Carson)
> CC:emc-p...@majordomo.ieee.org
> 
> Curiosity.  How long must airbags work?  A car can be driven for two decades
> or more, by an uncontrolled number of owners, and with no mandatory
> inspection or service.  How long is a manufacturer liable for the proper
> operation of those airbags?  Same question for anti-lock brakes.  If the
> warning light comes on and is ignored, who is at fault?  If the warning
> light is disabled by an owner, and the next owner suffers injury due to
> improper operation of either of these systems, who is at fault?  Don't give
> me the logical answer.  I can figure that out.  Knowing that the culpable
> seller is not a tempting target but the manufacturer is, in the present
> climate some bright lawyer will come up with a rationale for suing the
> manufacturer.  It is the climate that must be changed and the IEE guide that
> started this thread, in my opinion, appeases this trend rather than opposes
> it.
> 
> --
> >From: Cortland Richmond 
> >To: Andrew Carson 
> >Cc: emc-p...@majordomo.ieee.org
> >Subject: Re: EMC-related safety issues
> >Date: Thu, Jan 3, 2002, 12:22 PM
> >
> 
> >
> > As engineers, we should consider the safety
> > implications of what we design, test or otherwise
> > work on. EMI is part of that. What is considered a
> > safety risk depends a great deal on corporate
> > policy, the legal, political and popular climate in
> > one's state of residence, and the kind of equipment
> > under consideration.
> >
> > As it happens, the issue of pacemaker vulnerability
> > is addressed in more regulations than USC 47. That
> > is why, in the United States, we have not only a
> > limit on microwave oven leakage, but also pacemaker
> > warning signs on microwave ovens used by the public.
> >
> > The robotic arm is a great example. Others are
> > automotive airbags, or electronically controlled
> > brakes. These sort of things are the reason why
> > industry associations develop limits of their own.
> > Those limits accommodate both a performance
> > requirement and practical aspects; they can't make
> > the product too expensive to build or no one will be
> > able to sell them at a profit. They can't be
> > unreliable in the field or people won't buy them at
> > all. And they can't cause too many problems, or the
> > company will be sued. One factor weighs against
> > another.
> >
> > We are at the balance point.
> >
> > Regards,
> >
> > Cortland Richmond
> >
> > (What I write here is mine alone.
> > My employer does not
> > Concur, agree or else endorse
> > These words, their tone, or thought.)
> >
> > Andrew Carson wrote:
> >
> >> I get the idea that we a missing the whole point
> >> of this discussion.
> >>
> >> Should we as Professional Safety Engineers and
> >> Product designers consider the safety implications
> >> of EMC emissions ?
> >>
> >> The answer is a definite Yes. We have a clear duty
> >> of care and responsibility to consider all
> >> implications of our products being used in there
> >> intended application. Even if the consideration on
> >> EMC emissions and safety is "Do not be silly." We
> >> still have to at least consider it. ...
> >

RE: EMC-related safety issues

2002-01-04 Thread James, Chris


Sorry disagree about turn and brake lights not being in the same class.
Their very failure is often the reason for very serious accidents. I have
long wished that all car manufacturers had to by law fit bulb failure
warning devices to cars (but what happens when that fails).

In the UK it is an offence to drive a vehicle with defective lights,
(although many do). It is the driver's (not owner's) obligation to be
satisfied the vehicle they are driving is fit to be on the road irespective
of whether it passed it's MOT the previous day.

The UK mandatory annual vehicle inspection (MOT) for vehicles over 3 years
old, covers seat belts, brake efficiency on a rolling road, mirrors,
windshield cracks (a 20mm, 3/4inch crack in the wrong place will fail a
vehicle), tyres, wheel bearings, gaiters, steering components, structural
body condition, lights, smog emissions, etcI don't
believe airbags are tested but guess it will come, along with the inevitable
hike in price.

I'm surprised the US does not have a similar Federal requirement - with all
the vehicles this is a cash cow waiting to be milked.


Chris

-Original Message-
From: Ken Javor [mailto:ken.ja...@emccompliance.com]
Sent: 04 January 2002 02:40
To: Doug McKean; EMC-PSTC Discussion Group
Subject: Re: EMC-related safety issues



A signal light is easily replaceable in terms of time and money.  Most 
people don't use them (well, in good old Huntsville, AL, anyway, where a
favorite bumper sticker reads, "Turn signals, not just for smart people
anymore").  Failure of a light is not in the same class as an airbag
deploying at the wrong time or not deploying, or ditto for brakes.

--
>From: "Doug McKean" 
>To: "EMC-PSTC Discussion Group" 
>Subject: Re: EMC-related safety issues
>Date: Thu, Jan 3, 2002, 7:00 PM
>

>
> Point taken Ken, but consider signal lights.  They're
> essentially safety devices and they're supposed to
> be maintained on cars which have been transferred
> amongst several owners and are decades old.
> Same idea with windshields, I guess also.
>
> - Doug McKean
>
>
> ---
> This message is from the IEEE EMC Society Product Safety
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Re: EMC-related safety issues

I must disagree. The wording of Part 15  requiring users of Part 15 devices to 
accept interference, does not reduce
complaints; hardly any users actually know it is there, or what it means. Fewer 
care. If they are receiving one's
signals, they consider them intrusions to which they must react. They do NOT 
want someone telling them to live with
it. This has created some unfortunate situations.

Cortland
(What I write here is mine alone.
My employer does not
Concur, agree or else endorse
These words, their tone, or thought.)

John Shinn wrote:...

> the susceptability) to incidental RF.  Secondly, by requiring the label to say
> "must accept", eliminates a lot of complaints about LEGAL incidental as well
> as intentional radiators (you might also read that as easer to dismiss
> complaints).

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Re: EMC-related safety issues - lighting noise

2002-01-04 Thread Jacob Schanker


George is correct so far as normal fluorescent, and of course,
incandescent, lighting. These are not regulated for emissions in
the US. But the new energy-saving RF lighting devices (bulbs) are
regulated under FCC Part 18.

The limits appear to be quite generous. The regulations are found
in 18.305 for radiated (above 30 MHz) and in 18.307 for conducted
(including the AM/MW Broadcast band).

I recall that the ARRL fought the relaxation of the emission
limits because some lamps operate (if I tremember correctly) in
the amateur 20 meter band or nearby (maybe 13.56 MHz ??).

Jack

Jacob Z. Schanker, P.E.
65 Crandon Way
Rochester, NY 14618
Phone: 585 442 3909
Fax: 585 442 2182
j.schan...@ieee.org


- Original Message -
From: 
To: "Rich Nute" 
Cc: ; 
Sent: Thursday, January 03, 2002 4:32 PM
Subject: Re: EMC-related safety issues


|
|
|
| I think the issue is that the lamp is not an EMC regulated
| device.  In fact, in Europe, ITE conducted emissions must
| be regulated so as not to cause desk/room lights to "flicker",
| as in when a fuser lamp in a printer kicks on.
|
| Apparantly the proper functioning of lighting takes precedence
| over the propoer functioning of radios and the like affected by
| the lights?
|
| George
|
|
|
|
| Rich Nute  on
01/03/2002 04:08:51 PM
|
| Please respond to Rich Nute

|
| To:   jmw%jmwa.demon.co...@interlock.lexmark.com
| cc:   emc-pstc%majordomo.ieee@interlock.lexmark.com (bcc:
George
|   Alspaugh/Lex/Lexmark)
| Subject:  Re: EMC-related safety issues
|
|
|
|
|
|
|
| Hi John:
|
|
| >   >I've replaced the incandescent lamp on my bedside
| >   >table with a new energy-saving compact flourescent
| >   >lamp.  With the lamp on, I cannot listen to even
| >   >the strongest AM radio station on my clock radio
| >   >(on the same bedside table) due to the lamp
| >   >interference.  This must not be the usage
| >   >contemplated by EMC requirements.
| >
| >   Limits in the household environment are based on a 3 m
separation
| >   between source and receiver.
|
| Wonderful!
|
| Either the lamp or the radio must be on the opposite
| side of the room from my bedside table.  When I am in
| bed, one or the other is not controllable, and is
| therefore useless to me.
|
| Whine mode on:  I want both on my bedside table, and
| I want both to do all of their functions.  This IS
| not the usage contemplated by 3 m separation EMC
| requirements.
|
| :-)
|
|
| Best wishes for the New Year,
| Rich
|
|
|
|
| ---
| This message is from the IEEE EMC Society Product Safety
| Technical Committee emc-pstc discussion list.
|
| Visit our web site at:  http://www.ewh.ieee.org/soc/emcs/pstc/
|
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at:
| No longer online until our new server is brought online and
the old messages are imported into the new server.
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Re: EMC-related safety issues


I read in !emc-pstc that Kevin Harris  wrote (in
) about 'EMC-related
safety issues', on Thu, 3 Jan 2002:
>If the BSI site says that, then it is yet another proof of you can't always
>believe what you read. :) My Aug 2001 version of the BSI electronic catalog
>shows a publication date of 1996 for the BS EN ( but the document was
>actually released in late 1995) with an addendum A1 published in 1998. The
>hard copy sitting in front of me (from BSI)  agrees with the electronic
>catalog :)
>
>There was a very generous transition period which ended in January of 2001.

I'll check again. Maybe there was some sort of glitch.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
After swimming across the Hellespont, I felt like a Hero. 

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Re: EMC-related safety issues


I read in !emc-pstc that Rich Nute  wrote (in
<200201032108.naa11...@epgc264.sdd.hp.com>) about 'EMC-related safety
issues', on Thu, 3 Jan 2002:
>Whine mode on:  I want both on my bedside table, and 
>I want both to do all of their functions.  This IS 
>not the usage contemplated by 3 m separation EMC 
>requirements.  
>
>:-)
>

Use an incandescent lamp. For a bedside table, quite a low power lamp is
OK, especially if you use a low-voltage lamp. But keep a switch-mode
'electronic transformer' at least 3 m from the radio, of course! Or
stick to an ordinary transformer. Old technology is NOT always BAD!
Grandpa is your FRIEND.

Since it isn't practicable to reduce the emissions of CFLs well below
the limits of CISPR15/EN55015 without heroic measures, the 3 m
separation has to be observed, or CFLs have to be banned or made much
more costly. The latter possibilities are clearly not environmentally
acceptable.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
After swimming across the Hellespont, I felt like a Hero. 

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Re: EMC-related safety issues


I read in !emc-pstc that david_ster...@ademco.com wrote (in <2DF7C54A75B
dd311b61700508b64231002c5a...@nyhqex1.ademcohq.com>) about 'EMC-related
safety issues', on Thu, 3 Jan 2002:
>My copy of BS EN 50140-4:1996 

50140-4? ENV50140 was an early version of EN61000-4-3 and is withdrawn.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
After swimming across the Hellespont, I felt like a Hero. 

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Re: EMC-related safety issues


I read in !emc-pstc that geor...@lexmark.com wrote (in <200201032132.QAA
24...@interlock2.lexmark.com>) about 'EMC-related safety issues', on
Thu, 3 Jan 2002:
>I think the issue is that the lamp is not an EMC regulated
>device.  

Yes it is. EN55015 applies to emissions from lamps.

>In fact, in Europe, ITE conducted emissions must
>be regulated so as not to cause desk/room lights to "flicker",
>as in when a fuser lamp in a printer kicks on.

Well, that applies to everything connected to the public LV mains
supply, not just ITE. See EN61000-3-3.
>
>Apparantly the proper functioning of lighting takes precedence
>over the propoer functioning of radios and the like affected by
>the lights?

No, it's simply that it isn't considered reasonable to have a radio and
a CFL in close proximity. If you want a lamp and a radio close together,
use an incandescent lamp.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
After swimming across the Hellespont, I felt like a Hero. 

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Re: EMC-related safety issues

2002-01-04 Thread Ken Javor


A signal light is easily replaceable in terms of time and money.  Most 
people don't use them (well, in good old Huntsville, AL, anyway, where a
favorite bumper sticker reads, "Turn signals, not just for smart people
anymore").  Failure of a light is not in the same class as an airbag
deploying at the wrong time or not deploying, or ditto for brakes.

--
>From: "Doug McKean" 
>To: "EMC-PSTC Discussion Group" 
>Subject: Re: EMC-related safety issues
>Date: Thu, Jan 3, 2002, 7:00 PM
>

>
> Point taken Ken, but consider signal lights.  They're
> essentially safety devices and they're supposed to
> be maintained on cars which have been transferred
> amongst several owners and are decades old.
> Same idea with windshields, I guess also.
>
> - Doug McKean
>
>
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RE: EMC-related safety issues

2002-01-04 Thread John Shinn

Actually, if you consider that there are two issues here.  First, the TV and
Radio
manufacturers are required to no longer have a wide-open front end as was
prevalent
quite a few years ago.  This single action by the FCC improved the immunity
(decreased
the susceptability) to incidental RF.  Secondly, by requiring the label to
say
"must accept", eliminates a lot of complaints about LEGAL incidental as well
as
intentional radiators (you might also read that as easer to dismiss
complaints).

It was a start.

John Shinn

-Original Message-
From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Doug McKean
Sent: Thursday, January 03, 2002 2:36 PM
To: EMC-PSTC Discussion Group
Subject: Re: EMC-related safety issues

"Rich Nute" wrote:
>
> EMC?  Ha!

You raise a good point since the FCC legally can but
hasn't implemented an American version of immunity
standards.  The words "must accept" on the FCC labels
of your effected devices are evident of it.  Maybe some
day we will have do immunity testing.

- Doug McKean

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Re: EMC-related safety issues