Re: Define Continuous DC Voltage

[John Woodgate]

I read in !emc-pstc that eric.lif...@ni.com wrote (in
) about 'Define
Continuous DC Voltage', on Fri, 9 Nov 2001:
>John Woodgate commented:
>[...]
>>A digital signal that has one value at 0 V to ground and the other value
>>at voltage V consists of a d.c. voltage of amplitude V/2 plus an a.c.
>>voltage of (double) amplitude V/2. The frequency of the a.c. is
>>irrelevant.
>[...]
>
>Per IEC 60950:1999, also in UL 1950:1995 (but not in '1010 or UL 31x1),
>D.C. Voltage is defined as:
>  The average value of a voltage (as measured by a moving coil meter)
>having a
>  peak-to-peak ripple not exceeding 10% of the average value.
>  Note - Where peak-to-peak ripple exceeds 10% of the average value, the
>  requirements related to peak voltage are applicable.
>
>I could not find the V/2 clause in 950.  Perhaps its the TNV section of UL
>1950:1995, clause 6.2.1.1, though it differs in that the divisor is not 2,
>but what I'd call a reference voltage, 42.4 V and others.  Frequency here
>is limited to 100 Hz and below.  It also repeats the 10% ripple criteria in
>Table 8.

It isn't there, simply because 60950 is concerned with safety and not
with defining what 'd.c.' is as a concept, which is what my text is
about. The first part of the 60950 text is, however, entirely consistent
with my text. Given a moving-coil meter with a long enough averaging
time (much longer than the lowest frequency alternating voltage
present), the meter will read V/2. The second part is not about the
concept of 'd.c.', but entirely about how to treat, for safety purposes,
a voltage that is part d.c. and part a.c., when the a.c. part exceeds
10%.
>
>It seems unclear (for us '1010 users) as to how continuous in time a DC
>voltage from 42.4 V DC Peak to 60 V DC Peak must be to avoid falling into
>the AC Peak limits, in an application that switches circuits on/off either
>randomly or periodically.

It seems clear that the authors of 60950 did not take into account the
case that troubles you. But, in Europe anyway, if your product is a
'61010' product, you don't have to apply ANY of the provisions of 60950.
>
>Perhaps a simple voltage/frequency table derived from the Annex P leakage
>current model would allow our customers to use the full DC Voltage rating
>for sub 48 Hz switching rates, and specify a sliding scale of maximum rated
>voltage as the highest switching frequency goes up.

That should be proposed to the new IEC TC108 as an improvement to
IEC60950.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Eat mink and be dreary!

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Re: Define Continuous DC Voltage

[John Woodgate]

I read in !emc-pstc that Doug McKean  wrote (in
<000a01c1694c$1bc34ea0$3e3e3...@corp.auspex.com>) about 'Define
Continuous DC Voltage', on Fri, 9 Nov 2001:
>For John, there wasn't any mention of hazardous 
>in the original question.  Only what would qualify 
>as "continuous DC". 

What do you make of this extract from the original post, if it's not
about hazardous voltages?

QUOTE

I consulted two UL standards: 508C and 3121-1 (and it's kin 3101/3111-1,
all based on IEC 61010-1), both led me (by reference) to UL 1310 Class 2
Power Units.  UL 1310 has a clause (14.2.2) which indicates that a "DC
interrupted at a rate of 200 Hz or less" is limited to 24.8 V peak.  In
the same clause it mentions a "continuous" DC voltage of 60 V DC is
permissible.

UNQUOTE
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Eat mink and be dreary!

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RE: Define Continuous DC Voltage

[Chris Maxwell]

Sadly, I can't give that frequency; but I think I know the reasoning
behind Eric's question...

AC signals under 200Hz are especially dangerous to humans because AC
currents really screw up our nervous system and cause death by heart
attack at very low currents.  It only takes milliamps of 60Hz AC current
to kill a human being.

On the other hand, people can withstand far more current from a DC
source because it doesn't have the same effect on our nervous system.
(Come on, who hasn't put a 9V battery on their tongue to test it out?)

I think that this is the reasoning that the referenced standard uses to
give two limits for "AC" and "DC".  My GUESS is that someone (who loved
to torture living organisms) must have performed tests to figure out how
DC current affected people (or monkeys, or rats... something).  They
then must have performed tests with different AC frequencies.  Perhaps
they even plotted a graph of "hazardous" voltage/current versus
frequency.  I would imagine that this is the type of data used by the
IEC or any other safety organizationn to set hazardous voltage levels.
Problem is...the standards don't give a graph or table of hazardous
voltage vs. frequency, it just says "DC" and "AC".   Since we don't have
access to the graph we really don't know what happens at ultra low
frequencies.   (Although I have a few rodents in my basement who are
just asking to be test samples.)

Of course, now there is the gray area of interpretation. (which keeps us
all employed)

For example, how would a safety engineer classify a 40V thermostat
control signal (non current limited) with a five second hysteresis that
prevents it from switching any faster than once every five seconds (0.2
Hz).   Under normal conditions, this signal would switch once every
couple of hours (0.00014Hz).  Is this "hazardous AC" (after all it is
40V, and it does vary with time)?  Or is it "non-hazardous DC".  

Anybody want to tackle that question?  It may help us to figure out
Eric's initial problem.  Remember to show your work...partial credit
will be given :-)

Just to show that I'm game... I'll take a stab.  My opinion is that, if
it can be proven that this signal will switch at a frequency no higher
than 0.2 Hz under all normal and single fault conditions; then you have
a non-hazardous "DC" signal.  (Note that I'm not saying 0.2 Hz is the
cutoff, it's probably higher.)

OK... I've hung it out there.  Either agree with it or refute it.
Either way, we'll all learn something.

Chris Maxwell | Design Engineer - Optical Division
email chris.maxw...@nettest.com | dir +1 315 266 5128 | fax +1 315 797
8024

NetTest | 6 Rhoads Drive, Utica, NY 13502 | USA
web www.nettest.com | tel +1 315 797 4449 | 




> -Original Message-
> From: Ken Javor [SMTP:ken.ja...@emccompliance.com]
> Sent: Friday, November 09, 2001 1:22 PM
> To:   Tania Grant; Doug McKean; EMC-PSTC Discussion Group
> Subject:  Re: Define Continuous DC Voltage
> 
> I'm probably not providing any assistance, but what is the purpose of
> the categorization of continuous dc vs. that rate of change where it
> is not considered continuous anymore?  I don't think it should be tied
> to ability to deliver power to a load, which is in agreement with what
> Ms. Grant is saying below.  Pure dc provides power and no information.
> A signal uses power to transmit information.  If I have a security
> alarm sensor on a window which always sends a low-level dc until the
> window is broken then if I look at the physical parameters I could say
> that low-level signal was dc because it could be on for years, but its
> PURPOSE is to transmit information which makes it a signal.  Actually
> any single-sided digital transmission (meaning between 0 Volts and
> some Vcc) is dc in the classical sense because dc means direct
> current, as opposed to alternating current which changes direction.
> In the sense which people in this exchange have been using the
> terminology it refers to how much time rate of change is allowed.  But
> this is where the question as to purpose comes in.  If the issue is
> crosstalk, a low-level audio or video signal with lots of rate of
> change is a much more benign source than a 48 Vdc  source from which
> lots of switched CURRENT is drawn.  A dc POTENTIAL does NOT imply
> direct CURRENT unless CE limits have been applied to loads.  So the
> question that has to be answered first is what is the purpose of the
> discrimination implied by the term "continuous."
> 
> --
> From: "Tania Grant" 
> To: "Doug McKean" , "EMC-PSTC Discussion
> Group" 
> Subject: Re: Define Continuous DC Voltage
> Date: Thu, Nov 8, 2001, 9:47 PM
> 
> 
> 
> 
>   Well now, Doug, how about the vast gray area in between?   
>
>
>
>   What if it is 1/50th of an amp?   
>
>
>
>   taniagr...@msn.com  
>
>
>
>   
> 
>
>   - Original Message --

[SI-LIST] Re: emi shielding

[Ken Javor]

The mechanism for reflection is that em fields incident on a surface induce
currents to flow such that the flow of current opposes the field which
caused it.  The material must have enough absorption and homogeneity (i.e.,
limited apertures) such that the induced currents remain on the side of the
material where they were induced and do not re-radiate.  That is the
function of absorption and aperture control above 30 MHz.

--
>From: "Wani, Vijay (V)" 
>To: "'ghery.pet...@intel.com'" ,
"'emc-p...@majordomo.ieee.org'" ,
"'si-l...@freelists.org'" 
>Subject: RE: [SI-LIST] Re: emi shielding
>Date: Fri, Nov 9, 2001, 11:52 AM
>

>
> all:thanks for your time and response.
>
> I understand the frequency range we worry about (30MHz - 2GHz), any metal
> (or metallized plastic) would be overkill and effect of apertures will be
> mostly determing factor for shielding effectiveness.
> but, the shielding mechanism of conductive metals (or metallized plastics)
> is mostly reflective rather than absorbtion.
>
>  if we have a meterial with absorbtion shielding mechanism (in 30 MHz-2GHz
> frequency range), is there any advantage? i would guess, that will reduce
> antenna effect in the system. would appreciate any thoughts.
>
> vijay wani
> Dow Chemical
>
> -Original Message-
> From: Pettit, Ghery [mailto:ghery.pet...@intel.com]
> Sent: Friday, November 09, 2001 12:14 PM
> To: 'Wani, Vijay (V)'; 'emc-p...@majordomo.ieee.org';
> 'si-l...@freelists.org'
> Subject: [SI-LIST] Re: emi shielding
>
>
> Vijay,
>
> The relative proportions are a function of frequency and the relative
> conductivity and relative permittivity of the material.
>
> The attached file is from a MathCAD 7.0 model that I put together a while
> back.  The equations came from a Technit design guide published about 20
> years ago.
>
> You will note that in the frequency range that we usually worry about almost
> any metal you might use is overkill.  It is the apertures that create the
> problems.  The example in the document is copper.
>
> I hope this helps.
>
> Ghery Pettit, NCE
>
>
>
> -Original Message-
> From: Wani, Vijay (V) [mailto:vw...@dow.com]
> Sent: Friday, November 09, 2001 7:36 AM
> To: 'emc-p...@majordomo.ieee.org'; 'si-l...@freelists.org'
> Subject: emi shielding
>
>
>
> hello:
>
> as we know, threre are two main component of shielding effectiveness.
> (Absorbtion and Reflection). is there any way to find out.. what percentage
> of overall shielding is due to absorbtion / reflection for a given material?
>
> thank you in advance.
>
> Vijay Wani
> Dow Chemical
>
> ---
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Re: Define Continuous DC Voltage

[eric . lifsey]

Doug et al,

I think John realized that I was led down the path to UL 1310 and it's
strange clause (continuous) in an attempt to quantify how/when a DC voltage
becomes regarded to be an AC voltage in terms of hazard.  I wasn't clear on
that.

Best Regards,
Eric Lifsey





   
"Doug McKean"   
   
 
   
Sent by:   cc:  
   
owner-emc-pstc@majordomSubject: Re: Define 
Continuous DC Voltage   
o.ieee.org  
   

   

   
11/09/2001 12:26 PM 
   
Please respond to "Doug 
   
McKean" 
   

   

   





Well, to follow John's and Tania's comments ...

For John, there wasn't any mention of hazardous
in the original question.  Only what would qualify
as "continuous DC".  So, IMO, it doesn't matter
what the frequency is as I stated with regards to
an rms nor the level with regard to hazardous.
The rms converts any signal dc or ac to a
continuously delivered power to a load in terms
of real power.

Which brings me to Tania's question as in,
whatever level you wish to consider.  If it
is 1/50th, then so be it.

I thought it was an interesting question when
I started considering heating effects with say
fine pitch traces and such.

Anywho, just my two cents ...

Regards, Doug McKean





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RE: CISPR 22:1997

[Pettit, Ghery]

Jim,

Israel has backed off on the telecom port conducted emissions portion of
CISPR 22:1997.  I haven't seen an official document, but my contact tells me
that this has been done.

Russia is still requiring the telecom port conducted emissions test, in
spite of their regulatory folks being fully aware of the problems with it.

Japan (VCCI) has delayed implementation until the problems can be sorted
out.

I'm not sure what Australia is doing at this time.

Good luck.

Ghery Pettit
Intel


-Original Message-
From: jim.hulb...@pb.com [mailto:jim.hulb...@pb.com]
Sent: Friday, November 09, 2001 11:19 AM
To: emc-p...@ieee.org
Subject: CISPR 22:1997



The European Union has postponed mandatory compliance with CISPR 22:1997
(EN 55022:1998) until 1 August 2003.  This version of the standard includes
the new requirement for conducted emissions on cables connected to
telecommunications ports.

Have other countries that require compliance with CISPR 22 (or some
variation thereof) also postponed implementation of the 1997 version?  My
immediate concern is Australia.

Any information members of this group can share is greatly appreciated.

Jim Hulbert
Senior Engineer - EMC
Pitney Bowes


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CISPR 22:1997

[Jim . Hulbert]

The European Union has postponed mandatory compliance with CISPR 22:1997
(EN 55022:1998) until 1 August 2003.  This version of the standard includes
the new requirement for conducted emissions on cables connected to
telecommunications ports.

Have other countries that require compliance with CISPR 22 (or some
variation thereof) also postponed implementation of the 1997 version?  My
immediate concern is Australia.

Any information members of this group can share is greatly appreciated.

Jim Hulbert
Senior Engineer - EMC
Pitney Bowes


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Re: Define Continuous DC Voltage

[eric . lifsey]

Doug McKean commented:
[...]
>>Personally, I'd say when the source can deliver some
>>sufficient level of real power (rms level of power).
[...]

The device in question can drive several milliamps on each channel, which I
believe is a healthy shock.  As a limited energy source it is unlikely to
be a fire hazard.  Since the model of the body is roughly 2,000 Ohms,
that's a potential for up to 30 mA at 60 V DC and is probably rather
painful.  (There was a very good thread on fibrillation and other
biological aspects of current about four [?] years ago on this list.)  See
Annex D of '950 for the leakage current model, which is also influenced by
frequency.

John Woodgate commented:
[...]
>A digital signal that has one value at 0 V to ground and the other value
>at voltage V consists of a d.c. voltage of amplitude V/2 plus an a.c.
>voltage of (double) amplitude V/2. The frequency of the a.c. is
>irrelevant.
[...]

Per IEC 60950:1999, also in UL 1950:1995 (but not in '1010 or UL 31x1),
D.C. Voltage is defined as:
  The average value of a voltage (as measured by a moving coil meter)
having a
  peak-to-peak ripple not exceeding 10% of the average value.
  Note - Where peak-to-peak ripple exceeds 10% of the average value, the
  requirements related to peak voltage are applicable.

I could not find the V/2 clause in 950.  Perhaps its the TNV section of UL
1950:1995, clause 6.2.1.1, though it differs in that the divisor is not 2,
but what I'd call a reference voltage, 42.4 V and others.  Frequency here
is limited to 100 Hz and below.  It also repeats the 10% ripple criteria in
Table 8.

It seems unclear (for us '1010 users) as to how continuous in time a DC
voltage from 42.4 V DC Peak to 60 V DC Peak must be to avoid falling into
the AC Peak limits, in an application that switches circuits on/off either
randomly or periodically.

Perhaps a simple voltage/frequency table derived from the Annex P leakage
current model would allow our customers to use the full DC Voltage rating
for sub 48 Hz switching rates, and specify a sliding scale of maximum rated
voltage as the highest switching frequency goes up.

Thanks and Best Regards,
Eric Lifsey
Compliance Manager
National Instruments



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Re: Define Continuous DC Voltage

[Doug McKean]

Well, to follow John's and Tania's comments ... 

For John, there wasn't any mention of hazardous 
in the original question.  Only what would qualify 
as "continuous DC".  So, IMO, it doesn't matter 
what the frequency is as I stated with regards to 
an rms nor the level with regard to hazardous.  
The rms converts any signal dc or ac to a 
continuously delivered power to a load in terms 
of real power. 

Which brings me to Tania's question as in, 
whatever level you wish to consider.  If it 
is 1/50th, then so be it. 

I thought it was an interesting question when 
I started considering heating effects with say 
fine pitch traces and such. 

Anywho, just my two cents ... 

Regards, Doug McKean 


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Re: Define Continuous DC Voltage

[Ken Javor]

I'm probably not providing any assistance, but what is the purpose of the 
categorization of continuous dc vs. that rate of change where it is not
considered continuous anymore?  I don't think it should be tied to ability
to deliver power to a load, which is in agreement with what Ms. Grant is
saying below.  Pure dc provides power and no information.  A signal uses
power to transmit information.  If I have a security alarm sensor on a
window which always sends a low-level dc until the window is broken then if
I look at the physical parameters I could say that low-level signal was dc
because it could be on for years, but its PURPOSE is to transmit information
which makes it a signal.  Actually any single-sided digital transmission
(meaning between 0 Volts and some Vcc) is dc in the classical sense because
dc means direct current, as opposed to alternating current which changes
direction.  In the sense which people in this exchange have been using the
terminology it refers to how much time rate of change is allowed.  But this
is where the question as to purpose comes in.  If the issue is crosstalk, a
low-level audio or video signal with lots of rate of change is a much more
benign source than a 48 Vdc  source from which lots of switched CURRENT is
drawn.  A dc POTENTIAL does NOT imply direct CURRENT unless CE limits have
been applied to loads.  So the question that has to be answered first is
what is the purpose of the discrimination implied by the term "continuous."

--
From: "Tania Grant" 
To: "Doug McKean" , "EMC-PSTC Discussion Group"

Subject: Re: Define Continuous DC Voltage
List-Post: emc-pstc@listserv.ieee.org
Date: Thu, Nov 8, 2001, 9:47 PM


Well now, Doug, how about the vast gray area in between?



What if it is 1/50th of an amp?



taniagr...@msn.com 




- Original Message -

From: Doug McKean

Sent: Thursday, November 08, 2001 7:39 PM

To: EMC-PSTC Discussion Group

Subject: Re: Define Continuous DC Voltage



eric.lif...@ni.com wrote:
>
> So friends, how continuous must DC be to qualify as continuous DC?

Personally, I'd say when the source can deliver some
sufficient level of real power (rms level of power).
That is basically the definition of rms anyway.

To make the point with two ridiculous examples,
(1) if by shorting a 5 volt digital signal to ground
you measure 1/100th amps of rms current, then I
wouldn't call it DC.
(2) if by shorting a 5 volt digital signal to ground
you measure 10 amps or rms current, then I'd
most definitely call it DC.

But that's just me and my 2 cents worth.

- Doug McKean




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Re: emi shielding

[Ken Javor]

If you are using the coaxial test fixture per the ASTM SE test method you 
could insert a directional coupler with reverse power tap just before the
fixture and measure how much power is getting splashed back.  With that
number, plus the total loss in the system measured as the power getting
through the fixture vs. the known power out of the signal source, you can
back out what is reflected and what is absorbed.

--
>From: "Wani, Vijay (V)" 
>To: "'emc-p...@majordomo.ieee.org'" ,
"'si-l...@freelists.org'" 
>Subject: emi shielding
>Date: Fri, Nov 9, 2001, 9:36 AM
>

>
> hello:
>
> as we know, threre are two main component of shielding effectiveness.
> (Absorbtion and Reflection). is there any way to find out.. what percentage
> of overall shielding is due to absorbtion / reflection for a given material?
>
> thank you in advance.
>
> Vijay Wani
> Dow Chemical
>
> ---
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RE: [SI-LIST] Re: emi shielding

[Wani, Vijay (V)]

all:thanks for your time and response.

I understand the frequency range we worry about (30MHz - 2GHz), any metal
(or metallized plastic) would be overkill and effect of apertures will be
mostly determing factor for shielding effectiveness.
but, the shielding mechanism of conductive metals (or metallized plastics)
is mostly reflective rather than absorbtion. 

 if we have a meterial with absorbtion shielding mechanism (in 30 MHz-2GHz
frequency range), is there any advantage? i would guess, that will reduce
antenna effect in the system. would appreciate any thoughts.

vijay wani
Dow Chemical

-Original Message-
From: Pettit, Ghery [mailto:ghery.pet...@intel.com]
Sent: Friday, November 09, 2001 12:14 PM
To: 'Wani, Vijay (V)'; 'emc-p...@majordomo.ieee.org';
'si-l...@freelists.org'
Subject: [SI-LIST] Re: emi shielding


Vijay,

The relative proportions are a function of frequency and the relative
conductivity and relative permittivity of the material.

The attached file is from a MathCAD 7.0 model that I put together a while
back.  The equations came from a Technit design guide published about 20
years ago.

You will note that in the frequency range that we usually worry about almost
any metal you might use is overkill.  It is the apertures that create the
problems.  The example in the document is copper.

I hope this helps.

Ghery Pettit, NCE



-Original Message-
From: Wani, Vijay (V) [mailto:vw...@dow.com]
Sent: Friday, November 09, 2001 7:36 AM
To: 'emc-p...@majordomo.ieee.org'; 'si-l...@freelists.org'
Subject: emi shielding



hello:

as we know, threre are two main component of shielding effectiveness.
(Absorbtion and Reflection). is there any way to find out.. what percentage
of overall shielding is due to absorbtion / reflection for a given material?

thank you in advance.

Vijay Wani
Dow Chemical

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RE: Products for evaluation

[Gregg Kervill]

Sorry for the abrupt response but time is short and there are I believe
there are serious issues here.

If you would like to take some of these points off line please email me.



A Class III LASER is dangerous!

For UL/CSA you will need a FDA report. I have just completed just such a
project.


For CE Marking you might use that report (some may disagree because if it
not of the EU).

If you even need a CB Report you will need a IEC 825 (Number??) LASER REPORT


An OPEN ???  are there interlocks? - processes? - operating instruction?


The unit is definitely NOT a COMPONENT Nor can it ever be considered as
such.


Even if it was a component you WOULD NOT be able to sent it round the world.
There are many differing requirements - I'll leave it to people better
qualified (like John Woodgate) to give you the details (please John).







P.O. Box 310, Reedville,
Virginia 22539  USA

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

If the product only was a component I would just send it around the
world but it can function as a product by just "adding a PC" to a RS 232
port.

How should I tread this product when sending it to US/Canada ?

Can I just add a label on the product with a text like this:

For evaluation purpose only  ?

And what about EU, the manufacturer is located in EU ?

Best regards,

Kim Boll Jensen
Bolls Raadgivning
Consultant in type approvals


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[SI-LIST] Re: emi shielding

[Pettit, Ghery]

Vijay,

The relative proportions are a function of frequency and the relative
conductivity and relative permittivity of the material.

The attached file is from a MathCAD 7.0 model that I put together a while
back.  The equations came from a Technit design guide published about 20
years ago.

You will note that in the frequency range that we usually worry about almost
any metal you might use is overkill.  It is the apertures that create the
problems.  The example in the document is copper.

I hope this helps.

Ghery Pettit, NCE



-Original Message-
From: Wani, Vijay (V) [mailto:vw...@dow.com]
Sent: Friday, November 09, 2001 7:36 AM
To: 'emc-p...@majordomo.ieee.org'; 'si-l...@freelists.org'
Subject: emi shielding



hello:

as we know, threre are two main component of shielding effectiveness.
(Absorbtion and Reflection). is there any way to find out.. what percentage
of overall shielding is due to absorbtion / reflection for a given material?

thank you in advance.

Vijay Wani
Dow Chemical

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RE: emi shielding

[richwoods]

Absorbtion loss is given by

A(dB) = 3.34 t (f(Mhz)Gu) where

t = thickness in mils (sorry, my book is not metric based)
G = conductivity relative to copper (G = 1 for copper)
u = relative permeability to vacuum

Reflection loss is given by

R(dB) 20 log [(K_1)^2/4K] which is approx 20 log [Z(w)/4Z(b)] for K>10 

where Zw is the wave impedance and Zb is the surface impedance.

For plane waves

R(dB) = 108 + 10 log [G/uf(MHZ)]

All this is from EMC Handbook, Vol 3, Don White Consultants, 1973.

Richard Woods
Sensormatic Electronics
Tyco International





-Original Message-
From: Wani, Vijay (V) [mailto:vw...@dow.com]
Sent: Friday, November 09, 2001 10:36 AM
To: 'emc-p...@majordomo.ieee.org'; 'si-l...@freelists.org'
Subject: emi shielding



hello:

as we know, threre are two main component of shielding effectiveness.
(Absorbtion and Reflection). is there any way to find out.. what percentage
of overall shielding is due to absorbtion / reflection for a given material?

thank you in advance.

Vijay Wani
Dow Chemical

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[SI-LIST] Re: emi shielding

[Jeff Walden]

Vijay,
Check out FloEMC, http://www.floemc.com/. You can have the software
determine this by integrating the losses in the material, whether they are
resistive or dielectric to find the absorption.

Jeff Walden

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emi shielding

[Wani, Vijay (V)]

hello:

as we know, threre are two main component of shielding effectiveness.
(Absorbtion and Reflection). is there any way to find out.. what percentage
of overall shielding is due to absorbtion / reflection for a given material?

thank you in advance.

Vijay Wani
Dow Chemical

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Products for evaluation

[Kim Boll Jensen]

Hi all

A customer of mine have a product which have a controller unit with
mains power and an open Class 3B laser unit. The product will normally
be regarded as a component for build-in but it can also be used by
students for laser experiments etc. as it is.

The product is not in production yet but is ready for shipment in a
small quantity (around 25 units).

If the product only was a component I would just send it around the
world but it can function as a product by just "adding a PC" to a RS 232
port.

How should I tread this product when sending it to US/Canada ?

Can I just add a label on the product with a text like this:

For evaluation purpose only  ?

And what about EU, the manufacturer is located in EU ?

Best regards,

Kim Boll Jensen
Bolls Raadgivning
Consultant in type approvals


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RE: Most recent publications

[Geoff Lister]

I had a quick look at the ETSI site. The following link
has jumps to more information. The publications
search seems to have narrow date windows.

http://portal.etsi.org/Portal_Common/home.asp

It may give you the information you need. Santa
Claus has friends at ETSI.

Best regards,
Geoff Lister
Senior Engineer
Motion Media Technology Ltd.,
Bristol, UK.
http://www.motion-media.com 



-Original Message-
From: am...@westin-emission.no [mailto:am...@westin-emission.no]
Sent: 09 November 2001 08:42
To: emc-p...@majordomo.ieee.org
Subject: Most recent publications



Hi all,

I like the IEC page "Most recent publications" on
http://www.iec.ch/cgi-bin/procgi.pl/www/iecwww.p?wwwlang=e&wwwprog=newpub.p
Not because it gives you a lot of details regarding the standards, but it
keeps you informed about new publications.

Well, I had hoped we could download the standards, but I realize that Santa
Claus is not working in IEC.

My question is : Do ESTI have a similar page on the WEB, describing new
publications day-by-day, just like IEC are doing ?

Best regards
Amund Westin, Oslo/Norway





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Re: Define Continuous DC Voltage

[John Woodgate]

I read in !emc-pstc that Doug McKean  wrote (in
<000b01c1689b$3fc85e00$3e3e3...@corp.auspex.com>) about 'Define
Continuous DC Voltage', on Thu, 8 Nov 2001:
>> So friends, how continuous must DC be to qualify as continuous DC?
>
>Personally, I'd say when the source can deliver some 
>sufficient level of real power (rms level of power). 
>That is basically the definition of rms anyway. 
>
>To make the point with two ridiculous examples, 
>(1) if by shorting a 5 volt digital signal to ground 
>you measure 1/100th amps of rms current, then I 
>wouldn't call it DC. 
>(2) if by shorting a 5 volt digital signal to ground 
>you measure 10 amps or rms current, then I'd 
>most definitely call it DC. 

But that, while probably important, is not about 'continuity'. In any
case, IEC/EN60950 already defines what voltages and currents are
hazardous in various ways. 

A digital signal that has one value at 0 V to ground and the other value
at voltage V consists of a d.c. voltage of amplitude V/2 plus an a.c.
voltage of (double) amplitude V/2. The frequency of the a.c. is
irrelevant. I think the cited standards were written while this concept
was not loaded into memory. (;-)
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Eat mink and be dreary!

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Most recent publications

[amund]

Hi all,

I like the IEC page "Most recent publications" on
http://www.iec.ch/cgi-bin/procgi.pl/www/iecwww.p?wwwlang=e&wwwprog=newpub.p
Not because it gives you a lot of details regarding the standards, but it
keeps you informed about new publications.

Well, I had hoped we could download the standards, but I realize that Santa
Claus is not working in IEC.

My question is : Do ESTI have a similar page on the WEB, describing new
publications day-by-day, just like IEC are doing ?

Best regards
Amund Westin, Oslo/Norway



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Re: Define Continuous DC Voltage

[Tania Grant]

Well now, Doug, how about the vast gray area in between?

What if it is 1/50th of an amp?

taniagr...@msn.com
  
- Original Message -
From: Doug McKean
Sent: Thursday, November 08, 2001 7:39 PM
To: EMC-PSTC Discussion Group
Subject: Re: Define Continuous DC Voltage
  

eric.lif...@ni.com wrote:
>
> So friends, how continuous must DC be to qualify as continuous DC?

Personally, I'd say when the source can deliver some
sufficient level of real power (rms level of power).
That is basically the definition of rms anyway.

To make the point with two ridiculous examples,
(1) if by shorting a 5 volt digital signal to ground
you measure 1/100th amps of rms current, then I
wouldn't call it DC.
(2) if by shorting a 5 volt digital signal to ground
you measure 10 amps or rms current, then I'd
most definitely call it DC.

But that's just me and my 2 cents worth.

- Doug McKean




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