Re: Green/Yellow Earthing Leads

[Rich Nute]

Hello from San Diego:


One of our subscriber colleagues has pointed out that
my assertion that Europe uses yellow as the color of
the earthing wire is incorrect.

I recall when the green-yellow was agreed to for 
power cords and internal equipment wiring.  My
recall was that both yellow and green were used as 
earthing wire colors, hence the green-yellow 
compromise.

My recollection is in error.  I apologize for 
misleading you.


Best regards,
Rich





> In North America, the earthing conductor in
> building wiring is green.
>
> In Europe, the earthing conductor in building
> wiring is yellow.
>
> For power cords and equipment earthing conductors,
> a compromise was agreed to for green/yellow.
>
> Note that in North America, power cord and
> equipment earthing conductors may be green/yellow
> or green.
>
> In Europe, power cord and equipment earthing
> conductors may be green/yellow or yellow.
>
>
> Best regards,
> Rich
>
>
>

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Re: electric strength test

[Rich Nute]

Hi Greg:


>   > >Why does "True SELV" require basic insulation
>   > >between SELV and earth?
>   > >
>   > >What is the hazardous voltage source, and what
>   > >is the current path through the body if that 
>   > >basic insulation should fail?
>   > >
>   > >
>   
>   I believe (and I could be wrong) that it's a philosophy of keeping SELV 
>   intact under single fault conditions.   If there's a single fault bridging 
>   mains and earth, then an SELV circuit is exposed to mains voltage unless 
>   there is basic insulation protecting it.  Since it is estamited that close 
> to 
>   50% of the homes in the US have improperly grounded outlets, the earth 
>   connection itself is not taken into consideration as a reliable means of 
>   protection.  In other words, for the purposes of the standard, an open 
> earth 
>   connection is not considered a fault.

Thanks for the explanation.  

One implication of this explanation is that
an open earth connection is not a fault 
condition, but a normal condition.  (Failure
of basic insulation is the fault condition.)

This would suggest that it would be better to
double/reinforce insulate the mains against
earth, in which case SELV could be earthed.

(This also solves the problem of accessible
earthed parts becoming live when used on a
system with no earthing connection.)

But, unfortunately, the requirement remains
that "true SELV" cannot be connected to earth,
and must have basic insulation between it and
earth.


Best regards,
Rich









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Re: EN60950-1 Sect 2.5 Limited Power sources

[Rich Nute]

Hi Alex:


>   We use a linear (basically a transformer with a PTC thermistor) class II
>   SELV O/P stand alone power supply rated 10Vac, 5A. One of the labs tested
>   the O/P Isc with a direct application of the sc. The other lab tested the
>   O/P Isc by applying a load of 8A. The results were therefore interpreted
>   differently.

>   1.  What is the correct method to test for a Limited Power source in
>   determining what enclosure is required?

Limited Power Source is a combination of a number
of criteria:

output voltage;
output current;
output volt-amperes.

These are independent criteria.

Note that Isc is defined as:

"Maximum output current after 60 s of operation with 
 any non-capacitive load, including short-circuit."

Both labs are wrong.

If a power supply shuts down due to a short-circuit, then
it is necessary to determine the maximum current where the
power supply does not shut down.  Typically, this is about
twice rated output.  Since your power supply is rated 5 A,
then I would expect the overpower to take effect at about
10 A output.

When testing a power supply output for LPS, start at rated
load and gradually increase the load.  If the output 
exceeds 8 amps or any other criteria, then the output is
not LPS.

Then, introduce the single, worst-case fault in the
regulating circuit, and repeat the test.  In your case,
this means shorting the PTC, in which case the output will
certainly exceed 8 amperes.

By the way, your output also fails the output volt-amperes
criteria.  If the open-circuit output voltage is 10 volts, 
then the maximum VA is 50, or 5 amps.  

Since one lab only did the output short-circuit test, the
results are not correct.

Since the other lab did a single test at 8 amps, this is
more-or-less okay, but for the wrong reasons. 

Neither lab did the VA test!  The VA test would have proved 
the unit failed at 5 A output.

Neither lab introduced a fault in the regulating network!
(But, the didn't need to since the unit failed under normal
operating conditions.)

Both labs are wrong, but one came up with the correct
determination.  (Of course ONE had to be correct!)  :-)

If you use a PTC, then your output need not necessarily be 
considered "inherently limited."  In this case, your 
maximum output current is 100 amps and your maximum VA is 
250, i.e., 25 amps (with the PTC shorted).  The trick is 
to determine if your test houses can class the PTC as an 
"overcurrent protective device."  

A colleague claims that very few test houses really know
how to do LPS testing.  I concur, and your report confirms
this again.


Best regards,
Rich







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Bluetooth EMC testing

[Robert . Seay]

What specifications apply to Bluetooth EMC testing - not protocol testing. When 
doing EMC testing, is it necessary to establish communications with the 
Bluetooth device?  If so, what test equipment can be used - brand, model. 

Thanks,


Robert Seay
Flextronics Compliance Laboratories
762 Park Avenue
Youngsville, NC 27596
Phone: 919-554-0901
Fax: 919-556-2043
E-Mail: roberts.s...@flextronics.com


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Re: Green/Yellow Earthing Leads

[Rich Nute]

Hi Peter:


>   What is the percentage of color over a surface area for the insulated
>   green/yellow earthing conductor. Is it better to have more yellow than green
>   or more green than yellow. I know North Americans prefer more green than
>   yellow and Europeans like more yellow than green. Any historical reason? I
>   hope it has nothing to do with the Boston Tea Party! Can the group we come
>   up with some compromise?

In North America, the earthing conductor in
building wiring is green.

In Europe, the earthing conductor in building
wiring is yellow.

For power cords and equipment earthing conductors, 
a compromise was agreed to for green/yellow.

Note that in North America, power cord and 
equipment earthing conductors may be green/yellow 
or green.

In Europe, power cord and equipment earthing
conductors may be green/yellow or yellow.


Best regards,
Rich




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Re: SMPS EMC Emissions

[John Woodgate]

I read in !emc-pstc that John Barnes  wrote (in
<3d74d7d8.3...@iglou.com>) about 'SMPS EMC Emissions' on Tue, 3 Sep
2002:
>I've updated the statement to meet the current international standards
>for information technology equipment (ITE), 

Specifically, that EN 61000-3-2 **Class D** needs to be met by PCs and
monitors, I hope.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Interested in professional sound reinforcement and distribution? Then go to 
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

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Re: VCCI

[Hellflower]

Mike et al,

See the exact wording of exempted devices, in particular item (3) as I've 
copied for you below.

Amended: April 1, 2002, 15th Edition
15th Edition applied from: April 1, 2002
[...]
Article 3 (Scope of the Implementation)
These regulations shall apply to the ITE, defined in Article 4, which is 
shipped in Japan.
However, these regulations might not apply to the following types of 
equipment:
(1) ITE that is subject to, or under review of being subject to, other 
standards or laws
equivalent in objective to these regulations in Japan, even if the ITE 
definition in
Article 4 applies. Such ITE includes all radio equipment whose primary 
function is
radio transmission and reception as stipulated in the Radio Law, in-vehicle 
ITE, and
equipment stipulated in the Electric Appliance and Material Control Law, such 
as
household electrical appliances, and radio and television broadcast receivers.
(2) ITE in a telecom center (that is, ITE in buildings controlled by 
telecommunication
carriers).
(3) Control units designed to be used in industrial plants where the data 
processing
function is a secondary purpose.
(4) Testing and measuring instruments designed to be used for industrial, 
scientific, and
medical purposes where the data processing function is a secondary purpose 
(i.e., ISM
equipment).
(5) ITE whose power consumption is 6 nW or less.

http://www.vcci.or.jp/

Best Regards,
Eric Lifsey

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PCI Brackets Problems

[Knighten, Jim L]

Rick,

I have a similar experience with PCI card cage brackets.  This architecture
was never intended for today's  environment.
We have used various gasketing techniques.  Some OEMs now include clips on
the chassis to aid in the electrical seal with the card bracket.
A.K. Stamping has a patent on one add-on gasket (US 5,856,632).
The first problems we found were with ESD testing, not radiated EMI.  Now,
we have seen problems with both.  Even a gasketed PCI card cage is mediocre
as a shielded enclosure.
Regards,
Jim

Jim Knighten, Ph.D.
Teradata, a Division of NCR http://www.ncr.com
 
17095 Via Del Campo
San Diego, CA 92127
USA
Tel: 858-485-2537
Fax: 858-485-3788
jim.knigh...@ncr.com  

-Original Message-
From:   rbus...@es.com   [mailto:rbus...@es.com]
  
Sent:   Friday, August 30, 2002 7:54 AM
To: emc-p...@majordomo.ieee.org  
Subject:PCI Brackets Problems


I am fighting the age old problem of PCI brackets on various PC chassis not
making adequate electrical contact. Aperture leaks, especially at high
frequencies, is a continual problem, to say nothing about the flimsy
construction of the brackets. Has anyone had any success with the clips,
gaskets and other EMI solutions? If you have any suggestions on types, or
manufacturers please let me know.
Thanks in advance...
Rick Busche
Evans & Sutherland
rbus...@es.com  

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Jim Knighten, Ph.D.
Teradata, a Division of NCR http://www.ncr.com
17095 Via Del Campo
San Diego, CA 92127
USA
Tel: 858-485-2537
Fax: 858-485-3788
jim.knigh...@ncr.com


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Re: SMPS EMC Emissions

[Cortland Richmond]

Alex,

Are you speaking of radiation directly from a SMPS on a table? If this is
the case, why, yes, you may, ASK for margin, but you may find few vendors
willing to bid to that requirement. Few ITE makers would warrant their own
boards to meet FCC limits outside a cabinet!  But a SMPS should never be
close to marginally compliant in radiated emission from its power cord and
asking for margin is in such cases (I would say) a smart thing to do. How
much depends on vendor process variability. 

My own experience has been that radiated emissions above 30 MHz
attributable to SMPS were readily shielded -- once the PS was installed in
equipment. It took very little common-mode filtering to attenuate radiation
due to conducted noise once in the box, and the box was well enough
designed to avoid slots and openings. (Granted, that was earlier days, with
switching frequencies of 100 KHz or less.)

I did institute a practice of testing SMPS inside chassis they were
designed to fit, and the reason is rather amusing. A PS we were testing
with resistive load consistently failed conducted emissions. As was our
practice at the time, we were testing with PS and load on a table, into
LISN's installed in a shielded (not anechoic) chamber, thus ensuring we did
not measure ambients. But the vendor was puzzled, as HIS tests showed
everything within limits.  Engineers flew in from Hong Kong and witnessed
the tests. Yes, conducted emissions WERE too high. But efforts to reduce
them were not too successful.

About then I discovered that if we tested OUTSIDE the chamber, these PS's
_passed_. Inside, fail. Outside, pass. The SMPS output wiring was was
exciting resonance in the chamber and coupling onto the IEC power cord,
whence they showed up as conducted emissions to the LISN's.

>From that time forward, we built resistor load boards that fit in place of
a motherboard, and were able to see a MUCH reduced level of conducted
noise. (We also got a good idea how well the fan cooled things.) I do
recommend testing subassemblies in a manner as similar to their intended
use as possible. For one thing, we saved money on each PS that didn't need
design changes. And THAT adds up.

You make note of the effect of the SMPS on emissions it does not generate,
coming from the EUT it powers. This is a bit of a different bird. I believe
in not putting such emissions where a power supply will pass them, but
(depending on your design process) you may have little choice. In this
case, rather than specifying some margin for emissions to the PS maker (who
does not KNOW what you apply to its outputs) why not an attenuation
requirement? How much, may be derived by looking at RF current on the PS
output, with a current clamp, and comparing this to what's seen on the
power cord.

This kind of need is not unique to SMPS's, as many peripheral cards, having
been tested in a "quiet" computer, are offered for sale to a world of
"unquiet" ones. 


Ad Astra per Aspirin!

Cortland

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RE: Telephone Headset

[Chris K. Poore]

The 60950 was the route I was wanting to take since I am more familiar with
that standard.  I feel that I would be meeting the safety requirement of the
directive by applying that, but am also concerned with being as "correct" as
possible. I haven't dealt with the RTTE directive, so the information
concerning the input voltage limits was very helpful.

BTW: The headset is a pair of headphones with a boom mic attached.

Thank you for all your input - it has been VERY helpful.

Chris K. Poore
Staff Compliance Engineer
-
Percept Technology Labs, Inc.
4735 Walnut #E  Boulder, CO 80301
303-444-7480 ext. 113
303-444-1565 Fax
mailto:chr...@percept.com
http://www.percept.com

-Original Message-
From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of John Woodgate
Sent: Saturday, August 31, 2002 12:17 PM
To: emc-p...@majordomo.ieee.org
Subject: Re: Telephone Headset



I read in !emc-pstc that soundsu...@aol.com wrote (in <11c.164cd2d4.2aa2
2...@aol.com>) about 'Telephone Headset' on Sat, 31 Aug 2002:

>I would disagree on this one.  A telephone is covered under EN 60950,
>therefore the logical place for a telephone accessory would be the same
>standard.

Is a headset more like a telephone or more like a pair of headphones
with a boom mic attached?
>
>Actually, this points out the need for the number of technical standards to
>be minimized.   As time goes on, the standards need to be integrated.  It's
>becoming harder and harder to tell audio/video equipment from ITE.   There
is
>less and less justification for maintaining two sets of standards.Just
my
>opinion.

IEC TC108 is currently engaged in combining IEC 60065 and IEC 60950 into
one unified standard. You are allowed to hold your breath, but figure on
holding it for ten years, at the current estimate.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!

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RE: Telephone headsets

[Stone, Richard A (Richard)]

does anyone know about:
RRL a standard/requirement
in south korea?

what equipment must comply to it?
thank you,
Richard,

-Original Message-
From: richwo...@tycoint.com [mailto:richwo...@tycoint.com]
Sent: Friday, August 30, 2002 12:14 PM
To: emc-p...@majordomo.ieee.org
Subject: RE: Telephone headsets



Chris, the CE marking indicates that the product complies with all
applicable directives. The only two directives that might apply is the LV
and EMC directives. However, the LVD does not apply since the working
voltages are low. The EMC directive would apply if your equipment is likely
to cause interference or likely to be susceptable to interference. I tend to
believe that your equipment is not likely to cause interference, but it
might be susceptable to magnetic fields. So some immunity requirements may
apply. If so, your Declaration of Conformity would only claim compliance
with the EMC Directive. If the EMC Directive does not apply, then no
Declaration or CE marking is required.

Richard Woods
Sensormatic Electronics
Tyco International


-Original Message-
From: Chris K. Poore [mailto:chr...@percept.com]
Sent: Friday, August 30, 2002 10:02 AM
To: EMC-PSTC
Subject: Telephone headsets



We have some telephone headsets that we want to CE Mark, but are not sure
what safety standard to use.  Additionally, I don't see any category under
the CE Marking directive that would be entirely applicable.  The LVD seems
most logical, except that the input voltage to the headsets is well below
the 75DC, 50AC cutoff.  The headsets will connect to an OEM audio amplifier
that has been evaluated to the LVD, and seems to contain all the necessary
isolation (we are not even selling the amplifier). The primary reason for
wanting to CE Mark is because a competitor is doing it.

Is there a safety standard that we should use that is specific to these
telephone headsets for EU compliance?

Thanks,

Chris K. Poore
Staff Compliance Engineer
-
Percept Technology Labs, Inc.
4735 Walnut #E  Boulder, CO 80301
303-444-7480 ext. 113
303-444-1565 Fax
mailto:chr...@percept.com
http://www.percept.com


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Re: SMPS EMC Emissions

[John Barnes]

Alex,
When I was developing power supplies at my previous employer, I'd
include a statement like this in our Request For Quotation (RFQ):

"The power supply must meet the following limits with 6dB margin
when supplying power to an 10-ohm resistive load:
*  FCC Class B (USA).
*  CISPR 22-B (Europe).
*  VCCI-B (Japan).

The power supply must meet the following requirements:
*  EN 61000-3-2 Class A.
*  EN 61000-3-3. 
*  EN 61000-4-2 level 4.
*  EN 61000-4-3 level 2.
*  EN 61000-4-4 level 3.
*  EN 61000-4-5 level 3.
*  EN 61000-4-6 level 2.
*  EN 61000-4-8 level 1.
*  EN 61000-4-11."

I've updated the statement to meet the current international standards
for information technology equipment (ITE), but it is based on an RFQ
for a power supply that we used on at least three products.

The resistive loads were chosen to set each output to its maximum rated
continuous load at its nominal output voltage.

My previous employer also specified higher levels for EN 61000-4-2 and
EN 61000-4-4 than required for the CE Mark, as a matter of company
policy.  The southwest United States, for example, tends to be much
drier than Europe, so a higher electrostatic discharge immunity
requirement reduces field problems there.

John Barnes  KS4GL
dBi Corporation
http://www.dbicorporation.com/

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Re: Green/Yellow Earthing Leads

[Don_Borowski]

In North America, the earthing conductor is described as a green wire with a
yellow stripe, while in Europe it is described as a yellow wire with a green
stripe. Fortunately, there is enough tolerance in the specifications on both
sides of the pond that a single solution works in both locations.

Don Borowski
Schweitzer Engineering Labs
Pullman, Washington





Peter Merguerian  on 09/02/2002 08:21:04 AM

Please respond to Peter Merguerian 

To:   "\"EMC-PSTC (E-mail)\" <" 
cc:(bcc: Don Borowski/SEL)
Subject:  Green/Yellow Earthing Leads




Dear Group,

What is the percentage of color over a surface area for the insulated
green/yellow earthing conductor. Is it better to have more yellow than green
or more green than yellow. I know North Americans prefer more green than
yellow and Europeans like more yellow than green. Any historical reason? I
hope it has nothing to do with the Boston Tea Party! Can the group we come
up with some compromise?

BTW IEC 60 204 standard for electrical equipment for machinery states "the
bicolour combination GREEN-AND-YELOW shall be such that on any 15mm length
one of the colours covers at least 30% and not more than 70% of the surface
of the conductor, tje other colour covering the remainder of the surface".


This e-mail message may contain privileged or confidential information. If
you are not the intended recipient, you may not disclose, use, disseminate,
distribute, copy or rely upon this message or attachment in any way. If you
received this e-mail message in error, please return by forwarding the
message and its attachments to the sender.



PETER S. MERGUERIAN
Technical Director
I.T.L. (Product Testing) Ltd.
26 Hacharoshet St., POB 211
Or Yehuda 60251, Israel
Tel: + 972-(0)3-5339022  Fax: + 972-(0)3-5339019
Mobile: + 972-(0)54-838175
http://www.itl.co.il
http://www.i-spec.com





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VCCI

[Mike Cantwell]

I notice in all of the VCCI documents, that it only refers to ITE. Any
opinions on whether or not it applies to ISM equipment that is operated
through an industrial PC? This would definitely be a Class A device.

Thanks,
Mike



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RE: PFC or Harmonic Current Limitations outside Europe

[Joshua Wiseman]

Tom,

As I understand it, if you are a member of JEITA then it is a requirement.

Regards,
Josh

Josh Wiseman
EMC/Product Safety
(714) 368-2737
[mailto:jwise...@printronix.com]


-Original Message-
From: T.Sato [mailto:vef00...@nifty.ne.jp]
Sent: Friday, August 30, 2002 10:06 PM
To: emc-p...@majordomo.ieee.org
Subject: RE: PFC or Harmonic Current Limitations outside Europe



On Fri, 30 Aug 2002 12:36:50 -0700,
  Jim Eichner  wrote:

> Joshua:  Re Japan, I didn't have much luck on the JEITA website.  Can you
> give me a specific reference (standard name/number, URL, etc.)?  Also, is
> there a list of what types of products this requirement applies to?

http://home.jeita.or.jp/eps/harmonics/guideline/data/guideline_eng.pdf

It is a "guideline" issued by Ministry of Economy, Trade and Industry,
and I think it can be applied to almost any products if you want.

Regards,
Tom

--
Tomonori Sato  
URL: http://member.nifty.ne.jp/tsato/

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RE: SMPS EMC Emissions

[Brian O'Connell]

CONFLICT OF INTEREST ALERT: 
   My employer makes SMPS.

For both conducted emissions, an unit with PFC typically makes life easier.
For reduced radiated emissions, avoid the open "U" chassis units. Please
note that as customers demand greater efficiencies and reduced sizes, you
will see much higher main converter frequencies.

In any case, a supplier that (assuming your test technique is consistent)
produces units with a wide variance in emissions characteristics may be
indicative of poor design and/or no quality control.

Brian



-Original Message-
From: Jim Conrad [mailto:jc...@shore.net]
Sent: Tuesday, September 03, 2002 3:55 AM
To: Alex McNeil; emc-p...@majordomo.ieee.org
Subject: RE: SMPS EMC Emissions



Alex wrote:

"Do you think it is reasonable to specify in my power supply
specification
that the manufacturers SMPS should meet EN55022 Class B -6dB"

Yes.  I would ask for 6 dB margin since measurement uncertainty for
a typical conducted measurements system is 5.4 dB.   You must also
allow for unit to unit variations in manufacturing.  Sample 5 units
and apply the 80/80 rule and see if they still pass.

Jim

-Original Message-
From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Alex McNeil
Sent: Tuesday, September 03, 2002 4:57 AM
To: 'emc-p...@majordomo.ieee.org'
Subject: SMPS EMC Emissions


Hi Group,

First of all thank you to those who replied to my previous email. I
have not
had time to reply personally...yet.

I have noticed that the broadband noise of some SMPS are already
near to the
limits of EN55022 Class B (I tested with a max resistive load). This
gives
my product little scope for emissions at these broadband
frequencies,
especialy when my product is taking peak load e.g. printing.

The power supply manufacturer rightly claims that his product does
meet
EN55022 Class B.

Do you think it is reasonable to specify in my power supply
specification
that the manufacturers SMPS should meet EN55022 Class B -6dB or?
Have any of you come across a similar scenario?

As usual , I look forward to your professional opinions.

Kind Regards
Alex McNeil
Principal Engineer
Tel: +44 (0)131 479 8375
Fax: +44 (0)131 479 8321
email: alex.mcn...@ingenicofortronic.com


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[no subject]

[Raymond . Garner]

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RE: Green/Yellow Earthing Leads

[ron_wellman]

Hello Peter,

IEC 60173: Colors of the cores of flexible cables and cords, is still active 
and provides a coloring scheme for earthing conductors that is referenced in 
many other IEC standards like 60204.  

Regards,
+=+
|Ronald R. Wellman|Voice : 408-345-8229   |
|Agilent Technologies |FAX   : 408-553-2412   |
|5301 Stevens Creek Blvd.,|E-Mail: ron_well...@agilent.com|
|Mailstop 54L-BB  |WWW   : http://www.agilent.com |
|Santa Clara, California 95052 USA|   |
+=+


-Original Message-
From: Peter Merguerian [mailto:pmerguer...@itl.co.il]
Sent: Monday, September 02, 2002 8:21 AM
To: "EMC-PSTC (E-mail)" <
Subject: Green/Yellow Earthing Leads



Dear Group,

What is the percentage of color over a surface area for the insulated
green/yellow earthing conductor. Is it better to have more yellow than green
or more green than yellow. I know North Americans prefer more green than
yellow and Europeans like more yellow than green. Any historical reason? I
hope it has nothing to do with the Boston Tea Party! Can the group we come
up with some compromise?

BTW IEC 60 204 standard for electrical equipment for machinery states "the
bicolour combination GREEN-AND-YELOW shall be such that on any 15mm length
one of the colours covers at least 30% and not more than 70% of the surface
of the conductor, tje other colour covering the remainder of the surface".


This e-mail message may contain privileged or confidential information. If
you are not the intended recipient, you may not disclose, use, disseminate,
distribute, copy or rely upon this message or attachment in any way. If you
received this e-mail message in error, please return by forwarding the
message and its attachments to the sender.



PETER S. MERGUERIAN
Technical Director
I.T.L. (Product Testing) Ltd.
26 Hacharoshet St., POB 211
Or Yehuda 60251, Israel
Tel: + 972-(0)3-5339022  Fax: + 972-(0)3-5339019
Mobile: + 972-(0)54-838175
http://www.itl.co.il
http://www.i-spec.com





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Re: Consideration for blind end users ...

[mm]

>Consideration for blind end users ...
>
>Just a curiosity question which came up in a
>discussion with a sightless person elsewhere ...

>Q:  How well do you think the safety standards
>cover product use by sightless end users?

>Regards, Doug McKean

Doug,

Looks like things are (just?) getting underway.
Check out:
http://acceso2.uv.es/aenor/indexeng.htm

Were you will find (among other things):

- Draft ISO/IEC Guide 71- Guidelines for standardization to address the needs 
of older persons and people with disabilities (PDF format, 240KB)


Matt


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SMPS EMC Emissions

[Alex McNeil]

Forum addendum
I think I need to make it clearer that my main concern was for radiated
emissions

ps
Hi Jim,
Thanks for your reply

Kind Regards
Alex McNeil
Principal Engineer
Tel: +44 (0)131 479 8375
Fax: +44 (0)131 479 8321
email: alex.mcn...@ingenicofortronic.com

 -Original Message-
From:   Jim Conrad [mailto:jc...@shore.net] 
Sent:   Tuesday, September 03, 2002 11:55 AM
To: Alex McNeil; emc-p...@majordomo.ieee.org
Subject:RE: SMPS EMC Emissions

Alex wrote:

"Do you think it is reasonable to specify in my power supply
specification
that the manufacturers SMPS should meet EN55022 Class B -6dB"

Yes.  I would ask for 6 dB margin since measurement uncertainty for
a typical conducted measurements system is 5.4 dB.   You must also
allow for unit to unit variations in manufacturing.  Sample 5 units
and apply the 80/80 rule and see if they still pass.

Jim

-Original Message-
From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Alex McNeil
Sent: Tuesday, September 03, 2002 4:57 AM
To: 'emc-p...@majordomo.ieee.org'
Subject: SMPS EMC Emissions


Hi Group,

First of all thank you to those who replied to my previous email. I
have not
had time to reply personally...yet.

I have noticed that the broadband noise of some SMPS are already
near to the
limits of EN55022 Class B (I tested with a max resistive load). This
gives
my product little scope for emissions at these broadband
frequencies,
especialy when my product is taking peak load e.g. printing.

The power supply manufacturer rightly claims that his product does
meet
EN55022 Class B.

Do you think it is reasonable to specify in my power supply
specification
that the manufacturers SMPS should meet EN55022 Class B -6dB or?
Have any of you come across a similar scenario?

As usual , I look forward to your professional opinions.

Kind Regards
Alex McNeil
Principal Engineer
Tel: +44 (0)131 479 8375
Fax: +44 (0)131 479 8321
email: alex.mcn...@ingenicofortronic.com


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RE: SMPS EMC Emissions

[Jim Conrad]

Alex wrote:

"Do you think it is reasonable to specify in my power supply
specification
that the manufacturers SMPS should meet EN55022 Class B -6dB"

Yes.  I would ask for 6 dB margin since measurement uncertainty for
a typical conducted measurements system is 5.4 dB.   You must also
allow for unit to unit variations in manufacturing.  Sample 5 units
and apply the 80/80 rule and see if they still pass.

Jim

-Original Message-
From: owner-emc-p...@majordomo.ieee.org
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of Alex McNeil
Sent: Tuesday, September 03, 2002 4:57 AM
To: 'emc-p...@majordomo.ieee.org'
Subject: SMPS EMC Emissions


Hi Group,

First of all thank you to those who replied to my previous email. I
have not
had time to reply personally...yet.

I have noticed that the broadband noise of some SMPS are already
near to the
limits of EN55022 Class B (I tested with a max resistive load). This
gives
my product little scope for emissions at these broadband
frequencies,
especialy when my product is taking peak load e.g. printing.

The power supply manufacturer rightly claims that his product does
meet
EN55022 Class B.

Do you think it is reasonable to specify in my power supply
specification
that the manufacturers SMPS should meet EN55022 Class B -6dB or?
Have any of you come across a similar scenario?

As usual , I look forward to your professional opinions.

Kind Regards
Alex McNeil
Principal Engineer
Tel: +44 (0)131 479 8375
Fax: +44 (0)131 479 8321
email: alex.mcn...@ingenicofortronic.com


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SMPS EMC Emissions

[Alex McNeil]

Hi Group,

First of all thank you to those who replied to my previous email. I have not
had time to reply personally...yet. 

I have noticed that the broadband noise of some SMPS are already near to the
limits of EN55022 Class B (I tested with a max resistive load). This gives
my product little scope for emissions at these broadband frequencies,
especialy when my product is taking peak load e.g. printing.

The power supply manufacturer rightly claims that his product does meet
EN55022 Class B.

Do you think it is reasonable to specify in my power supply specification
that the manufacturers SMPS should meet EN55022 Class B -6dB or?
Have any of you come across a similar scenario?

As usual , I look forward to your professional opinions.

Kind Regards
Alex McNeil
Principal Engineer
Tel: +44 (0)131 479 8375
Fax: +44 (0)131 479 8321
email: alex.mcn...@ingenicofortronic.com


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