Re: [PSES] God EMC practice

[Jim Bacher]

What I have always set as a target is 6 dB better than spec on prototype /
first units tested, then 3 dB better on production audits.

That may no longer be good enough. The reason is a lot of products now have
radio receivers in them as in Bluetooth, wifi, NFC, and RFID. If your
unintentionally radiation is at the same frequency range as your receiver,
your radio performance will be degraded even if you are 6 dB down from the
limit.

Another thing to consider is that the rf noise floor is increasing. One
solution to help minimize the increasing floor is to lower the
unintentionally radiation requirements. So it could be in another 10 years
the limits might become 10 dB more strict.

Learn from the EMC experts, a number of which are on this list, and your
products will easily meet the margins I suggested.


Jim Bacher, JB Consulting
Product Regulatory Compliance Consultant
https://trc.guru/
IEEE Life Senior Member j.bac...@ieee.org

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Re: [PSES] God EMC practice

[John Woodgate]

CISPR standards mostly require a search for worst-case, but give examples of
acceptable placement.
 
With best wishes DESIGN IT IN! OOO - Own Opinions Only
 <http://www.jmwa.demon.co.uk/> www.jmwa.demon.co.uk J M Woodgate and
Associates Rayleigh England
 
Beware averages! They hide or discard data, and may distort it (them?).
 
From: Cortland Richmond [mailto:k...@earthlink.net] 
Sent: Saturday, September 2, 2017 10:53 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] God EMC practice
 
In ancient times, the FCC required we perform RE testsby manipulating
peripheral and cable placement to maximize emissions; our tech at Tandy was
fiendishly clever, but we had to draw the line short of wrapping cables
around the (CRT) monitor.

Lots of stories...

Cortland Richmond
 
On 9/1/2017 8:10 PM, Brent DeWitt wrote:
I agree with Jim that your calculated measurement uncertainty is the minimum
margin that one should apply.  This could be doubled by assuming the second
assessing laboratory had the same uncertainty, but in the opposite
direction!  In practice, I believe that the products cabling, and therefore
the setup uncertainty, may become dominant.  When I perform radiated
emissions measurements on a product with multiple cables, I observe a wide
span of potentially "interesting" emissions on the SA/receiver, then grab
the entire bundle of cables and simply toss them randomly.  If things wiggle
by a couple of dB, I move on.  If things swing by ten dB, I've got my work
cut out for me to maximize and I advise the customer to take a much more
generous approach to their margin requirements.
 
Brent G DeWitt
Milford, MA
 
 
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Re: [PSES] God EMC practice

[Cortland Richmond]

In ancient times, the FCC required we perform RE testsby manipulating 
peripheral and cable placement to maximize emissions; our tech at Tandy 
was fiendishly clever, but we had to draw the line short of wrapping 
cables around the (CRT) monitor.


Lots of stories...

Cortland Richmond


On 9/1/2017 8:10 PM, Brent DeWitt wrote:


I agree with Jim that your calculated measurement uncertainty is the 
minimum margin that one should apply.  This could be doubled by 
assuming the second assessing laboratory had the same uncertainty, but 
in the opposite direction!  In practice, I believe that the products 
cabling, and therefore the setup uncertainty, may become dominant. 
 When I perform radiated emissions measurements on a product with 
multiple cables, I observe a wide span of potentially “interesting” 
emissions on the SA/receiver, then grab the entire bundle of cables 
and simply toss them randomly.  If things wiggle by a couple of dB, I 
move on.  If things swing by ten dB, I’ve got my work cut out for me 
to maximize and I advise the customer to take a much more generous 
approach to their margin requirements.


Brent G DeWitt
Milford, MA





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Re: [PSES] God EMC practice

[Brent DeWitt]

I agree with Jim that your calculated measurement uncertainty is the minimum
margin that one should apply.  This could be doubled by assuming the second
assessing laboratory had the same uncertainty, but in the opposite
direction!  In practice, I believe that the products cabling, and therefore
the setup uncertainty, may become dominant.  When I perform radiated
emissions measurements on a product with multiple cables, I observe a wide
span of potentially "interesting" emissions on the SA/receiver, then grab
the entire bundle of cables and simply toss them randomly.  If things wiggle
by a couple of dB, I move on.  If things swing by ten dB, I've got my work
cut out for me to maximize and I advise the customer to take a much more
generous approach to their margin requirements.

 

Brent G DeWitt
Milford, MA

 

 

 

From: Knighten, Jim L [mailto:jim.knigh...@teradata.com] 
Sent: Friday, September 01, 2017 12:05 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] God EMC practice

 

A good practice is to use your calculated measurement uncertainty for
emissions as your minimum margin requirement.

That will often put you in the 3-4 dB range.

 

Jim

 



James L. Knighten, Ph.D.

Teradata

17095 Via Del Campo

San Diego, CA 92127

858-485-2537

 

From: Kim Boll Jensen [mailto:k...@bolls.dk] 
Sent: Friday, September 01, 2017 6:01 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> 
Subject: [PSES] God EMC practice

 

Hi

 

One of our customers want to know if there are some good practice for
emission compliance. I normally recommend 3 dB margin, but I don't have any
reference to why this is OK.

 

I know that some companies have internal rules for 3 or even 6 dB margin to
compensate for production deviations and for many years ago VDE did have
some rules like that.

 

Does anyone have some good references on this subject?

 

Best regards,

 

Mr. Kim Boll Jensen

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Re: [PSES] God EMC practice

[John Woodgate]

This sounds like more 'by guess and by god'. It's like saying the speed limit 
is 30, but it's actually 25. 
 
With best wishes John Woodgate
3 Bramfield Road East, RAYLEIGH Essex SS6 8RG UK OOO – Own Opinions Only
 <http://www.jmwa.demon.co.uk/> www.jmwa.demon.co.uk J M Woodgate and 
Associates 
 
Beware averages! They hide or discard data, and may distort it (them?).
 
 
From: Schaefer, David [mailto:dschae...@tuvam.com] 
Sent: Friday, September 1, 2017 4:36 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] God EMC practice
 
The vehicle area is different as well. Standards like EN ISO 14982 and ISO 
13766 have limits, then add 25% for immunity, or subtract 2 dB for emissions. 
That is intended to account for doing type testing. Whether that’s a valid 
method is up for debate. 
 
E-marking also has a requirement for Conformity of Production. Manufacturers 
must ensure that their products are still under the limit(with a 4 dB 
relaxation), or not susceptible. That is usually interpreted as testing a 
production sample every 2-3 years.
 
 
David Schaefer
EMC Chief Technical Advisor
TÜV SÜD America Inc
Office: 651 638 0251
Cell: 612 578 6038
Fax: 651 638 0285
 
 
From: Patrick [mailto:conwa...@gmail.com] 
Sent: Friday, September 01, 2017 10:21 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> 
Subject: Re: [PSES] God EMC practice
 
God and Compliance Margin...  two topics that generate a lot of preaching!  
I think everyone has a "tradition" of what worked for them, and what did 
not.
 
Here is my sermon on margin:
 
I don't consider myself a monk of the EMI Chamber... 
...but over the years I have preached various margins.
...margins are always situational, always depending on the business, and 
the products.
...call it relativism?
 
 
On one end of the extreme, I've been in the aerospace industry.
Here, a single unit is built, and flown successfully, with *zero dB* of 
margin.  
 
On the other end, consumer products.
Here, just one or two units comply during development.
Then the factory produces a million units a month for a year.
Yes, that is 12 million units based on a couple of passing samples!
In this industry, initial margin can not predict performance of the 
500,00th unit.
So, the industry performs on-going EMC audits.
 
 
In both those cases, the dogma of margin was irrelevant.  
For aerospace, what mattered was coexistence.  
For commercial, it required an ongoing liturgy of audits.  
 
 
What really drives margin is the product, the market, and the target usage.
Everything else is just "tradition" & "hearsay".
Every company needs enlightened margin decisions based on their own 
circumstances.
 
 
 
Thanks for the bit of humor to end the week!
 
-Patrick
 
On Fri, Sep 1, 2017 at 7:01 AM, Kim Boll Jensen mailto:k...@bolls.dk> > wrote:
Hi
 
One of our customers want to know if there are some good practice for emission 
compliance. I normally recommend 3 dB margin, but I don't have any reference to 
why this is OK.
 
I know that some companies have internal rules for 3 or even 6 dB margin to 
compensate for production deviations and for many years ago VDE did have some 
rules like that.
 
Does anyone have some good references on this subject?
 
Best regards,
 
Mr. Kim Boll Jensen
-

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-- 
//
Patrick
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Re: [PSES] God EMC practice

[Schaefer, David]

The vehicle area is different as well. Standards like EN ISO 14982 and ISO 
13766 have limits, then add 25% for immunity, or subtract 2 dB for emissions. 
That is intended to account for doing type testing. Whether that’s a valid 
method is up for debate.

E-marking also has a requirement for Conformity of Production. Manufacturers 
must ensure that their products are still under the limit(with a 4 dB 
relaxation), or not susceptible. That is usually interpreted as testing a 
production sample every 2-3 years.


David Schaefer
EMC Chief Technical Advisor
TÜV SÜD America Inc
Office: 651 638 0251
Cell: 612 578 6038
Fax: 651 638 0285


From: Patrick [mailto:conwa...@gmail.com]
Sent: Friday, September 01, 2017 10:21 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] God EMC practice

God and Compliance Margin...  two topics that generate a lot of preaching!
I think everyone has a "tradition" of what worked for them, and what did 
not.

Here is my sermon on margin:

I don't consider myself a monk of the EMI Chamber...
...but over the years I have preached various margins.
...margins are always situational, always depending on the business, and 
the products.
...call it relativism?


On one end of the extreme, I've been in the aerospace industry.
Here, a single unit is built, and flown successfully, with *zero dB* of 
margin.

On the other end, consumer products.
Here, just one or two units comply during development.
Then the factory produces a million units a month for a year.
Yes, that is 12 million units based on a couple of passing samples!
In this industry, initial margin can not predict performance of the 
500,00th unit.
So, the industry performs on-going EMC audits.


In both those cases, the dogma of margin was irrelevant.
For aerospace, what mattered was coexistence.
For commercial, it required an ongoing liturgy of audits.


What really drives margin is the product, the market, and the target usage.
Everything else is just "tradition" & "hearsay".
Every company needs enlightened margin decisions based on their own 
circumstances.



Thanks for the bit of humor to end the week!

-Patrick

On Fri, Sep 1, 2017 at 7:01 AM, Kim Boll Jensen 
mailto:k...@bolls.dk>> wrote:
Hi

One of our customers want to know if there are some good practice for emission 
compliance. I normally recommend 3 dB margin, but I don't have any reference to 
why this is OK.

I know that some companies have internal rules for 3 or even 6 dB margin to 
compensate for production deviations and for many years ago VDE did have some 
rules like that.

Does anyone have some good references on this subject?

Best regards,

Mr. Kim Boll Jensen
-


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Jim Bacher <j.bac...@ieee.org<mailto:j.bac...@ieee.org>>
David Heald <dhe...@gmail.com<mailto:dhe...@gmail.com>>



--
//
Patrick
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-
--

Re: [PSES] God EMC practice

[John Woodgate]

If you are manufacturing in Europe, or selling products in Europe, you have
to do all those things if you want a quiet life.
 
With best wishes John Woodgate
3 Bramfield Road East, RAYLEIGH Essex SS6 8RG UK OOO - Own Opinions Only
 <http://www.jmwa.demon.co.uk/> www.jmwa.demon.co.uk J M Woodgate and
Associates 
 
Beware averages! They hide or discard data, and may distort it (them?).
 
 
From: Ted Eckert [mailto:07cf6ebeab9d-dmarc-requ...@ieee.org] 
Sent: Friday, September 1, 2017 4:10 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] God EMC practice
 
First, you can find a lengthy discussion from 10 years ago in the archive of
this list server.
 <https://www.mail-archive.com/emc-pstc@listserv.ieee.org/msg42809.html>
https://www.mail-archive.com/emc-pstc@listserv.ieee.org/msg42809.html
 
Second, Jim Bacher gave a presentation on this subject at the 2016
International Symposium on Product Compliance Engineering (ISPCE). It wasn't
presented as a formal paper, so there isn't a paper available through the
IEEE system. Jim's presentation only gave a few topics and he used the time
for a discussion with the audience, but I can provide some of the topics for
consideration.
 
What is the uncertainty of measurement for your setup? Is your spectrum
analyzer accurate to within 2 dB, 1 dB or something better? What about your
preamplifier, cables and other equipment? How far below the limit do you
need to measure to know that you pass based on the accuracy of your
equipment?
 
How well do you understand test site variations? We generally accept +/- 4
dB variation. Antenna patterns vary and the laboratory staff have differing
skills at finding the placement of cables and other items that maximize the
signal.
 
How stable are your products in manufacturing? Are there variations that
could affect emissions? How sensitive are emissions to cable routing within
the equipment? Do you have an EMC engineer signing off on all engineering
changes? 
 
Are you getting updates on part changes from all your suppliers? What
happens if an IC manufacturer does a die shrink or otherwise changes the die
in a way that maintains the performance of the IC within its specification
but sharpens the edge rates of transitions? 
 
Do you routinely test production? If so, you may know what type of variation
to expect based on your testing and processes. This would allow you to
determine the margin that is acceptable based on your specific products and
processes. Otherwise, you may want more margin to ensure that market
surveillance authorities won't get a measurement over the limit if they
audit one of your products.
 
Ted Eckert
Microsoft Corporation
 
The opinions expressed are my own and do not necessarily reflect those of my
employer.
 
From: Kim Boll Jensen [mailto:k...@bolls.dk] 
Sent: Friday, September 1, 2017 6:01 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> 
Subject: [PSES] God EMC practice
 
Hi
 
One of our customers want to know if there are some good practice for
emission compliance. I normally recommend 3 dB margin, but I don't have any
reference to why this is OK.
 
I know that some companies have internal rules for 3 or even 6 dB margin to
compensate for production deviations and for many years ago VDE did have
some rules like that.
 
Does anyone have some good references on this subject?
 
Best regards,
 
Mr. Kim Boll Jensen
-

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Re: [PSES] God EMC practice

[Pete Perkins]

Ted et al,

 

Thank you for the treatise on present EMC practice.  

 

If the reader wants a treatise on God you must go to a much
older archive - a few thousand years older; in case anyone wanted to know. 

 

:>) br,  Pete

 

Peter E Perkins, PE

Principal Product Safety & Regulatory Affairs Consultant

PO Box 23427

Tigard, ORe  97281-3427

 

503/452-1201

 

 <mailto:p.perk...@ieee.org> p.perk...@ieee.org

 

From: Ted Eckert [mailto:07cf6ebeab9d-dmarc-requ...@ieee.org] 
Sent: Friday, September 1, 2017 8:10 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] God EMC practice

 

First, you can find a lengthy discussion from 10 years ago in the archive of
this list server.

 <https://www.mail-archive.com/emc-pstc@listserv.ieee.org/msg42809.html>
https://www.mail-archive.com/emc-pstc@listserv.ieee.org/msg42809.html

 

Second, Jim Bacher gave a presentation on this subject at the 2016
International Symposium on Product Compliance Engineering (ISPCE). It wasn't
presented as a formal paper, so there isn't a paper available through the
IEEE system. Jim's presentation only gave a few topics and he used the time
for a discussion with the audience, but I can provide some of the topics for
consideration.

 

What is the uncertainty of measurement for your setup? Is your spectrum
analyzer accurate to within 2 dB, 1 dB or something better? What about your
preamplifier, cables and other equipment? How far below the limit do you
need to measure to know that you pass based on the accuracy of your
equipment?

 

How well do you understand test site variations? We generally accept +/- 4
dB variation. Antenna patterns vary and the laboratory staff have differing
skills at finding the placement of cables and other items that maximize the
signal.

 

How stable are your products in manufacturing? Are there variations that
could affect emissions? How sensitive are emissions to cable routing within
the equipment? Do you have an EMC engineer signing off on all engineering
changes? 

 

Are you getting updates on part changes from all your suppliers? What
happens if an IC manufacturer does a die shrink or otherwise changes the die
in a way that maintains the performance of the IC within its specification
but sharpens the edge rates of transitions? 

 

Do you routinely test production? If so, you may know what type of variation
to expect based on your testing and processes. This would allow you to
determine the margin that is acceptable based on your specific products and
processes. Otherwise, you may want more margin to ensure that market
surveillance authorities won't get a measurement over the limit if they
audit one of your products.

 

Ted Eckert

Microsoft Corporation

 

The opinions expressed are my own and do not necessarily reflect those of my
employer.

 

From: Kim Boll Jensen [mailto:k...@bolls.dk] 
Sent: Friday, September 1, 2017 6:01 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> 
Subject: [PSES] God EMC practice

 

Hi

 

One of our customers want to know if there are some good practice for
emission compliance. I normally recommend 3 dB margin, but I don't have any
reference to why this is OK.

 

I know that some companies have internal rules for 3 or even 6 dB margin to
compensate for production deviations and for many years ago VDE did have
some rules like that.

 

Does anyone have some good references on this subject?

 

Best regards,

 

Mr. Kim Boll Jensen

-


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Re: [PSES] God EMC practice

[Patrick]

the 80/80 rule is just the dogma of mathematics. (excuse the religious
overtone...)

here is a real-world story
if a customer buys 1000 laptop computers (or set top boxes, or cell phones,
or whatever ...), and they have an ESD problem, does the 80/80 calculation
prevent them from returning all 1000 units, and buying from a competitor
instead?  All the customer cares about is the one, or the one thousand,
that they purchase.


The 80/80 rule might keep you out of court, but it will never save your
business.

My opinion only

-Patrick

On Fri, Sep 1, 2017 at 10:30 AM, Douglas Smith  wrote:

> How would you relate the tolerance of placement of system components like
> cables or PCs (in cm) to measurement uncertainty? Just setting up for the
> next test can make a few dB difference. In a large system, it may even
> affect antenna placement in the chamber to get the right distance to the
> EUT.
>
> Separately, in ESD testing, the poor specification of the simulator in
> standards, like IEC 61000-4-2, leads to uncertainty (that one cannot
> calculate) that far exceeds any uncertainty calculation one could make on
> ESD testing. Until we fix the standards, uncertainty calculation for ESD
> testing is meaningless. What is needed is a maximum di/dt limit everywhere
> on the current waveform and a radiation spec on the simulator. And this is
> only for contact discharge. For air discharge, the large uncertainty of the
> discharge itself will likely dominate unless hundreds of discharges are
> used at each point to reach statistical significance.
>
> Doug Smith
> Sent from my iPhone
> IPhone:  408-858-4528 <(408)%20858-4528>
> Office:702-570-6108 <(702)%20570-6108>
> Email: d...@dsmith.org
> Website: http://dsmith.org
>
> On Fri, Sep 1, 2017 at 9:05, Knighten, Jim L 
> wrote:
>
> A good practice is to use your calculated measurement uncertainty for
> emissions as your minimum margin requirement.
>
> That will often put you in the 3-4 dB range.
>
>
>
> Jim
>
>
>
> 
>
> James L. Knighten, Ph.D.
>
> Teradata
>
> 17095 Via Del Campo
>
> San Diego, CA 92127
>
> 858-485-2537 <(858)%20485-2537>
>
>
>
> *From:* Kim Boll Jensen [mailto:k...@bolls.dk]
> *Sent:* Friday, September 01, 2017 6:01 AM
> *To:* EMC-PSTC@LISTSERV.IEEE.ORG
> *Subject:* [PSES] God EMC practice
>
>
>
> Hi
>
>
>
> One of our customers want to know if there are some good practice for
> emission compliance. I normally recommend 3 dB margin, but I don't have any
> reference to why this is OK.
>
>
>
> I know that some companies have internal rules for 3 or even 6 dB margin
> to compensate for production deviations and for many years ago VDE did have
> some rules like that.
>
>
>
> Does anyone have some good references on this subject?
>
>
>
> Best regards,
>
>
>
> Mr. Kim Boll Jensen
>
> -
> 
>
> This message is from the IEEE Product Safety Engineering Society emc-pstc
> discussion list. To post a message to the list, send your e-mail to <
> emc-p...@ieee.org>
>
> All emc-pstc postings are archived and searchable on the web at:
> http://www.ieee-pses.org/emc-pstc.html
>
> Attachments are not permitted but the IEEE PSES Online Communities site at
> http://product-compliance.oc.ieee.org/ can be used for graphics (in
> well-used formats), large files, etc.
>
> Website: http://www.ieee-pses.org/
> Instructions: http://www.ieee-pses.org/list.html (including how to
> unsubscribe) <http://www.ieee-pses.org/list.html>
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>
> For help, send mail to the list administrators:
> Scott Douglas 
> Mike Cantwell 
>
> For policy questions, send mail to:
> Jim Bacher 
> David Heald 
> -
> 
>
> This message is from the IEEE Product Safety Engineering Society emc-pstc
> discussion list. To post a message to the list, send your e-mail to <
> emc-p...@ieee.org>
>
> All emc-pstc postings are archived and searchable on the web at:
> http://www.ieee-pses.org/emc-pstc.html
>
> Attachments are not permitted but the IEEE PSES Online Communities site at
> http://product-compliance.oc.ieee.org/ can be used for graphics (in
> well-used formats), large files, etc.
>
> Website: http://www.ieee-pses.org/
> Instructions: http://www.ieee-pses.org/list.html (including how to
> unsubscribe) <http://www.ieee-pses.org/list.html>
> List rules: http://www.ieee-pses.org/listrules.html
>
> For help, send mail to the list administrators:
> Scott Douglas 

Re: [PSES] God EMC practice

[Ted Eckert]

First, you can find a lengthy discussion from 10 years ago in the archive of 
this list server.
https://www.mail-archive.com/emc-pstc@listserv.ieee.org/msg42809.html

Second, Jim Bacher gave a presentation on this subject at the 2016 
International Symposium on Product Compliance Engineering (ISPCE). It wasn't 
presented as a formal paper, so there isn't a paper available through the IEEE 
system. Jim's presentation only gave a few topics and he used the time for a 
discussion with the audience, but I can provide some of the topics for 
consideration.

What is the uncertainty of measurement for your setup? Is your spectrum 
analyzer accurate to within 2 dB, 1 dB or something better? What about your 
preamplifier, cables and other equipment? How far below the limit do you need 
to measure to know that you pass based on the accuracy of your equipment?

How well do you understand test site variations? We generally accept +/- 4 dB 
variation. Antenna patterns vary and the laboratory staff have differing skills 
at finding the placement of cables and other items that maximize the signal.

How stable are your products in manufacturing? Are there variations that could 
affect emissions? How sensitive are emissions to cable routing within the 
equipment? Do you have an EMC engineer signing off on all engineering changes?

Are you getting updates on part changes from all your suppliers? What happens 
if an IC manufacturer does a die shrink or otherwise changes the die in a way 
that maintains the performance of the IC within its specification but sharpens 
the edge rates of transitions?

Do you routinely test production? If so, you may know what type of variation to 
expect based on your testing and processes. This would allow you to determine 
the margin that is acceptable based on your specific products and processes. 
Otherwise, you may want more margin to ensure that market surveillance 
authorities won't get a measurement over the limit if they audit one of your 
products.

Ted Eckert
Microsoft Corporation

The opinions expressed are my own and do not necessarily reflect those of my 
employer.

From: Kim Boll Jensen [mailto:k...@bolls.dk]
Sent: Friday, September 1, 2017 6:01 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] God EMC practice

Hi

One of our customers want to know if there are some good practice for emission 
compliance. I normally recommend 3 dB margin, but I don't have any reference to 
why this is OK.

I know that some companies have internal rules for 3 or even 6 dB margin to 
compensate for production deviations and for many years ago VDE did have some 
rules like that.

Does anyone have some good references on this subject?

Best regards,

Mr. Kim Boll Jensen
-


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discussion list. To post a message to the list, send your e-mail to 
mailto:emc-p...@ieee.org>>

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Re: [PSES] God EMC practice

[Douglas Smith]

How would you relate the tolerance of placement of system components like 
cables or PCs (in cm) to measurement uncertainty? Just setting up for the 
next test can make a few dB difference. In a large system, it may even 
affect antenna placement in the chamber to get the right distance to the 
EUT.
Separately, in ESD testing, the poor specification of the simulator in 
standards, like IEC 61000-4-2, leads to uncertainty (that one cannot 
calculate) that far exceeds any uncertainty calculation one could make on 
ESD testing. Until we fix the standards, uncertainty calculation for ESD 
testing is meaningless. What is needed is a maximum di/dt limit everywhere 
on the current waveform and a radiation spec on the simulator. And this is 
only for contact discharge. For air discharge, the large uncertainty of the 
discharge itself will likely dominate unless hundreds of discharges are 
used at each point to reach statistical significance.


Doug Smith Sent from my iPhone IPhone: 408-858-4528 Office: 702-570-6108 
Email: d...@dsmith.org Website: http://dsmith.org
On Fri, Sep 1, 2017 at 9:05, Knighten, Jim L  
wrote:
A good practice is to use your calculated measurement uncertainty for 
emissions as your minimum margin requirement.


That will often put you in the 3-4 dB range.



Jim





James L. Knighten, Ph.D.

Teradata

17095 Via Del Campo

San Diego, CA 92127

858-485-2537



From: Kim Boll Jensen [mailto:k...@bolls.dk]
Sent: Friday, September 01, 2017 6:01 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] God EMC practice



Hi



One of our customers want to know if there are some good practice for 
emission compliance. I normally recommend 3 dB margin, but I don't have any 
reference to why this is OK.




I know that some companies have internal rules for 3 or even 6 dB margin to 
compensate for production deviations and for many years ago VDE did have 
some rules like that.




Does anyone have some good references on this subject?



Best regards,



Mr. Kim Boll Jensen

-


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[http://product-compliance.oc.ieee.org/] can be used for graphics (in 
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Re: [PSES] God EMC practice

[Cortland Richmond]

My first post-military (21 years) employer, did statistical quality 
testing in 1983-87,   but that was because they were producing TEMPEST 
qualified systems too; it was habit.  My second employer a (defunct firm 
in Forth Worth) tested before sending systems out for FCC approval, and 
also the peripherals they were going to sell with them, which (we didn't 
buy those) sometimes SCREAMED.


I suspect a factory in (say) Malaysia doesn't bother to test anything 
rolling off the production line once they got the FCC label on a like 
EUT -- even if it just looks like theirs.


Cortland Richmond

On 9/1/2017 11:21 AM, Patrick wrote:

So, the industry performs on-going EMC audits.


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Re: [PSES] God EMC practice

[Knighten, Jim L]

A good practice is to use your calculated measurement uncertainty for emissions 
as your minimum margin requirement.
That will often put you in the 3-4 dB range.

Jim


James L. Knighten, Ph.D.
Teradata
17095 Via Del Campo
San Diego, CA 92127
858-485-2537

From: Kim Boll Jensen [mailto:k...@bolls.dk]
Sent: Friday, September 01, 2017 6:01 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] God EMC practice

Hi

One of our customers want to know if there are some good practice for emission 
compliance. I normally recommend 3 dB margin, but I don't have any reference to 
why this is OK.

I know that some companies have internal rules for 3 or even 6 dB margin to 
compensate for production deviations and for many years ago VDE did have some 
rules like that.

Does anyone have some good references on this subject?

Best regards,

Mr. Kim Boll Jensen
-


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discussion list. To post a message to the list, send your e-mail to 
mailto:emc-p...@ieee.org>>

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Attachments are not permitted but the IEEE PSES Online Communities site at 
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David Heald mailto:dhe...@gmail.com>>

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Re: [PSES] God EMC practice

[John Woodgate]

You are right: I replied only to the OP by mistake. I have now forwarded the 
post to this list.
 
With best wishes John Woodgate
3 Bramfield Road East, RAYLEIGH Essex SS6 8RG UK OOO – Own Opinions Only
 <http://www.jmwa.demon.co.uk/> www.jmwa.demon.co.uk J M Woodgate and 
Associates 
 
Beware averages! They hide or discard data, and may distort it (them?).
 
 
From: msherma...@comcast.net [mailto:msherma...@comcast.net] 
Sent: Friday, September 1, 2017 4:55 PM
To: John Woodgate 
Subject: Re: [PSES] God EMC practice
 
John --
Maybe I deleted a previous email without reading down to the URL, but I'm not 
remembering such a link in this thread. 
Mike Sherman
Graco Inc. 

Sent from XFINITY Connect Mobile App

-- Original Message --

From: John Woodgate
To: EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> 
Sent: September 1, 2017 at 10:46 AM
Subject: Re: [PSES] God EMC practice
Some people may take that approach, known in British English as 'by guess and 
by god' (whichever god).  But there IS math that not only should give the 
people involved more confidence, but provides evidence for convincing managers, 
surveillance officers, and, in the last resort, the judge, that everything is 
in order.
 
The document whose URL I gave explains  in fairly simple terms how to use the 
math.  
 
With best wishes John Woodgate
3 Bramfield Road East, RAYLEIGH Essex SS6 8RG UK OOO – Own Opinions Only
 <http://www.jmwa.demon.co.uk/> www.jmwa.demon.co.uk J M Woodgate and 
Associates 
 
Beware averages! They hide or discard data, and may distort it (them?).
 
 
From: Patrick [mailto:conwa...@gmail.com] 
Sent: Friday, September 1, 2017 4:21 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> 
Subject: Re: [PSES] God EMC practice
 
God and Compliance Margin...  two topics that generate a lot of preaching!  
I think everyone has a "tradition" of what worked for them, and what did 
not.
 
Here is my sermon on margin:
 
I don't consider myself a monk of the EMI Chamber... 
...but over the years I have preached various margins.
...margins are always situational, always depending on the business, and 
the products.
...call it relativism?
 
 
On one end of the extreme, I've been in the aerospace industry.
Here, a single unit is built, and flown successfully, with *zero dB* of 
margin.  
 
On the other end, consumer products.
Here, just one or two units comply during development.
Then the factory produces a million units a month for a year.
Yes, that is 12 million units based on a couple of passing samples!
In this industry, initial margin can not predict performance of the 
500,00th unit.
So, the industry performs on-going EMC audits.
 
 
In both those cases, the dogma of margin was irrelevant.  
For aerospace, what mattered was coexistence.  
For commercial, it required an ongoing liturgy of audits.  
 
 
What really drives margin is the product, the market, and the target usage.
Everything else is just "tradition" & "hearsay".
Every company needs enlightened margin decisions based on their own 
circumstances.
 
 
 
Thanks for the bit of humor to end the week!
 
-Patrick
 
On Fri, Sep 1, 2017 at 7:01 AM, Kim Boll Jensen mailto:k...@bolls.dk> > wrote:
Hi
 
One of our customers want to know if there are some good practice for emission 
compliance. I normally recommend 3 dB margin, but I don't have any reference to 
why this is OK.
 
I know that some companies have internal rules for 3 or even 6 dB margin to 
compensate for production deviations and for many years ago VDE did have some 
rules like that.
 
Does anyone have some good references on this subject?
 
Best regards,
 
Mr. Kim Boll Jensen
-

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-- 
//
Patrick
-

[PSES] FW: [PSES] God EMC practice

[John Woodgate]

Please see the URL below.
 
With best wishes John Woodgate
3 Bramfield Road East, RAYLEIGH Essex SS6 8RG UK OOO - Own Opinions Only
 <http://www.jmwa.demon.co.uk/> www.jmwa.demon.co.uk J M Woodgate and
Associates 
 
Beware averages! They hide or discard data, and may distort it (them?).
 
 
From: John Woodgate [mailto:jmw1...@btinternet.com] 
Sent: Friday, September 1, 2017 2:12 PM
To: 'Kim Boll Jensen' 
Subject: RE: [PSES] God EMC practice
 
Go to: http://www.jmwa.demon.co.uk/Illustrations%20of%2080-80%20rule.pdf
 
This is a presentation delivered by an expert on the subject to a CENELEC
committee.
 
With best wishes John Woodgate
3 Bramfield Road East, RAYLEIGH Essex SS6 8RG UK OOO - Own Opinions Only
 <http://www.jmwa.demon.co.uk/> www.jmwa.demon.co.uk J M Woodgate and
Associates 
 
Beware averages! They hide or discard data, and may distort it (them?).
 
 
From: Kim Boll Jensen [mailto:k...@bolls.dk] 
Sent: Friday, September 1, 2017 2:01 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> 
Subject: [PSES] God EMC practice
 
Hi
 
One of our customers want to know if there are some good practice for
emission compliance. I normally recommend 3 dB margin, but I don't have any
reference to why this is OK.
 
I know that some companies have internal rules for 3 or even 6 dB margin to
compensate for production deviations and for many years ago VDE did have
some rules like that.
 
Does anyone have some good references on this subject?
 
Best regards,
 
Mr. Kim Boll Jensen
-

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Re: [PSES] God EMC practice

[John Woodgate]

Some people may take that approach, known in British English as 'by guess and 
by god' (whichever god).  But there IS math that not only should give the 
people involved more confidence, but provides evidence for convincing managers, 
surveillance officers, and, in the last resort, the judge, that everything is 
in order.
 
The document whose URL I gave explains  in fairly simple terms how to use the 
math.  
 
With best wishes John Woodgate
3 Bramfield Road East, RAYLEIGH Essex SS6 8RG UK OOO – Own Opinions Only
 <http://www.jmwa.demon.co.uk/> www.jmwa.demon.co.uk J M Woodgate and 
Associates 
 
Beware averages! They hide or discard data, and may distort it (them?).
 
 
From: Patrick [mailto:conwa...@gmail.com] 
Sent: Friday, September 1, 2017 4:21 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] God EMC practice
 
God and Compliance Margin...  two topics that generate a lot of preaching!  
I think everyone has a "tradition" of what worked for them, and what did 
not.
 
Here is my sermon on margin:
 
I don't consider myself a monk of the EMI Chamber... 
...but over the years I have preached various margins.
...margins are always situational, always depending on the business, and 
the products.
...call it relativism?
 
 
On one end of the extreme, I've been in the aerospace industry.
Here, a single unit is built, and flown successfully, with *zero dB* of 
margin.  
 
On the other end, consumer products.
Here, just one or two units comply during development.
Then the factory produces a million units a month for a year.
Yes, that is 12 million units based on a couple of passing samples!
In this industry, initial margin can not predict performance of the 
500,00th unit.
So, the industry performs on-going EMC audits.
 
 
In both those cases, the dogma of margin was irrelevant.  
For aerospace, what mattered was coexistence.  
For commercial, it required an ongoing liturgy of audits.  
 
 
What really drives margin is the product, the market, and the target usage.
Everything else is just "tradition" & "hearsay".
Every company needs enlightened margin decisions based on their own 
circumstances.
 
 
 
Thanks for the bit of humor to end the week!
 
-Patrick
 
On Fri, Sep 1, 2017 at 7:01 AM, Kim Boll Jensen mailto:k...@bolls.dk> > wrote:
Hi
 
One of our customers want to know if there are some good practice for emission 
compliance. I normally recommend 3 dB margin, but I don't have any reference to 
why this is OK.
 
I know that some companies have internal rules for 3 or even 6 dB margin to 
compensate for production deviations and for many years ago VDE did have some 
rules like that.
 
Does anyone have some good references on this subject?
 
Best regards,
 
Mr. Kim Boll Jensen
-

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<emc-p...@ieee.org <mailto:emc-p...@ieee.org> >
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Jim Bacher <j.bac...@ieee.org <mailto:j.bac...@ieee.org> >
David Heald <dhe...@gmail.com <mailto:dhe...@gmail.com> > 



 
-- 
//
Patrick
-

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Attachments are not permitted but the IEEE PSES Online Communities site at 
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Jim Bacher mailto:j.bac...@ieee.org> &g

Re: [PSES] God EMC practice

[Patrick]

God and Compliance Margin...  two topics that generate a lot of preaching!
I think everyone has a "tradition" of what worked for them, and what
did not.

Here is my sermon on margin:

I don't consider myself a monk of the EMI Chamber...
...but over the years I have preached various margins.
...margins are always situational, always depending on the business,
and the products.
...call it relativism?


On one end of the extreme, I've been in the aerospace industry.
Here, a single unit is built, and flown successfully, with *zero dB* of
margin.

On the other end, consumer products.
Here, just one or two units comply during development.
Then the factory produces a million units a month for a year.
Yes, that is 12 million units based on a couple of passing samples!
In this industry, initial margin can not predict performance of the
500,00th unit.
So, the industry performs on-going EMC audits.


In both those cases, the dogma of margin was irrelevant.
For aerospace, what mattered was coexistence.
For commercial, it required an ongoing liturgy of audits.


What really drives margin is the product, the market, and the target usage.
Everything else is just "tradition" & "hearsay".
Every company needs enlightened margin decisions based on their own
circumstances.



Thanks for the bit of humor to end the week!

-Patrick

On Fri, Sep 1, 2017 at 7:01 AM, Kim Boll Jensen  wrote:

> Hi
>
>
>
> One of our customers want to know if there are some good practice for
> emission compliance. I normally recommend 3 dB margin, but I don't have any
> reference to why this is OK.
>
>
>
> I know that some companies have internal rules for 3 or even 6 dB margin
> to compensate for production deviations and for many years ago VDE did have
> some rules like that.
>
>
>
> Does anyone have some good references on this subject?
>
>
>
> Best regards,
>
>
>
> Mr. Kim Boll Jensen
> -
> 
>
> This message is from the IEEE Product Safety Engineering Society emc-pstc
> discussion list. To post a message to the list, send your e-mail to <
> emc-p...@ieee.org>
>
> All emc-pstc postings are archived and searchable on the web at:
> http://www.ieee-pses.org/emc-pstc.html
>
> Attachments are not permitted but the IEEE PSES Online Communities site at
> http://product-compliance.oc.ieee.org/ can be used for graphics (in
> well-used formats), large files, etc.
>
> Website: http://www.ieee-pses.org/
> Instructions: http://www.ieee-pses.org/list.html (including how to
> unsubscribe) 
> List rules: http://www.ieee-pses.org/listrules.html
>
> For help, send mail to the list administrators:
> Scott Douglas 
> Mike Cantwell 
>
> For policy questions, send mail to:
> Jim Bacher 
> David Heald 
>



-- 
//
Patrick

-

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All emc-pstc postings are archived and searchable on the web at:
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Re: [PSES] God EMC practice

[alfred1520list]

Hi Kim,

I've just had a chat with a compliance test lab engineer on this very topic 
yesterday. He said their measurements have a 3 dB uncertainty between labs. So 
it world seem when everything is as accurate as possible, 3dB margin would 
ensure you will always pass, possibly without any margin. So the 6 dB rules 
would give you 3 dB margin.

That's my humanly guess. God had different rules that we can't Divine:)

Best Regards,
Alfred


On September 1, 2017 6:01:20 AM PDT, Kim Boll Jensen  wrote:
>Hi
>
> 
>
>One of our customers want to know if there are some good practice for
>emission compliance. I normally recommend 3 dB margin, but I don't have
>any
>reference to why this is OK.
>
> 
>
>I know that some companies have internal rules for 3 or even 6 dB
>margin to
>compensate for production deviations and for many years ago VDE did
>have
>some rules like that.
>
> 
>
>Does anyone have some good references on this subject?
>
> 
>
>Best regards,
>
> 
>
>Mr. Kim Boll Jensen
>
>
>-
>
>This message is from the IEEE Product Safety Engineering Society
>emc-pstc discussion list. To post a message to the list, send your
>e-mail to 
>
>All emc-pstc postings are archived and searchable on the web at:
>http://www.ieee-pses.org/emc-pstc.html
>
>Attachments are not permitted but the IEEE PSES Online Communities site
>at http://product-compliance.oc.ieee.org/ can be used for graphics (in
>well-used formats), large files, etc.
>
>Website:  http://www.ieee-pses.org/
>Instructions:  http://www.ieee-pses.org/list.html (including how to
>unsubscribe)
>List rules: http://www.ieee-pses.org/listrules.html
>
>For help, send mail to the list administrators:
>Scott Douglas 
>Mike Cantwell 
>
>For policy questions, send mail to:
>Jim Bacher:  
>David Heald: 

-- 
Sent from my Android phone with K-9 Mail. Please excuse my brevity.

-

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Re: [PSES] God EMC practice

[john Allen]

I'm sure some agencies and companies have rules for this aspect, but I'm not
sure about "God"! J

 

From: Kim Boll Jensen [mailto:k...@bolls.dk] 
Sent: 01 September 2017 14:01
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] God EMC practice

 

Hi

 

One of our customers want to know if there are some good practice for
emission compliance. I normally recommend 3 dB margin, but I don't have any
reference to why this is OK.

 

I know that some companies have internal rules for 3 or even 6 dB margin to
compensate for production deviations and for many years ago VDE did have
some rules like that.

 

Does anyone have some good references on this subject?

 

Best regards,

 

Mr. Kim Boll Jensen

-


This message is from the IEEE Product Safety Engineering Society emc-pstc
discussion list. To post a message to the list, send your e-mail to


All emc-pstc postings are archived and searchable on the web at:
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Attachments are not permitted but the IEEE PSES Online Communities site at
http://product-compliance.oc.ieee.org/ can be used for graphics (in
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List rules: http://www.ieee-pses.org/listrules.html 

For help, send mail to the list administrators:
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Mike Cantwell  

For policy questions, send mail to:
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David Heald  


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[PSES] God EMC practice

[Kim Boll Jensen]

Hi

 

One of our customers want to know if there are some good practice for
emission compliance. I normally recommend 3 dB margin, but I don't have any
reference to why this is OK.

 

I know that some companies have internal rules for 3 or even 6 dB margin to
compensate for production deviations and for many years ago VDE did have
some rules like that.

 

Does anyone have some good references on this subject?

 

Best regards,

 

Mr. Kim Boll Jensen


-

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