Re: [PSES] I would like to hear your thoughts please

[Bill Owsley]

 All the test labs I have used have a qualifier that the results are only for 
the specimen/s submitted.
As the manufacturer, I provide the rational to include in the test report for 
the configuration/s submitted.
For about 4 decades, a minimum and a maximum configs have sufficed.
ps.  If the marketing model number changes for various configs, that generally 
gets a some degree of testing with notes added to test report to explain the 
differences and commonalities, and the front page gets modified that the test 
report covers these additional models.

On Friday, April 12, 2024, 2:59:06 PM EDT, Lauren Crane 
<1afd08519f18-dmarc-requ...@listserv.ieee.org> wrote:  
 
 
I think one could postulate a worst case hardware/software combination, but it 
would have to be well defended in text along the lines of “no other 
configuration could be worst case because…” followed by a discussion of the 
physical aspects of the other configurations and what they imply, based on 
‘first principles’, regarding emissions and susceptibility. Even then, if there 
are many configurations (e.g., more than 5?), it would be wise to test a one or 
two for which your written hypothesis might be less certain.
 
  
 
The EMCD guidelines (19 Dec 2018) seem to me to be accepting of this idea…
 
  

   - “The EMC assessment needs to take into account all normal intended 
operating conditions of the apparatus. In cases where the apparatus can take 
different configurations, the electromagnetic compatibility assessment must 
confirm that the apparatus meets the essential requirements, “in all possible 
configurations identified by the manufacturer as representative of its intended 
use”[quoting Annex II.2]”.
   - “Where apparatus can take different configurations, the EMC assessment 
shall confirm that the apparatus meets the essential requirements in all of the 
configurations foreseeable by the manufacturer as representative of normal use 
in intended applications.The manufacturer is responsible for identifying the 
possible configurations and the choice of the worst case(s). The use of the 
worst case approach needs to be documented in the technical documentation”[35]. 
[35]=” Within the immunity and emission phenomena to be covered, different 
worst case selections may occur (because of non-related phenomena). This may 
increase the number of cases to be investigated “
 

 
Note particularly - the guide highlights the obligation of deciding worst case 
is placed on the manufacturer. If you provide them some guidance but remind 
them the decision of testing fewer or more of the configurations rests with 
them, they may have a softer attitude towards more testing.  
 
  
 
Best regards, 
 
-Lauren
 

Confidential – Limited Access and Use


From: Bill Owsley <00f5a03f18eb-dmarc-requ...@listserv.ieee.org>
Sent: Friday, April 12, 2024 1:19 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] I would like to hear your thoughts please
 
  
 
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The usual response is that it depends...
 
More 'light' reading !  To start !
 
https://www.fcc.gov/sites/default/files/32-KDB-996369-Modules-TCB_Oct_2023.pdf
 
  
 
  
 
On Wednesday, April 10, 2024, 5:22:12 PM EDT, Lfresearch 
<00734758d943-dmarc-requ...@listserv.ieee.org> wrote: 
 
  
 
  
 
Sorry for the late reply, but I did feel the need to express strong 
disagreement with some statements here.
 
  
 
Lets take there first one: how will you know which is worst case if you don’t 
test. Seriously? I would answer this by saying that an EMC engineer with any 
proficiency can make an educated decision as to what would be the worst case, 
further, if one can’t do that you shouldn’t probably be in EMC Engineering. Is 
the old saying from school days “ You should have an idea of the answer before 
doing the problem “ no longer stressed in school!
 
  
 
The back reference to Boeing is utter BS, sorry Gert, but as someone who 
contracts for Boeing I take a very strong exception to that ridiculous 
statement. There is absolutely NO correlation between a poor quality 
subcontractor and the EMC performance of an EUT. It may be true for airbus, but 
leave my Boeing alone please.
 
  
 
Back to the problem at hand, and serious answers only please.
 
  
 
At what point(s) does one draw the line eliminating the need for testing 
similar designs.
 
  
 
Thanks in advance,
 
  
 
Derek Walton.
 



 

On Apr 6, 2024, at 7:55 AM, Gert Gremmen F4LDP  wrote:
 
  
 

Dear All,

Within the framework of the EMCD, all configurations shall be conform, so if 
you choose to actually test,
all configurations shall be part of the test. The subject of worse case is a 
"miroir d'alouette"... how will you ever know which
is worst case without 

Re: [PSES] I would like to hear your thoughts please

[Lauren Crane]

I think one could postulate a worst case hardware/software combination, but it 
would have to be well defended in text along the lines of “no other 
configuration could be worst case because…” followed by a discussion of the 
physical aspects of the other configurations and what they imply, based on 
‘first principles’, regarding emissions and susceptibility. Even then, if there 
are many configurations (e.g., more than 5?), it would be wise to test a one or 
two for which your written hypothesis might be less certain.

The EMCD guidelines (19 Dec 2018) seem to me to be accepting of this idea…


  *   “The EMC assessment needs to take into account all normal intended 
operating conditions of the apparatus. In cases where the apparatus can take 
different configurations, the electromagnetic compatibility assessment must 
confirm that the apparatus meets the essential requirements, “in all possible 
configurations identified by the manufacturer as representative of its intended 
use”[quoting Annex II.2]”.
  *   “Where apparatus can take different configurations, the EMC assessment 
shall confirm that the apparatus meets the essential requirements in all of the 
configurations foreseeable by the manufacturer as representative of normal use 
in intended applications. The manufacturer is responsible for identifying the 
possible configurations and the choice of the worst case(s). The use of the 
worst case approach needs to be documented in the technical documentation”[35]. 
[35]=” Within the immunity and emission phenomena to be covered, different 
worst case selections may occur (because of non-related phenomena). This may 
increase the number of cases to be investigated “
Note particularly - the guide highlights the obligation of deciding worst case 
is placed on the manufacturer. If you provide them some guidance but remind 
them the decision of testing fewer or more of the configurations rests with 
them, they may have a softer attitude towards more testing.

Best regards,
-Lauren


Confidential – Limited Access and Use
From: Bill Owsley <00f5a03f18eb-dmarc-requ...@listserv.ieee.org>
Sent: Friday, April 12, 2024 1:19 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] I would like to hear your thoughts please



External Email: Do NOT reply, click on links, or open attachments unless you 
recognize the sender and know the content is safe. If you believe this email 
may be unsafe, please click on the “Report Phishing” button on the top right of 
Outlook.


The usual response is that it depends...
More 'light' reading !  To start !
https://www.fcc.gov/sites/default/files/32-KDB-996369-Modules-TCB_Oct_2023.pdf


On Wednesday, April 10, 2024, 5:22:12 PM EDT, Lfresearch 
<00734758d943-dmarc-requ...@listserv.ieee.org>
 wrote:


Sorry for the late reply, but I did feel the need to express strong 
disagreement with some statements here.

Lets take there first one: how will you know which is worst case if you don’t 
test. Seriously? I would answer this by saying that an EMC engineer with any 
proficiency can make an educated decision as to what would be the worst case, 
further, if one can’t do that you shouldn’t probably be in EMC Engineering. Is 
the old saying from school days “ You should have an idea of the answer before 
doing the problem “ no longer stressed in school!

The back reference to Boeing is utter BS, sorry Gert, but as someone who 
contracts for Boeing I take a very strong exception to that ridiculous 
statement. There is absolutely NO correlation between a poor quality 
subcontractor and the EMC performance of an EUT. It may be true for airbus, but 
leave my Boeing alone please.

Back to the problem at hand, and serious answers only please.

At what point(s) does one draw the line eliminating the need for testing 
similar designs.

Thanks in advance,

Derek Walton.


On Apr 6, 2024, at 7:55 AM, Gert Gremmen F4LDP 
mailto:g.grem...@cetest.nl>> wrote:

Dear All,

Within the framework of the EMCD, all configurations shall be conform, so if 
you choose to actually test,
all configurations shall be part of the test. The subject of worse case is a 
"miroir d'alouette"... how will you ever know which
is worst case without carrying out the test ? A pre-scan is informative but the 
radiated emission test contains already a pre-scan (peak) for the final 
QP-measurement.  We already require a EMC risk analysis which is a kind of 
pre-scan too. How many pre-pre-prescans will we need to be sure ?
"to repeat some (which?) test to make sure nothing was broken" it's another 
discipline, but that is how Boeing lost a door in flight. And that  is not a 
unregulated sector without thorough quality scans (understatement), and still 
it happens. Imagine the costs and effort for Boeing to rebuild their reputation 
? Didn't we all learned the exponential graph of EMC costs versus development 
time ?
If you need proof (for authorities, or for 

Re: [PSES] I would like to hear your thoughts please

[Bill Owsley]

 The usual response is that it depends...
More 'light' reading !  To start !
https://www.fcc.gov/sites/default/files/32-KDB-996369-Modules-TCB_Oct_2023.pdf

On Wednesday, April 10, 2024, 5:22:12 PM EDT, Lfresearch 
<00734758d943-dmarc-requ...@listserv.ieee.org> wrote:  
 
 Sorry for the late reply, but I did feel the need to express strong 
disagreement with some statements here.
Lets take there first one: how will you know which is worst case if you don’t 
test. Seriously? I would answer this by saying that an EMC engineer with any 
proficiency can make an educated decision as to what would be the worst case, 
further, if one can’t do that you shouldn’t probably be in EMC Engineering. Is 
the old saying from school days “ You should have an idea of the answer before 
doing the problem “ no longer stressed in school!
The back reference to Boeing is utter BS, sorry Gert, but as someone who 
contracts for Boeing I take a very strong exception to that ridiculous 
statement. There is absolutely NO correlation between a poor quality 
subcontractor and the EMC performance of an EUT. It may be true for airbus, but 
leave my Boeing alone please.
Back to the problem at hand, and serious answers only please.
At what point(s) does one draw the line eliminating the need for testing 
similar designs.
Thanks in advance,
Derek Walton.


On Apr 6, 2024, at 7:55 AM, Gert Gremmen F4LDP  wrote:
 
 Dear All,
 
 Within the framework of the EMCD, all configurations shall be conform, so if 
you choose to actually test, 
 all configurations shall be part of the test. The subject of worse case is a 
"miroir d'alouette"... how will you ever know which
 is worst case without carrying out the test ? A pre-scan is informative but 
the radiated emission test contains already a pre-scan (peak) for the final 
QP-measurement.  We already require a EMC risk analysis which is a kind of 
pre-scan too. How many pre-pre-prescans will we need to be sure ?
 "to repeat some (which?) test to make sure nothing was broken" it's 
another discipline, but that is how Boeing lost a door in flight. And that  is 
not a unregulated sector without thorough quality scans (understatement), and 
still it happens. Imagine the costs and effort for Boeing to rebuild their 
reputation ? Didn't we all learned the exponential graph of EMC costs versus 
development time ?
 If you need proof (for authorities, or for yourself), nothing can replace the 
actual test. 
 
 Gert Gremmen
 
 On 6-4-2024 0:47, Lfresearch wrote:
  
 Hi folks,

I would like to advise a client at where to draw the line on what needs 
testing. I would like to solicit opinions besides my own. Otherwise it’s the 
fox urging the chicken coop…

So a manufacturer that makes a product of which there will be several variants. 
All use the same board, but have different sections of circuits populated. This 
may require slightly different code to run on the same uP in each case.

So.. The burning question is can we perform and analysis that postulates a 
worse case hardware/software combination and test just one configuration? Or, 
do we have to do every combination?

Or, are there some guidelines about where we draw the line of what to test and 
what can be claimed as similarity?

Off list responses are welcome too.

Thanks,

Derek Walton
LFResearch/SSCLabs.

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