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

Lfresearch Wed, 10 Apr 2024 14:22:14 -0700

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 <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 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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