The basic question is, "How good is good enough?"
Risk standards for product safety address that question to some
extent, but it applies to every lab measurement, whether the
applicable standards (or regulations) consider it or not.
Best regards,
John McBain
On Sat, Aug 12, 2023 at 2:26 AM John Woodgate <[email protected]> wrote:
But crossing t's and dotting i's is exactly what is required by
competence standards, including the several ISO 170XX series.
Furthermore, standards specify performance of test equipment, if
possible, and only if that is not possible, they specify design.
If that is not possible, they specify construction, and indeed
many CISPR and other standards specify test set-ups with elaborate
drawings.
EMC testing is DIFFICULT. It does involve extensive experience and
it is costly. Management systems are/should be in place to catch
errors. Daily and weekly verifications are required. In many
cases, running tests on a known sample are OK, but that's dodgy
for ESD, because repeated testing WILL cause damage.
On 2023-08-12 03:25, Ken Javor wrote:
No way am I jumping in the middle of this debate, but it is
extremely useful in another way.
A few observations:
ESD is by its very nature a chaotic event (air discharge more so
than contact).
It is not entirely surprising that someone who has spent decades
working on something would find examples of non-idealities in the
work of technicians doing rote work following canned test
procedures. A test facility isn’t going to make a profit
employing a septuagenarian devoted to crossing every “t” and
dotting every “i.” (Written by someone pushing that age bracket
pretty hard).
IFF (if and only if) Mr. Smith’s observations are correct, that
is an indictment of the test requirement/method. That is, it is
the responsibility of the standards committees to write these
such that they can be adequately performed by the average test
facility and personnel. If it takes someone with five decades of
experience, and they must spend an inordinate amount of time
($$$) to get it right, then the standard is a failure.
--
Ken Javor
(256) 650-5261
*From: *"doug emcesd.com <http://emcesd.com>" <[email protected]>
<mailto:[email protected]>
*Reply-To: *"doug emcesd.com <http://emcesd.com>"
<[email protected]> <mailto:[email protected]>
*Date: *Friday, August 11, 2023 at 11:26 AM
*To: *<[email protected]>
<mailto:[email protected]>
*Subject: *Re: [PSES] thoughts on ESD test lab problems
I didn’t say most labs are bad. Errors do happen and for me
almost every lab I have used has made a mistake. These errors are
rare but do happen and the effect of a single error can be very
costly.
One lab made an especially bad mistake for a small company that
engaged me that cost the company a lot of money, has since
improved their game by instituting quality procedures they should
have had anyway. The lab gave the company passing data but in
fact the plot looked like the technician forgot to plug the
antenna in, noise level of the instrumentation!
Based on that, the company signed a contract for price and
delivery for a million units of their product. The ultimate fix
needed was a different core design of an inductor that cost them
US $0.30. $300k is a lot of money for a small company.
I can give many more examples. Usually the problem causes a
product to fail when it actually should have passed. I have many
examples that happened to me over the last 40 years in both
private and commercial labs.
The errors are still rare, but do happen. Over enough testing a
person, like myself, will encounter an error with any given lab.
Of the errors I have encountered, three were the result of the
staff in the lab not being competent (over a span of 40 years),
the rest were just simple mistakes, maybe another dozen or so.
Again, this was over decades, so rare, but many millions of
dollars were at stake in each case.
In two cases, the lab personnel became a bit belligerent when I
gently suggested they performed the test incorrectly. In
both cases, the labs relented and retested after we examined the
test standard and they realized they were testing incorrectly.
A lab client needs to keep an eye out to make sure such an error
does not happen to them.
On the other hand, I have seen a lot of great labs. One, in
Silicon Valley, I consider to be the best in the industry! But
they did make one mistake on a test for me years ago, minimal
impact at the time and it can't happen again.
Doug Smith
Sent from my iPhone
IPhone: 408-858-4528
Office: 702-570-6108
Email: [email protected]
Website: http://dsmith.org
------------------------------------------------------------------------
*From:* John Woodgate <[email protected]> <mailto:[email protected]>
*Sent:* Friday, August 11, 2023 07:02
*To:* [email protected] <[email protected]>
<mailto:[email protected]>
*Subject:* Re: [PSES] thoughts on ESD test lab problems
That's right. It is good to call attention to problems that may
well be deeply hidden or not recognized as a possibility, but it
is necessary to concentrate on the facts and leave out peripheral
matters that don't help to deal with the issue.
On 2023-08-11 14:28, Larry K. Stillings wrote:
You could certainly word this in a different way that doesn’t
generalize how “most” test labs are bad and/or incompetent.
How about in the future you find a different way to word things.
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