In my experience and opinion, they are wasting your time and money.
Bob Heller
3M Product Safety, 76-1-01
St. Paul, MN 55107-1208
Tel: 651- 778-6336
Fax: 651-778-6252
=========================================================================
"Gary McInturff"
<Gary.McInturff@worldwidep To:
[email protected]
ackets.com> "\"EMC-PSTC (E-mail)\"
<"
cc: (bcc: Robert
E. Heller/US-Corporate/3M/US)
05/23/2002 11:08 AM Subject: RE:
Accreditation - testing ourselves and a new question.
Please respond to "Gary
McInturff"
Amund
I'm not quite sure I understand this. Are you saying that for
pre-qualification only, that you want to run the gear? If that's the case I
don't believe that their accreditation speaks to that in any fashion, but
their business insurance etc might have something to say about it. If my
main income was coming from the continued operation and calibration of some
very expensive equipment, it would have to be a very special case before I
let others operate it and potentially put it at risk.
In fact the test lab I use has a branch near me. The measuring
equipment, ground plane and structures were all purchased by me for a third
company some years ago when I ran the EMI lab and I physically operated it
for many years. Obviously, I am intimately familiar with it, but I keep my
hands off of it, unless they ask me to make a quick check or something.
If it is for accreditation then I think the hang-up is going to be in
the quality manuals and documents that are part of the lab's accreditation.
There is a section on the test personnel and their past and future training
etc. You are not an employee of the lab so wouldn't fall under their
quality guidelines, or necessarily adhere to their processes. To insure
that they would have to sit there and oversee you, even if they were to
allow. So they are going to charge you for the lab personnel anyway.
As long as we are talking about procedural changes I would like to
ask how test labs are treating the various input voltages available in most
equipment. This would be for radiated emissions not conducted. Conducted
emissions tests at different voltages are pretty clear in my mind, but not
radiated emissions.
Until just recently all of the labs I am aware of, and I used three
or four, all used the same process for radiated emissions. Under the
assumption that the logic operated at the same 5, 3.3 or 2.2 volts not
matter what the input power range was. The radiated emissions was performed
at generally 120 Vac, in the US. One lab always ran it at 230, as CISPR 22
made reference to the input voltage, while the US largely left it
unaddressed other than noting that they accept the CISPR 22 limits and
procedures as long as they are used both in amplitude and frequency range.
I once saw a reference, may be Taiwan, that specified testing at
multiple voltages, but even then only for Class B equipment.
My primary lab has started, a prescan at each voltage under
consideration, 120 and 230, and then selected a test voltage. It has now
advanced to doing a much more intense scan at 100, 120 , 230 volts and then
selecting a voltage (variances are often more equipment temperature related
than voltage related, in my opinion and are in the noise floor - less than
1 dB). Only then does the test begin. The last time I was there the
"pre-scan" took three hours. Then we could look for a full range of
suspects, and finals. What used to be about a 4 hour process has become an
8 hour process, doubling my test expenses.
Other than their desire for accuracy, which is a bit difficult to
argue against, I can't find justification in the standards that demand it
and it is eroding my budget. So basically I need to have a sanity check and
either quit complaining at the test house or force the issue. In all other
respects they do a great job and I enjoy working with them.
This is ITE equipment with an auto ranging switch mode power supply.
Gary
-----Original Message-----
From: [email protected] [mailto:[email protected]]
Sent: Thursday, May 23, 2002 5:25 AM
To: "EMC-PSTC (E-mail)" <
Subject: Accreditation - testing ourselves
Hi all,
An EMC test lab is accredited according to ISO/IEC 17025. They are also
accredited for many tests as the IEC61000-4-series, EN55022 and many other.
We have previously done some EMC pre-testing in this lab and we have
operated the test equipment ourselves. Now, they won't let us do that with
reference to their accreditation status. The test lab personnel have to
operate the test equipment. Does it make sense, is there any restriction in
the accreditation ?
We have always made a clear cut between pre-testing and accredited testing.
Best regards
Amund Westin
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