I have had to justify changes as remaining compliant with a standard, a
similar case to the standard changing, and i too have been reluctant to
do so without tests to show that this assertion is correct.
This has often been where, due to the nonavailability of a part years or
decades old and no longer made, a new one has had to be used. For THAT
kind of change, it is often useful and sufficient to show that the
waveforms and spectra where the new meets the old are better than the
older design, or at least no worse.
And where I took care that this test was not only good enough, but
LOOKED good enough, it has usually been considered acceptable.
Sometimes the signals and waveforms at that interface may not be better
or even as good as the older design, and in those cases, it may still be
possible to demonstrate continued compliance with a partial compliance
test in the spectrum where the change might reasonably be expected to
make a difference. This is harder to do, but may not be harder than
completely re-qualifying the EUT.
Some standards may nevertheless not allow such a test.
Some of us may remember when, in 2004, certain medical equipment
manufacturers who, despite knowing that it was going to happen, had not
acted on the knowledge, awoke to the realization that all their older
kit being sold in Europe would "suddently" have to be 10 dB less
susceptible to RF and transients than before. I got a nice (if
underpaid - heh) contract out of that, which started as writing a test
and verification plan for a new product my customer suddenly had no
engeering staff for. It went beyond that, technical skills sometimes
being less evident among otherwise qualified personnel than credentials
suggest*. But I consider myself privileged to have helped, possibly,
save lives with the products that emerged. Immensely so.
* Look at Robert M. Pirsig about "mechanic's feel" in _Zen and the Art
of Motorcycle Maintainance_. I'd give a page number except that, since
Zen & has no index or footnotes, I'd have to read through it (again;
it's open on the table) to find where he talks about that. if you have
felt good about your work, you may already know what he is talking about.
Cortland Richmond
On 9/2/2013 0707, ce-test, qualified testing bv - Gert Gremmen wrote:
Well said.
We do agree....
But the phrase as John used, is used too often to "just self declare"
based on "what the designer knows" , or what he assumes. Or his purchase
department.
It's just a bit more complex than saying the directive does not oblige to test.
The "evidence" part requires a thoroughly written (as I see it) assessment to
the essential requirements,
what in 99.9 % of the cases leads to new (partial) testing.
An assessment that requires a bit more knowledge and experience than counting
data ports.
-
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