In message <[email protected]>, dated Tue, 15 Sep 2015, Monrad
Monsen <[email protected]> writes:
. We have to be careful about how much EMC testing is mandated.
Today, the standards committees are going beyond the original intent
(reduce interference by mandating emissions limits) and now are trying
to become too scientific about the exact measurement uncertainty and
careful characterization of the nonconductive table, etc. All of this
is occurring even though the number of FCC interference complaints per
year has dropped to almost non-existent. Also, I never see any
electrical fast transient (EFT) failures at the European mandated levels
In Europe, *no* testing is mandatory. Certainly no standard can mandate
anything, but the EMC Directive does not mandate testing either. It's
entirely the choice of the manufacturer. There is no requirement to
waste time and money on tests that will undoubtedly be passed.
The subject of measurement uncertainty is complicated and can be
confusing, but its application does help to eliminate false 'FAIL'
results. Ditto the non-conducting table: that was highlighted by large
(6 dB) differences in measured results. And the permittivity of the 100
mm spacer can affect the results where it is used. A waterlogged wood
block give very good results!
--
OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk
When I turn my back on the sun, it's to look for a rainbow
John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK
-
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