From: Sar Saloth (sarsaloth_at_yahoo.com)
Date: 2002-03-14 16:05:29
>
> > I have seen one EMI test report from a European
> > notified body for a medical device that clearly did not understand the
> test
> > specifications. Some other Europeans I had spoken with also didn't
> > comprehend some of the important points of the test specification (most
> > importantly the requirement to modulate the carrier to at least 80%
>
>I guess this is AM ?
Yes. I think there are some subtleties for whether you use sine-wave
modulation or whether you use square-wave (maybe different depth of
modulation or something).
> > with a
> > frequency approximately in the middle of the pass-band for the device
> under
> > test).
>
>To detect the effect of demodulated HF instead of only a seemingly drifting
>offset voltage ?
Yes. And I have seen a device that was given a complete PASS by a notified
body, but they did not modulate the signal. The EEG channels were AC
coupled, so that drifting offset just disappeared and had no impact. The
test specification is clear about requiring modulation. I think the real
trick to getting a product out cheap is to find such a lab. (damn, I still
wish I had the report). As long as a failure doesn't hurt anyone.
Sar
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This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:40 BST