Ooooh, you're bringing up the snakes nest again. We just had this
conversation on this forum not too long ago. First of all your
experiences are unique, others have commented upon the problem, and yes
it included some big names. One of the things that can happen to you is
that you get a signal out of the PC that rattles around in you
equipment. Your note suggests that this is not true, but do make
certain.
After that you really only have two choices. 1) Disqualify the
vendor of PC your using and find another. (this could take a bit of a
search), 2) Examine the PC and make sure that all of the mating edges,
enclosure, I/O pcB's and connectors etc, are clean and making contact.
One of the problems is that in shipping these things around they loosen
up and lose their shielding capability. A very common cause of failure
seems to be the monitor, and possibly the fact that the monitor is
sitting on the case and deforming the computer enclosure.
The debate still rages whether or not you can modify equipment
made by others to allow you to pass. The FCC was strangely quiet on
this issue when one of the members asked them about it. I would read
that as a no.
I have had to find a computer that was quite for some of my
tests as well. Once you find it (and it won't be that difficult). Hang
on to it. Not only do I allow others to use this computer, I try my
darndest not to ship it anywhere. The test house I use is very good
about allowing me a little space to store it in.
Good luck.
Gary
-----Original Message-----
From: MartinJP [SMTP:marti...@pebio.com]
Sent: Tuesday, November 10, 1998 10:25 AM
To: emc-p...@ieee.org
Subject: Emissions testing with support equipment
EMC Professionals,
Our equipment requires the use of a personal computer to
operate.
We sell these PC's with our system. We test radiated
emissions as a
system including the PC. We have recently tested PC's from
two very
well known PC manufacturers. They have both failed Class B
limits.
This makes it impossible for our "system" to pass Class B
limits.
When we isolate the PC from the test chamber, our
instrument passes.
I am sure that we are not the only company that has this
problem.
Can you please provide me with your experiences on this
issue and what
solution you came up with.
All responses are appreciated.
Regards
Joe Martin
EMC/Product Safety Engineer
P.E. Biosystems
marti...@pebio.com
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