Re: [SI-LIST] : Comments from your SI seminar (SendII)`

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From: Mike Mayer (Mike.Mayer@cp.artesyn.com)
Date: Thu Oct 28 1999 - 06:40:43 PDT


>>>>> "Denomme," == Denomme, Paul S <Paul.Denomme@viasystems.com> writes:

[...]

> I went to several courses at the PCB Design East, and each
> course instructor had their own opinion on what they believe is
> the correct way of doing things. It is sad that our industry
> cannot take a concensus and come up with the CORRECT way of
> doing things. Instead of using testing and empirical data to
> determine what is accurate, they bicker about why ones methods
> will or won't work.

Part of it is that people want "rules of thumb". Alot of these issues
are complicated enough that there are few general rules. The other
thing is, as you point out, the dependence on empirical data. The
CompactPCI Specification says that "CompactPCI boards shall not
connect earth ground (on front panel) through a low impedance path to
logic ground used on board." I seem to recall seeing a paper measuring
the difference in radiated emissions between boards with logic ground
connected to chassis ground and with them connected, the conclusion
being that emissions were lower when they were connected. The
CompactPCI spec does not say why they require them to be isolated, si
I don;t know if there is a good reason or if they were just using a
"rule of thumb".

-- 
=============================================================================
Mike Mayer                               Artesyn Communication Products, Inc
Senior Hardware Design Engineer          Madison, WI
Mike.Mayer@cp.artesyn.com                http://www.artesyn.com/cp
=============================================================================

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