[SI-LIST] Re: Book - (Chassis - signal ground)

Hi all,
You might be interested in some EMC training software
that analyses this issue in excrutiating detail.
If you are interested go to the RMCEMC Website
at http://www.ieee.org/rmcemc

Charles Grasso
RMCEMC ViceChair

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Bill Owsley
Sent: Friday, June 22, 2001 7:43 AM
To: si-list@xxxxxxxxxxxxx; 'si-list@xxxxxxxxxxxxx'
Subject: [SI-LIST] Re: Book - (Chassis - signal ground)



I seem to recall the subject was vigorously debated before and may be in
the archives.
- Bill

At 01:38 AM 06/22/2001 -0700, Larry Miller wrote:

>This is impossible in any but the smallest systems.
>
>We have quite a number of EMI experts on this reflector; I am surprised
that
>we are not hearing from them....
>
>The problem is much more complex than the posts to this thread indicate.
>
>Larry Miller
>
>-----Original Message-----
>From: Ashok Babu K [mailto:k.ashokbabu@xxxxxxxxxxxxx]
>Sent: Thursday, June 21, 2001 11:55 PM
>To: si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Re: Book - (Chassis - signal ground)
>
>
>
>I feel that if signal ground is to be connected to the chassis ground, then
>that connection should be done at one single point only. If connections are
>done at multiple points, that would eventually cause ground loops. Such
>ground loops will cause EMI radiations, ground bounce etc.
>
>More discussions are welcome.
>
>Regards,
>Ashok.
>
>
>----- Original Message -----
>From: "Paul Hamilton" <paulh@xxxxxxxxxxxx>
>To: <si-list@xxxxxxxxxxxxx>
>Sent: Friday, June 22, 2001 12:06 PM
>Subject: [SI-LIST] Re: Book - (Chassis - signal ground)
>
>
> >
> > An issue to consider might be ESD (EMC electrostatic discharge)
> > susceptibility. A complex system could present several current paths for
>ESD
> > strikes which may be difficult to manage. Isolating signal ground from
> > chassis (and also ensuring that signal ground cannot take an ESD strike)
> > would be one way to guard against ESD hassles. I've had grief with a
>simple
> > clam style enclosure about the size of a telephone - and chassis was
> > isolated from signal ground except at one point.
> >
> > Paul Hamilton.
> >
> > -----Original Message-----
> > From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
>On
> > Behalf Of Alex Horvath
> > Sent: Friday, 22 June 2001 9:34
> > To: si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Re: Book
> >
> >
> > Someone recommended Henry Ott's book "noise reduction techniques in
> > Electronic Systems" and I have this book and didn't find it very useful
>for
> > chassis grounding (it's very old). He actually recommends separating
>chassis
> > and digital ground. I think this is based on how systems in the past
often
> > had shielded cables going from one chassis to another. Often the ground
> > potentials are different in those systems and large currents can flow in
>the
> > shield and thus in the chassis. The large currents in the chassis can
>cause
> > noise and or the ground reference to change if the digital ground is
part
>of
> > the chassis. Most telecomm systems I work with today don't have any
>shielded
> > cables or for that matter any ground connections between chassis. Also,
>all
> > of the telecom companies I have worked at have tied digital ground to
the
> > chassis (also PC's are made this way).
> >
> > snip ..
> >
> >
> > _____________________________________________________
> > Thorlock International Ltd.    enquiries@xxxxxxxxxxxx
> > +61 8 9351 9200 (tel)          +61 8 9351 9522 (fax)
> >
> >
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> >
> >
>
>
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----------------------------
Bill Owsley,   owsley@xxxxxxxxx
919) 392-8341

Compliance Engineer
Cisco Systems
7025 Kit Creek Road
POB 14987
RTP. NC. 27709


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