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Date: Thu, 24 May 2012 11:34:38 -0400
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Subject: Re: [geda-user] Chassis ground vs Circuit ground
From: Bob Paddock <graceindustries AT gmail DOT com>
To: geda-user AT delorie DOT com
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On Thu, May 24, 2012 at 10:45 AM, Joshua Lansford
<Joshua DOT Lansford AT laserlinc DOT com> wrote:
> Hello.
>   I have an Ethernet Jack with a separate chassis ground.  The grounds
> connect by zero ohm resistors beside the jack.  Supposedly this keeps noise
> from following the cable onto board.  I saw somewhere not connect chassis
> and  together on the board but though the enclosure.  The card with plated
> edges slides into a metal extrusion.  Should both edges be chassis ground or
> should one be circuit ground?   This supposedly keeps a DC difference from
> developing but dissipates noise.  What are your opinions about how to deal
> with chassis ground vs circuit ground?

This is one of those areas that there is no right answer.
The requirements vary by country and even the industry within the country.
That is why the zero ohm resistor is there, so it can go either way
depending on where it is being sent.

Electrically I'd prefer to not have signal ground be chassis ground.
Chassis ground is a good place to hook up the negative side of your
Arc Welder (really, I've seen that).  Regulations say they have to be
connected because my five volt logic might be a shock hazard (compared
to the Arc Welder?)...

For an example: In Coal Mines in Australia any green colored wire must
go to Earth Ground.
So we had to replace our rainbow colored ribbon cables with gray ones
in our system.