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Subject: Signal vs. Chassis Ground

Date: 05/29/00 at 8:32 PM
Posted by: Dave Jones
E-mail: dave@djdesign.com
Message Posted:

When designing industrial video equipment it is usually best as far as signal quality to not have the video signal ground connected to the earth ground because of noise induced into the video signal via the earth ground.
I know that most safety standards around the world require the chassis of a machine to be earth grounded, but do they require the signal ground to also be earth grounded?
The problem comes when a machine somewhere (usually improperly wired) induces a potential in the signal ground that is fairly large relative to the earth ground. Then you can end up with a potential between the signal connectors (which are usually issolated from the chassis) and the chassis.

Anybody know if this is part of any safety standards, and/or what is the best approach to solving this delema?


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