Re: Ground fault clamp thingummy. Sorry, non-political post.

From: Tim Shoppa (shoppa_at_trailing-edge.com)
Date: 09/19/04 

Date: 19 Sep 2004 02:10:39 -0700

Keith Wootten <keithw@nononono.co.uk> wrote in message news:<VjamMVCXewSBFwuG@clara.co.uk>...
> Any advice on this test-bench safety problem?
>
> I have some metal-cased equipment whose body should be nominally at
> ground potential, held there by a cable shield. The cable is very long
> and I can't ground the equipment body locally as the resulting loop
> interferes with its operation.

The standard solution (well, other than dyking off the ground pin
from the mains cable): two channels to scope, one of them the signal in
the tested equipment, the other the ground from the tested equipment,
and scope in differential mode.

Other than that, I can only recommend isolation transformers etc. as
a way of getting around existing ground loop problems, and even these
have safety issues if you don't properly do single-point grounding to
the clean side.

Tim.

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