Re: Oscilloscope grounding question...

Default User wrote:

Hi,

How can you find out if a conductor is safe to ground?

For example, in a battery powered circuit since it is isolated from mains, I
should be able to ground it through the scopes ground lead and since it is
an isolated circuit, very little if any current should leak.

But what about various mains power supplies? How do you know if their
output is a ground that can be grounded safely?

I've been using a cheap meter I don't care that much about ($4) that does
current measurement. I have a cable that connects the mains ground pin only
to a wire and before I hook it up to the scope's ground, I've been using the
meter to test to see if any current flows through it to the ground first.

Is there a better method?

Check voltage, not current.

Even with a $4 meter, it probably has an internal fuse. Odds are that
when you check a 'hot' chassis for safety, you'll blow this fuse without
noticing. From that point on, the meter will read zero, which you will
assume to be a safe condition.

Think through what it is you are hooking up before doing so. That little
'gotcha' probably means you haven't considered other ways to fry
something.

--
Paul Hovnanian paul@xxxxxxxxxxxxx
-----------------------------------------------------------------------
Procrastinators: The leaders for tomorrow.
.

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