From: Alan Pearce <kiwiantipodean@googlemail.com>
To: "piclist@mit.edu" <piclist@mit.edu>
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Date: Tue, 29 Dec 2020 13:58:35 -0800
Subject: Re: [EE] Eliminating external noise through PS
Thread-Topic: [EE] Eliminating external noise through PS
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On Tue, 29 Dec 2020 20:34:20 +0000
madscientistatlarge <madscientistatlarge@protonmail.com> wrote:

> When you measure with the scope, how are you grounding the Probe?
> Those convenient wires with alligator clips make good antennas, best
> to take a wire, preferably beryllium copper because it's springy, and
> wrap one end around the exposed ground just behind the tip, then bend
> it to point the same way as the signal probe and trim to length so
> you are grounding it right where you are measuring.=20

Reminds me of a work colleague about 30 years ago, who was attempting
to fault find a bit slice CPU. He had about 2 feet of hookup wire from
the ground terminal on the front of the scope to an easily accessible
grounding point which I don't remember the location of, but it could
have been on the backplane. he then wondered why he couldn't see any
signals in the circuit under investigation except a mighty large mains
frequency sine wave at seemingly much higher amplitude than the the TTL
signal he was trying to measure. He seemed a bit put out that it didn't
do what he wanted.
--=20
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