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Date: Sun, 05 Jul 2015 15:16:52 +0100
From: "Peter C.J. Clifton" <pcjc2 AT cam DOT ac DOT uk>
To: geda-user AT delorie DOT com
Subject: Re: [geda-user] OFFTOPIC: New toy...
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On 2015-07-03 23:16, Evan Foss (evanfoss AT gmail DOT com) [via 
geda-user AT delorie DOT com] wrote:
> Ok. It is odd how many people I know use non-isolated probes on things
> like the 3PH power to the motor.

My background was power electronics at university, so it seems obvious.. 
(likewise, I'm also sure I've accidentally grounded circuits with an 
oscilloscope ground probe before now).

A 100:1 non-isolated probe should be good for probing mains, motors, but 
obviously the ground needs to reference a chassis earth, not any other 
line (or neutral) conductor.

Peter