Multicomp Pro Non-Contact Voltage Tester vs. Real Life

RE: Multicomp Pro Non-Contact Voltage Tester vs. Real Life

jw0752 — Tue, 26 Jan 2021 03:27:05 GMT

My son who is a maintenance technician at a manufacturing company and works with machines calls these testers "Chicken Sticks". They are critical protection when messing with lethal voltage wiring.

John

RE: Multicomp Pro Non-Contact Voltage Tester vs. Real Life

jw0752 — Tue, 26 Jan 2021 03:22:22 GMT

I would be real cautious about attaching a ground strap to my body for routine electronics work. It is one thing to do it when working on static sensitive devices and quite another when servicing a piece of general equipment. I can see where the probe itself should have a ground wire for reference but perhaps not attached to you.

John

RE: Multicomp Pro Non-Contact Voltage Tester vs. Real Life

jc2048 — Mon, 25 Jan 2021 22:44:19 GMT

The 9V labeller and the vacuum probably have wall blocks that are double-insulated and don't have a ground connection to the secondary side. The dc coming out is dc between the two output wires, but not necessarily dc with respect to ground. I think you'd find, if you looked at the output wires with a scope [just the tip of the probe, so that the measurement is with respect to the scope ground, otherwise if you clip the probe ground to either wire you're earthing the secondary side], that they have some 60Hz/50Hz on them.

With the ground wire one, I think, effectively, you're doing the test backwards. Your body has capacitance to the electric wiring all around you as well as ground, so rather than your body being a true ground reference, it's always got some ac voltage on it. If you want to experiment with it, place an insulated mains lead where you can reach it with your other hand, back the probe away from the earth cable until it just doesn't register, then move your free hand closer to the mains cable and the probe should start to register again [if my theory is correct]. Basically, the probe is working in reverse and the handle is sensing the ac potential on you, whilst the tip is doing the capacitance-to-ground reference part of things [the electronics in the probe can't tell the difference].