I'm doing some rewiring and have run into some confusion. I have a240V circuit, which, when on shows about 240V on my multimeter. WhenI flip it's breaker, though, it shows some number of mV (instead of0). This confused me.I mentioned this to someone else, and they asked what the amperage waswhen the breaker was off. Seemed like a good question. So I went andpicked up a clamp meter that detects amperage. It showed 0. Thisseemed strange, so I called the company (Ideal) and they said I had toput a load on the circuit to detect any amperage. Ok, but thatdefeats the point...Or does it? Maybe that it says 0A when the breaker is off, combinedwith a few mV means it's not a problem at all?

Hi,If you are using DVM, it's OK. DVM has too high an input impedance, it'll pick up suck stray voltage. That is why I still keep and useold Simpson 260 analog meter.

very low voltage -- dangerous?

Jan 05, 2008 42 Replies

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krw 18 years ago

Ever hear of a "Vacuum Tube Volt Meter"? ;-)

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Tony Hwang 18 years ago

Hmmm, If you know VTVM, you must be an old fart, LOL! I still have one and it works 100%.

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AZ Nomad 18 years ago

I once tried a neon test meter and it was even worse. It *constantly* read voltage when it was just stray fields through insulation. I ended up setting up a test light using the light fixture I was in the process of installing. A 60W test light.

A better solution would be to slap a 5K resistor across the probes of the meter. Do the math to make sure that it won't smoke at line voltages. (W=E^2/R)

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