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View Full Version : How to use a voltmeter


Oneill474
May 22, 2008, 11:02 AM
If you had four mysterious wires all painted the same. One of these wires were hot.

Would you touch each wire with the red probe and the black probe
To the metal frame . And watch the meter for activity. Do you have to set the meter before you start testing . Like ac or a car battery

Its just a hypothetical question. I was just curious how you would use the meter under various situation. For instance in the utility room I have a conduit
Pipe that shocks me, if I touch it barefooted. Does that mean a hot wire has broken somewhere in the pipe and is energizing it?

KISS
May 22, 2008, 11:39 AM
Assuming this is AC wiring, one of the easiest tests are each wire to ground or what you think is ground. A reading of the mains voltage means it's a HOT wire. A reading of nothing could mean the ground isn't grounded.

donf
May 22, 2008, 03:08 PM
Hey,

I would start by making sure I knew the source of those four wires! Electricity/Electronics is not a game to be played with a Divining Rod!

You should be able to tell us what the four wires look like. Where the wires originate.

To use the meter, for AC voltages, Set the meter to the highest setting of AC. By the way, are you using an analog (moving needle) or a digital meter?

By the way, don't feel to bad about the partial info. I just got hammered for doing it myself the other day.

Red Probe to test wires. Black probe to Ground.

Stratmando
May 23, 2008, 01:11 PM
If this is house wiring and it is AC Volts, I would first measure between a known good ground and each of the wires to look for voltage, Identify any hots and cap for now, then measure resistance between each of the remaining wires and ground. Resistance could be a bulb, a fan, or anything plugged into receptacle.
Always check for the pressence of voltage before doing resistance measurements.
On house wiring probes can be reversed and will not be a problem. If you were measuring Batteries or DC volts it would read a negative number on a digital meter, and on an analog meter needle would want to "peg" backwards, just reverse leads.