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suburbanbeat 26th January 2020 05:20 AM

Need super basic help using my voltmeter
Hi all. Picked up a voltmeter at a yard sale and haven't had occasion to use it until now. I'm trying to use it to, very simply, identify the neutral and hot wire of a power cord, where neither has identifying markings.

I've got my red and black probes plugged into the right jacks, but I don't know what settings to use to get a basic readout of current.

Once I have the right settings, my understanding is that I'm to touch the black wire to a metal object and the red to the wire. Whichever shows a high current is hot, and whichever shows ~0 is neutral, yes?

But first... what the heck do I set this thing to? I'm in the United States. Thanks a lot!

Jay Rose 26th January 2020 05:32 AM

You want ~V (AC volts) and whatever range is over 120. Or set it to the heist range and then back down. Or use auto, if there is one.

CAUTION: there WILL be hazardous voltages on the probes. Lots of us measure these things every day. But don’t do it unless you understand the risks and safety procedures and are comfortable with them. You could be hurt.

David Kulka 26th January 2020 11:30 AM

To identify neutral and hot use the AC volts setting as Jay noted above and connect one probe to something close to ground potential. That could be a water pipe, an electrical conduit, a metal door frame, or just dirt or soil. Then (carefully) use the other probe to measure voltage on the two conductors you want to test. Hot will be approx. 120 volts and neutral should be between zero and 5 volts.

Black probe plugs into the COM jack, red into the jack on the right. Don't use the 10A jack for this test. You will be measuring voltage, not current.

DrewE 26th January 2020 09:12 PM

If by "power cord" you mean one you plug into an outlet, the best approach would be to unplug it and use the continuity beeper function (which is with the switch straight up, indicated by the radiating concentric arcs next to the diode symbol). You'd put the black test lead in the middle "COM" jack on the meter, and the red lead in the righthand jack that's used for everything except 10A range current measurements. On the plug of the cord, the hot is the narrower blade. Touch one lead (for this it doesn't matter which one) to the narrower prong, and the other to the wire ends in succession. The one that beeps is connected to the hot prong.

If it's a three prong plug with the flat blades equal in width, the hot is the blade immediately clockwise from the round ground prong as you're looking down at the plug. If it's a two blade plug with both blades the same size, it doesn't matter as the plug is not polarized and can be plugged into the outlet in either orientation and so which one is hot will not always be the same.

If you have no plug, and are looking so as to install one properly, the hot should be connected to the fuse and power switch in the device, assuming it has one or the other or both of them.