Simple Voltmeter Stuff
Feb 17, 2019
A customer called and asked questions about the electrical system on his machine. I asked if he had a voltmeter. There was a long pause, then he said, "Yes, but I don't know how to use it."
The problem was that he had purchased a fairly high-tech voltmeter, thinking "more is better." There were so many settings and options that he never figured out how to use it. So here's a primer for ANY voltmeter:
First, find the on/off switch. Some meters have a separate button or switch. Others turn on anytime the dial that changes settings is moved. Whatever the case, get the meter so there are numbers showing on the digital display screen.
Second, look at all the possible settings and find a capital "V" with straight and dashed lines horizontal above the "V." That setting is for Direct Current (DC) volts, and is what you want for farm equipment. When you set the meter to read DC volts it will show "0.00" on the display screen.
Third, go to a tractor, truck or other machine with 12-volt batteries, and touch the red lead from the tester to the positive terminal. Then touch the black lead to the negative terminal. The display will read from 11.5 to 13 volts, depending on the condition of the battery. At its simplest, that's how to use a voltmeter. Test for voltage anywhere on the machine by touching the red lead to a wire that should have voltage and the black lead to either the frame or a wire grounded to the battery's negative terminal.
Yes, it can be more complicated that that. Yes, you can set the meter to read alternating current (AC), check resistance, read milli-amps and all sorts of other things. But the first step is to learn how to read DC voltage. Once you have confidence to do that you can learn the rest on the fly.
Or, you can find the owner's manual that came with the unit and learn how to do it all. That's my plan, to someday find my owner's manual and learn how to use ALL the settings on my multimeter.