How to Use a Multimeter

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By Dave Donovan
eHow Contributing Writer

Article Rating: (6 Ratings)

In many of my How Tos, I recommend using a multimeter to perform certain electrical tests. If you are unsure about what a multimeter is—or how to use one—then this article should help you to become more familiar.

When performing electrical work, it's always good to have a multimeter on hand instead of a regular voltage meter because a multimeter allows you to handle any tests that may need to be performed.

Difficulty: Easy

Instructions

Things You'll Need:

Multimeter

Step 1

Basic Multimeter

First off, there a number of different types of multimeters. Some have a huge assortment of specialized settings while others have a dial with just a few settings. If you aren't familiar with multimeters and you wish to purchase one, then opt for the one with the fewest number of settings. If you accidentally set the multimeter to the wrong setting when testing something, you can ultimately destroy the meter. Leave the big-boy meters to the professionals. Multimeters are commonly called ohmmeters.
Step 2

On the front of the multimeter you will see a dial, some settings and a few ports on the bottom. These ports are where the leads get plugged into. When testing for voltage, resistance or continuity, the red lead always gets plugged into the port featuring VmA and the black lead gets plugged into the port labeled COM. If you are testing for amperage, then it requires a clamp probe that gets plugged into the COM and A ports. There may be another port labeled 10ADC, but that one is rarely used. All of the ports are usually color coded so you know which probe goes in which port.
Step 3

Around the dial you will see a variety of numbers and signs. On basic multimeters there should be ones that read V, A and a sign that resembles an O with feet. Testers that offer the ability to test continuity will have another setting with a sign that resembles a right-pointing arrow and a plus sign.
Step 4

The V setting is used to test for voltage, the A setting is for testing amperage and the O with the feet is used for testing ohms, or resistance.
Step 5

When you want to test an outlet to see if it is powered, you will want to set the tester to the V setting.

If you are building something with electronics, you can test the resistance of a resistor by setting the tester to read ohms. Just be sure that the resistor has no power flowing through it and it is not soldered to the board yet.

If you want to test a fuse to see if it is blown, set the tester to read continuity and with the fuse removed from its clamps, touch one probe to each end of the fuse. If you get a reading with a beeping sound, the fuse is still good. If you get a reading of OL, then it is bad.
Step 6

Testing for amperage requires a clamp type of probe and cannot be accomplished with the two individual probes. If you have the clamp add-on for your tester, it gets plugged into the A and COM ports. Then, you clamp the tester over the circuit wire you wish to test. You will use this function only in the electrical panel and only on the hot wire, so it is vital to be extra careful when testing for amperage. An easier way would be to purchase a plug that features a looped wire specifically for amperage testing.