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Select the appropriate function.
Make sure the device is unplugged and the switch is ON.
Connect the multimeter's probes to the device.
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A multimeter tests electrical continuity. It also can measure the amount of alternating current (AC or household current) or direct current (DC or battery current) in a plugged-in or live circuit. It can check voltage, too. For example, a multimeter can verify that there are about 120 volts in an AC circuit or that a 9-volt battery is fully charged. In addition, a multimeter can check resistance. A continuity tester checks resistance, but answers YES or NO. A multimeter checks resistance and reports how many ohms (the measurement of resistance) a circuit has.
Multimeters are relatively inexpensive. Multimeters are available in digital and analog models. Digital multimeters will display readings in numbers. Analog multimeters indicate values with a needle over a scale.
The analog unit shown was $10 and the digital multimeter was $20, though you can pay $50 or more for more accurate models. The ones used in this book are sufficient for most electrical tests.
You can use a multimeter to test motors, switches, controllers, and many other electrical gadgets. Specific instructions will come with the multimeter (also called a volt-ohmmeter or VOM) you purchase.
Here's how to use a multimeter to test an electric appliance:
- Disconnect the cord from the power source, except when testing a live circuit.
- Plug the test leads in to the multimeter.
- Select the function (ACV, DVC, RESISTANCE) and the range (maximum reading expected).
- Connect the probes to the cord or appliance component.
- Interpret the reading. The Fix-It Guides and the device's owner's manual will tell you what to expect—and what to do about it.
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