A volt meter does exactly what its name implies--it measures voltage. This device differs from meters that measure ohms or amperage. For those types of measurements a device called a multi meter is used. Volt meters are available in analog styles that use needles for measurements, and digital styles which usually use an LED number display. Using a voltmeter is very easy, and here is a guide to help you learn how to use one.
Connect Probes to the Volt Meter
Attach the red probe to the positive connector and the black probe to the negative connector.
Select the Measurement Type
Determine what type of measurement you want to perform. If you want to measure direct current, for example a car battery or common household battery, select the DCV setting. To measure alternating current, like that comes from a wall outlet, use the ACV setting.
Choose a Range Setting
Most voltmeters come with setting options for both DCV and ACV settings. Select the voltage range that is appropriate for the piece of equipment you wish to test. For example, if you're testing a 12 volt appliance or piece of equipment, choose a range setting of between 10 and 14 volts.
Turn on the Voltmeter
Find the on/off selector for the volt meter and switch it to the on position.
Hold the probes of the volt meter by the rubber or plastic insulated handles and touch each probe to the appropriate wire or connector. Touch the red probe to the positive wire and the black probe to the negative wire.
View the Measurement
Observe the needle on the analog voltmeter or the LED display on a digital voltmeter and determine the voltage output by the equipment you are testing.
Volt Meter Buyer's Guide
Before you go out and buy a volt meter, there are a few things you should consider when making your purchase.
What to Look for in a Volt Meter
How good a volt meter you actually need depends on how often you will be using it. If you frequently make repairs on electrical systems or other electrical devices, you might want to spend a little more money on a quality voltmeter with more options. Purchase a quality LED display voltmeter because the difference in price between an analog display and LED display is minimal or none.
If you're looking for the highest quality voltmeter, you should choose one made by Fluke. If you're just looking for something for occasional use around the house, but also want something reliable, go to Sears and pick up one of their Craftsman voltmeters for between $20 and $40. If you just need something to keep in the trunk, go to RadioShack and find one for $5 or $10 that will work just fine in most cases.
Voltmeters and other types of handheld meters all lose their accuracy over time. You can have a handheld voltmeter recalibrated for about $50, but you probably don't need to spend that much on a unit anyway.