Attach alligator clips to the probes before you turn on the meter. These are useful for hands-free operation and keep fingers out of dangerous areas. A battery is good if the reading is within 20 percent of the rating on the battery or appliance. In other words, a reading of 7.2 or higher means a 9-volt battery is acceptable.
Don't use a meter with a cracked housing or probes with bare wires showing. Never use the ohm setting on a multimeter on live voltage. You will damage the meter. Use a voltage probe or test light if you just want to check if a circuit is live.
How to Use a Voltmeter. As its name implies, a voltmeter measures voltage. Some models also measure ohms and amperage; these are called multimeters. Meters are available in analog and digital styles.
Plug the probes into the meter. Red goes to the positive (+) and black to the negative (-).
Turn the selector dial or switch to the type of measurement you want. To measure direct current - a battery, for example - use DCV. To measure alternating current, such as a wall outlet, use ACV.
Choose the range setting. The dial may have options from 5 to 1000 on the DCV side and 10 to 1000 on the ACV side. The setting should be the top end of the voltage you are reading. Not all voltmeters have this setting.
Turn the meter on.
Hold the probes by the insulated handles and touch the red probe to the positive side of a DC circuit or either side of an AC circuit. Touch the other side with the black probe.
Read the digital display or analog dial.