How to Use a Voltmeter on a 12 Volt


A voltmeter is any device that measures the difference in electrical potential between two points. You'll typically use a device called a multimeter to measure voltage; a multimeter also measures other electrical quantities. A common application of a voltmeter is to measure the actual voltage of a 12-volt battery.

Things You'll Need

  • Electrical circuit
  • Voltmeter
  • Two leads with alligator clips
  • Locate the settings on the multimeter's selector knob for direct voltage. This group of settings should have a label such as "V" or "V=." Each setting in this group should be labeled with the maximum voltage that the setting can measure.

  • Set the selector knob for the multimeter. In the case of a 12-volt battery, you already know that the voltage won't be much higher than 13 volts. You may therefore set the selector knob to the lowest setting with a maximum voltage higher than 12 volts. This will frequently be a setting labeled "20V."

  • Insert the plug for the black lead into the jack labeled "COM," "-" or something similar. Insert the plug for the red lead into the jack with a label that contains the characters "V" or "+."

  • Connect the alligator clip for the multimeter's black probe to the battery's negative terminal. Connect the alligator clip for the multimeter's red probe to the battery's positive terminal.

  • Interpret the voltage of the 12-volt battery. A fully charged 12-volt battery should have a voltage of 13.2 volts that will slowly discharge down to 12.65 volts. A battery with a charge of 75 percent should have a voltage 12.45 volts, and a battery with no charge at all should still have a voltage 11.89 volts.


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