How to Test the Amperage of a Circuit


Voltage remains constant, but amperes alter, depending on the current draw of the electrical device. For example, a lamp in your home uses 110 volts to operate, but the amperes needed to power it are likely to be about 1 ampere. An electric heater still uses 110 volts, but it's likely to use up to 15 amperes. An accurate and simple way to test the amperes of a circuit is to use a multimeter.

Things You'll Need

  • Protective gloves
  • Screwdriver
  • Multimeter
  • Put on protective gloves, if you're testing the amperes of an electrical circuit in your home to prevent accidental electric shock. However, if you're testing the amperes of a low-voltage battery operated circuit, it's not necessary to wear gloves.

  • Turn on the electrical device that's connected to the circuit you want to test the amperes of. The electrical equipment needs to be operating, so it draws amperes through the circuit.

  • Look on the electrical device to find the terminals where the wires connect to the device. You may need to open a panel using a screwdriver to access the wires, depending on the type of device. There may be two or three terminals. Look to the side of the terminals to find the "+" and "-" marks. If it has three terminals, the third is marked "T" or "Gnd."

  • Turn on the multimeter. Turn the dial or press the appropriate button to select the amperes setting on the meter.

  • Hold the plastic red-colored insulated prong from the meter in one hand and the plastic black insulated prong from the meter in your other hand. Place the tip of the red prong onto the "+" terminal and the tip of the black prong onto the "-" terminal.

  • Read the meter to find out the amperes of the circuit. Remove the prongs from the terminals and turn off the meter. Turn off the electrical device and replace the access panel, if necessary.

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  • Photo Credit Polka Dot Images/Polka Dot/Getty Images
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