Here’s how you can measure amperage, or how much electricity is flowing through the circuit:
1. Connect the black probe to the common (COM) jack on the multimeter. Plug the red probe into the jack labelled as A. This may also appear as “10A” or “20A” depending on the multimeter make and model.
2. Set your multimeter to the amperage meter function (A⎓). Some multimeters will automatically adjust amperage measurement settings while other meters may require you to choose from a range of high or low amp settings. You want to select the setting that is higher than what you are measuring. By setting your meter to handle more amps than you expect to measure, you help protect against blowing the fuses if the current is stronger than you thought. If the current is significantly higher than the amp setting, you could damage the meter.
3. Detach the positive wire from the power source. This process is called “breaking the circuit.” In order to test the amount of current flowing through a circuit, you have to attach the multimeter so it completes that circuit.
4. Touch the red probe to the power side of the positive wire. Touch the black probe to the other wire. Power will be restored to the circuit once you touch the black probe to the wire.
5. Check your reading. If your digital multimeter reading is negative, switch the black and red probes for a positive reading. It should be the same number, but without a minus symbol.