The input jack on the DMM labeled with an A is to be used for ____.

• A. Volts
• B. Ohms
• C. Hz
• D. Amps

Answer: (D)

That input is for measuring current (amps). Measuring current requires the meter to be placed in series with the circuit so all the current flows through the meter’s internal shunt resistor. So you plug the red probe into the current input and the black probe into the common, break the circuit, and let the current pass through the meter. Be sure to choose the correct current range and ensure the meter’s fuse is intact for protection. This is different from voltage or resistance measurements, which use the other inputs and are arranged so the meter isn’t in the path of the current. If you’re measuring frequency, use the appropriate Hz function on the meter, which uses the same general input path as voltage measurements, depending on the model.