How to Measure Electrical Components Using a Multimeter

by Michael O. Smathers
A multimeter allows you to measure electrical current, voltage and resistance.

A multimeter allows you to measure electrical current, voltage and resistance.

A multimeter is a common device used to troubleshoot and measure the properties of electricity in components, such as voltage, current and impedance/resistance. Learning to correctly use a multimeter allows you to troubleshoot delicate electronic components by determining how electricity is flowing through them. You need to know how to use the two probes and when to have current flowing through a device you intend to measure.

Measuring Voltage

Turn on the device to be measured.

Set the multimeter to either VDC or VAC. This indicates whether you're testing direct current (DC) voltage or alternating current (AC) voltage.

Plug the red wire into the positive socket on the multimeter and the black wire into the negative. According to Science Buddies Electronics Primer, the negative socket is marked with "COM" for "common" and the positive socket is marked with "V" for "voltage."

Touch the positive lead to the terminal of the device that has a positive voltage and the negative lead to the negatively-charged terminal. This applies when testing DC. When testing AC, there is no positive or negative voltage. You'll be able to determine whether you have the leads connected properly by looking at the measurement; if the voltage reading on the multimeter is negative, switch the leads.

Measuring Resistance

Switch the multimeter reading to ohms to detect resistance.

Turn off power to the appliance or component you intend to measure.

Touch the leads to opposite sides of the component at electrical contact points or wires, so electricity can flow through the component and the meter can measure resistance.

Measuring Current

Set the multimeter to read amperage.

Turn off power to the component and break the circuit by removing a wire from its connection point.

Plug the black lead into the negative socket, marked "COM," and the red lead into one of the amperage sockets. According to the Northwestern University website, multimeters typically have sockets rated at 300 mA and 10 A, or 300 milliamps and 10 amps. Always plug the red lead into the 10 A socket until you're sure that the current is less than 300 mA.

Connect your leads to the open ends of the circuit to reclose the circuit. Turn the power on and get your reading.

Turn the power off and reconnect the original circuit.

Warnings

  • Set the range on your multimeter as high as possible to avoid damage. You can always lower the range if necessary.
  • Keep the multimeter and all electrical components completely dry. Water lowers electrical resistance and can damage the meter or cause injury due to electrical shock.

About the Author

Michael Smathers studies history at the University of West Georgia. He has written freelance online for three years, and has been a Demand Studios writer since April 2009. Michael has written content on health, fitness, the physical sciences and martial arts. He has also written product reviews and help articles for video games on BrightHub, and martial arts-related articles on Associated Content.

Photo Credits

  • Polka Dot Images/Polka Dot/Getty Images