Testing voltage requires the use of a multimeter or electrical tester. Non-contact voltage testers can also be used but they are not as accurate as a quality meter.
How to Check Voltage
Some meters will autodetect if the voltage being measured is AC or DC. Other meters have different settings for alternating and direct current.
It’s important to choose the correct setting for the circuit you are working on. Incorrect setting of the dial can lead to false readings which can be dangerous if you are testing for zero energy to make sure a circuit is safe to work on.
- If your meter has removable leads, place the black lead in the COM port and the red lead in the Voltage port. Multimeters will often have different ports to use depending on the measurement being taken.
- Turn your tester on to the correct voltage setting. Remember not to exceed the voltage rating of your tester.
- Place one lead on a neutral/common or ground. This will serve as a reference point for the actual part of the circuit you wish to test. Voltage is a difference in electrical potential between two points. A neutral/common or ground should have no voltage in normal conditions and that’s why they serve as a good reference point.
- Place your second lead where you want to measure voltage. Be careful not to create a short circuit with your meter lead while putting it on energized components.
As long as the circuit you are testing is intact this check will show the correct voltage. Things like a broken neutral wire, bad grounding, and induction can cause false readings.
A good habit to get into is putting the black test lead on the reference point and the red lead on the energized part of the circuit. This is important for DC circuits because having the test leads backward will display the wrong polarity on your meter. For example -24v instead of 24v.