A non-contact voltmeter can help you quickly check for the presence of live wiring without touching bare metal. While a standard voltmeter can give you a precise measurement of voltage in a circuit, you must touch the meter's probe to the circuit to do it. A non-contact meter will signal you if a wire has voltage in it greater than a certain level, but it will not give an exact reading.
How to Use Non-Contact Volt Meters?
Plug a table lamp into an electrical outlet, and turn it on.
Turn the voltmeter on. If the voltmeter is a multifuction meter, turn its non-contact voltmeter mode on. Hold it to within 1 inch of the lamp's electrical cord. The voltmeter should give a clear indication of the presence of voltage. It may flash a light, make a beeping sound or both. If it does not, check the meter's battery and replace it if necessary. Try the test again.
Turn the lamp off. Move the meter back and forth over the lamp cord. It should still give a voltage reading, since the lamp is plugged in.
Unplug the lamp. Hold the meter near the lamp cord. It should not indicate a voltage.
Hold the meter next to the outlet. It should indicate a voltage.
Tips & Warnings
- Some non-contact voltmeters are sensitive enough to detect voltages as low as 24 volts. This is handy for tracing low-voltage wiring such as doorbell circuits (Reference 2, page 17).
- Metal conduit, shielding, outlet boxes and panels will interfere with the meter's ability to detect a voltage.