Where do you use a voltage tester?

A voltage tester is designed to test for the presence of an electrical current. It is different from a multimeter, which can perform the same basic test, but also measures the voltage, current, resistance, and more. Both devices are useful for home electrical system repairs, and they function essentially the same. However, a multimeter requires more preparation to connect the multimeter leads to the correct jacks, select between testing AC or DC current, and to move the rotary dial to the appropriate setting for the desired test.

This added complexity is more than you need if you are just testing an outlet, light switch, wires, or even a battery for an electric current. A simple voltage tester is more affordable and easier to use. Use this guide to learn how to use a voltage tester to check if power is off before starting an electrical project.

Safety Considerations

Whenever you are dealing with the home electrical system it's important to proceed with caution to help avoid accidental electrocution. A voltage tester is one tool that can help keep you safe while you work on the electrical system, but it's necessary to note that a voltage tester can give a false reading. If the batteries are dying or the voltage tester is faulty, it may beep or vibrate while testing a dead circuit.

However, the real risk is if the voltage tester doesn't beep or vibrate while testing a live circuit. For this reason, it's recommended to test the voltage tester before every use. Additionally, it's a good idea to wear insulated gloves that can help protect you from electric shock.

Before You Begin

Receiving a false positive on a dead circuit can be annoying, but isn't as dangerous as receiving a false negative when the circuit is still live. Before using the voltage tester on a circuit, outlet, or light switch that appears dead, test the voltage tester on an outlet that you know is live to ensure that the voltage tester is functioning properly. Typically, this is a receptacle that is already verifiably powering a lamp, microwave, radio, TV, or computer.

Turn the connected device on to ensure that the outlet is live and powering the device. After this quick check, turn the device off and use the voltage tester to check the outlet for an electrical current. The tester should flash, beep, or both flash and beep to indicate that the outlet is live. If the tester does not respond, then the batteries may need to be changed or the voltage tester may be faulty.

There are three main types of voltage testers. The most common option is a contact voltage tester, which uses two metal probes to test the flow of electricity. There are also non-contact voltage testers which can detect an electrical current from about an inch away, instead of coming into direct contact with the outlet or exposed wiring. A third type of voltage tester, called a receptacle tester, is made for testing outlets. This device plugs directly into a three prong outlet to provide information about the electrical current.

Step 9

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More on Using a Two-Lead Circuit Tester

The two-lead circuit tester shown here also tests for voltage. When you touch a live hot wire (black or any other color except green and white) with one lead and a neutral (white) or ground (green or bare copper) with the other, the neon test lamp should light. It confirms that the power is on and that you have a complete (good) circuit. If the light doesn’t come on, either the power is off or you have a bad circuit.

This tool comes in especially handy in older homes when you want to know if an equipment ground wire (green insulated or bare copper) is actually connected to ground elsewhere in the system.

You often have to check this when you replace older ungrounded switches with grounded ones as now required by the National Electrical Code. You often find an unused bare ground wire folded back into the box, and you have to test it to make sure that it’s connected to the rest of the grounding system before hooking up your new switch.

CAUTION: Avoid touching a live hot wire and don’t let it touch anything else. Hold the tester leads by the insulated portion while making contact. And turn the circuit off again as soon as you finish the test.