What is the device called that detects electricity?

Device to verify the function of an electrical outlet

A receptacle tester for North American wiring

An electrical outlet tester, receptacle tester, or socket tester is a small device containing a 3-prong power plug and three indicator lights, used for quickly detecting some types of incorrectly-wired electrical wall outlets or campsite supplies.

Tests and limitations

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A receptacle tester being used to check for some types of improper wiring of an outlet. For this particular tester, proper wiring is indicated by the two yellow lights.

The outlet tester checks that each contact in the outlet appears to be connected to the correct wire in the building's electrical wiring. It can identify several common wiring errors, including swapped phase and neutral, and failure to connect ground.

The tester confirms continuity and polarity of the electrical connections, but it does not verify current-carrying ability,[1] electrical safety (which requires impedance testing),[2] insulation breakdown voltage, or loop connection of ring mains.[3]

Simple three-light testers cannot detect some potentially serious house wiring errors, including neutral and ground interchanged at the receptacle. There may be a "bootleg ground", where the neutral and ground pins have been connected together at the receptacle, which cannot be detected either.[4] These problems can be detected with a multimeter and a test load, to verify that the ground connection is separate from the neutral and is not carrying normal circuit return current, or more typically by using a more-sophisticated multifunction tester.[4]

A quick supplemental screening test for these simple miswiring errors can be performed using a non-contact voltage tester (NCVT) or non-contact voltage detector.[4] If a problem is thus identified, it can be investigated further using more-advanced equipment, or the outlet in question can be de-energized and disassembled for careful scrutiny.[4]

Some receptacle testers include an additional test button to test the triggering of GFCI devices, which supplements the built-in test button on the GFCI and can be used for testing outlets downstream from a GFCI receptacle. "Plug-in analyzers" may include earth loop impedance and other checks.[5]: 48–49 

History

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An early reference that describes the typical outlet tester circuit was published in Popular Mechanics in the March issue of 1967, and consists of two 27 kΩ resistors, one 100 kΩ resistor, and three NE-51 neon lamp bulbs with 100 kΩ resistors.[6]

See also

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References

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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.