A receptacle tester is a device that indicates if the live, neutral, and ground wires are properly connected at the power receptacle or power outlet. It contains selector switches and indicator lights, which are usually neon bulbs that drain very little current. The connection of the alternating current (AC) wall outlet should be correct before the receptacle is certified as safe to use. Receptacle testers are also used to verify that the neutral wire is not shorted to ground. This is confirmed as indicated by a good neutral-to-ground separation indicator or its equivalent.
Also called outlet tester, the receptacle tester is used by electrical inspectors to make sure that electrical wiring meets technical and safety standards. Polarized plugs ensure that the connections for live, neutral, and ground are consistent so that people cannot plug them in the wrong way. There is only one orientation wherein the power plug can be inserted into the AC wall outlet. This is very important because any modification that defeats the polarized nature of the plug and outlet is a safety risk.
One possible fault with the receptacle wiring is that only one wire is connected to the receptacle. If there is only one wire connected and it is the live wire, there is high risk of people getting electrocuted. Most equipment will have a resistance to neutral that is relatively low, as well as a relatively low resistance from neutral to ground. The ground is usually connected to conductive parts of the appliance or equipment casing. Again, if people touch an ungrounded unit or a unit with no neutral connection, electrocution risk is imminent.
It is possible to use electrical as well as electronic test equipment to confirm the proper wiring of the AC receptacle. Only the receptacle tester can show the results very quickly. If there are many receptacles to test, a receptacle tester and a voltmeter can be used. A voltmeter or multi-tester can quickly show the voltage from live to neutral, then to ground. If the two voltages are not the same, it indicates there is a live connection and there is no short circuit between the neutral and the ground.
The ground wire and the neutral wire are designed to be separate. There are some erroneous cases where the neutral wire is shorted to the ground wire at the receptacle. This may complicate the effective energy sources for the appliance or equipment. During lightning storms, electromagnetic discharge may induce currents into the grounding system. If the neutral is grounded, the input voltage to the appliance or equipment could surge beyond safe levels and create damage that could have been prevented by proper wiring.