A socket tester is a portable electrical instrument used to test for correct operation and wiring standards on power outlet sockets. It is typically a hand-held instrument that either plugs directly into the socket with pins mounted on the tester or comes equipped with a short lead and plug. Depending on the sophistication of the socket tester, a range of status indications may be returned including disconnected phases, reversed phases, and, in the case of a top end instrument, earth loop impedance. Most testers display test results on an array of light emitting diodes (LEDs), and some also allow for an earth leakage test to be carried out with the push of a button. Socket testers are available for most common industrial and domestic voltages and pin configurations.
Power outlet sockets are typically the most numerous of electrical devices in homes and commercial buildings. They are also the first line of contact between the power grid and the consumer, thereby making their correct and safe operation a critical consideration. Tests should ideally be carried out on a regular basis to check for faults, but the large number of sockets typically present in any single venue can make this an arduous and time consuming task. A socket tester can speed the process up considerably and return reliable and accurate information about the status of the tested sockets.
These instruments are usually small, portable units often no more than a couple of inches square. They are either equipped with a set of pins mounted on the casing which plug directly into the socket or have a short lead and separate plug. Once plugged into the socket, an array of LEDs on the face of the instrument give an immediate indication of a number of relevant conditions. These include the presence of power on the socket and whether the ground, neutral, and live feeds are connected to the correct pins.
Additional functionality is available in high end socket tester units such as ground loop impedance which is one of the most critical factors for safe socket functioning. Other models include a ground fault test button which allows the operator to test earth leakage units (ELUs) for correct operation; this is an equally critical safety function of socket circuits. Most socket tester models are configured for two and three pin 115–230 volt sockets, although there are variants available which can test high voltage industrial sockets.