400V Voltage Tester, 12 to 400V AC, 12 to 500V DC, IEC 61243-3

This is the tester an electrician, a fridge technician or a maintenance fundi keeps in a top pocket. It tells you whether a circuit is live before you put a hand or a spanner on it, which is the first thing you do at a distribution board, a socket, a light fitting, a control panel or a vehicle wiring loom.

It is a two pole tester rather than a pen, and that is the important difference. Both probes go onto the circuit, one on each conductor, and the reading comes from the voltage between them. That is a low impedance test, which means it does not give a false live reading from induced voltage on a long cable the way a non-contact pen sometimes does. A row of LEDs shows the voltage level rather than a single lamp, so you can see roughly what is present, and the polarity indication tells you which side is positive on a direct current circuit. The range is 12 to 400 volts alternating and 12 to 500 volts direct, which covers household wiring, three phase panels and vehicle and battery systems. It conforms to IEC/EN 61243-3, the safety standard written for this class of tester.