Unlike voltage detectors, voltage testers need to come into contact with an electrical supply to function. Voltage testers have metal probes which are inserted into the electrical circuit. Voltage is tested in parallel with the circuit, so the tester is not a necessary part of the circuit. Forgotten what “in parallel” means? See: Wonkee Donkee’s lesson on electricity.
Voltage testers take an actual voltage reading and give a numerical range to work from, rather than simply identifying the presence of voltage.
Voltage testers can give an exact numerical value if they have a screen, but more often the indicators are in the form of an LED scale. This scale will give a range rather than an exact number for the voltage.
So, for example, there could be LEDs labelled 6, 12, 24, 60, 120, 230 and 400. Then if you were to then test something with a voltage of 30, the 6,12 and 24 LEDs would light up; indicating that you have a voltage between 24 and 60. Remember to check the instructions for each individual model to check how it works though.
What can voltage testers be used on?
Voltage testers can be used on DC as well as AC voltages, so it is possible to test batteries with a voltage tester. Like a voltage detector, these devices can also be used to test plug sockets and circuit breaks. However, they can additionally test continuity and polarity because they are doubled probed and in contact with the circuit.