Testing & Teaching
Two-Pole Tester (voltage indicator)
In short
A two-pole tester, a voltage indicator, is the instrument safe isolation is done with. It has two probes and a ladder of lights (LEDs).
If this is your home: this page is written for heating engineers. Mains wiring and gas appliances are not DIY jobs; call a Gas Safe registered engineer. If you smell gas, leave the building and call the National Gas Emergency Service on 0800 111 999.
What it is
A TWO-POLE TESTER, a voltage indicator, is the instrument SAFE ISOLATION is done with. It has two probes and a ladder of lights (LEDs). It has no ranges to set, and it does not read resistance.
The method:
- Prove it on the proving unit.
- Test every conductor against every other.
- Read dead on all of them.
- Prove it again.
A reading on a live circuit proves it too.
What the meter reads
230 volts (230 V): every light (LED) is lit. Dead: none.
DC as well, either way round: direct current (DC), as on an OpenTherm pair. With nothing on the pair, about 24 V DC, it lights the 12 and 24 V LEDs.
The PROVED lamp means the TESTER works, never that the circuit is dead. It is this simulator's own: a tester on site simply lights on a known live.
It lights on the proving unit, or on a live circuit of 50 V or more. It goes out on a dead reading. So after the dead test, prove the tester again.
Where it connects
Also in testing & teaching
Read the explanation
- Safe isolation in five steps: prove, confirm live, isolate, test every pair, prove again
Heating wiring is done dead. Prove the tester, confirm the supply is live, isolate and lock off, test every pair, prove the tester again. Why each step matters.
Practise it in the simulator.
Runs in the browser on a laptop or desktop. Cancel any time.