When properly specified, socket testers provide a fast and effective solution to identify potentially unsafe installations and wiring faults of power outlets. They can be particularly useful as a service tool prior to installing new plant and equipment. Clearly socket testers are not an alternative to the full verification of wiring installations, however as a first line indicator they are an essential tool for all maintenance teams.

You may well be familiar with the Martindale Buzz-IT and Check Plug, the UK’s favourite test plugs for polarity and fault checking of 13A wall sockets, but did you know Martindale now offers a complete range of industrial socket testers for single and 3 phase systems.

  • The CP Series for single phase industrial sockets – 230V and 110V models
  • The PC Series for 3 phase supplies – 16A, 32A, 63A models for 4 and 5 pin configurations

The CP Series of industrial socket testers from Martindale includes both 230V and 110V models and two new models now cater for sockets rated at 32A.


Martindale CP201 230V single phase industrial socket tester

The Martindale CP201 is an industrial version of the classic check plug, is available with either a 16A or 32A plug to BS 4343 / IEC309. It’s capable of identifying 28 fault conditions. Other products in the range include the CP301 for use on 110V centre tapped circuits fitted with a yellow 110V 16A or 32A CT plug. Fault indications include Line 1, Line 2 and centre tap faults, plus Line 1 or 2 centre tap reversal.

Before carrying out any socket testing it’s important to understand what they are capable of and the different types available. All socket testers check that the earth, live and neutral are the right way around (called polarity testing). Some offer added features – they may include a buzzer in addition to LEDs to indicate a good socket or they may show a combination of indicators to identify which particular fault type is present. There is one fault that a socket tester and indeed no other piece of equipment can easily find – the swapping of the Earth and Neutral wires. This is because the earth and neutral are common at the substation, (if not closer), so electrically they are indistinguishable.

On plugging in the tester, faults are instantly indicated by one or more of the LEDs failing to illuminate, with the pattern of lit LEDs indicating the type of fault detected. Common fault conditions can be quickly identified from the look up chart displayed on the front of the label. This approach is fail-safe in the unlikely event of any the LEDs failing to operate.

For 3 phase supplies, the PC104 and PC105 can be used for identifying 7 wiring condition faults and also confirm the phase rotation sequence with bright LED indication.


Martindale PC105 five pin 3 phase socket tester

The range of 3 Phase Industrial Socket Testers cover 4 and 5 pin socket configurations and 16, 32 and 63 amp versions are available. The testers are enclosed in a tough rubber holster to withstand harsh of on-site environments.

See information on the complete range