Technology

How does a PAT tester work?

Electrical devices are an essential part of our daily and working lives, but when not maintained correctly, they can pose significant risks.

That’s why regular testing is critical for ensuring safe working and living environments. One common testing device is the PAT tester, available from RS, which we’ll go into more detail about in this article.

What is PAT testing?

Before we can dive into PAT testers and their working functions, we’ll need to define what PAT testing is.

PAT stands for portable appliance testing. In Australia, you’ll also commonly hear the process referred to as ‘Test & Tag’. It involves testing electrical equipment with detachable plugs and leads to ensure safety, efficiency, and quality.

PAT inspection is a routine process in Australia, New Zealand, the United Kingdom, and the Republic of Ireland. It’s also a legal requirement in some areas.

The process involves visually inspecting electrical equipment for any defects, testing flexible cables for proper condition, and where necessary, conducting one or more of the following tests:

  • Earthing or grounding continuity,
  • Insulation soundness,
  • Exposed metal presence.

While quick visual checks are important for electrical maintenance, regular testing by a trained technician or other competent person is crucial.

What is a PAT tester?

A PAT tester is a specialised device technicians use to perform portable appliance tests. They will immediately provide a ‘pass’ or ‘fail’ rating while testing, indicating whether the appliance is compliant with safety and quality regulations.

Most simple testers will use a lights system, with one light representing a ‘pass’ and the other representing a ‘fail’ result. You’ll also typically see options for Class I or Class II appliances.

Some more advanced PAT testers offer additional information, conducting further tests such as:

  • Earth continuity resistance,
  • Fuse testing,
  • Lead polarity,
  • Protective conductor measurement (or earth leakage tests),
  • Insulation resistance tests.

You can also find computerised PAT testers that can connect to software via Bluetooth, making it easy for technicians to record and store test data.

How PAT testers work

PAT testers work differently depending on the type of test being carried out. For example, during an insulation resistance test, the device internally shorts together the neutral and live pins within the appliance.

Earth leakage tests are an alternative option when insulation resistance tests aren’t possible. It involves plugging a Class I electrical appliance directly into the tester and activating the procedure. The appliance will briefly switch on and the tester will monitor the current flowing between the in-line and neutral conductors.

Earth continuity tests involve the user inserting the appliance’s mains plug into the PAT testing device and connecting a test lead to an earth point on the appliance. A test current will pass along the earth cable from the plug’s pin to the appliance’s bodywork. The tester will then measure the connections’ resistance and return a pass or fail result.

Conclusion

PAT testing plays a crucial role in keeping appliances safe, compliant, and performing as expected. The PAT tester is an essential device in this process, allowing clear and accurate measurements to determine if electrical equipment is suitable for use.

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