PAT testers are accurate instruments so it is important to make sure that they continue
to measure correctly. A faulty tester could fail to pick up faults with electrical
appliances, which could result in putting property and people at risk. Annual calibration
of your tester will prevent this and ensure the accuracy of your testers.
Note: The IEE PAT Testing Code of Practice says “The accuracy of a test instrument
should be verified and recorded annually or in accordance with the manufacturer’s
The benefits of using the manufacturer to carry out the calibration is that they
can often extend the warranty on the PAT Tester and carry out any upgrades.