A test instrument, for calibration purposes, could be likened to a piano getting tuned. There are two parts to the process; first the tuner will check the individual keys are in tune and if not, then each will be adjusted to be ‘in tune’.
Testing instruments often have many test functions with different ranges, outputs, voltages and currents. These all need to be checked and where necessary an adjustment will need to be carried out on the individual test if it is out of specification, much like the piano keys being out of tune!
Manufacturers will not, mostly, freely give out calibration adjustment procedures so whilst many companies may claim they have a calibration ‘check lab’ they may not be able to put an out of specification tester back into specification. Also, often a password is required to access the calibration menu. In the past replacing components was very much a part of putting an instrument back into specification, however today this is much less common. Most manufacturers rely on adjustments made via the calibration menu using the firmware (not the electronic component hardware).
To operate a real calibration check and adjustment facility a company needs:
- Suitably qualified and trained staff
- Adjustment procedures and passwords for the equipment they calibrate.
- The correct (usually very expensive) test equipment which itself must be checked for accuracy periodically.
Metrotest calibrates thousands of testers annually, with approximately 70-80% of these requiring adjustment.
Metrotest are consistently striving to be better; the latest calibration equipment we are going to be purchasing has been quoted at $100,000 per unit and we will need at least 3 of these to service our calibration bases. Every item in our calibration lab is expensive even our soldering irons (not used often) cost around $5,000 each. When you hear a company say they have a calibration service, it will often be something crude and cheap.
Metrotest won’t take shortcuts or provide a dodgy anything just to make or save money, when all is said and done lives may depend on what we do!
All test equipment should be checked periodically for calibration if out of specification then an adjustment to bring back into specification is required.
Choose your calibration provider carefully or you could be just wasting your money!
By keeping your PAT tester (and all other testers) in calibration you are making sure your PAT is delivering dependable results. The Standard AS/NZS3760:2010 Appendix A A6 states ‘the equipment required to carry out the tests detailed in this Standard should be subject to routine verification at regular intervals to ensure it is working correctly and its accuracy is maintained.’
The manufacturers of the equipment recommend annual calibration, but also the amount of use your tester gets should be taken into account as well. If it is being used on a daily basis, doing many hundreds of tests a week, you may want to consider having the calibration checked every 6 months. If your PAT is infrequently used then a period of 18 months between calibrations may be more appropriate.
We provide an affordable, fast calibration service on Metrel and Sonel Calibrators and if you really can’t be without your tester whilst it comes to us, then we can organise a loan tester for you.
Is your tester in need of calibration?