Now sing along to that tune from Kool and the Gang…Caliiiiibration…

Now that you’ve hopefully got a nice happy tune in your head, it’s unfortunately time to delve into what can be a bit of a pain in the backside for anyone with an electrical test instrument: calibration.

It’s a process that’s really a serious requirement for test instruments, particularly since there are so many factors that can affect the efficiency and overall accuracy of your test instrument.

Imagine, for example, you’re working up a height with your clamp meter when, without warning, it leaps out of your hand for no apparent reason and falls down to the cold, hard concrete below.  Grimacing inside, you descend your ladder not daring to look at the damage to your expensive piece of equipment, but upon reaching the ground, you force your eyes open and – amazingly – your tester has survived the drop and looks perfectly fine.

At least on the outside.

On the inside, the drop to terra firma may have actually damaged something internally, meaning your tester is actually no longer capable of generating accurate results, or could actually be dangerous to use.

When something like this happens, getting your tester checked over, calibrated and – if needed – repaired, is absolutely essential. So many jobs rely on the abilities of your tester to generate accurate results, so it simply isn’t worth continuing to use a tester that could actually be generating completely wrong results as this is dangerous both to yourself and your customers.

There’s all kinds of other factors that could potentially damage your tester as well and throw off the accuracy of the delicate components. Little bumps, jolts, electrical surges, knocks and all kinds of general happenings during your day-to-day work can cause your tester to become inaccurate.

That’s why we recommend you always ensure your tester is accurately calibrated at least once a year. It may seem like a daunting prospect and you’ll be without your tester for a while, but we really can’t stress enough how important this is to ensure you’re working at your maximum accuracy and safety.

How Does Calibration Work?

In order to give you a greater idea of how calibration actually works, we asked our in-house calibration experts to give us the general breakdown on the process.

  • When we calibrate an instrument we make sure that it conforms to manufacturers specifications. For example, the manufacturer states a certain accuracy on a certain range. We test multiple points on that range to verify that the readings the instrument gives us are within that accuracy tolerance.
  • For example in a real world situation: when PAT testing you have set pass and fail limits, this limit is 0.2ohm, any value under .2 will pass a class 1 earth bond test, any value over .2 should fail.  We test at .14 and .26 (these are the 2 ranges closest to .2 that our calibrators will reach. Lets say the instrument under test reads .18 when we apply .26 this would fail by the manufacturers specs, however if the customer isnt aware of this he could passing items that should be failing a PAT test. But how does the customer know that his meter is reading correctly? That’s why we calibrate them.
  • When we calibrate an instrument we like to test every range, (e.g Multifunction tester:- we test, continuity, insulation, loop, RCD etc) we also perform general operation tests, does every character on the display illuminate?, do all the controls work(e.g rotary dials, switches, buttons, back lights, buzzers etc)
  • We also like to use the customers leads as then we can check everything they use, as sometimes the tester can be fine but the test leads might be faulty, this could mean that a resistance has incurred on the lead which will give faulty readings. If the leads have suffered damage even the slightest movement can effect your reading.

It’s Like New Again!

After going through the calibration process, you may be surprised to see your test results gained by your tester have changed dramatically. If you’ve been operating for a long time with an inaccurate tester, performing the calibration is likely to have a massive effect.

Even with only minor inaccuracies, a tester still isn’t working correctly and you’re providing inaccurate measurements to whoever you work for. Calibration makes sure that your tester works just like its brand new and shipped straight from the manufacturers, complete with the parameters they set during their extensive testing procedures.

Here at PASS we actually have some rather dandy calibration options available.

Written by Barry Atkins at www.tester.co.uk