An age-old question we’re asked all too often, and so let’s look to see if we can find a definitive answer. I recently posed the same question across my social media channels.

As expected, the responses were wide and varied: annually, annually with a record of self-checks, every other year with a record of self-checks and even never providing a record of self-checks. 
 
But provided to who, I hear you ask? The schemes with whom instrument owners are registered to - think NICEIC, NAPIT etc. 
 
However, it’s not the registering schemes who are responsible for stating how often your multifunction or installation testers should be calibrated/certified.
 
The IET puts the onus on the instrument manufacturer and instrument owners to determine the calibration interval of their test equipment: Guidance Note 3 - “In all cases, the type and frequency of recalibration or checking should be as specified by the instrument manufacturer. However, the user should take into account ambient environmental and usage factors, as appropriate.
 
With this in mind, here is a one-stop reference as recommended by top industry manufacturers (in alphabetical order):

Conclusion: the responses recommend AT LEAST annual calibration checks. In addition, the majority also endorse self-checks using a calibration check box. 
 
Like the IET’s guidance, Fluke and Megger also suggest the frequency of calibration should be determined by you. But what does this mean? Special consideration needs to be paid to environmental and usage factors:

 • Is the tester stored in a constant temperature environment that is dry for long periods of time?
 • Is the tester used infrequently?

If the answer is yes to both of the above, you could extend the calibration interval - but make sure you’re keeping a record of self-checks as reinforcement. 

 • Is the tester likely to have been handled roughly?
 • Is the tester regularly transported/stored in a vehicle?

If yes to either of the above, the required calibration intervals will be more frequent. 

Test-Meter has an accredited calibration/repair centre and as such, we receive hundreds of MFTs and other equipment every week requiring annual calibration, repair, or both. We can tell when a tester has been looked after, but also when a tester has been subject to, let’s say more frequent use!

And so, here are our top 5 recommendations that concludes the answer to this article:

1. 1. Determine the usage frequency of your testers (annual calibration if you’re using your tester for a couple of days per month. Bi-annual calibration if you’re using your MFT for testing more regularly)
2. 2. Store your tester in a dry, constant temperature environment (office, under the stairs)
3. 3. Regardless of usage frequency/storage conditions, always keep a record of self-checks. Monthly checks will suffice (see our range of calibration checkboxes here)
4. 4. Visually inspect your test leads/testing accessories every time you use your tester for safety, but also for materials that could give you high resistance readings (dust/grit/grime)
5. 5. Make sure your batteries are charged, but more importantly not leaking (check out our guidance here on batteries)

Our skilled technicians pride themselves on offering a 5-star service for your instrument calibration and servicing needs. We’ve been on the tools as contractors, and we appreciate that down-time is a big no. As such we offer an express 24 hour-turn around from the time we receive your tester if required. In addition, we’ll always ensure your tester is updated to the latest firmware to keep your instrument up-to-date with never-ending regulation changes. Book your next calibration here: www.test-meter.co.uk/calibration