When I trained as an electrical apprentice in the 70s most test instruments were analogue and there were few of them; compared to what’s in an average sparky or techs tool case today. Back then, to be bluntly honest, very few Instruments ever saw the inside of a calibration lab, if they did it was most likely the people using them were involved in research and development, aviation or medical areas.
Today there are certain sections of industries that will get away without any checking of calibration, but the majority of specialized testers will be checked. From the 1940s to the 1990s the average sparky probably had ‘access’ to a ‘megger’, likely didn’t own it, but could gain access to one if he needed to use it. When I say megger (not the brand) I’m meaning a high voltage Insulation Resistance Tester which back then the probable output voltage was 500 and early units before the 1970s were hand driven wind up models!
The only other common instrument was the ‘Multi meter‘; again analogue until the late 70s and DMMs (digital multi meters) started turning up about the same time as females joined our industry, not sure what the connection is, but I’m sure we would be worse off without them.
Today things are totally different; some people tend to like and use stand alone instruments while others use multi function ones; there are advantages and disadvantages both ways.
That said; most electricians will have, as a minimum, the ability to do the following tests, either from a Multi function Instrument or stand alone tester. Loop test, RCD trip time and ramp current, RCD Phase rotation, 250-1000V insulation resistance test, earth resistance test. On top of this they’ll have a Multi meter and ……some other things like a PAT Tester, Cable Locator, Lux Meter, Tacho’s, Thermal Imaging Camera. Anyone comparing then and now will see the huge increase in the number of test Instruments in use and with this then also comes the need to make sure these Instruments are working correctly AND giving correct readings.
Today if there is actually a failure in the hardware itself it is likely to appear on start up, the instrument will lock the user out or display ‘Hardware Error’; effectively making it inoperable until it’s been repaired, BUT if the Instrument is just giving incorrect readings of the results this WILL NOT normally be obvious, hence all results may be meaningless! This will, potentially, open a mine field in the worst case scenarios when it comes to liability and insurance claims. I can assure the reader from first hand experience that unfortunately the one in a thousand chance can; and does happen; to someone and probably to everyone at some time.
So the question is what test instruments should have the calibration checked, how often and where should this be done?
Priority should be placed on the instruments YOU use and use frequently where accuracy of the results is crucial, for example most people will have excess measuring abilities amongst their test instruments that they may NEVER use. Let’s consider a PAT Tester (Portable Appliance Tester), these testers have multiple test functions often including an RCD test function, if you never use this function as you use a stand alone RCD tester, then accuracy of this function is irrelevant as you don’t use it!
Or another example with a PAT, most have a substitute leakage test function, this is not recognized as a valid test under AS/NS legislation, therefore why would you care about the accuracy of these results?
Or the Multi function Installation Tester that has a lux meter function you never use, again in this case accuracy doesn’t matter. The point is everyone will have different requirements on accuracy amongst their kit, focus on what’s essential first, going back to the analogue instruments many of you may have used in the past, sometimes all we were looking for was ‘meter needle movement’ that was sufficient for what you were doing. Accuracy is not essential everywhere, but where it is essential calibration needs to be verified, usually this will be outsourced to a calibration facility.
The other thing to be considered is the likelihood of damage or abuse which may happen to a tester; this will increase where something is used frequently, moved around a lot and there are multiple users. Metrotest have approx 30 PATs in use within our own testing business used by our techs, these PATs are normally checked for calibration and adjusted, where necessary, every 6 months BUT these PATs will likely do 150 tests per day AND accuracy of these results is essential. We don’t need to calibrate this frequently, but our use level is very high, so it makes sense for us to do it this frequently. I do however have to say if you have ISO/IANZ accreditation or a similar auditing system there will be specific requirements you have to meet to maintain the accreditation.
Before Sending Test equipment for calibration you’ll need to decide where. A few things you need to consider here are:
• What experience, expertise and qualification does the company you’re thinking of sending your test equipment to have?
• What calibration equipment do they have? There are the backyard operations which operate with very basic calibration equipment. These companies are mainly geared to on online sales, often focusing on PAT sales, giving dodgy advice and training, to them it’s just dollars! I would personally avoid these knowing what I know, this probably sounds like a competitors sales pitch, but remember sometimes it can be true!
• Companies that are authorized distributors of manufacturers with their own in house full service and repair facility, in my opinion, are your best option.
In one of our calibration labs we have lots of specialized calibration equipment which mostly costs in excess of ten thousand, 3 new units are costing around thirty thousand a piece! Much of our own lab equipment is sent out to other external labs for its calibration check; obviously we only do this where we can’t do it internally. You can buy calibration test boxes for under a thousand dollars, how will you know what they use to check the calibration of your testers? The results on the calibration certificate (if provided ) should have numerical value results of each test checked by the calibrator, some of our latest calibrators will automatically check/adjust where necessary and print results automatically (we can sell you one almost one hundred thousand dollars each). Our soldering irons used in the calibration/repair lab are four thousand dollars each. The head of our calibration lab comes from an avionics background, he’s not into its ‘ rough enough’; unfortunately that’s not the case everywhere!
Calibration passwords are often also required on test instruments, without these the calibration lab will likely NOT be able to perform adjustments if adjustments are required and they will also not be able to remove calibration reminders if they are displayed without this password. Calibration labs WILL NOT usually give these out to any non authorized parties, including other calibration labs, most will have legal agreements with manufacturers preventing them doing so.
So moral of story is CHECK BEFORE SENDING testers to calibration facilities that they will have the ability to do adjustments and remove calibration reminders. Think of it like this; if you buy a new Mazda car and it needs some work you wouldn’t take it to the Nissan dealer for technical support. Nor should the Mazda dealer have to give out technical information to non verified third parties who may not necessarily be experienced to do the necessary work without risking harm to the car. By not giving out this information they are helping to protect your car against misadventure.
Another service Metrotest offers, some others may as well, is what we call ‘MedCal’ (medical and calibration). This effectively is a service (not repair) on equipment being calibrated, it costs a little more but may be beneficial in preventing breakdowns. Our experienced technicians will look for upcoming problems that could cause a major problem in the near future. Things looked at will include internal battery voltages, internal connections, checking for signs of overheating, looking for loose screws/fittings as well as a clean out and in some circumstances lubricating moving parts. This MedCal can be done on various equipment, it seems particularly popular for PAT testers and their printers and Seaward, Metrel, Megger are all common brands which may have this service, it’s not just units we have sold.
All SupaPATs, including the AlphaPATs, METROiPATs and any other printing PATs like Sonel, Megger and Seaward are all available for the MedCal service, just let us know when booking a calibration and we can let you know the costs.
Calibration costs vary depending on what is involved in the calibration and between service providers, sometimes the cost of calibrations will make some things like cheap clamp and multi meters uneconomical to calibrate.