Why calibrate your test equipment?

Test and measurement equipment is essential to the electrical trade, be it for electrical, data or control systems. Whether it’s for commissioning a new installation or finding a fault in an existing one, electrical tradespeople and technicians put a lot of faith in the readings from these instruments. But how can they be certain what’s being reported is correct?

Modern electrical and data test equipment is generally very sophisticated and has become vital for contractors to provide a professional service to their clients. Many instruments can analyse complex parameters and have digital outputs so measurements can be downloaded to PCs for inclusion in professional reports. And some of these reports are pivotal in making major decisions about infrastructure, processes or facilities that can have far-reaching consequences for a client.

So why would a contracting firm spend all that time and money to get the right test equipment for their business to provide a high level of service to their clients, and then put all that at risk by not ensuring the accuracy of the results they compile? That’s essentially what’s at risk if contractors don’t ensure their test equipment is properly calibrated.

Calibration of test equipment is not mandated in standards; however, AS/NZS 3760 outlines critical requirements for in-service safety inspection and testing of electrical equipment, while AS 17025 addresses the competency requirements for testing and calibration laboratories - both of which provide important guidelines in ensuring the accurate, and therefore professional, output from contractors.

Testers being used in the field, whether on a construction site or in service, are typically subjected to some fairly rough treatment - bouncing around in the back of a car, dropped on site, knocked against hard objects, etc. Tester manufacturers understand these environments and design them to take a reasonable amount of harsh treatment. But they are precision instruments that do react adversely to the environments they’re used in. Even if they’re treated carefully and not knocked about, changes in ambient temperatures and humidity levels will cause a shift in their readings over time. These challenges are well understood by most electrical tester manufacturers and advise regular adjustments to the instruments to ensure their outputs are accurate and therefore dependable.

One such manufacturer who acknowledges the importance of regular calibrations is Agilent. The company has an extensive portfolio of test instruments that covers many applications and industries. Right from the time Agilent set up operations in Australia (as Hewlett-Packard at the time), it established a calibration laboratory. Some 35 years later, Agilent operates one of the largest calibration laboratories in the Southern Hemisphere, with capabilities that range from DC to many GHz.

Keith Baucke, Support Business Manager for Agilent’s Service Solution Unit, runs the calibration laboratory and has a clear understanding of the value calibration provides to the users of test instruments.

“Anyone who operates test equipment must understand how important measurement is to them,” states Baucke. “If it is important - to validate equipment or plant is operating correctly or if the right electrical environment is in place - then it’s important to calibrate. If it’s not that important - perhaps to check for presence of voltage or current - then don’t worry about it.

“A key rationale is that if the output being measured is important, then calibrating is equally important.”

Calibration is defined as a measurement referenced to a ‘known’ standard. Calibrating test instruments should be important to contractors as it gives them confidence in the measurements being made, provides proof of validated measurements and ultimately enables more time to be spent on core competencies that generate income, rather than having to retest or rework an installation if there isn’t confidence in the results.

I recently heard of a contracting firm that, after installing several hundred CCTV systems over the period of a year, believed its waveform monitor was out of spec because it wasn’t showing the picture that was expected. Both the monitor and the signal generator it was normally paired up with were performance-verified, only to find the monitor was well within spec, but the signal generator was out of spec, which meant the company had probably set up hundreds of systems incorrectly for at least the previous year.

Baucke advises that if test instruments need to be calibrated, there is only one way to do it: “There is only one level of calibration - the measurement of a parameter against a known standard. Everything else is comfort only. Unless full testing is completed against validated standards and data recorded, then the time and expense in ‘inter-comparison’ type measurement is wasted, because the next time someone uses that device they need to do it again. You either need measurement confidence or you don’t.

“The consequences of not calibrating can be quite detrimental to a business. We see a lot of test instruments from many diverse companies and applications, and for those organisations that haven’t calibrated their equipment for some time, we can typically experience 10-25% failure rates. One customer had over 35% of his working standards fail calibration as either minor faults or out-of-specification conditions.”

In situations where test equipment doesn’t need to be calibrated - such as being used to simply verify current or voltage - they should be labelled ‘Uncalibrated instrument - for indication only’. That way they’re not accidentally used for measurement purposes and don’t unnecessarily incur any ongoing costs of calibration.

Whole-of-life considerations

Test instruments are typically part of the day-to-day activities of most contracting firms, so they are an important asset. As such, a whole-of-life view should be taken of them, considering the value they bring to the company as well as the total cost of ownership, part of which includes calibration.

As important business tools for contracting firms, test instruments must have their life cycles mapped out to maximise the return on their investment. Obviously, effort must be put in at first to ensure the right instrument is chosen for the tasks at hand. But factors such as calibration, repair and preventative maintenance should also be addressed. By including these factors into the procurement process, they can form part of the utilisation process and assist contractors to not forget to have their instruments in optimal condition. Suppliers like Agilent can include calibration plans as part of the initial purchase under a capex budget, rather than drawing operating funds over the years that follow. Support services can also include calibration-due notification, calibration status report, calibration certificates and asset lists.

“Contractors need to understand the consequences of inaccurate measurements brought on by the use of uncalibrated test instruments,” adds Baucke. “For critical applications, the consequences could be ten times the cost of the test instruments, or even more. On top of that, a contractor’s reputation is put on the line.

“The major electrical contractors that we deal with would never consider doing things by half. They’re typically very professional and have calibration programs scheduled for all their test gear, so that when their field staff go out, they’re confident that whatever results they obtain, the readings accurately indicate the situation.

“A big area that is impacting the electrical industry is portable appliance testing (PAT), where calibration is crucial. Contractors conducting PAT testing are dealing with people’s safety and they’re carrying an extended duty of care to not only ensure the equipment is safe, but that the equipment being tested is safe and fit for purpose, and not posing a serious risk to other workers or the public in general.”