When you book your metrology equipment in for a calibration, you’ll be asked whether you require the calibration to be carried out to traceable or UKAS standards. But do you know what’s covered under each option?

Many of our customers are confused about the difference between traceable and UKAS calibrations and often ask us for advice when it comes to deciding on the right standard of calibration for their equipment.

With so much information available on the subject, we’ve brought it together in one place to help make your decision.

The importance of traceable calibrations

The International Bureau of Weights and Measures (BIPM) helpfully define a calibration as, “the documented comparison of the measurement device to be calibrated against a traceable device”.

In practice, this means the reference standard (or traceable device) used in a calibration must have been calibrated using an even higher-level standard than the one being performed.

The traceability should be part of an unbroken chain of calibrations, leading back to the highest-level calibration which has been performed in a national calibration centre (or equivalent).

The unbroken chain of calibrations provides a historical trace back to a known standard. If a calibration is performed on an instrument and the reference device cannot be traced to a known standard, then the calibration is effectively worthless as you couldn’t be certain the reference device is accurate.

How does a UKAS calibration differ?

A UKAS calibration can also be considered traceable. The difference between the two is that UKAS calibrations are carried out under the remit of an ISO/IEC 17025 quality system by a laboratory that has been accredited by UKAS, to ensure the consistency and accuracy of results.

To become UKAS accredited, laboratories have to meet a very stringent set of requirements. UKAS stipulates criteria around factors including employee training, calibration procedures and lab facilities, as well as regularly externally auditing the laboratory to ensure these standards are being upheld.

Why UKAS?

In what situation would you require UKAS calibrations over traceable calibrations? Here are some of the reasons our customers choose to opt for UKAS calibrations:

  • Industry specific: UKAS calibrations are performed under the most stringent conditions, therefore industries where safety is critical, such as aerospace, oil and gas, and pharmaceuticals, may lean more towards UKAS calibrations for the added level of trust they provide.
  • Operational use: Within certain operational environments an inaccurate reading from metrology equipment could pose a massive risk to safety. On the other hand, for non-critical operations such as production testing and simple reference checks some customers feel a traceable calibration is acceptable.
  • Quality manual: It’s not uncommon for quality assessors to instruct businesses to calibrate instruments to UKAS standards. This could be a result of a stipulation from the governing or regulatory body of an industry.
  • Customer request: Some end customers may request their suppliers have metrology equipment calibrated to UKAS standards to ensure a consistent result all the way along the supply chain, as well as providing an added level of assurance that all the equipment used in production was accurate.

Still not sure?

We offer our customers the choice of either traceable or UKAS calibrations. If you’re unsure on which option is right for you, our experts are on hand to offer some advice. We’d love to hear from you!

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