I was recently in a discussion with someone about ISO 17025 calibration requirements. It was my understanding that all equipment associated with the tests within our ISO 17025 scope needed to have an uncertainty value reported with each calibration. However, my coworker said only tests that actually use the uncertainty value as a part of their test results calculations require an uncertainty value. Meaning, we have may have tests performed within our ISO 17025 scope but the equipment doesn’t need an uncertainty value?
Could you please provide some clarity on this?
First let us understand why the measurement uncertainty is required. This is to support the metrological traceability requirement for any measurement made.
The definition of metrological traceability per ISO Guide 99:2007 is:
“Property of a measurement result whereby the result can be related to a reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty”.
Therefore, if you require your measurements to be traceable, then measurement uncertainty is required. Since this definition of Metrological Traceability was defined per ISO Guide 99 in 2007, there has been confusion on the requirement for reporting measurement uncertainty. The current version of ISO/IEC 17025:2005 does not help by stating “and/or” requirement in Section 188.8.131.52.1 when reporting measurement results with measurement uncertainty.
Whenever such ambiguity exists in the standards, International Laboratory Accreditation Cooperation provides guides and policy documents for clarification for accrediting bodies and accredited laboratories. The ILAC P14:2013 is one such document which provides policy guidance in reporting measurement uncertainties for the laboratories and for accrediting bodies to enforce.
In short, if any equipment (and its associated measurements) requires metrological traceability, then measurement uncertainty must be estimated for that equipment regardless of if it is within the ISO/IEC 17025 scope of accreditation or not.
Dilip A Shah
ASQ CQE, CQA, CCT
President, E = mc3 Solutions
Chair, ASQ Measurement Quality Division (2012-2013)
Secretary and Member of the A2LA Board of Directors (2006-2014)
For more information on this topic, please visit ASQ’s website.