Metrology Monday! #77 Over-Interpretation of Accreditation Requirements
Today’s topic comes from our Fluke Technical Support.? While we are focused on answering questions and providing solutions for our hardware and software products, sometimes our customers come to us with issues that were raised by technical assessors.? I was a technical and lead assessor for an accreditation body for nearly 10 years before I came to Fluke, so I can say with good authority that assessors are not perfect, we can make mistakes.
The issue today that was brought up was that a customer was told by their assessor that they needed to report uncertainty in the same unit (including prefix) as the nominal value, and thus cannot use scientific notation with the base value if the nominal value has a prefix.
An example would be as follows:
Nominal Value????????????? Measured Value????????????? Uncertainty (k=2)
50.000 mv????????????????????? 49.986 mv????????????????????? 5 E-06 volts
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Let’s start with what ISO/IEC 17025 requires.? Section 7.8.2.1 require the that we report (m) “the results with, where appropriate, the units of measurement;” and 7.8.4.1 requires (a) “the measurement uncertainty of the measurement result presented in the same unit as that of the measurand or in a term relative to the measurand (e.g. percent).”
Now, let’s jump over to the VIM.? Definition 1.9 is measurement unit, also known as unit of measurement or unit.? The VIM definition is “real scalar quantity, defined and adopted by convention, with which any other quantity of the same kind can be compared to express the ratio of two quantities as a number.”? Note 1 goes on to say that “Measurement units are designated by conventionally assigned names and symbols.”? Definition 1.16 for the International System of Units also differentiates between the names of units and their prefixes.
It is very clear that the unit of measurement in our example is the volt?and that a millivolt and a microvolt quantity can be compared to express the ratio of the two quantities as a number.?
So there you have it, if you have an assessor that tries to tell you that a prefix is a unit, you have all of the information to explain that it is in fact, not.? Don’t be afraid to appeal findings, especially if you have objective evidence such as this to support your position.? #MetrologyMonday #FlukeMetrology
Field Service at Ametek/Newage
7 个月Great article!
Owner, DGI Metrology-Dimensional Gauge
7 个月A conversation log overdue! Our lab has had accreditation for over 25 years. The one constant in all those years is a lack of consistency in the interpretation of the Standard among the assessors and even between the registrar and ILAC. But yes, always push back when you know you're correct. It happens often that we must modify our procedures to please one assessor only to change the same procedure back to its original to appease the next assessor.
Head & Quality Manager, PTP NMIP, National Metrology Institute of Pakistan, Assessor, Expert & Trainer of ISO/IEC 17025:2017, ISO/IEC 17043:2023 & ISO 13528:2022.
7 个月Explained clearly with reference to VIM.
Executive Director at Proficiency Testing Canada
7 个月Well said Jeff. I am an assessor and I always make it very clear during the closing meeting that they can dispute any finding and that nobody will hold it against them if the choose to do so. Any assessor that takes a disagreement personally should not be an assessor.
Software Portfolio Product Manager at Fluke Corporation
7 个月Glad to have this written down so clearly to point people to. It comes up a lot lately.