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Alliance Calibration Blog

The Calibration Bench | Blog

Reference Only or Calibrate?

Posted by Phil Wiseman on Aug 4, 2020 1:14:57 PM

Is calibration required or should it be marked reference only?

What is the difference between calibration not required and reference only?

 

For users of measurement and test equipment -MTE- these are questions that arise on a regular basis.

AMS 2750 F makes it very clear what must be calibrated and even goes as far as to specify calibration accuracy.  This specific standard is focused on pyrometry and is highly descriptive in regards to instruments used and calibration. 

 

ISO 9001:2015 is not as clear cut. ISO 9001:2015 is focused on Risk-based thinking. Calibration is intrinsic in Risk-based thinking in1.3.3, Inputs and Outputs in 4.4.1, the necessary Infrastructure to accomplish this in 7.1.3, measurement traceability in 7.1.5.2(the actual word calibration is mentioned) and performance Evaluation in 9.1 just to name a few.

What Does It Really Mean When Something Is Marked For Reference Only?

For reference Only

When MTE is marked "Reference Only" then you need to consider if it still is Measurement & Test Equipment.

Consider the following from About Calibration published by Fluke.

"Test and measurement devices that were manufactured within specifications can deteriorate over time due to age, heat, weathering, corrosion, exposure to electronic surges, accidental damage, and more.  Even the best test and measurement instruments can possess manufacturing imperfections, random noise, and long-term drift that can cause measurement errors.  These errors, such as being off a few millivolts or degrees, can be propagated to products or processes being tested, with the potential to falsely reject a good unit or result or to falsely accept a bad unit or result.

Ensuring that test and measurement equipment is of sufficient accuracy to verify product or process specifications is necessary to trust and build on the results of scientific experiments, ensure the correct manufacture of goods or products, and conduct fair trade across country borders."

If there is an impact on product quality, marking something "Reference Only" or "Does Not Require Calibration" does not make sense.

Example: You use a measuring tape to determine the size of a box for shipping. Does this impact product quality? Probably not.

You use a measuring tape to measure the product. Does this impact product quality? Most likely yes.

 

A Risk Assessment should be performed before making any decisions on marking marking something "Reference Only" or "Does Not Require Calibration.

ISO 9001:2015 Section 1.2 highlights - evidence based decision making

Without a proper risk assessment as to calibration requirements you would be hard pressed to defend your decision as evidence based decision making.

Calibration is essentially risk management. How do you lower your risk of measurements that are potentially inaccurate over the lifetime of your valuable test and measurement equipment_ Regular calibration, of course

ISO 9001:2015 section 1.3.3 Risk Based thinking states " To conform to the requirements of this international based standard, an organization needs to plan and implement actions to address risks and opportunities."

This makes it clear that before you determine if something does not need calibration, the risks of not calibrating must be addressed. 

 

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