How to Audit a Calibration Company



Do you have the correct audit checklist?


One of our long-standing customers was recently purchased and the new owners required an audit of all suppliers. Not unusual. We are audited on a regular basis by our customers and accreditation bodies.audit-checklist1

What made this audit interesting is the audit checklist provided by the new ownership.  The checklist was designed for ISO 9001.  We are accredited to ISO 17025. Not a big deal, right? What is the difference?


There are similarities between ISO 9001 and ISO 17025. Both have requirements for Management, Document Control, Management Reviews, Non-Conformance, etc.

In fact, the introduction section of ISO 17025 specifically states " Testing and calibration laboratories that comply with this International Standard will therefore also operate in accordance with ISO 9001."

However, using an ISO 9001 audit checklist for a calibration company can seem like shoving a square peg in a round hole at times. A key difference is in the selection of methods used for calibration. This came up during this audit using the customer's audit list in reference to ISO 9001 Section 7. This is covered in ISO 17025 Section 5.    Section 5 also addresses the estimation of measurement uncertainty and this is a concept that is foreign to many. Likewise, measurement traceability is also addressed in section 5. Again, a concept unfamiliar to many outside of the calibration world.


Where does the Scope of Accreditation fit on the audit checklist?

The Scope of Accreditation is a document that delineates the best measurement capabilities of a calibration laboratory and the methods and standards used.  This Scope clearly states what a Laboratory is accredited to calibrate. Just because a Laboratory is accredited does not mean they are accredited for every calibration. For example, a calibration laboratory is not accredited for Light. They can still perform the calibration, but it is not accredited. You need to know this. These disciplines are not listed on their scope of accreditation. Length is another good example. A calibration laboratory can be accredited for length but has a limit determined by methods and standards used. Does it make sense to send a 36" device in for calibration when the lab is only accredited to 6 inches?  

A review of the Scope of Accreditation should be included on your audit checklist.


ISO 17025 accreditation bodies also require PT( Proficiency Testing).

What is Proficiency Testing?

  • A known artifact is sent to several calibration laboratories
  • The artifact is calibrated
  • Measurement Uncertainty must be stated in the results
  • The results are compared to peer Laboratories
  • A Pass or Fail result is issued
It is standard practice that every calibration laboratory discipline( Length, Mass, Time, etc) participates in a proficiency test during the accreditation cycle. Ask to review these documents. If a calibration laboratory has a failure ask for the documented steps taken to improve.

There are some KEY differences between ISO 9001 and ISO 17025.


Want to learn more?

Download the whitepaper on the differences between ISO 9001 and ISO 17025

 Download the Whitepaper  on   ISO 9001  &  ISO 17025


Phil Wiseman

Phil Wiseman

Phil Wiseman is Chief Marketing Officer at Alliance Calibration. He earned a B.S. in Chemical Physics from Centre College. Phil is an ASQ Certified Quality Auditor and ASQ Certified Manager of Quality/Organizational Excellence.

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