This month’s question

Can a manufacturer use reference-only monitoring and measurement equipment to accomplish in-process checks as long as these items are verified later by inspection using calibrated or verified equipment? Must all measurements be verified by properly calibrated equipment?

Our response

The practice of using reference-only devices for in-process measurements is not noncompliant with AS9100. The formal inspections to accept product would require the use of calibrated equipment.

In subclause, the standard clearly states, “The organization shall determine and provide the resources needed to ensure valid and reliable results when monitoring or measuring is used to verify the conformity of products and services to requirements.”1

In subclause, the standard states, “When measurement traceability is a requirement, or is considered by the organization to be an essential part of providing confidence in the validity of measurement results…”2

Users and auditors should look at formal inspection steps and final buy-off to determine whether any nonconformities were escapes from in-process measurements being conducted without calibrated devices. Customer complaints also can be analyzed to see whether any escapes were a result of failed in-process inspections. If so, the organization did not properly determine and provide the appropriate resources.


  1. SAE International, AS9100D—Quality Management Systems—Requirements for aviation, space and defense organizations, subclause
  2. Ibid, subclause

Editor’s Note

This post originally appeared on ASQ’s Ask the Standards Experts blog at https://asqasktheexperts.com.

This response was written by L.L. “Buddy” Cressionnie, president, ASD Expertise LLC.

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