Measurement System Change Control governs changes that can affect the quality of measurement results.

A measurement process may become different when there is a change to:

  • gage;
  • fixture;
  • software;
  • operator method;
  • environment;
  • specification;
  • sampling method.

The purpose is to determine whether the previous evidence of measurement adequacy is still valid.

Define significant changes

Not every change requires a full new study.

Examples that may be significant include:

  • new measurement technology;
  • new fixture design;
  • software algorithm change;
  • tighter tolerance;
  • different part family.

Measurement System Analysis helps evaluate whether the measurement process is adequate for its intended use.

Change control asks whether that conclusion still applies after the change.

Assess the effect

Review how the change could affect:

  • bias;
  • repeatability;
  • reproducibility;
  • resolution;
  • stability.

A software change may alter results even when the physical gage is unchanged.

Define required verification

Possible verification includes:

  • reference check;
  • calibration;
  • repeatability test;
  • focused Gage R&R;
  • full MSA.

Gage R&R helps quantify repeatability and reproducibility where operator and equipment variation matter.

Match verification effort to the significance of the change.

Control the transition

During transition, define:

  • old method status;
  • new method approval;
  • affected product;
  • data comparability.

Do not mix old and new measurement results without understanding whether they are equivalent.

Update the operational definition

Operational Definition helps standardize what is measured, how it is measured, and how results are interpreted.

If the method changes, the operational definition may need revision.

Update monitoring

Measurement System Monitoring helps detect drift through reference checks, calibration status, repeatability signals, environmental controls, and reaction rules.

New measurement technology may require different monitoring.

Review affected decisions

If a significant measurement issue is discovered after change, determine whether earlier product or process decisions need review.

Examples include:

  • acceptance decisions;
  • capability results;
  • process adjustments.

Common mistakes

Changing measurement software without verification, assuming calibration alone proves equivalence, ignoring tolerance changes, mixing old and new data without comparison, updating equipment but not the operational definition, failing to revise monitoring, and approving the new method before required evidence is complete are common mistakes.

Practical sequence

  1. identify the proposed measurement change.
  2. determine whether it is significant.
  3. assess possible effects on measurement quality.
  4. define required verification.
  5. control old and new methods during transition.
  6. complete the required study.
  7. update operational definitions.
  8. update monitoring.
  9. review affected decisions if needed.
  10. release the changed system only when evidence supports use.

The practical lesson

Measurement System Change Control protects data integrity when the measurement process changes.

A previously acceptable measurement system should not be assumed acceptable after a change that can alter how results are produced.