GPS – Presentation of measurement results


Guidance on Measurement Uncertainty Evaluation

lecture* – Example: Cylinder measurement uncertainties Fishbone diagram for measurement of cylinder

lecture* – Example: Vehicle closure panel measurement bil


Five steps:

1 Analyse measurement system. Error budget

Note: A full evaluation of measurement uncertainty includes not only the measurand but also uncertainties when measuring the various influence parameters which might affect the measurand, as usefully captured in with a complete Measurement System Analysis. A list of typical sources of error & uncertainty in the GPS context is given in [ISO/TS 14253-2:1999 §7]

Note: An example of a measurement error & uncertainty budget is given in GPS standard [ISO/TS 14253-2:1999 §9.3.10]


2 Correct for known measurement errors


3 Evaluate (standard) measurement uncertainties with methods of type A alternatively type B

The GPS approach [ISO/TS 14253-2:1999 §8] to estimating measurement uncertainty is based on the GUM method.

Note – Qualitative & quantitative measurements


4 Combine standard measurement uncertainties => uc

The GPS approach [ISO/TS 14253-2:1999 §8.6] to combining different standard measurement uncertainties is divided into two categories:


5 Expand measurement uncertainty => U = k• uc


GPS – examples

The GPS standards refer to a “Procedure for Uncertainty Management – PUMA” to be applied when quantifying a measurand, be it a GPS characteristic of a workpiece or a metrological characteristic of a GPS measuring equipment [ISO/TS 14253-2:1999]. This standard contains several examples of uncertainty budgets:

  • Calibration of a setting ring (Annex A of [ISO/TS 14253-2:1999])
  • Design of a calibration hierarchy – steel shaft diameter measurement with an external micrometer and calibration of the latter (Annex B of [ISO/TS 14253-2:1999])
  • Measurement of roundness (Annex C of [ISO/TS 14253-2:1999])

Specific GPS examples of the evaluation of measurement uncertainty with coordinate measurement machines (CMM) are given in[ISO/TS 15530-3] and [ISO/TS 23165:2006]:

GPS – Specification of demands on Measurement System
GPS – Use of measurement results. Conformity assessment


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