The National Metrology Laboratory of South Africa Feedback presentation for SAAMF meeting – 05 May 2005 Eddie Tarnow Metrologist CSIR-NML
Questions for SAACB • Can an ISO/TS 16949: 2002 certification programme ensure systems and processes which deliver products which conform to a technical specification? • Are customer specific MSA requirements addressed in ISO/TS 16949: 2002 audits? • To what degree are customer specific MSA requirements addressed in ISO/TS 16949: 2002 audits? • Would ISO/TS 16949:2002 auditors benefit from additional training in Measurement System Analysis?
Definitions “Calibration” “International Vocabulary of Basic and General Terms in Metrology” – Second Edition, 1993. • “Set of operations that establish, under specified conditions, the relationship between values of quantities indicated by a measuring instrument or measuring system, or values represented by a material measure or a reference material, and the corresponding values realised by standards.” • NOTES: • The result of a calibration permits either the assignment of values of measureands to the indications or the determination of corrections with respect to the indications. • A calibration may also determine other metrological properties such as the effect of influence quantities. • The result of a calibration may be recorded in a document, sometimes called a calibration certificate or a calibration report.
Definitions “Calibration” “Measurement Systems Analysis” - MSA Third Edition, March 2005. “A set of operations that establish, under specified conditions, the relationship between a measuring device and a traceable standard of known reference value and uncertainty. Calibration may also include steps to detect, correlate, report, or eliminate by adjustment any discrepancy in accuracy of the measuring device being compared.”
Definitions “Verification” “Eddie’s definition.” “Periodic measurements of a traceable standard of known reference value and uncertainty for the purpose of maintaining confidence in the ability of an instrument or measuring system to continue to perform measurements with the required accuracy.”
Definitions “Validation” “Eddie’s definition.” • “A set of operations which prove that a system is fit for its intended purpose .” • NOTES: • A system can be a measuring instrument, a measuring system, a software programme or a spreadsheet. • The intended purpose for a measuring instrument or measuring system implies that the required measurement is performed with the desired accuracy, (uncertainty of measurement). • Validation need only be performed once, during a system commissioning or after a change has been made.
Definitions “Uncertainty of Measurement” “International Vocabulary of Basic and General Terms in Metrology” – Second Edition, 1993. • “The parameter, associated with the result of a measurement, that characterises the dispersion of the values that could reasonably be attributed to the measureand.” • NOTES: • The parameter may be, for example, a standard deviation (or a given multiple of it), or the half-width of an interval having a stated level of confidence. • Uncertainty of measurement comprises, in general, many components. Some of these components may be evaluated from the statistical distribution of the results of series of measurements and can be characterised by experimental deviations. The other components, which can also be characterised by standard deviations, are evaluated from assumed probability distributions based on experience or other information.
Definitions “Uncertainty of Measurement cont.” “International Vocabulary of Basic and General Terms in Metrology” – Second Edition, 1993. • NOTES: • It is understood that the result of the measurement is the best estimate of the value of the measureand, and that all components of uncertainty, including those arising from systematic effects, such as components associated with corrections and reference standards, contribute to the dispersion.
Definitions “Uncertainty of Measurement ” “Measurement Systems Analysis” - MSA Third Edition, March 2005. “A parameter associated with the result of a measurement that characterises the dispersion of the values that could reasonably be attributed to the measureand; the range assigned to a measurement result that describes, within a defined level of confidence, the limits expected to contain the true measurement result. Uncertainty is a quantified expression of the measurement reliability.
Uncertainty of measurement Result of a measurement, y, and result of measurement, complete statement y’
Uncertainty of measurement Example of conformance proved
Uncertainty of measurement Example of non - conformance proved
Uncertainty of measurement Example of neither conformance nor non - conformance proved
ISO/TS 14253-1 Uncertainty of measurement reduces conformance range
MSA Discussion Is an MSAconducted? NO YES Why not adequatelyaudited as partof 16949? Why not? Notnecessary? YES Are 16949 auditorsexpected to do this? An unreasonableexpectation? Then who checks themeasurement system? NO YES NO YES Can they do it? Who is? The OEMs? OEMs need to takeresponsibility – control plan? Must be done, thenby whom? YES YES NO But they don’t - Action required NO Auditors need toput in the effort Do they have theskills? YES Don’t have the skills,training required How comemeasurementproblems? NO
MSA Discussion • Who conducts the MSA? (supplier/OEM?) • Are FOP, (first of production), tests conducted? • Who is responsible for conducting these tests, OEMs or suppliers? • Who is responsible for evaluating that the measurement system is capable of performing the required measurements with the desired level of accuracy? • Do these tests form part of the control plan? • Is the understanding that an MSA addresses the measurement accuracy of a measurement system or merely its repeatability/reproducibility?