1、Metrological Traceability of Dimensional Measurements to the SI Unit of LengthASME B89.7.5-2006(Technical Report)ASME B89.7.5-2006(Technical Report)MetrologicalTraceability ofDimensionalMeasurements to theSI Unit of LengthThree Park Avenue New York,NY 10016Date of Issuance:July 17,2006This Technical
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6、0016-5990Copyright 2006 byTHE AMERICAN SOCIETY OF MECHANICAL ENGINEERSAll rights reservedPrinted in U.S.A.CONTENTSForeword.ivCommittee Roster.viAbstract.11Introduction.12Requirements for Metrological Traceability of Dimensional Measurements.23Details of Dimensional Metrological Traceability.34Exampl
7、es of Demonstrating Metrological Traceability.3iiiFOREWORDThe ISO Guide to the Expression of Uncertainty in Measurement(GUM)is now the internation-ally accepted method to express measurement uncertainty 1.The U.S.has adopted the GUMas a national standard 2.The evaluation of measurement uncertainty h
8、as been applied for sometimeatnationalmeasurementinstitutes,butmorerecently,issuessuchasmeasurementtraceabilityand laboratory accreditation are resulting in its widespread use in calibration laboratories.Given the potential impact on business practices,national and international standards commit-tee
9、s are working to publish new standards and technical reports that will facilitate the integrationof the GUM approach and consideration of measurement uncertainty.In support of this effort,ASME B89 Committee on Dimensional Metrology has formed Division 7:Measurement Uncer-tainty.Measurement uncertain
10、ty has important economic consequences for calibration and measure-ment activities.In calibration reports,the magnitude of the uncertainty is often taken as anindication of the laboratory quality,and smaller uncertainty values generally are of higher valueand cost.ASME B89.7.3.1,Guidelines for Decis
11、ion Rules:Determining Conformance to Specifica-tions 3,addresses the role of measurement uncertainty when accepting or rejecting productsbased on a measurement result and product specification.ASME B89.7.3.2,Guidelines for theEvaluation of Dimensional Measurement Uncertainty 4,provides a simplified
12、approach(relativeto the GUM)to the evaluation of dimensional measurement uncertainty.ASME B89.7.3.3,Guide-lines For Assessing the Reliability of Dimensional Measurement Uncertainty Statements 5,examines how to resolve disagreements over the magnitude of the measurement uncertaintystatement.Finally,A
13、SME B89.7.4.1,Measurement Uncertainty And Conformance Testing:RiskAnalysis6,providesguidanceontherisksinvolvedinanyproductacceptance/rejectiondecision.Historically,measurement traceability was an effort to ensure accuracy through paperwork;the requirement to show calibration reports forced instrumen
14、ts and standards to be calibrated.The International Vocabulary of Basic and General Terms in Metrology(VIM)7 definition oftraceability now requires a GUM-compliant uncertainty statement that provides a quantitativeaccuracy statement of the measurement result,a significant improvement over a calibrat
15、ion reportnumber.The VIM definition does not specify the requirements regarding the“stated references,”i.e.,measurement standards,or what constitutes an appropriate terminus for the“unbroken chainof comparisons.”In a standard on“General requirements for the competence of testing andcalibration labor
16、atories,”ISO 17025 8 states(in para.5.6.2.1.1),“A calibration certificate bearingan accreditation body logo from a calibration laboratory accredited to this International Standard,forthecalibrationconcerned,issufficientevidenceoftraceabilityforthecalibrationdatareported.”In this report,the concept of traceability developed in ISO 17025 is used as the basis to extendbeyond calibration laboratories and into the industrial metrology domain.The ambiguity in the VIM definition of what constitutes a r