ASME_B89.7.5-2006.pdf

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 Report will be revised when the Society approves the issuance of a new edition.Therewill be no addenda issued to this edition.ASME is the registered trademark of The American Society of Mechanical Engineers.ASME does not“approve,”“rate,”or“endorse”any item,construction,proprietary device,or activity.ASME does not take any position with respect to the validity of any patent rights asserted in connection with anyitems mentioned in this document,and does not undertake to insure anyone utilizing a standard against liability forinfringement of any applicable letters patent,nor assume any such liability.Users of a code or standard are expresslyadvised that determination of the validity of any such patent rights,and the risk of infringement of such rights,isentirely their own responsibility.Participation by federal agency representative(s)or person(s)affiliated with industry is not to be interpreted asgovernment or industry endorsement of this code or standard.No part of this document may be reproduced in any form,in an electronic retrieval system or otherwise,without the prior written permission of the publisher.The American Society of Mechanical EngineersThree Park Avenue,New York,NY 10016-5990Copyright 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.34Examples 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 has 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-tees 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 uncertainty 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 Decision 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 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,ASME 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 instruments 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 calibration 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 laboratories,”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