ASME_B89.7.3.2-2007.pdf

Guidelines for the Evaluationof Dimensional Measurement UncertaintyASME B89.7.3.2-2007(Technical Report)ASME B89.7.3.2-2007(Technical Report)Guidelines forthe Evaluationof DimensionalMeasurementUncertaintyThree Park Avenue New York,NY 10016Date of Issuance:March 2,2007This 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 assumes 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 2007 byTHE AMERICAN SOCIETY OF MECHANICAL ENGINEERSAll rights reservedPrinted in U.S.A.CONTENTSForeword.ivCommittee Roster.vAbstract.11Scope.12Simplifications in the Evaluation of Measurement Uncertainty.13Basic Concepts and Terminology of Uncertainty.14Combining Uncertainty Sources.65Basic Procedure for Uncertainty Evaluation.76Examples.7Figure1Measurement Uncertainty Quantities.2Table1Measurement and Validity Conditions.7Nonmandatory AppendicesAType A Evaluation of Standard Uncertainty.11BType B Evaluation of Standard Uncertainty.12CInfluence Quantities.14DThermal Effects in Dimensional Measurements.16EBibliography.19iiiFOREWORDThe ISO Guide to the Expression of Uncertainty in Measurement(GUM)is now the internation-ally accepted method of expressing measurement uncertainty 1.The U.S.has adopted the GUMas a national standard 2.The evaluation of measurement uncertainty has been applied for sometime at national measurement institutes but more recently issues such as measurement traceabilityand laboratory accreditation are resulting in its widespread use in calibration laboratories.Given the potential impact to 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 the consideration of measurement uncertainty.In support of thiseffort,ASME B89 Committee for Dimensional Metrology has formed Division 7 MeasurementUncertainty.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 quality of the laboratory,and smaller uncertainty values generally are of highervalue and of higher cost.ASME B89.7.3.1,Guidelines for Decision Rules in Determining Confor-mance to Specifications 3,addresses the role of measurement uncertainty when accepting orrejecting products based on a measurement result and a product specification.This document,ASMEB89.7.3.2,GuidelinesfortheEvaluationofDimensionalMeasurementUncertainty,providesa simplified approach(relative to the GUM)to the evaluation of dimensional measurementuncertainty.ASMEB89.7.3.3,GuidelinesforAssessingtheReliabilityofDimensionalMeasurementUncertainty Statements 4,examines how to resolve disagreements over the magnitude of themeasurement uncertainty statement.Finally,ASME B89.7.4,Measurement Uncertainty and Con-formance Testing:Risk Analysis 5,provides guidance on the risks involved in any productacceptance/rejection decision.With the increasing number of laboratories that are accredited,more and more metrologistswill need to develop skills in evaluating measurement uncertainty.This report provides guidancefor both the novice and experienced metrologist in this endeavor.Additionally,this report maybe used to understand the accuracy of measurements at a more comprehensive level than thevariationcapturedby“GageRepeatabilityandReproducibility”(GR&R)studies.Thiswillprovidea higher level of confidence in the measurements and aid in determining if a measurement systemis capable of meeting the expected capability as a percentage of specified tolerance.Emphasis isplaced on simplified uncertainty evaluation appropriate for the reader who is experienced inmeasurement procedures but is new to uncertainty evaluation.Comments and suggestionsfor improvement of thisTechnical Report are welcome.They shouldbe addressed to The American Society of Mech