1、ASME B897.3200GUIDELINES FOR DECISION RULES-CONSIDERING MEASUREMENTUNCERTAINTIN DETERMINCONFORMANCE TOPECIFIGATIONSAN AMERICAN NATIONAL STANDARDE米S)The American Society ofineersNot tor ResaleThe American Society ofMechanical EngineersA N AM E RI C AN N A T ION A L S TA N D A R DGUIDELINES FOR DECISI
2、ON RULES:CONSIDERING MEASUREMENTUNCERTAINTY IN DETERMININGCONFORMANCE TOSPECIFICATIONSASME B89.7.3.1-2001No reproduction or networking permitled without Fcense from IHSNot for ResaleDate of Issuance:March 18,2002This Standard will be revised when the Society approves the issuance of anew edition.The
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10、 ResaleFOREWORDThe intent of these guidelines is to facilitate the development of understanding betweensuppliers and customers regarding measurement uncertainty in the decision to accept or toreject a product.Metrologists are continuously faced with the task of making decisions inthe presence of mea
11、surement uncertainty.To formalize this task,procedures known asdecision rules have been developed.A decision rule is a prescription for the acceptanceor rejection of products based on the measurement result of a characteristic of the product,the permissible variation associated with that characteris
12、tic,and the uncertainty of themeasurement result.For workpieces,the permissible variation is commonly called thetolerance;for instruments it is often given by the specification limits or maximum permissibleerror(MPE).The terminology of ISO 14253-1 has been adopted and the permitted variationof a pro
13、ducts characteristic is referred to as the specification zone.This document isintended to provide guidance on decision rules and their implementation.A related document,ASME B89.7.2-1999,Dimensional Measurement Planning,specifiesrequirements for preparation and approval of dimensional measurement pl
14、ans and for theuse of approved plans in making dimensional measurements.The dimensional measurementplan must contain or reference all information for making measurements,including specificationof a decision rule.ASME B89.7.3.1 serves as a resource to the dimensional measurementplanner by providing t
15、erminology and specifying the requirements for decision rules foruse in dimensional measurement plans.The Guide to the Expression of Uncertainty in Measurement,(GUM),NCSL Z540-2-1997 provides a unified means of evaluating and expressing the uncertainty of a measurementresult;consequently the calcula
16、tional details of evaluating the uncertainty of a measurementresult will not be discussed.Unless otherwise stated,the term measurement uncertaintywill be used to mean the expanded uncertainty,U,with a coverage factor of two,whichis the most common coverage factor used nationally and internationally.
17、Although all traceable measurement results include an uncertainty statement not allmeasurement results involve decision rules.(See ISO International Vocabulary of Basic andGeneral Terms in Metrology.)Many calibrations,particularly at National MeasurementInstitutes(NMIs),typically state a description
18、 of the measurement,its result,and itsuncertainty;decision rules are not involved since there are no specifications.Most products,however,have stated specifications and a decision must be reached regarding the productscharacteristic relative to its stated specifications.The decision rule in use shou
19、ld be well documented to prevent ambiguity in the acceptanceor rejection of product.The selection of a particular decision rule is ultimately a businessdecision;some of the factors to be considered are outlined in nonmandatory AppendicesA and D.The concept of a decision rule has a long history and o
20、ver the years has developedmany variations including gauge makers rule,test accuracy ratio(TAR),test uncertaintyratio(TUR),“four-to-one rule,.”“gauging ratio,.”“guard bands,“gauging limit,”and manymore.Most of these terms were defined before the development of the GUM and henceconcepts such as accur
21、acyor uncertaintywere nebulously defined.One of the motivationsof these guidelines is to explicitly define the decision rule concept and have some well-documented decision rules that can be referenced.Consequently,these guidelines haveencapsulated some of the commonly used procedures and their specifically-named deci-sion rules.e with ASMENo reproduction or networking permitlod without licenso from IHSNot for Resale
