1、ASME B89.7.3.3-2002GUIDELINES FOR ASSESSING THE RELIABILITY OFDIMENSIONAL MEASUREMENTUNCERTAINTY STATEMENTSAN AMERICAN NATIONAL STANDARDIntentionally left blank AN AMERICAN NATIONAL STANDARDGUIDELINES FOR ASSESSING THE RELIABILITY OFDIMENSIONAL MEASUREMENTUNCERTAINTY STATEMENTSASME B89.7.3.3-2002Dat
2、e of Issuance: February 21, 2003This Standard will be revised when the Society approves the issuance of anew edition. There will be no addenda issued to this edition.ASME will issue written replies to inquiries concerning interpretation oftechnical aspects of this Standard.ASME is the registered tra
3、demark of The American Society of Mechanical Engineers.This code or standard was developed under procedures accredited as meeting the criteria forAmerican National Standards. The Standards Committee that approved the code or standardwas balanced to assure that individuals from competent and concerne
4、d interests have had anopportunity to participate. The proposed code or standard was made available for public reviewand comment that provides an opportunity for additional public input from industry, academia,regulatory agencies, and the public-at-large.ASME does not “approve,” “rate,” or “endorse”
5、 any item, construction, proprietary device,or activity.ASME does not take any position with respect to the validity of any patent rights asserted inconnection with any items mentioned in this document, and does not undertake to insure anyoneutilizing a standard against liability for infringement of
6、 any applicable letters patent, nor assumeany such liability. Users of a code or standard are expressly advised that determination of thevalidity of any such patent rights, and the risk of infringement of such rights, is entirely theirown responsibility.Participation by federal agency representative
7、(s) or person(s) affiliated with industry is not tobe interpreted as government or industry endorsement of this code or standard.ASME accepts responsibility for only those interpretations of this document issued inaccordance with the established ASME procedures and policies, which precludes the issu
8、anceof interpretations by individuals.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 2003 byTHE
9、 AMERICAN SOCIETY OF MECHANICAL ENGINEERSAll Rights ReservedPrinted in U.S.A.CONTENTSForeword ivCommittee Roster vCorrespondence With the B89 Committee . viAbstract . 11 Scope 11.1 1Objective 1.2 1Applicability .1.3 1Purpose .2 Definitions . 13 The Nature of Disagreements in Uncertainty Statements 2
10、3.1 2General .3.2 2Disagreements Involving Single Measurement Systems .3.3 2Disagreements Involving Multiple Measurement Systems .4 Causes of Disagreement in Measurement Results HavingUncertainty Statements . 44.1 4General .4.2 4Blunders 4.3 4GUM Noncompliance and Uncorrected Systematic Errors 4.4 4
11、Poorly Realized or Incompletely Define Measurand .4.5 5Statistically Rare Measurement Results 4.6 5Incomplete Uncertainty Statements 5 Methods of Resolution 55.1 5General .5.2 5Significanc of Disagreement .5.3 6Comparison of Uncertainty Budgets .5.4 8Direct Measurement of the Measurand 6 References
12、. 10Figures1 3Examples of Measurement Agreement and Disagreement .2 3Example of Product Conformance Disagreement .iiiFOREWORDThe ISO Guide to the Expression of Uncertainty in Measurement (GUM) is now theinternationally-accepted method of expressing measurement uncertainty. The U.S. has adoptedthe GU
13、M as a national standard. (See ANSI/NCSL Z540-2.) The evaluation of measurementuncertainty has been applied for some time at national measurement institutes but morerecently issues such as measurement traceability and laboratory accreditation are resultingin its widespread use in calibration laborat
14、ories.Given the potential impact to business practices, national and international standardscommittees are working to publish new standards and technical reports that will facilitatethe integration of the GUM approach and the consideration of measurement uncertainty. Insupport of this effort, ASME B
15、89 Committee for Dimensional Metrology has formed Division7, Measurement Uncertainty.Measurementuncertaintyhasimportanteconomicconsequencesforcalibrationandmeasure-ment activities. In calibration reports, the magnitude of the uncertainty is often taken asan indication of the quality of the laborator
16、y, and smaller uncertainty values generally areof higher value and of higher cost. In the sorting of artifacts into classes or grades,uncertainty has an economic impact through the use of decision rules. ASME B89.7.3.1,Guidelines to Decision Rules in Determining Conformance to Specifcations, address
17、es theroleofmeasurementuncertaintywhenacceptingorrejectingproductsbasedonameasurementresult and a product specifcation.With increasing use of measurements from laboratories that are accredited, and subsequentmeasurement uncertainty statements, signifcant economic interests are at stake, so it is not
18、surprising that metrologists might disagree over the magnitude of the measurement uncertaintystatements. While the selection of a decision rule is a business decision, the evaluation ofthe measurement uncertainty is a technical activity. This report provides guidance forresolving disagreements invol
19、ving measurement uncertainty statements.This report was approved by the American National Standards Institute on April 22, 2002.Comments and suggestions for improvement of this Technical Report are welcomed. Theyshould be addressed to: ASME, Secretary, B89 Committee, Three Park Avenue, New York,NY 1
20、0016-5990ivASME STANDARDS COMMITTEE B89Dimensional Metrology(The following is the roster of the Committee at the time of approval of this Standard.)OFFICERSB. Parry, ChairD. Beutel Vice ChairM. Lo, SecretaryCOMMITTEE PERSONNELJ. B. Bryan, Bryan AssociatesT. Carpenter, US Air Force Metrology LabsT. C
21、harlton, Jr., Charlton AssociatesG. A. Hetland, International Institute of GDNTR. J. Hocken, University of North CarolinaM. Liebers, Professional InstrumentsS. D. Phillips, NISTJ. Salsbury, Mitutoyo AmericaD. A. Swyt, NISTB. R. Taylor, Renishaw PLCR. C. Veale, NISTSUBCOMMITTEE 7: MEASUREMENTUNCERTAI
22、NTYG. Hetland, Chair, International Institute of GDNTD. Swyt, Vice Chair, NISTW. Beckwith, Brown however, they should not contain proprietary names orinformation.Requests that are not in this format will be rewritten in this format by the Committeeprior to being answered, which may inadvertently cha
23、nge the intent of the original request.ASME procedures provide for reconsideration of any interpretation when or if additionalinformation that might affect an interpretation is available. Further, persons aggrieved byan interpretation may appeal to the cognizant ASME Committee or Subcommittee. ASMEd
24、oes not “approve,”“certify,”“rate,” or “endorse” any item, construction, proprietary device,or activity.Attending Committee Meetings. The B89 Main Committee regularly holds meetings, whichare open to the public. Persons wishing to attend any meeting should contact the Secretaryof the B89 Main Commit
25、tee.viASME B89.7.3.3-2002GUIDELINES FOR ASSESSING THE RELIABILITY OFDIMENSIONAL MEASUREMENT UNCERTAINTY STATEMENTSABSTRACTThe primary purpose of this technical report is toprovide guidelines for assessing the reliability of mea-surement uncertainty statements. Applying these guide-lines can assist b
26、usinesses in avoiding disagreementsaboutmeasurementuncertaintystatementsandinresolv-ing such disagreements should they occur. Disagree-ments over uncertainty statements involving both singlemeasurement systems and multiple measurement sys-tems (each having their own uncertainty statement)are conside
27、red. Guidance is provided for examininguncertainty budgets as the primary method of assessingtheir reliability. Additionally, resolution by direct mea-surement of the measurand is also discussed.1 SCOPE1.1 ObjectiveThis technical report provides guidance in assessingthereliabilityofastatementofmeasu
28、rementuncertaintyin question, that is, in judging whether that stateduncertainty can be trusted to include the values thatcould reasonably be attributed to the measured quantity(measurand) with which that stated uncertainty is asso-ciated.1.2 ApplicabilityThis report is most applicable to statements
29、 of uncer-tainty in the results of dimensional measurements basedupon the ISO Guide to Expression of Uncertainty inMeasurement (GUM). (Also called ANSI/NCSLZ540-2.)1.3 PurposeThis technical report helps parties to avoid potential,or resolve actual, disagreements over the magnitude ofa stated measure
30、ment uncertainty, particularly whenthat uncertainty is part of a determination of conformityof a manufactured product to a dimensional specification.12 DEFINITIONS1acceptance zone: the set of values of a characteristic,for a specifie measurement process and decision rule,that results in product acce
31、ptance when a measurementresult is within this zone.2decision rule: a documented rule, meeting the require-ments of section 3 of ASME B89.7.3.1, that describeshow measurement uncertainty will be allocated withregard to accepting or rejecting a product according toits specificatio and the result of a
32、 measurement.expanded uncertainty: quantity definin an intervalabout the result of a measurement that may be expectedto encompass a large fraction of the distribution ofvaluesthatcouldreasonablybeattributedtothemeasur-and. See GUM, 2.3.5.guard band: the magnitude of the offset from thespecificatio l
33、imit to the acceptance or rejection zoneboundary.3, 4, 5, 6, 7, 81Many of these definition are selected from ASME B89.7.3.1. Thefigure from that document are omitted here for brevity.2When claiming product acceptance, it is important to state thedecision rule; e.g., “acceptance using the XX rule.”3T
34、he symbol g is deliberately used for the guard band, instead ofthe symbol U employed in ISO 14253-1 since U is reserved forthe expanded uncertainty which is associated with a measurementresult and hence it is confusing to attach U to a specificatiolimit. The evaluation of U is a technical issue, whi
35、le the evaluationof g is a business decision.4The guard band is usually expressed as a percentage of theexpanded uncertainty, i.e., a 100% guard band has the magnitudeof the expanded uncertainty U.5Two-sided guard banding occurs when a guard band is applied toboth the upper and lower specificatio li
36、mits. (In some exceptionalsituations the guard band applied within the specificatio zone,gIn,couldbedifferentattheupperspecificatio limitandatthelowerspecificatio limit. This would reflec a different risk assessmentassociated with an upper or lower out-of-specificatio conditiondepending on whether t
37、he characteristic was larger or smaller thanallowed by the specificatio zone.) If both the upper and lowerguard bands are the same size then this is called symmetric two-sided guard banding.6A guard band is sometimes distinguished as the upper or lowerguard band, associated with the upper or lower s
38、pecificatio limit.Subscripts are sometimes attached to the guard band notation, g,to provide clarity, e.g., gUpand gLo. See ASME B89.7.3.1, Fig. 1.GUIDELINES FOR ASSESSING THE RELIABILITY OFDIMENSIONAL MEASUREMENT UNCERTAINTY STATEMENTSASME B89.7.3.3-2002measurand: particular quantity subject to mea
39、sure-ment. See VIM 2.6.9N:1 decision rule: a situation where the width of thespecifcation zone is at least N times larger than theuncertainty interval for the measurement result.10rejection zone: the set of values of a characteristic,for a specifed measurement process and decision rule,that results
40、in product rejection when a measurementresult is within this zone.11specification zone (of an instrument or workpiece): theset of values of a characteristic between, and including,the specifcation limits.12, 13, 14stringent acceptance: the situation when the accept-ance zone is reduced from the spec
41、ifcation zone bya guard band(s).15, 16stringent rejection: the situation when the rejectionzone is increased beyond the specifcation zone by aguard band.17uncertainty interval (of a measurement): the set ofvalues of a characteristic about the result of a measure-mentthatmaybeexpectedtoencompassalarg
42、efractionof the distribution of values that could reasonably beattributed to the measurand.18, 197The guard band, g, is always a positive quantity; its location, e.g.,inside or outside the specifcation zone, is determined by the typeof acceptance or rejection desired. See ASME B89.7.3.1, Section 4.8
43、While these guidelines emphasize the use of guard bands, anequivalent methodology is to use gauging limits as in ASMEB89.7.2-1999.9The specifcation of a measurand may require statements aboutsuch quantities as time, temperature, and pressure.10A common example is the 4:1 ratio.11When claiming produc
44、t rejection, it is important to state thedecision rule; e.g., “rejection using the XX rule.”12The width of the specifcation zone is a positive number.13In the case of workpieces, the width of the specifcation zone isidentical to the tolerance.14Specifcationzoneisequivalentto“toleranceinterval”or“tol
45、erancezone” defned in ISO 3534-2.15Stringent acceptance and relaxed rejection occur together in abinary decision rule.16The stringent acceptance zone is analogous to the conformancezone described in ISO 14253-1.17Relaxed acceptance and stringent rejection occur together in abinary decision rule.18Th
46、ewidthoftheuncertaintyintervalistypicallytwicetheexpandeduncertainty.19The uncertainty interval for the mean of repeated measurementsmay decrease with increasing numbers of measurements.23 THE NATURE OF DISAGREEMENTS INUNCERTAINTY STATEMENTS3.1 GeneralIn an ideal situation, customers and suppliers w
47、illaddress the issue of measurement uncertainty whenthey discuss the product specifcations. Agreeing onthe measurement plan, the corresponding magnitude ofthe measurement uncertainty, and the decision rule (ifapplicable), will avoid future disagreements regardingthe acceptance/rejection of a product
48、. However, it isrecognized that two experts can produce two differentuncertainty statements often varying as much as 25%due to differing assumptions and data (as described insection 5). Resolving these differences at the contractstage is potentially less contentious than doing so afteran argument de
49、velops over the acceptance or rejectionof the product.3.2 Disagreements Involving SingleMeasurement SystemsIn manysituations there is onlya single measurementsystem; e.g., a customer agrees to accept the suppliersmeasurement results provided that the supplier usesstringent acceptance with a 100% guard band (i.e., theguard band equals the expanded uncertainty). In thisexample, a disagreement may arise if the customerfeels the supplier has underestimated the measurementuncertainty. Although there is a single measurementsystem, the supplier and the customer have developeddiffering uncertainty
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