ASTM_E_2428_-_15a.pdf

Designation:E242815aStandard Practice forCalibration and Verification of Torque Transducers1This standard is issued under the fixed designation E2428;the number immediately following the designation indicates the year oforiginal adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 The purpose of this practice is to specify the procedurefor the calibration of torque transducers.NOTE1Verification by deadweight and a lever arm is an acceptablemethod of verifying the torque indication of a testing machine.Tolerancesfor weights used are tabulated in Practice E2624;methods for calibrationof the weights are given in NIST Technical Note 577,Methods ofCalibrating Weights for Piston Gages.21.2 The values stated in SI units are to be regarded asstandard.Other metric and inch-pound values are regarded asequivalent when required.1.3 This practice is intended for the calibration of statictorque measuring instruments.The practice is not applicablefordynamicorhigh-speedtorquecalibrationsormeasurements,nor can the results of calibrations performed inaccordance with this practice be assumed valid for dynamic orhigh speed torque measurements.1.4 This standard does not purport to address all of thesafety concerns,if any,associated with its use.It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:3E29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE2624 Practice for Torque Calibration of Testing Machinesand Devices2.2 ASME Standard:B46.1 Surface Texture42.3 BIPM Standard5JCGM 200 International vocabulary of metrologyBasic andgeneral concepts and associated terms(VIM)3.Terminology3.1 Definitions:3.1.1 primary torque standarda deadweight force appliedthrough a lever arm or wheel,all displaying metrologicaltraceability to the International System of Units(SI).3.1.1.1 Discussionfor further definition of the term met-rological traceability,refer to the latest revision of JCGM:200.3.1.2 secondarytorquestandardaninstrumentormechanism,the calibration of which has been established by acomparison with a primary torque standard(s).3.2 Definitions of Terms Specific to This Standard:3.2.1 calibration equationa mathematical relationship be-tween deflection and torque established from the calibrationdata for use with the torque transducer in service,sometimescalled the calibration curve.3.2.1.1 DiscussionTorque transducers have torque-to-deflection relationships that can be fitted to polynomial equa-tions.3.2.2 continuous-reading devicea class of instrumentswhose characteristics permit interpolation of torque valuesbetween calibrated torque values.3.2.2.1 DiscussionSuch instruments usually have torque-to-deflection relationships that can be fitted to polynomialequations.Departures from the fitted curve are reflected in theuncertainty(see 8.5).3.2.3 creepThe change in deflection of the torque trans-ducer under constant applied torque.3.2.3.1 DiscussionCreep is expressed as a percentage ofthe output change at a constant applied torque from an initial1This practice is under the jurisdiction ofASTM Committee E28 on MechanicalTesting and is the direct responsibility of Subcommittee E28.01 on Calibration ofMechanical Testing Machines and Apparatus.Current edition approved May 15,2015.Published May 2015.Originallyapproved in 2008.Last previous edition approved in 2015 as E242815.DOI:10.1520/E2428-15A.2Available from National Institute of Standards and Technology(NIST),100Bureau Dr.,Stop 1070,Gaithersburg,MD 20899-1070,http:/www.nist.gov.3For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.4Available from American Society of Mechanical Engineers(ASME),ASMEInternational Headquarters,Two Park Ave.,New York,NY 10016-5990,http:/www.asme.org.5BIPM,Pavillon de Breteuil,F-92312 Svres Cedex.http:/www.bipm.orgCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 time following the achievement of mechanical and electricalstability and the time at which the test is concluded.Valid creeptests may require the use of primary torque standards tomaintain adequate stability of the applied torque during the testtime interval.Creep results from a time dependent,elasticdeformation of the instrument mechanical element.In the caseof torque transducers,creep is adjusted by strain gage designand process modifications to reduce the strain gage response tothe inherent time-dependent elastic deflection.3.2.4 creep recoveryThe non-return to zero following acreep test