ASTM_F_2537_-_06_2017.pdf

Designation:F253706(Reapproved 2017)Standard Practice forCalibration of Linear Displacement Sensor Systems Used toMeasure Micromotion1This standard is issued under the fixed designation F2537;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 This practice covers the procedures for calibration oflinear displacement sensors and their corresponding powersupply,signal conditioner,and data acquisition systems(lineardisplacement sensor systems)for use in measuring micromo-tion.It covers any sensor used to measure displacement thatgives an electrical voltage output that is linearly proportional todisplacement.This includes,but is not limited to,linearvariable differential transformers(LVDTs)and differentialvariable reluctance transducers(DVRTs).1.2 This calibration procedure is used to determine therelationship between output of the linear displacement sensorsystem and displacement.This relationship is used to convertreadings from the linear displacement sensor system intoengineering units.1.3 This calibration procedure is also used to determine theerror of the linear displacement sensor system over the range ofits use.1.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.5 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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Terminology2.1 Definitions:2.1.1 calibrated range,ndistance over which the lineardisplacement sensor system is calibrated.2.1.2 calibration certificate,ncertification that the sensormeets indicated specifications for its particular grade or modeland whose accuracy is traceable to the National Institute ofStandards and Technology or another international standard.2.1.3 core,ncentral rod that moves in and out of thesensor.NOTE1It is preferable that the sensors prevent the core from exitingthe sensor housing.2.1.4 data acquisition system,nsystem generally consist-ing of a terminal block,data acquisition card,and computerthat acquires electrical signals and allows them to be capturedby a computer.2.1.5 differential variable reluctance transducer(DVRT),na linear displacement sensor made of a sensor housing anda core.The sensor housing contains a primary coil and asecondary coil.Core position is detected by measuring thecoils differential reluctance.2.1.6 linear displacement sensor,nan electrical sensorthat converts linear displacement to electrical output.2.1.7 linear displacement sensor system,na system con-sisting of a linear displacement sensor,power supply,signalconditioner,and data acquisition system.2.1.8 linear variable differential transformer(LVDT),nalinear displacement sensor made of a sensor housing and acore.The sensor housing contains a primary coil and twosecondary coils.When an ac excitation signal is applied to theprimary coil,voltages are induced in the secondary coils.Themagnetic core provides the magnetic flux path linking theprimary and secondary coils.Since the two voltages are ofopposite polarity,the secondary coils are connected in seriesopposing in the center,or null position.When the core isdisplaced from the null position,an electromagnetic imbalanceoccurs.This imbalance generates a differential ac outputvoltage across the secondary coils,which is linearly propor-tional to the direction and magnitude of the displacement.When the core is moved from the null position,the inducedvoltage in the secondary coil,toward which the core is moved,increases while the induced voltage in the opposite secondarycoil decreases.1This practice is under the jurisdiction ofASTM Committee F04 on Medical andSurgical Materials and Devices and is the direct responsibility of SubcommitteeF04.15 on Material Test Methods.Current edition approved Dec.15,2017.Published January 2018.Originallyapproved in 2006.Last previous edition approved in 2011 as F2537 06(2011).DOI:10.1520/F2537-06R17.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recommendations issued by