ASTM_E_2730_-_10_2015e2.pdf

Designation:E273010(Reapproved 2015)2Standard Practice forCalibration and Use of Thermocouple Reference JunctionProbes in Evaluation of Electronic Reference JunctionCompensation Circuits1This standard is issued under the fixed designation E2730;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.1NOTENote 12 was moved to a new location below Table 2 in November 2015.1.Scope1.1 This guide covers methods of calibration and use ofthermocouple reference junction probes(cold junction com-pensation probes)in the evaluation of electronic referencejunction compensation circuits.Their use with instruments thatmeasure only voltage is also covered.1.2 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.1.3 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:2E220 Test Method for Calibration of Thermocouples ByComparison TechniquesE230 Specification and Temperature-Electromotive Force(EMF)Tables for Standardized ThermocouplesE344 Terminology Relating to Thermometry and Hydrom-etryE563 Practice for Preparation and Use of an Ice-Point Bathas a Reference TemperatureE1129/E1129M Specification for Thermocouple ConnectorsE1684 Specification for Miniature Thermocouple Connec-torsE1750 Guide for Use of Water Triple Point CellsE2623 Practice for Reporting Thermometer Calibrations2.2 Other References:NIST Monograph 175 Temperature-Electromotive ForceReference Functions and Tables for the Letter-DesignatedThermocouple Types Based on the ITS-90ASTM MNL12 Manual On The Use Of Thermocouples InTemperature MeasurementBIPM JCGM 100:2008 Evaluation of Measurement DataGuide to the Expression of Uncertainty in Measurement3.Terminology3.1 DefinitionsThe definitions given in Terminology E344shall apply to this guide.3.2 Definitions of Terms Specific to This Standard:3.2.1 correction,nan offset value added to the result of ameasurement to obtain a correct result.NOTE1This definition is from Test Method E220.3.2.2 reference junction compensation,nthe electrical cor-rection of the indication of a thermocouple such that thecorrected indication is equivalent to the emf or temperature theinstrument would indicate if the reference junctions werephysically maintained at 0C.3.2.3 reference junction probe,na probe constructed fromthermocouple materials and high purity copper wire for thepurpose of serving as the reference junction for a thermocoupleassembly.Reference junction probes may be constructed aspart of the measuring probe or they can be manufacturedseparately and later attached to thermocouple sensors via plugsor other connection types.3.2.4 UUT,nUnit Under Test.4.Summary of Guide4.1 Calibration of a Reference Junction Probe(RJP)con-sists of establishing the emf error in the RJP relative to theapplicable thermocouple reference function by placing themeasuring junction and the reference junctions at knowntemperatures while measuring the voltage with a digital volt-meter(DVM)or potentiometer.Three methods are described1This practice is under the jurisdiction ofASTM Committee E20 on TemperatureMeasurement and is the direct responsibility of Subcommittee E20.04 on Thermo-couples.Current edition approved June 15,2015.Published June 2015.Originallyapproved in 2010.Last previous edition approved in 2010 as E2730 10.DOI:10.1520/E2730-10R15E02.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 for establishing the two known temperatures and thus thetemperature difference.For the temperature measurement,many devices such as Standard Platinum Resistance Thermom-eters(SPRTs),Platinum Resistance Thermometers(PRTs),thermistors,or thermocouples,and a variety of readout instru-ments are suitable,depending on the required accuracy.Themeasured voltage at the copper leads indicates the emf asso-ciated with the temperature difference of the references.Erroris determined by comparing the observed emf to the calculatedemf for the known temperature difference.The emf error isthen applied as a correction.The corrected emf can then beconverted to temperature.NOTE2In particular,cold work should be avoided in the sections ofcopper and thermocouple wire that pass from the top of the ice bath toambient temperature con