ASTM_E_2488_-_09_2014.pdf

Designation:E248809(Reapproved 2014)Standard Guide forthe Preparation and Evaluation of Liquid Baths Used forTemperature Calibration by Comparison1This standard is issued under the fixed designation E2488;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.INTRODUCTIONMany of the Standards and Test Methods under the jurisdiction of ASTM committee E20 onTemperature Measurement make reference to the use of controlled temperature fluid baths for thecalibration of thermometers by the comparison method.In this method the thermometer under test ismeasured while immersed in an isothermal medium whose temperature is simultaneously determinedby a calibrated reference thermometer.The uncertainty of all such comparison calibrations dependsupon how well the isothermal conditions can be maintained.The bath temperature must be stable overtime and uniform within the working space at the operating temperatures.This guide provides basicinformation,options and instructions that will enable the user to prepare and evaluate controlledtemperature baths for calibrations.1.Scope1.1 This guide is intended for use with controlled tempera-ture comparison baths that contain test fluids and operatewithin the temperature range of 100C to 550C.1.2 This guide describes the essential features of controlledtemperature fluid baths used for the purpose of thermometercalibration by the comparison method.1.3 This guide does not address the details on the design andconstruction of controlled-temperature fluid baths.1.4 This guide describes a method to define the workingspace of a bath and evaluate the temperature variations withinthis space.Ideally,the working space will be as close aspossible to isothermal.1.5 This guide does not address fixed point baths,ice pointbaths or vapor baths.1.6 This guide does not address fluidized powder baths.1.7 This guide does not address baths that are programmedto change temperature.1.8 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.9 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:2E1 Specification for ASTM Liquid-in-Glass ThermometersE344 Terminology Relating to Thermometry and Hydrom-etryE644 Test Methods for Testing Industrial Resistance Ther-mometersE839 Test Methods for Sheathed Thermocouples andSheathed Thermocouple Cable2.2 Other Documents:ITS-90 The International Temperature Scale of 19903NIST Monograph 126 Platinum Resistance Thermometry4NIST Monograph 150 Liquid-in-Glass Thermometry4NIST SP 250-22 Platinum Resistance Thermometer Calibra-tions41This guide is under the jurisdiction of ASTM Committee E20 on TemperatureMeasurement and is the direct responsibility of Subcommittee E20.07 on Funda-mentals in Thermometry.Current edition approved Dec.1,2014.Published December 2014.Originallyapproved in 2009.Last previous edition approved in 2009 as E2488 09.DOI:10.1520/E2488-09R14.2For 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.3Preston-Thomas,H.,METROLOGIA,Vol.27,1990,pp 3-10 and 107(errata).Mangum,B.W.,JOURNAL OF RESEARCH,National Institute of Standards andTechnology,Vol 95,1990,p.69.4Available from National Institute of Standards and Technology(NIST),100Bureau Dr.,Stop 1070,Gaithersburg,MD 20899-1070,http:/www.nist.gov.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 NIST SP 250-23 Liquid-in-Glass Thermometer CalibrationService42.3 Military Standards:MIL-STD-202G Test Methods for Electronic and ElectricalComponent Parts53.Terminology3.1 Standard terms used in this guide are defined in Termi-nology E344.3.2 Definitions of Terms Specific to This Standard:3.2.1 bath gradient error,nthe error caused by tempera-ture differences within the working space of the bath.3.2.2 immersion error,nan error caused by heatconduction,radiation or both between the temperature sensingportion of the sensor used in the bath and the environmentexternal to the measurement system.Immersion error is causedby an incorrect immersion length and the resulting incorrectthermal contact of the temperature sensing portion of thesensor with the medium under measurement.3.2.3 isothermal,adjof,related to,or designating a regionof nominally uniform temperature.3.2.4 thermal stability,nthe degree of variability of thetemperatur