ASTM_E_1933_-_14.pdf

Designation:E193314Standard Practice forMeasuring and Compensating for Emissivity Using InfraredImaging Radiometers1This standard is issued under the fixed designation E1933;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.Scope*1.1 This practice covers procedures for measuring andcompensating for emissivity when measuring the surfacetemperature of a specimen with an infrared imaging radiom-eter.21.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 These procedures may involve use of equipment andmaterials in the presence of heated or electrically-energizedequipment,or both.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:3E1316 Terminology for Nondestructive Examinations3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 reflected temperaturethe temperature of the energyincident upon and reflected from the measurement surface ofthe specimen.3.1.2 surface-modifying materialany tape,spray,paint orthe like that is used to change the emissivity of the specimensurface.3.2 See also Terminology E1316.4.Summary of Practice4.1 Two procedures are given for measuring the emissivityof a specimen surface,the contact thermometer method and thenon-contact thermometer method.4.2 Aprocedure is also given for compensating for the errorproduced by emissivity using the computer built into aninfrared imaging radiometer.5.Significance and Use5.1 The emissivity of a specimen can cause surface tem-perature measurement errors.Two procedures are provided formeasuring and compensating for this error source.5.2 These procedures can be used in the field or laboratory,using commonly available materials.5.3 These procedures can be used with any infrared radi-ometers that have the required computer capabilities.5.4 The values of emissivity are defined only in terms of theprocedure for the purpose of process control and nondestruc-tive evaluation of materials.6.Interferences6.1 Contact Thermometer MethodContact thermometerscan act as heat sinks and change the temperature of thespecimen.6.2 Noncontact Thermometer Method:6.2.1 The use of surface-modifying materials can changethe heat transfer properties and temperature of the specimen.Any such errors can be minimized by applying surface-modifying materials to the smallest area that satisfies themeasurement accuracy requirements of the radiometer andinfrared thermographer.6.2.2 Before the surface-modifying material is applied to anarea of the specimen adjacent to the area where the emissivityis to be measured(as directed in 8.2.4),errors can beminimized by viewing the imager display to ensure that bothareas have the same temperature.6.2.3 When removing a surface-modifying material,as di-rected in 8.2.7,errors can be minimized by ensuring that thesurface is returned to its original condition.1This practice is under the jurisdiction of ASTM Committee E07 on Nonde-structive Testing and is the direct responsibility of Subcommittee E07.10 onSpecialized NDT Methods.Current edition approved Oct.1,2014.Published October 2014.Originallyapproved in 1997.Last previous edition approved in 2005 as E1933-99a(2010).DOI:10.1520/E1933-14.2These procedures are adapted from the Guideline for Measuring and Compen-sating for Reflected Temperature,Emittance and Transmittance developed by theInfraspection Institute,425 Ellis Street,Burlington,NJ 08016.3For 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.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.3 Both procedures require the specimen to be at a tem-perature that is at least 10C warmer or cooler than the ambienttemperature.Potential errors can be minimized by ensuring thestability of the temperature difference between the specimenand the ambient temperature during the procedure.Also,theemissivity measurement accuracy can be increased by increas-ing this temperature difference.6.4 The emissivity of a specimen may be specific to thetemperature of the specimen and the spectral waveband of theinfrared imaging radiometer used to make the measurement.Therefore,the temperature of the specimen and the spectralwaveband of the radiometer should be noted along with t