ASTM_E_1213_-_14_2018.pdf

Designation:E121314(Reapproved 2018)Standard Practice forMinimum Resolvable Temperature Difference for ThermalImaging Systems1This standard is issued under the fixed designation E1213;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 determination of the minimumresolvable temperature difference(MRTD)capability of thecompound observer-thermal imaging system as a function ofspatial frequency.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 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.Referenced Documents2.1 ASTM Standards:2E1316 Terminology for Nondestructive Examinations3.Terminology3.1 Definitions:3.1.1 differential blackbodyan apparatus for establishingtwo parallel isothermal planar zones of different temperatures,and with effective emissivities of 1.0.3.1.2 See also Terminology E1316.4.Summary of Practice4.1 A standard four-bar target is used in conjunction with adifferential blackbody that can establish one blackbody isother-mal temperature for the set of bars and another blackbodyisothermal temperature for the set of conjugate bars,which areformed by the regions between the bars(see Fig.1).The targetis imaged onto the monochrome video monitor of a thermalimaging system where the image is viewed by an observer.Thetemperature difference between the bars and their conjugates,initially zero,is increased incrementally only until the observercan distinguish the four bars.This critical temperature differ-ence is the MRTD.4.2 The spatial distribution of temperature of each targetmust be measured remotely at the critical temperature differ-ence that determines the MRTD.The mean temperature of eachbar must not differ from that of any other bar by more than themeasured MRTD.A similar requirement applies to the tem-perature of each conjugate bar.Otherwise the MRTD value isunacceptable.4.3 The background temperature and the spatial frequencyof each target must be specified together with the measuredvalue of MRTD.4.4 The probability of resolution must be specified togetherwith the reported value of MRTD.5.Significance and Use5.1 This practice relates to a thermal imaging systemseffectiveness for discerning details in a scene.5.2 MRTD values provide estimates of resolution capabilityand may be used to compare one system with another.(LowerMRTD values indicate better resolution.)5.3 Due to the partially subjective nature of the procedure,repeatability and reproducibility are apt to be poor and MRTDdifferences less than 0.2 C are considered to be insignificant.NOTE1Values obtained under idealized laboratory conditions may ormay not correlate directly with service performance.6.Apparatus6.1 The apparatus consists of the following: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 Nov.1,2018.Published December 2018.Originallyapproved in 1987.Last previous edition approved in 2014 as E1213 14.DOI:10.1520/E1213-14R18.2For 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 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 the World Trade Organization Technical Barriers to Trade(TBT)Committee.1 6.1.1 Comparison Charts(Targets),comprised of four pe-riodic bars of aspect ratio(width:height)1:7,as shown in Fig.1.6.1.2 Differential Blackbody,temporally stable and control-lable to within 0.1 C.6.1.3 Infrared Spot Radiometer,calibrated with the aid of ablackbody source to an accuracy within 0.1 C.NOTE2Comparison charts may be fabricated by cutting slots in metaland coating with black paint of emissivity greater