ASTM_E_1311_-_14.pdf

Designation:E131114Standard Practice forMinimum Detectable Temperature Difference for ThermalImaging Systems1This standard is issued under the fixed designation E1311;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 the determination of the minimumdetectable temperature difference(MDTD)capability of acompound observer-thermal imaging system as a function ofthe angle subtended by the target.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 problems,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: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 field of view(FOV)the shape and angular dimen-sions of the cone or the pyramid that define the object spaceimaged by the system;for example,rectangular,4-deg wide by3-deg high.3.1.2.1 DiscussionThe size of the field of view is custom-arily expressed in units of degrees.3.1.3 See also Terminology E1316.4.Summary of Practice4.1 A standard circular target is used in conjunction with adifferential blackbody that can establish one blackbody isother-mal temperature for the target and another blackbody isother-mal temperature for the background by which the target isframed.The target,at an undisclosed orientation,is imagedonto the monochrome video monitor of a thermal imagingsystem whence the image may be viewed by an observer.Thetemperature difference between the target and the background,initially zero,is increased incrementally until the observer,in alimited duration,can just distinguish the target.This criticaltemperature difference is the MDTD.NOTE1Observers must have good eyesight and be familiar withviewing thermal imagery.4.2 The temperature distributions of each target and itsbackground are measured remotely at the critical temperaturedifference that defines the MDTD.4.3 The background temperature and the angular subtensefor each target are specified together with the measured valueof MDTD.The(fixed)field of view included by the back-ground is also specified.4.4 The probability of detection is specified together withthe reported value of MDTD.5.Significance and Use5.1 This practice gives a measure of a thermal imagingsystems effectiveness for detecting a small spot within a largebackground.Thus,it relates to the detection of small materialdefects such as voids,pits,cracks,inclusions,and occlusions.5.2 MDTD values provide estimates of detection capabilitythat may be used to compare one system with another.(LowerMDTD values indicate better detection capability.)5.3 Due to the partially subjective nature of the procedure,repeatability and reproducibility are apt to be poor and MDTDdifferences less than 0.2C are considered to be insignificant.NOTE2Values 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 Oct.1,2014.Published October 2014.Originallyapproved in 1989.Last previous edition approved in 2010 as E1311-89(2010).DOI:10.1520/E1311-14.2For 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.*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 6.1.1 Target Plates,containing single or multiple circulartargets of area(s)not greater than 5%of the combined areas oftarget and background(that is,FOV area),and with thedistance from the center of the target to the center of the FOVequal to one third of the height or the diameter of the FOV.SeeFig.1.NOTE3A target plate may be fabricated by cutting one or morecircular apertures in a metal plate of high thermal conductivity,such asaluminum,and coating with black paint of emissivity greater than 0.95.Inthis case an aperture would constitute a target,and the coated metalsurrounding the target and within the field of view of the thermal imag