1、Designation: E1897 97 (Reapproved 2010)Standard Test Methods forMeasuring and Compensating for Transmittance of anAttenuating Medium Using Infrared Imaging Radiometers1This standard is issued under the fixed designation E1897; the number immediately following the designation indicates the year ofori
2、ginal 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 These test methods cover procedures for measuring andcompensat
3、ing for transmittance when using an infrared imag-ing radiometer to measure the temperature of a specimenthrough an attenuating medium, such as a window, filter oratmosphere.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.
4、3 These test methods 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 estab
5、lish 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 of Terms Specific to This Standard:3.1.1 attenuating mediuma
6、 semi-transparent solid, liquidor gas, such as a window, filter, external optics and/or anatmosphere that attenuates radiation.3.1.2 blackbody simulatora device with an emissivityclose to 1.00 that can be heated or cooled to a stabletemperature.3.1.3 filtera semi-transparent material that attenuates
7、 cer-tain wavelengths of radiation.3.1.4 infrared thermographerthe person using an infraredimaging radiometer.3.1.5 reflected temperaturethe temperature of the energyincident upon and reflected by the measurement surface of thespecimen.3.1.6 windowa semi-transparent material that separatesconditione
8、d and unconditioned atmospheres and attenuatescertain wavelengths of radiation.3.2 See also Terminology E1316.4. Summary of Test Method4.1 Using the computer built into an infrared imagingradiometer, a method is given for measuring the transmittanceof an attenuating medium.4.2 Using the computer bui
9、lt into an infrared imagingradiometer, a method is given for compensating for errorswhen measuring the temperature of a specimen through anattenuating medium when the emissivity of the specimen andthe transmittance of the attenuating medium are known.4.3 Using the computer built into an infrared ima
10、gingradiometer, a method is given for measuring and compensatingfor unknown transmittance and emissivity errors when thespecimen temperature is known.5. Significance and Use5.1 The transmittance of an attenuating medium can causeerrors for an infrared thermographer using an infrared imagingradiomete
11、r to measure the temperature of a specimen throughthe medium. Three test methods are given for measuring andcompensating for this error source.5.1.1 Atest method is given for measuring the transmittanceof an attenuating medium.5.1.2 A test method is given for compensating for errorswhen measuring th
12、e temperature of a specimen having aknown emissivity through an attenuating medium with aknown transmittance.5.1.3 A test method is given for measuring and compensat-ing for transmittance and emissivity errors when the specimentemperature is known.5.2 These test methods can be used in the field or l
13、aboratoryusing commonly available materials.1These test methods are under the jurisdiction of ASTM Committee E07 onNondestructive Testing and is the direct responsibility of Subcommittee E07.10 onSpecialized NDT Methods.Current edition approved May 1, 2010. Published June 2010. Originallyapproved in
14、 1997. Last previous edition approved in 2002 as E1897-97 (2002). DOI:10.1520/E1897-97R10.2For 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 Sum
15、mary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.3 These test methods can be used with any infraredradiometers that have the required computer capabilities.6. Interferences6.1 Test Method for Measuring t
16、he Transmittance of anAttenuating Medium:6.1.1 This test method requires a blackbody simulator withan emissivity of 0.95 or greater that is at least 20 C warmerthan ambient temperature. Potential errors can be minimizedby ensuring the stability of the temperature difference betweenthe source and the
17、 ambient temperature during the test. Also,the transmittance measurement accuracy can be increased byincreasing this temperature difference.6.1.2 Errors can be minimized by ensuring that the tempera-ture of the attenuating medium is as close as possible to thereflected temperature incident upon the
18、specimen.6.1.3 The compositions and thicknesses of attenuating me-dia can vary within the same specimen. Errors can be mini-mized by measuring through the same portion of the specimenevery time.6.2 Test Method for Compensating for Unknown ErrorsWhen Measuring the Temperature of a Specimen With a Kno
19、wnEmissivity Through an Attenuating Medium Having a KnownTransmittance:6.2.1 Errors can be minimized by ensuring that the tempera-ture of the attenuating medium is as close as possible to thereflected temperature incident upon the specimen.6.3 The transmittance of an attenuating medium may bespecifi
20、c to the temperature of the medium and the spectralwaveband of the radiometer used to make the measurement.Therefore, the temperature of the measured specimen and thespectral waveband of the radiometer used should be noted withthe measured transmittance value.6.4 The use of these test methods to com
21、pensate for thetransmittance of an attenuating medium is valid only whenmeasuring the temperatures of specimens that are opaque in thewaveband of the infrared imaging radiometer.7. Apparatus7.1 A calibrated infrared imaging radiometer with a built-incomputer that allows the infrared thermographer to
22、 inputreflected temperatures and emissivity values.7.2 The test method for measuring the transmittance of anattenuating medium requires a tripod or device to support theinfrared imaging radiometer.7.3 The test method for measuring the transmittance of anattenuating medium requires a high-emissivity
23、source that isheated to a stable temperature at least 20 C above ambienttemperature.7.4 The test method for measuring and compensating forunknown transmittance and emissivity errors when the speci-men temperature is known requires a calibrated thermometer tomeasure the temperature of the specimen.8.
24、 Procedure8.1 To measure the transmittance of an attenuating medium,use the following sequential steps:8.1.1 Place the infrared imaging radiometer on the tripod orsupport device at the desired location and distance from theblackbody simulator.8.1.2 Point the infrared imaging radiometer at the black-
25、body simulator and focus on a portion that has an emissivity of0.95 or greater. Make sure that the blackbody simulator is at astable temperature at least 20 C above the ambient tempera-ture.8.1.3 Use an appropriate infrared imaging radiometer mea-surement function (such as spot temperature, crosshai
26、rs orisotherm) to measure and compensate for the reflected tem-perature error incident upon the blackbody simulator.8.1.4 With the imagers computer emittance control still setto 1.00, measure and record the apparent temperature of thissame portion of the blackbody simulator.8.1.5 Position the attenu
27、ating medium between the imagersdetector or lens and the blackbody simulator.8.1.6 Without moving the imager, adjust its computersemissivity control until the imagers computer indicates thesame temperature recorded in 8.1.4. The indicated “emissivity”value is the transmittance of the attenuating med
28、ium, at thisblackbody simulator temperature and radiometers spectralwaveband.8.1.7 Repeat 8.1.1 through 8.1.6 a minimum of three timesand average the transmittance values to yield an averagetransmittance.8.2 To measure the temperature of a specimen having aknown emissivity through an attenuating med
29、ium having aknown transmittance, use the following sequential steps.8.2.1 Point the infrared imaging radiometer at the specimenand focus on the portion where the temperature is to bemeasured. Place the attenuating medium having a knowntransmittance between the imagers detector or lens and thespecime
30、n.8.2.2 Instead of 1.00, enter the measured transmittancepercentage of the attenuating medium under the imagersemissivity input (sometime referred to as “emittance” or “E”).Use an appropriate infrared imaging radiometer function (suchas spot temperature, crosshairs or isotherm) to measure andcompens
31、ate for the reflected temperature error incident uponthe specimen.8.2.3 Calculate the combined emissivity and transmittancecorrection value by multiplying the known emissivity of thespecimen times the known transmittance of the attenuatingmedium. Record this combined correction value.8.2.4 Repeat 8.
32、2.1 through 8.2.3 a minimum of three timesand average the values to yield an average combined correctionvalue.8.2.5 Compensate for emissivity and transmittance errors byentering the combined correction value recorded in 8.2.3 in theinfrared radiometric imagers computer under the “emissivity”input.8.
33、3 To measure and compensate for unknown transmittanceand emissivity errors when the specimen temperature isknown, use the following sequential steps. Use an appropriateinfrared imaging radiometer function (such as spot tempera-ture, crosshairs or isotherm) to measure and compensate for thereflected
34、temperature error incident upon the specimen.E1897 97 (2010)28.3.1 Point the imager at the specimen and the portion of thespecimen having an unknown emissivity. Place the attenuatingmedium(s) with an unknown transmittance(s) between theimagers detector or lens and the specimen.8.3.2 With another the
35、rmometer, measure and record thetemperature of the portion of the specimen delineated with theinfrared imaging radiometers measurement function.8.3.3 With the imager still focused on the same portion ofthe specimen, adjust the imagers computer emissivity controluntil the indicated temperature is the
36、 same as the temperaturejust recorded in 8.3.2. Record this “emissivity” value which isthe combined correction value for errors produced by thetransmittance of the attenuating medium and the emissivity ofthe specimen, at this medium temperature and radiometersspectral waveband.8.3.4 Repeat 8.3.1 thr
37、ough 8.3.3 a minimum of three timesand average the emissivity values to yield an average combinedcorrection value.8.3.5 Enter this average combined correction value in theimager computer under the emissivity input to compensate forerrors produced by this attenuating medium when measuring aspecimen w
38、ith the same emissivity.9. Precision and Bias9.1 PrecisionA measure of the precision of these testmethods can be inferred from the results of the replicate testsspecified in 8.1.7, 8.2.4, and 8.3.4.9.2 BiasThe bias cannot be determined by these testmethods because the values of transmittance are def
39、ined onlyin terms of the test methods.10. Keywords10.1 attenuating medium; blackbody simulator; emissivity;filter; imaging, infrared; infrared examination; infrared testing;infrared thermography; nondestructive testing; radiometry;reflected temperature; temperature compensation; transmit-tance; temp
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