1、Designation: E2847 131E2847 14Standard Test Method forCalibration and Accuracy Verification of Wideband InfraredThermometers1This standard is issued under the fixed designation E2847; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、 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 NOTETitle corrected editorially in September 2013.1. Scope1.1 This test method covers electronic instruments intend
3、ed for measurement of temperature by detecting the intensity ofthermal radiation exchanged between the subject of measurement and the sensor.1.2 The devices covered by this test method are referred to as infrared thermometers in this document.1.3 The infrared thermometers covered in this test method
4、 are instruments that are intended to measure temperatures below1000C, measure thermal radiation over a wide bandwidth in the infrared region, and are direct-reading in temperature.1.4 This guide covers best practice in calibrating infrared thermometers. It addresses concerns that will help the user
5、 performmore accurate calibrations. It also provides a structure for calculation of uncertainties and reporting of calibration results to includeuncertainty.1.5 Details on the design and construction of infrared thermometers are not covered in this test method.1.6 This test method does not cover inf
6、rared thermometry above 1000C. It does not address the use of narrowband infraredthermometers or infrared thermometers that do not indicate temperature directly.1.7 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only.1.8 The valu
7、es stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information only and are not considered standard.2. Referenced Documents2.1 ASTM Standards:2E344 Terminology Relating to Thermometry and Hydrome
8、tryE1256 Test Methods for Radiation Thermometers (Single Waveband Type)E2758 Guide for Selection and Use of Wideband, Low Temperature Infrared Thermometers3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 cavity bottom, nthe portion of the cavity radiation source forming the end
9、 of the cavity.3.1.1.1 DiscussionThe cavity bottom is the primary area where an infrared thermometer being calibrated measures radiation.3.1.2 cavity radiation source, na concave shaped geometry approximating a perfect blackbody of controlled temperature anddefined emissivity used for calibration of
10、 radiation thermometers.1 This practice is under the jurisdiction of ASTM Committee E20 on Temperature Measurement and is the direct responsibility of Subcommittee E20.02 on RadiationThermometry.Current edition approved May 1, 2013May 1, 2014. Published July 2013May 2014. Originally approved in 2011
11、. Last previous edition approved in 20112013 as E284711.DOI: 10.1520/E284713131. DOI: 10.1520/E284714.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards D
12、ocument Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, AST
13、M recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.2.1
14、 DiscussionA cavity radiation source is a subset of thermal radiation sources.3.1.2.2 DiscussionTo be a cavity radiation source of practical value for calibration, at least 90 % of the field-of-view of a radiation thermometer isexpected to be incident on the cavity bottom. In addition, the ratio of
15、the length of the cavity versus the cavity diameter is expectedto be greater than or equal to 5:1.3.1.3 cavity walls, nthe inside surfaces of the concave shape forming a cavity radiation source.3.1.4 customer, nthe individual or institution to whom the calibration or accuracy verification is being p
16、rovided.3.1.5 distance-to-size ratio (D:S), nsee field-of-view.3.1.6 effective emissivity, nthe ratio of the amount of energy over a given spectral band exiting a thermal radiation source tothat predicted by Plancks Law at a given temperature.3.1.7 field-of-view, na usually circular, flat surface of
17、 a measured object from which the radiation thermometer receivesradiation. (1)33.1.7.1 DiscussionMany handheld infrared thermometers manufacturers include distance-to-size ratio (D:S) in their specifications. Distance-to-sizeratio relates to the following physical situation: at a given distance (D),
18、 the infrared thermometer measures a size (S) or diameter,and a certain percentage of the thermal radiation received by the infrared thermometer is within this size. Field-of-view is ameasure of the property described by distance-to-size ratio. (1)3.1.8 flatplate radiation source, na planar surface
19、of controlled temperature and defined emissivity used for calibrations ofradiation thermometers.3.1.8.1 DiscussionA flatplate radiation source is a subset of thermal radiation sources.3.1.9 measuring temperature range, ntemperature range for which the radiation thermometer is designed. (1)3.1.10 pur
20、ge, na process that uses a dry gas to remove the possibility of vapor on a measuring surface.3.1.11 radiance temperature, ntemperature of an ideal (or perfect) blackbody radiator having the same radiance over a givenspectral band as that of the surface being measured. (2)3.1.12 thermal radiation sou
21、rce, na geometrically shaped object of controlled temperature and defined emissivity used forcalibration of radiation thermometers.3.1.13 usage temperature range, ntemperature range for which a radiation thermometer is designed to be utilized by the enduser.4. Summary of Practice4.1 The practice con
22、sists of comparing the readout temperature of an infrared thermometer to the radiance temperature of aradiation source. The radiance temperature shall correspond to the spectral range of the infrared thermometer under test.4.2 The radiation source may be of two types. Ideally, the source will be a c
23、avity source having an emissivity close to unity(1.00). However, because the field-of-view of some infrared thermometers is larger than typical blackbody cavity apertures, alarge-area flatplate source may be used for these calibrations. In either case, the traceable measurement of the radiance tempe
24、ratureof the source shall be known, along with calculated uncertainties.4.3 The radiance temperature of the source shall be traceable to a national metrology institute such as the National Institute ofStandards andTechnology (NIST) in Gaithersburg, Maryland or the National Research Council (NRC) in
25、Ottawa, Ontario, Canada.5. Significance and Use5.1 This guide provides guidelines and basic test methods for the accuracy verification of infrared thermometers. It includes testset-up and calculation of uncertainties. It is intended to provide the user with a consistent method, while remaining flexi
26、ble in thechoice of calibration equipment. It is understood that the uncertainty obtained depends in large part upon the apparatus and3 The boldface numbers in parentheses refer to a list of references at the end of this standard.E2847 142instrumentation used. Therefore, since this guide is not pres
27、criptive in approach, it provides detailed instruction in uncertaintyevaluation to accommodate the variety of apparatus and instrumentation that may be employed.5.2 This guide is intended primarily for calibrating handheld infrared thermometers. However, the techniques described in thisguide may als
28、o be appropriate for calibrating other classes of radiation thermometers. It may also be of help to those calibratingthermal imagers.5.3 This guide specifies the necessary elements of the report of calibration for an infrared thermometer. The required elementsare intended as a communication tool to
29、help the end user of these instruments make accurate measurements. The elements alsoprovide enough information, so that the results of the calibration can be reproduced in a separate laboratory.6. Sources of Uncertainty6.1 Uncertainties are present in all calibrations. Uncertainties are underestimat
30、ed when their effects are underestimated oromitted. The predominant sources of uncertainty are described in Section 10 and are listed in Table 1 and Table X1.1 of AppendixX1.6.2 Typically, the most prevalent sources of uncertainties in this method of calibration are: (1) emissivity estimation of the
31、calibration source, (2) size-of-source of the infrared thermometer, (3) temperature gradients on the radiation source, (4) improperalignment of the infrared thermometer with respect to the radiation source, (5) calibration temperature of the radiation source, (6)ambient temperature and (7) reflected
32、 temperature. The order of prevalence of these uncertainties may vary, depending on use ofproper procedure and the type of thermal radiation source used. Depending on the temperature of the radiation source, thecalibration method of the radiation source, the optical characteristics of the infrared t
33、hermometer and the detector and filtercharacteristics of the infrared thermometer, the contribution of these uncertainties may change significantly in the overalluncertainty budget.7. Apparatus7.1 Thermal Radiation Source:7.1.1 There are two different classes of thermal radiation sources which can b
34、e used for infrared thermometer calibrations: acavity source and a flatplate source. Some sources may be considered a hybrid of both categories. Each of these sources hasadvantages and disadvantages. The cavity source provides a source of radiation that has a more predictable emissivity. However,the
35、 flatplate source can usually be made less expensively, and can be made with a diameter large enough to calibrate infraredthermometers with low distance to size ratios (D:S).7.1.2 Ideally, the size of the thermal radiation source should be specified by the infrared thermometer manufacturer. In manyc
36、ases, this information may not be available. In these cases a field-of-view test should be completed as discussed in E1256. Theportion of signal incident on the infrared thermometer that does not come from the source should be accounted for in theuncertainty budget.7.1.3 Cavity Source:7.1.3.1 Acavit
37、y source can be constructed in several shapes as shown in Fig. 1. In general, a high length-to-diameter ratio (L:D)or radius-to-diameter ratio (R:D) in the spherical case will result in a smaller uncertainty.Asmaller conical angle will also resultin a smaller uncertainty.7.1.3.2 The location of a re
38、ference or a control probe, or both, and the thermal conductivity of the cavity walls are importantconsiderations in cavity source construction. In general, a reference or control probe should be as close as practical to the centerof the area where the infrared thermometer will typically measure, ty
39、pically the cavity bottom. If there is a separation between thelocation of the reference probe and the cavity surface, cavity walls with a higher thermal conductivity will result in a smalleruncertainty due to temperature gradients in this region.TABLE 1 Components of UncertaintyUncertainty Componen
40、t Discussion Evaluation MethodSource UncertaintiesU1 Calibration Temperature 10.4 10.4.1U2 Source Emissivity 10.5 10.2.3, X2.4 (example)U3 Reflected Ambient Radiation 10.6 10.2.2, X2.5 (example)U4 Source Heat Exchange 10.7 10.7.1U5 Ambient Conditions 10.8 10.8.1U6 Source Uniformity 10.9 10.9.1Infrar
41、ed Thermometer UncertaintiesU7 Size-of-Source Effect 10.11 Test Methods E1256U8 Ambient Temperature 10.12 Appendix X3U9 Atmospheric Absorption 10.13 X2.3U10 Noise 10.14 10.14.1U11 Display Resolution 10.15 10.15.2E2847 1437.1.3.3 The walls of the cavity source can be treated in several different ways
42、.Apainted or ceramic surface will generally resultin higher emissivity than an oxidized metal surface. By the same measure an oxidized metal surface will generally result in higheremissivity than a non-oxidized metal surface. In some cases, it may be impossible to paint the cavity source surface. Th
43、is isespecially true at high temperatures.7.1.3.4 The effective emissivity of the cavity source shall be calculated to determine the radiance temperature of the cavity.Calculation of effective emissivity is beyond the scope of this standard. Determination of effective emissivity can bemathematically
44、 calculated or modeled.7.1.4 Flatplate Source:7.1.4.1 A flatplate source is a device that consists of a painted circular or rectangular plate. The emissivity is likely to be lesswell defined than with a cavity source.This can be partially overcome by performing a radiometric transfer (see Scheme II
45、in 7.3.7)to the flatplate source. However, the radiometric transfer should be carried out with an instrument operating over a similar spectralband as the infrared thermometer under test.7.1.4.2 A cavity source is the preferred radiometric source for infrared thermometer calibrations. The cavity sour
46、ce has twomain advantages over a flatplate source. First, the cavity source has better defined emissivity and an emissivity much closer to unitydue to its geometric shape. Second, along with the emissvity being closer to unity, the effects of reflected temperature are lessened.Temperature uniformity
47、 on the flatplate source may be more of a concern as well. However, a flatplate source has a main advantageover a cavity source. The temperature controlled flatplate surface can be much larger than a typical cavity source opening, allowingfor much smaller D:S ratios (greater field-of-view).7.2 Apert
48、ure:7.2.1 An additional aperture may not be needed for all calibrations. An aperture is typically used to control scatter. If used, theaperture should be temperature-controlled or reflective. An aperture should be used if recommended by the infrared thermometermanufacturer. If an aperture is used fo
49、r calibration, this information should be stated in the report of calibration. The informationthat shall be included is the aperture distance, the aperture size, and the measuring distance. A possible configuration for apertureuse is shown in Fig. 2.7.2.2 In Fig. 2, dapr is the aperture distance. The measuring distance is shown by dmeas.7.3 Transfer Standard:FIG. 1 Cavity ShapesE2847 1447.3.1 The thermal radiation source shall be calibrated with a transfer standard traceable to a national metrological institute suchas the National Institute of Stan
