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Designation: E2847 − 13

StandardPractice for
Calibration and Accuracy Verification of Wideband Infrared
Thermometers1
This standard is issued under the fixed designation E2847; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.

1. Scope 2. Referenced Documents

1.1 This guide covers electronic instruments intended for 2.1 ASTM Standards:2
measurement of temperature by detecting the intensity of E344 Terminology Relating to Thermometry and Hydrom-
thermal radiation exchanged between the subject of measure- etry
ment and the sensor. E1256 Test Methods for Radiation Thermometers (Single
1.2 The devices covered by this guide are referred to as Waveband Type)
infrared thermometers in this document. E2758 Guide for Selection and Use of Wideband, Low
Temperature Infrared Thermometers
1.3 The infrared thermometers covered in this guide are
instruments that are intended to measure temperatures below 3. Terminology
1000°C, measure thermal radiation over a wide bandwidth in 3.1 Definitions of Terms Specific to This Standard:
the infrared region, and are direct-reading in temperature.
iTeh Standards
3.1.1 cavity bottom, n—the portion of the cavity radiation
1.4 This guide covers best practice in calibrating infrared source forming the end of the cavity.
thermometers. It addresses concerns that will help the user 3.1.1.1 Discussion—The cavity bottom is the primary area
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perform more accurate calibrations. It also provides a structure
for calculation of uncertainties and reporting of calibration
where an infrared thermometer being calibrated measures
radiation.
results to include uncertainty.
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1.5 Details on the design and construction of infrared
3.1.2 cavity radiation source, n—a concave shaped geom-
etry approximating a perfect blackbody of controlled tempera-
thermometers are not covered in this guide. ture and defined emissivity used for calibration of radiation
thermometers.
1.6 This guide does not cover infrared thermometry ASTM E2847-13
above 3.1.2.1 Discussion—A cavity radiation source is a subset of
1000°C. It does /catalog/standards/astm/df32f175-d5f8-40e2-bd40-61d95ad81f8b/astm-e2847-13
not address the use of narrowband infrared thermal radiation sources.
thermometers or infrared thermometers that do not indicate 3.1.2.2 Discussion—To be a cavity radiation source of
temperature directly. practical value for calibration, at least 90 % of the field-of-view
1.7 The values stated in SI units are to be regarded as the of a radiation thermometer is expected to be incident on the
standard. The values given in parentheses are for information cavity bottom. In addition, the ratio of the length of the cavity
only. versus the cavity diameter is expected to be greater than or
1.8 The values stated in inch-pound units are to be regarded equal to 5:1.
as standard. The values given in parentheses are mathematical 3.1.3 cavity walls, n—the inside surfaces of the concave
conversions to SI units that are provided for information only shape forming a cavity radiation source.
and are not considered standard. 3.1.4 customer, n—the individual or institution to whom the
calibration or accuracy verification is being provided.
1
This practice is under the jurisdiction of ASTM Committee E20 on Temperature
3.1.5 distance-to-size ratio (D:S), n—see field-of-view.
Measurement and is the direct responsibility of Subcommittee E20.02 on Radiation
2
Thermometry. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved May 1, 2013. Published July 2013. Originally approved contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
in 2011. Last previous edition approved in 2011 as E2847–11. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
E2847–13. the ASTM website.

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1
 E2847 − 13
3.1.6 effective emissivity, n—the ratio of the amount of 5. Significance and Use
energy over a given spectral band exiting a thermal radiation 5.1 This guide provides guidelines and basic test methods
source to that predicted by Planck’s Law at a given tempera- for the accuracy verification of infrared thermometers. It
ture. includes test set-up and calculation of uncertainties. It is
3.1.7 field-of-view, n—a usually circular, flat surface of a intended to provide the user with a consistent method, while
measured object from which the radiation thermometer re- remaining flexible in the choice of calibration equipment. It is
ceives radiation. (1)3 understood that the uncertainty obtained depends in large part
3.1.7.1 Discussion—Many handheld infrared thermometers upon the apparatus and instrumentation used. Therefore, since
manufacturers include distance-to-size ratio (D:S) in their this guide is not prescriptive in approach, it provides detailed
specifications. Distance-to-size ratio relates to the following instruction in uncertainty evaluation to accommodate the
physical situation: at a given distance (D), the infrared ther- variety of apparatus and instrumentation that may be em-
mometer measures a size (S) or diameter, and a certain ployed.
percentage of the thermal radiation received by the infrared 5.2 This guide is intended primarily for calibrating handheld
thermometer is within this size. Field-of-view is a measure of infrared thermometers. However, the techniques described in
the property described by distance-to-size ratio. (1) this guide may also be appropriate for calibrating other classes
3.1.8 flatplate radiation source, n—a planar surface of of radiation thermometers. It may also be of help to those
controlled temperature and defined emissivity used for calibra- calibrating thermal imagers.
tions of radiation thermometers.
5.3 This guide specifies the necessary elements of the report
3.1.8.1 Discussion—A flatplate radiation source is a subset
of calibration for an infrared thermometer. The required
of thermal radiation sources.
elements are intended as a communication tool to help the end
3.1.9 measuring temperature range, n—temperature range user of these instruments make accurate measurements. The
for which the radiation thermometer is designed. (1) elements also provide enough information, so that the results of
3.1.10 purge, n—a process that uses a dry gas to remove the the calibration can be reproduced in a separate laboratory.
possibility of vapor on a measuring surface.
iTeh Standards
3.1.11 radiance temperature, n—temperature of an ideal (or
perfect) blackbody radiator having the same radiance over a
6. Sources of Uncertainty
6.1 Uncertainties are present in all calibrations. Uncertain-

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given spectral band as that of the surface being measured. (2)
3.1.12 thermal radiation source, n—a geometrically shaped
ties are underestimated when their effects are underestimated
or omitted. The predominant sources of uncertainty are de-

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object of controlled temperature and defined emissivity used scribed in Section 10 and are listed in Table 1 and Table X1.1
for calibration of radiation thermometers. of Appendix X1.
3.1.13 usage temperature range, n—temperature range for 6.2 Typically, the most prevalent sources of uncertainties in
which a radiation thermometer is designed to be utilized by the this method of calibration are: (1) emissivity estimation of the
end user. ASTM E2847-13
calibration source, (2) size-of-source of the infrared
/catalog/standards/astm/df32f175-d5f8-40e2-bd40-61d95ad81f8b/astm-e2847-13
thermometer, (3) temperature gradients on the radiation source,
4. Summary of Practice (4) improper alignment of the infrared thermometer with
respect to the radiation source, (5) calibration temperature of
4.1 The practice consists of comparing the readout tempera- the radiation source, (6) ambient temperature and (7) reflected
ture of an infrared thermometer to the radiance temperature of temperature. The order of prevalence of these uncertainties
a radiation source. The radiance temperature shall correspond may vary, depending on use of proper procedure and the type
to the spectral range of the infrared thermometer under test. of thermal radiation source used. Depending on the tempera-
4.2 The radiation source may be of two types. Ideally, the ture of the radiation source, the calibration method of the
source will be a cavity source having an emissivity close to radiation source, the optical characteristics of the infrared
unity (1.00). However, because the field-of-view of some thermometer and the detector and filter characteristics of the
infrared thermometers is larger than typical blackbody cavity
apertures, a large-area flatplate source may be used for these
calibrations. In either case, the traceable measurement of the TABLE 1 Components of Uncertainty
radiance temperature of the source shall be known, along with Uncertainty Component Discussion Evaluation Method
Source Uncertainties
calculated uncertainties. U Calibration Temperature 10.4 10.4.1
1

4.3 The radiance temperature of the source shall be trace- U2 Source Emissivity 10.5 10.2.3, X2.4 (example)
U3 Reflected Ambient Radiation 10.6 10.2.2, X2.5 (example)
able to a national metrology institute such as the National U4 Source Heat Exchange 10.7 10.7.1
Institute of Standards and Technology (NIST) in Gaithersburg, U5 Ambient Conditions 10.8 10.8.1
Maryland or the National Research Council (NRC) in Ottawa, U6 Source Uniformity 10.9 10.9.1
Infrared Thermometer Uncertainties
Ontario, Canada. U7 Size-of-Source Effect 10.11 Test Methods E1256
U8 Ambient Temperature 10.12 Appendix X3
U9 Atmospheric Absorption 10.13 X2.3
U10 Noise 10.14 10.14.1
3
The boldface numbers in parentheses refer to a list of references at the end of U11 Display Resolution 10.15 10.15.2
this standard.