ASTM E1933-99a

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Designation:E1933–99a
Standard Test Methods for
Measuring and Compensating for Emissivity Using Infrared
Imaging Radiometers
This standard is issued under the fixed designation E 1933; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 4.2 A test method is also given for compensating for the
error produced by emissivity using the computer built into an
1.1 These test methods cover procedures for measuring and
infrared imaging radiometer.
compensating for emissivity when measuring the surface
temperature of a specimen with an infrared imaging radiom-
5. Significance and Use
eter.
5.1 The emissivity of a specimen can cause surface tem-
1.2 The values stated in SI units are to be regarded as the
perature measurement errors. Two test methods are provided
standard.
for measuring and compensating for this error source.
1.3 These test methods may involve use of equipment and
5.2 Thesetestmethodscanbeusedinthefieldorlaboratory,
materials in the presence of heated or electrically-energized
using commonly available materials.
equipment, or both.
5.3 These test methods can be used with any infrared
1.4 This standard does not purport to address all of the
radiometers that have the required computer capabilities.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
6. Interferences
priate safety and health practices and determine the applica-
6.1 Contact Thermometer Method—Contact thermometers
bility of regulatory limitations prior to use.
can act as heat sinks and change the temperature of the
2. Referenced Documents specimen.
6.2 Noncontact Thermometer Method:
2.1 ASTM Standards:
6.2.1 The use of surface-modifying materials can change
E 1316 Terminology for Nondestructive Examinations
the heat transfer properties and temperature of the specimen.
3. Terminology Any such errors can be minimized by applying surface-
modifying materials to the smallest area that satisfies the
3.1 Definitions of Terms Specific to This Standard:
measurement accuracy requirements of the radiometer and
3.1.1 reflected temperature—the temperature of the energy
infrared thermographer.
incident upon and reflected from the measurement surface of
6.2.2 Before the surface-modifying material is applied to an
the specimen.
area of the specimen adjacent to the area where the emissivity
3.1.2 surface-modifying material—any tape, spray, paint or
is to be measured (as directed in 8.2.4), errors can be
the like that is used to change the emissivity of the specimen
minimized by viewing the imager display to ensure that both
surface.
areas have the same temperature.
3.2 See also Terminology E 1316.
6.2.3 When removing a surface-modifying material, as di-
4. Summary of Test Method rected in 8.2.7, errors can be minimized by ensuring that the
surface is returned to its original condition.
4.1 Two test methods are given for measuring the emissivity
6.3 Both test methods require the specimen to be at a
of a specimen surface, the contact thermometer method and the
temperature that is at least 10°C warmer or cooler than the
non-contact thermometer method.
ambient temperature. Potential errors can be minimized by
ensuring the stability of the temperature difference between the
These test methods are under the jurisdiction of ASTM Committee E-7 on
specimenandtheambienttemperatureduringthetest.Also,the
Nondestructive Testing and are the direct responsibility of Subcommittee E07.10 on
emissivity measurement accuracy can be increased by increas-
Emerging NDT Methods.
ing this temperature difference.
Current edition approved Dec. 10, 1999. Published February 2000. Originally
published as E 1933–97. Last previous edition E 1933–99. 6.4 The emissivity of a specimen may be specific to the
These test methods are adapted from the Guideline for Measuring and
temperature of the specimen and the spectral waveband of the
Compensating for Reflected Temperature, Emittance and Transmittance developed
infrared imaging radiometer used to make the measurement.
by Infraspection Institute, 1971 Shelburne Road, Shelburne, VT 05482, 1993.
Therefore, the temperature of the specimen and the spectral
Annual Book of ASTM Standards, Vol 03.03.
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E1933–99a
waveband of the radiometer should be noted along with the 8.1.6 Repeat procedures 8.1.1 through 8.1.5 a minimum of
measured emissivity value. three times and average the emissivity values to yield an
6.5 These test methods are valid only for specimens that are average emissivity.
opaque in the waveband of the infrared imaging radiometer. 8.2 Noncontact Thermometer Method:
6.6 As the emissivity of a specimen decreases, its reflectiv- 8.2.1 Place the infrared imaging radiometer on the tripod or
ity increases. Careful consideration and avoidance of potential support device at the desired location and distance from the
error sources, including the precise determination of reflected specimen.
temperature in 8.1.3 and 8.2.3, is required to accurately 8.2.2 Point the infrared imaging radiometer at the specimen
measure the emissivity values of specimens having lower and focus on the portion where the emissivity is to be
emissivities. For materials with emissivities less than 0.5, m
...