ASTM E307-72(2014)
(Test Method)Standard Test Method for Normal Spectral Emittance at Elevated Temperatures
Standard Test Method for Normal Spectral Emittance at Elevated Temperatures
SIGNIFICANCE AND USE
5.1 The significant features are typified by a discussion of the limitations of the technique. With the description and arrangement given in the following portions of this test method, the instrument will record directly the normal spectral emittance of a specimen. However, the following conditions must be met within acceptable tolerance:
5.1.1 The effective temperatures of the specimen and blackbody must be within 1 K of each other. Practical limitations arise, however, because the temperature uniformities are often not better than a few degrees Kelvin.
5.1.2 The optical path length in the two beams must be equal, or the instrument should operate in a nonabsorbing atmosphere or a vacuum, in order to eliminate the effects of differential atmospheric absorption in the two beams. Measurements in air are in many cases important, and will not necessarily give the same results as in a vacuum, thus the equality of the optical paths for dual beam instruments becomes very critical.Note 3—Very careful optical alignment of the spectrophotometer is required to minimize differences in absorptance along the two paths of the instrument, and careful adjustment of the chopper timing to reduce “cross-talk” (the overlap of the reference and sample signals) as well as precautions to reduce stray radiation in the spectrometer are required to keep the zero line flat. With the best adjustment, the “100 % line” will be flat to within 3 %; both of these measurements should be reproducible within these limits (see 7.3, Note 6).
5.1.3 Front-surface mirror optics must be used throughout, except for the prism in prism monochromators and the grating in grating monochromators, and it should be emphasized that equivalent optical elements must be used in the two beams in order to reduce and balance attenuation of the beams by absorption in the optical elements. It is recommended that optical surfaces be free of SiO2 and SiO coatings; MgF2 may be used to stabilize mirror surfaces for exten...
SCOPE
1.1 This test method describes a highly accurate technique for measuring the normal spectral emittance of electrically conducting materials or materials with electrically conducting substrates, in the temperature range from 600 to 1400 K, and at wavelengths from 1 to 35 μm.
1.2 The test method requires expensive equipment and rather elaborate precautions, but produces data that are accurate to within a few percent. It is suitable for research laboratories where the highest precision and accuracy are desired, but is not recommended for routine production or acceptance testing. However, because of its high accuracy this test method can be used as a referee method to be applied to production and acceptance testing in cases of dispute.
1.3 The values stated in SI units are to be regarded as the standard. The values in parentheses are for information only.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
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Designation: E307 − 72 (Reapproved 2014)
Standard Test Method for
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Normal Spectral Emittance at Elevated Temperatures
This standard is issued under the fixed designation E307; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope specimen; it is the ratio of radiant flux emitted by a specimen
per unit area (thermal-radiant exitance) to that emitted by a
1.1 This test method describes a highly accurate technique
blackbodyradiatoratthesametemperatureandunderthesame
for measuring the normal spectral emittance of electrically
conditions. Emittance must be further qualified in order to
conducting materials or materials with electrically conducting
convey a more precise meaning. Thermal-radiant exitance that
substrates,inthetemperaturerangefrom600to1400K,andat
occurs in all possible directions is referred to as hemispherical
wavelengths from 1 to 35 µm.
thermal-radiant exitance. When limited directions of propaga-
1.2 The test method requires expensive equipment and
tion or observation are involved, the word directional thermal-
rather elaborate precautions, but produces data that are accu-
radiantexitanceisused.Thus,normalthermal-radiantexitance
rate to within a few percent. It is suitable for research
is a special case of directional thermal-radiant exitance, and
laboratories where the highest precision and accuracy are
means in a direction perpendicular (normal) to the surface.
desired, but is not recommended for routine production or
Therefore, spectral normal emittance refers to the radiant flux
acceptance testing. However, because of its high accuracy this
emitted by a specimen within a narrow wavelength interval
test method can be used as a referee method to be applied to
centered on a specific wavelength and emitted in a direction
production and acceptance testing in cases of dispute.
normal to the plane of an incremental area of a specimen’s
surface. These restrictions in angle occur usually by the
1.3 The values stated in SI units are to be regarded as the
standard. The values in parentheses are for information only. method of measurement rather than by radiant flux emission
properties.
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
NOTE 1—All the terminology used in this test method has not been
standardized. Terminology E349 contain some approved terms. When
responsibility of the user of this standard to establish appro-
agreement on other standard terms is reached, the definitions used herein
priate safety and health practices and determine the applica-
will be revised as required.
bility of regulatory limitations prior to use.
4. Summary of Test Method
2. Referenced Documents
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4.1 The principle of the test method is a direct comparison
2.1 ASTM Standards:
of the radiant flux from a specimen at a given temperature to
E349Terminology Relating to Space Simulation
the radiant flux of a blackbody at the same temperature and
under the same environmental conditions of atmosphere and
3. Terminology
pressure. The details of this test method are given by Harrison
3.1 Definitions of Terms Specific to This Standard:
et al (3) and Richmond et al (4).
3.1.1 spectral normal emittance—the term as used in this
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4.2 The essential features of the test method are the use of
specification follows that advocated by Jones (1), Worthing
adouble-beamratio-recordinginfraredspectrophotometerwith
(2), and others, in that the word emittance is a property of a
variable slit widths, which combines and compares the signals
from the specimen and the reference blackbody through a
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monochromator system which covers the wavelength range
This test method is under the jurisdiction of ASTM Committee E21 on Space
Simulation andApplications of SpaceTechnology and is the direct responsibility of
from1to35µm(Note 2). According to Harrison et al (3) a
Subcommittee E21.04 on Space Simulation Test Methods.
differential thermocouple with suitable instrumentation is used
Current edition approved April 1, 2014. Published April 2014. Originally
to maintain a heated specimen and the blackbody at the same
approvedin1968.Lastpreviouseditionapprovedin2008asE307–72(2008).DOI:
10.1520/E0307-72R14. temperature.
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For referenced ASTM standards, visit the ASTM website, www.astm.org, or
NOTE 2—An electronic-null, ratio-recording spectrophotometer is pre-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
ferred to an optical-null instrument for this use. It may be difficult to
Standards volume information, refer to the standard’s Document Summary page on
obtain an
...
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