ASTM E1175-87(2003)
(Test Method)Standard Test Method for Determining Solar or Photopic Reflectance, Transmittance, and Absorptance of Materials Using a Large Diameter Integrating Sphere
Standard Test Method for Determining Solar or Photopic Reflectance, Transmittance, and Absorptance of Materials Using a Large Diameter Integrating Sphere
SIGNIFICANCE AND USE
To overcome the inadequacies of conventional spectrophotometric measurement techniques when nonhomogeneous materials are measured, a large integrating sphere may be used.5 ,6 Since the beam employed in such spheres is large in comparison to the disparaties of the materials being tested, the nonisotropic nature of the specimen being measured is essentially averaged, or integrated out of the measurement, in a single experimental determination.
Solar and photopic optical properties may be measured either with monofunctional spheres individually tailored for the measurement of either transmittance6 or reflectance, or may be measured with a single multifunctional sphere that is employed to measure both transmittance and reflectance.5
A multifunctional sphere is used for making total solar transmittance measurements in both a directional-hemispherical and a directional-directional mode. The solar absorptance can be evaluated in a single measurement as one minus the sum of the directional hemispherical reflectance and transmittance. When a sample at the center of the sphere is supported by its rim, the sum of the reflectance and transmittance can be measured as a function of the angle of incidence. The solar absorptance is then one minus the measured absorptance plus transmittance.
SCOPE
1.1 This test method covers the measurement of the absolute total solar or photopic reflectance, transmittance, or absorptance of materials and surfaces. Although there are several applicable test methods employed for determining the optical properties of materials, they are generally useful only for flat, homogeneous, isotropic specimens. Materials that are patterned, textured, corrugated, or are of unusual size cannot be measured accurately using conventional spectrophotometric techniques, or require numerous measurements to obtain a relevant optical value. The purpose of this test method is to provide a means for making accurate optical property measurements of spatially nonuniform materials.
1.2 This test method is applicable to large specimens of materials having both specular and diffuse optical properties. It is particularly suited to the measurement of the reflectance of opaque materials and the reflectance and transmittance of semitransparent materials including corrugated fiber-reinforced plastic, composite transparent and translucent samples, heavily textured surfaces, and nonhomogeneous materials such as woven wood, window blinds, draperies, etc.
1.3 The values stated in SI units are to be regarded as the standard. The values given 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. (For specific safety hazards, see Note.)
General Information
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Standards Content (Sample)
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Designation: E 1175 – 87 (Reapproved 2003)
Standard Test Method for
Determining Solar or Photopic Reflectance, Transmittance,
and Absorptance of Materials Using a Large Diameter
1
Integrating Sphere
This standard is issued under the fixed designation E 1175; 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 E 892 Tables for Terrestrial Solar Spectral Irradiance at Air
3
Mass 1.5 for a 37° Tilted Surface
1.1 Thistestmethodcoversthemeasurementoftheabsolute
E 903 Test Method for SolarAbsorptance, Reflectance, and
total solar or photopic reflectance, transmittance, or absorp-
2
Transmittance of Materials Using Integrating Spheres
tance of materials and surfaces. Although there are several
applicable test methods employed for determining the optical
3. Terminology
properties of materials, they are generally useful only for flat,
3.1 Definitions:
homogeneous, isotropic specimens. Materials that are pat-
3.1.1 absorptance, n—see Terminology E 772.
terned, textured, corrugated, or are of unusual size cannot be
3.1.2 integrating sphere—optical device used to either col-
measured accurately using conventional spectrophotometric
lect flux reflected or transmitted from a sample into a hemi-
techniques, or require numerous measurements to obtain a
sphere or to provide isotropic irradiation of a sample from a
relevant optical value. The purpose of this test method is to
complete hemisphere.
provideameansformakingaccurateopticalpropertymeasure-
3.1.2.1 Discussion—It consists of a cavity that is approxi-
ments of spatially nonuniform materials.
mately spherical in shape with apertures for admitting and
1.2 This test method is applicable to large specimens of
detecting flux and usually having additional apertures over
materials having both specular and diffuse optical properties. It
which sample and reference specimens are placed.
is particularly suited to the measurement of the reflectance of
3.1.3 photopic optical properties, n—absorptance, reflec-
opaque materials and the reflectance and transmittance of
tance, and transmittance of a sample evaluated as the weighted
semitransparentmaterialsincludingcorrugatedfiber-reinforced
average of the measured property, with the wavelength by
plastic, composite transparent and translucent samples, heavily
wavelength of the product of the spectral irradiance for the
textured surfaces, and nonhomogeneous materials such as
measurement and the Commission Internationale de
woven wood, window blinds, draperies, etc.
4
l’Eclairage (CIE) photopic spectral response, as the weighting
1.3 The values stated in SI units are to be regarded as the
function.
standard. The values given in parentheses are for information
3.1.4 photopic response, n—spectral response of the aver-
only.
age human eye when fully adapted to daylight conditions.
1.4 This standard does not purport to address all of the
3.1.5 reflectance, n—see Terminology E 772.
safety concerns, if any, associated with its use. It is the
3.1.6 transmittance, n—see Terminology E 772.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
4. Summary of Test Method
bility of regulatory limitations prior to use. (For specific safety
4.1 This test method describes a procedure and apparatus
hazards, see Note 1.)
for determining the area-averaged optical properties of com-
2. Referenced Documents plex or nonuniform materials and surfaces. This test method
employs a large diameter integrating sphere and a source
2.1 ASTM Standards:
2
capable of illuminating a representative area of the test
E 772 Terminology Relating to Solar Energy Conversion
specimen’s surface.
1
These test methods are under the jurisdiction of ASTM Committee E44 on
Solar, Geothermal, and Other Alternative Energy Sources and is the direct
responsibility of Subcommittee E44.05 on Solar Heating and Cooling Subsystems
and Systems.
3
Current edition approved July 31, 1987. Published September 1987. Originally Annual Book of ASTM Standards, Vol 14.02.
4
approved in 1987. Last previous edition approved in 1996 as E 1175–87(1996). Commission Internationale de l’Eclairage (CIE), International Light Vocabu-
2
Annual Book of ASTM Standards, Vol 12.02. lary, 3rd Ed., Bureau Central de la CIE, Paris, 1970.
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E 1175 – 87 (2003)
4.2 Transmittanceisdeterminedwiththespecimenmounted incidencefrom0°(normalincidence)to60°fromnormalinthe
5,6
externally at
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