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)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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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
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
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-
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.
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:
capable of illuminating a representative area of the test
E 772 Terminology Relating to Solar Energy Conversion
specimen’s surface.
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.
Current edition approved July 31, 1987. Published September 1987. Originally Annual Book of ASTM Standards, Vol 14.02.
approved in 1987. Last previous edition approved in 1996 as E 1175–87(1996). Commission Internationale de l’Eclairage (CIE), International Light Vocabu-
Annual Book of ASTM Standards, Vol 12.02. lary, 3rd Ed., Bureau Central de la CIE, Paris, 1970.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 1175 – 87 (2003)
4.2 Transmittanceisdeterminedwiththespecimenmounted incidencefrom0°(normalincidence)to60°fromnormalinthe
5,6
externally at the sphere entrance port. Reflectance is deter- transmittance mode, using natural sunlight as source. When
mined by placing the specimen in the center of the integrating employing an artificial source for either simulated solar or
sphere, in accordance with the diagram in Fig. A1.2 of Test photopic measurements, the off-angle mechanism may either
Method E 903. For measurement of reflectance of partially be made a part of the sphere (with a fixed position lamp) or a
transmitting samples, the sample should be backed by a black part of the source assembly (with a fixed position sphere).
opaque absorber to eliminate the transmitted flux from the 6.3 For reflectance measurements, a center-positioned
measurement. sample mount that has two degrees of freedom is required: in
4.3 The source may be either natural sunlight or an artificial and out of the sample beam, and rotation about the sample
source that closely approximates an Air Mass 1.5 solar energy beam to provide incident angles from 0° to 660°. The sample
distribution in accordance with Tables E 892. mount shall be designed so that the flux transmitted by the
4.4 Relevant optical properties are determined by the ratio sample is absorbed, for measurement of reflectance, or so that
of the total sphere flux transmitted or reflected by the specimen the sample is supported by its rim for simultaneous measure-
to the total sphere flux, or both when no specimen is in place. ment of reflectance plus transmittance.
4.5 The use of a spectrally flat or spectrally sensitive 6.4 The interior of the integrating sphere shall be uniformly
detector determines whether a solar or a photopic optical coated with a spectrally flat paint having a minimum hemi-
characteristic is measured. spherical reflectance of 0.85 in the spectral region of interest.
For photopic measurements only, nearly any flat interior white
5. Significance and Use
paint will suffice. For solar and ultraviolet measurements, a
good barium sulfate-pigmented sphere paint is required.
5.1 To overcome the inadequacies of conventional spectro-
photometric measurement techniques when nonhomogeneous 6.5 Astable source illuminant having a spectral distribution
approximating that of a standard solar spectrum of Air Mass
materials are measured, a large integrating sphere may be
5,6
used. Since the beam employed in such spheres is large in 1.5 (Tables E 892) shall be employed for simulated solar
comparison to the disparaties of the materials being tested, the measurements. Other sources may be employed for photopic
nonisotropic nature of the specimen being measured is essen- measurements if the spectral energy distribution is essentially
tially averaged, or integrated out of the measurement, in a flat in the 475 to 650-nm region.
single experimental determination. 6.6 For natural sunshine illumination, a solar siderostat (or
5.2 Solar and photopic optical properties may be measured heliostat) arrangement is required to provide uniform illumi-
eitherwithmonofunctionalspheresindividuallytailoredforthe nation (unless the sphere is itself operated in an altazimuthal
measurement of either transmittance or reflectance, or may be tracking mode). Data should be taken during the time of day
measuredwithasinglemultifunctionalspherethatisemployed that ensures a normal incident global (hemispherical) irradi-
to measure both transmittance and reflectance. ance of at least 900 W/m .
5.3 A multifunctional sphere is used for making total solar
NOTE 1—Warning: Suitable eye protection is required when working
tran
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