Home>ASTM Standards>ASTM E971-11(R2019) pdf free download

ASTM E971-11(R2019) pdf free download

ASTM E971-11(R2019) pdf free download.Standard Practice for Calculation of Photometric Transmittance and Reflectance of Materials to Solar Radiation
1. Scope
1.1 This practice describes the calculation of luminous (photometric) transmittance and reflectance of materials from spectral radiant transmittance and reflectance data obtained from Test Method E903. 1.2 Determination of luminous transmittance by this prac- tice is preferred over measurement of photometric transmit- tance by methods using the sun as a source and a photometer as detector except for transmitting sheet materials that are inhomogeneous, patterned, or corrugated. 1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 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 appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.5 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
3. Terminology
3.1 Definitions—For definitions of other terms used in this practice, refer to Terminology E772. 3.1.1 illuminance, n—luminous irradiance. 3.1.2 luminous (photometric), adj—referring to a radiomet- ric quantity, indicates the weighted average of the spectral radiometric quantity, with the photopic spectral luminous efficiency function given in Annex A1 being the weighting function (see Appendix X1). 3.1.3 radiant flux, Φ = dQ ⁄dt [Watt(W)], n—power emitted, transferred, or received in the form of electromagnetic waves or photons. See radiometric properties and quantities. 3.1.4 solar irradiance at a point ofa surface, E s = dΦ ⁄dA , n—the quotient of the solar flux incident on an element of a surface containing the point, by the area of that element, measured in watts per square metre. 3.1.5 solar, adj—(1) referring to a radiometric term, indi- cates that the quantity has the sun as a source or is character- istic of the sun. (2) referring to an optical property, indicates the weighted average of the spectral optical property, with the solar spectral irradiance E sλ used as the weighting function. 3.1.6 spectral, adj—(1) for dimensionless optical properties, indicates that the property was evaluated at a specific wavelength, λ, within a small wavelength interval, ∆λ about λ. Symbol wavelength in parentheses, as L (350 nm, 3500Å), or as a function of wavelength, symbol L(λ). (2) for a radiometric quantity, indicates the concentration of the quan- tity per unit wavelength or frequency, indicated by the sub- script lambda, as L λ = dL/dλ, at a specific wavelength. The wavelength at which the spectral concentration is evaluated may be indicated by the wavelength in parentheses following the symbol, L λ (350 nm).
4. Summary of Practice
4.1 Spectral transmittance or reflectance data between wavelengths of 380 and 760 nm (3800 to 7600 Å), which have been obtained in accordance with Test Method E903, are multiplied by solar spectral irradiance values provided in Standard Tables G173 and by the photopic spectral luminous efficiency function (see Annex A1). The resulting product is integrated over the spectral range from 380 to 760 nm using a summation procedure to approximate the integral. This sum- mation procedure is then repeated with the product of the solar energy spectral distribution and the photopic spectral luminous efficiency. The ratio of the two integrals is the solar luminous (photometric) transmittance or reflectance of the measured sample.

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