This Test Method specifies a single relatively simple to implement common integration technique, the Modified Trapezoid Rule, to integrate digital or tabulated spectral data. The intent is to produce greater consistency and comparability of weathering and durability test results between various exposure regimes, calculation of materials properties, and laboratories with respect to numerical results that depend upon the integration of spectral distribution data. 1.2 Weathering and durability testing often requires the computation of the effects of radiant exposure of materials to various optical radiation sources, including lamps with varying spectral power distributions and outdoor and simulated sunlight. Changes in the spectrally dependent optical properties of materials, in combination with exposure source spectral data, are often used to evaluate the effect of exposure to radiant sources, develop action spectra, classify, evaluate, or rate sources with respect to reference or exposure source spectral distributions. 1.3 The data applications described in section 1.2 often require the use of tabulated reference spectral distributions, digital spectral data produced by modern instrumentation, and the integrated version of that data, or combinations (primarily multiplication) of spectrally dependent data. 1.4 Computation of the bulk optical properties mentioned above require the integration of measured wavelength dependent digital data, sometimes in conjunction with tabulated wavelength dependent reference or comparison data. 1.5 The term integration in the previous sections refers to the numerical approximation to the true integral of continuous functions, represented by discrete, digital data. There are numerous mathematical techniques for performing numerical integration. Each method provides different levels complexity, accuracy, ease of implementation and computational efficiency, and of course resultant magnitudes. Thus the need for a standard integration technique to simplify the comparison of results from different laboratories, measurement instrumentation, or exposure regimes.
KeywordsIntegration, Solar, Spectrum, Spectral Data, Reflectance, Transmittance, Absorptance, Optical Properties
The title and scope are in draft form and are under development within this ASTM Committee.Back to Top
Ballot Item Approved as G214-2015 and Pending Publication