Calculating the Diffuse Responsivity of Solar Pyranometers

Pyranometers are used to measure the global and diffuse components of solar irradiance. One of the methods to calculate the unshade (global) responsivity of a pyranometer is the standard shading method, described in the Annual Book of ASTM Standards, section 14, volume 14.02. In this paper, the standard method is used to calculate the shade (diffuse) responsivity of a pyranometer by accounting for the zenith and azimuth response of the pyranometer. A discussion of the effect of pyranometer offset on the calculated responsivity is also presented.