5.4.1. Star pyranometers (according to Dirmhirn)
With star pyranometers, which are widely used in meteorology, the intensity of global radiation (radiant intensity) is measured indirectly, via measurement of the temperature difference between black and white copper plates arranged in the horizontal plane (star shape). The (solar) radiation heats the black plates stronger than the white ones. This temperature difference is measured using a thermopile (i.e. a serial arrangement of thermocouples) attached to the underside of the surfaces. This differential measurement principle minimizes the influence of ambient temperature. The advantage of star pyranometers is their robustness and a broad spectral range. Their main disadvantage is their rather inert reaction to radiation changes.