The 240-8111 Pyrradiometer is a total hemispherical radiometer, used for exact determination of net radiation in short-wave and long-wave radiation range (0.3 to >30 µm) with two separately working receivers and with a built-in Pt-100 resistance thermometer to determine reference temperature. Two black, radiation absorbing plates act as sensors, one facing upward and one facing downward. Each transfers the energy absorbed to a separate 90-junction copper-constantan thermopile. Both of the two outputs are approximately 15 µV/Wm², one representing downward total radiation and the other representing upward total radiation. The difference between these two provides net radiation.
Lupolene domes shield the thermopiles from wind and moisture. Lupolene is essentially transparent to radiation from 0.3 to 60 microns. Two desiccant tubes are supplied to remove water vapor from inside the instrument housing. For long-term applications, fittings permit attachment of a nitrogen source for continuous purging. Levels are embedded in both the top and bottom faces of the pyrradiometer, and a 10" mounting arm is included.