Collection: Pyrgeometer

A pyrgeometer (from ancient Greek πῦρ /pyr/ "fire" and γῆ /geo/ "earth") is used to measure the atmospheric counter-radiation arriving from the hemisphere; this is thermal radiation in the range from about 4 µm.
Structure and function
A pyrgeometer basically consists of an edge filter that keeps out the solar part of the radiation and a black surface that absorbs the transmitted radiation and thus becomes warm.