silver-disk pyrheliometer

silver-disk pyrheliometer

[′sil·vər ′disk ¦pīr‚hē·lē′äm·əd·ər]
(engineering)
An instrument used for the measurement of direct solar radiation; it consists of a silver disk located at the lower end of a diaphragmed tube which serves as the radiation receiver for a calorimeter; radiation falling on the silver disk is periodically intercepted by means of a shutter located in the tube, causing temperature fluctuations of the calorimeter which are proportional to the intensity of the radiation.