normal-incidence pyrheliometer

normal-incidence pyrheliometer

[′nȯr·məl ¦in·səd·əns ¦pīr‚hē·lē′äm·əd·ər]
(engineering)
An instrument that measures the energy in the solar beam; it usually measures the radiation that strikes a target at the end of a tube equipped with a shutter and baffles to collimate the beam.