RADIOMETER

radiometer. Radiometer, n. the forestaff, an instrument for taking the altitude of celestial bodies

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Ra′di‐om″e‐ter (–ŏm″ē̍‐tẽr), n. [[L. radius radius + -meter: cf. F. radiomètre.]] 1. 1. (Naut.) A forestaff.
2. 2. (Physics) An instrument designed for measuring the mechanical effect of radiant energy.
☞ It consists of a number of light disks, blackened on one side, placed at the ends of extended arms, supported on a pivot in an exhausted glass vessel. When exposed to rays of light or heat, the arms rotate.