hemispherical pyrheliometer

hemispherical pyrheliometer

[‚he·mē′sfir·ə·kəl ‚pīr‚hē·lē′äm·əd·ər]
(engineering)
An instrument for measuring the total solar energy from the sun and sky striking a horizontal surface, in which a thermopile measures the temperature difference between white and black portions of a thermally insulated horizontal target within a partially evacuated transparent sphere or hemisphere.