1) Measuring instrument 
A pyrheliometer is an instrument for measurement of direct beam solar irradiance. Sunlight enters the instrument through a window and is directed onto a thermopile which converts heat to an electrical signal that can be recorded. The signal voltage is converted via a formula to measure watts per square metre. It is used with a solar tracking syste...
instrument for measuring heating effect of sun
• (n.) An instrument for measuring the direct heating effect of the sun`s rays.
(from the article `sunlight`) The Eppley pyrheliometer measures the length of time that the surface receives sunlight and the sunshine`s intensity as well. It consists of two ...
A device that measures the intensity of direct beam solar radiation.
An instrument used for measuring direct beam solar irradiance. Uses an aperture of 5.7
Pyr·he`li·om'e·ter noun [ Greek ... fire + ... sun + -meter .] (Physics) An instrument for measuring the direct heating effect of the sun's rays. 
The pyrheliometer is an instrument devised by Pouillet for measuring the intensity of the heat of the sun. It consists of a shallow cylindrical vessel of thin silver or copper, containing water or mercury in which a thermometer is plunged. The upper surface of the vessel is covered with lamp- black so as to make it absorb as much heat as possible, ...
pyrheliometer 1. An apparatus for measuring the heating effects of the sun. 2. A general term for the class of actinometers (name for any instrument used to measure the intensity of radiant energy, particularly that of the sun) that measure the intensity of direct solar radiation. Actinometers may be classified, accordingly to the quantities that...
A device that measures the intensity of direct beam solar radiation.
an instrument for measuring the total intensity of the sun's energy radiation.