exposed object, the Bellani spherical pyranometer is used. The radiation is integrated over a spherical surface and over a certain time. Fairly accurate daily total radiation values can be obtained provided the instruments are scrupulously evacuated before filling with alcohol, properly exposed and well calibrated.
14 - Total radiation (solar and terrestrial) and net radiation (net flux downward and upward total radiation) are measured with black coated heat-flux photo-sensors, in which thermocouples are embedded to measure the temperature difference between the two sides of a thin uniform plate with well known thermal properties. Errors due to convection and plate temperature are avoided by using forced ventilation, appropriate shields and temperature
