Pyrheliometer Sensor for determining direct solar radiation

Pyrheliometers (from Gr. pyros = "fire" and helios = "sun", literally: sun fire measuring instrument) belong to the meteorological radiation measuring instruments (pyrometry = radiation measurement). They measure the direct irradiance (in watts per square metre) from the direction of the sun. In the past, they were also called pyroheliometers.The radiation is absorbed by a black thermopile or thermometer (for example, a black-coloured metal strip) or a black hollow body of known heat capacity. The incident radiation leads to heating, from which the radiation flux can be calculated. Depending on the type of wind-protective covering, only the short-wave radiation component (quartz glass) or the total radiation (plastic) can be measured. Measuring devices that measure the total irradiation, so-called pyranometers, work without shielding the indirect irradiation and are useful for measuring the performance of solar energy systems.