The radiation is absorbed by a black thermopile or thermometer (for example, a black-colored metal strip) or a black hollow body of known heat capacity. The incident radiation causes heating, from which the radiant flux can be calculated. Depending on the type of wind-protective cover, only the shortwave radiation component (quartz glass) or the entire radiation (plastic) can be measured. Measuring devices that measure total irradiance, so-called pyranometers, operate without shielding the indirect irradiance and are useful for measuring the performance of solar energy systems.
