A pyranometer (from Greek πῦρ pyr "fire" and οὐρανός ouranós "sky") is used to measure incoming global solar radiation. In other words, a pyranometer is a sensor for measuring the sun's irradiance (in watts per square meter) with a field of view of 180 degrees.
Pyranometers are widely used in meteorology, climatology, building physics, and solar energy research. They are used in meteorological stations, usually mounted horizontally and next to solar cells, usually parallel to the solar cell surface. The ISO 9060 standard for pyranometers, which is also recognized by the World Meteorological Organization, distinguishes three classes. The best class is called "secondary standard," the second best "first class," and the last "second class."
