A pyranometer (from the Greek word ‘fire’) sometimes called a solarimeter, is used to measure broadband solar irradiance on a planar surface and is a sensor that is designed to measure the solar radiation flux density in W/m2 (watts per metre square) from a field of view of 180 degrees.

Not all of the solar energy reaching Earth’s outer atmosphere reaches the surface of the Earth. Some of this energy is reflected back out into space and some of it is absorbed in the atmosphere itself. On a typical summer day at midday in temperate latitudes, about 1000 W/m2 actually reaches Earth’s surface. This is a quite a lot of energy, enough to power 10×100 Watt light bulbs.

A typical pyranometer does not require any power to operate and are frequently used in meteorology, climatology, solar energy studies and building physics. They can be seen in many meteorological stations, often installed horizontally and next to solar panels, and the sensor is mounted in the surface plane of the panel.The pyranometer, has a glass dome shaded from the Sun’s beam and the shading is accomplished either by an occulting (concealing) disc or a shading arm.