The RA01 is a 2-component radiation sensor. It measures the 2 components of the surface radiation balance. By using a thermopile sensor, the work of the device is passive. It generates 4 output voltage proportional to the solar SW and LW flux. The solar radiation sensor and LW sensor is called pyrgeometer. A Pt100 temperature sensor is in the pyrgeometer in order to calculate the sky and the surface temperature.