The CS325DM, manufactured by Atonometrics as the RC18, is a silicon solar irradiation sensor commonly used as a “reference cell” in solar photovoltaic (PV) monitoring applications. This solar radiation sensor has a temperature operating range that allows it to work effectively in different environments. The sensor element was designed to correspond to PV modules, including spectral selectivity and incident angle modifier. The data signals are Modbus RTU RS-485 or analog.