Solar Radiation SensorFor use with Vantage Pro and Vantage Pro2. (Already included with Vantage Pro Plus and Vantage Pro2 Plus.)Measures solar radiation and is required (along with an anemometer and a temperature/humidity sensor) if you wish to monitor evapotranspiration.Diffuser element and housing are carefully designed for accurate cosine response. Silicon photo diode provides good match to solar spectrum. Two-piece housing minimizes radiation heating, allows convection cooling of the sensor, and prevents the trapping of water or dust. Includes built-in level and 2' (0.6M) cable.Compatible with both original Vantage Pro and Vantage Pro2.You may also need a UV Sensor (#6490) and Sensor Mounting Shelf (#6673).