Snow, rain, dew, dirt, dust, salt, etc. can buildup on hemispheres of the Pyranometers and Pyrgeometers and can affect the measurements. Therefore, instruments that cannot be inspected and cleaned regularly may wish to include a Ventilator to blow a steady stream of air over the hemispheres to reduce this buildup. This is particularly true in remote stations where maintenance is rarely performed. In fact, researchers in Arctic/Antarctic regions have even implemented heaters to help reduce ice and grime buildup.
A “muffin” fan in the base continuously blows air over both the instrument case and the instrument dome. The clear plastic upper housing allows the instrument, connector, and desiccator window to be easily viewed. A white enameled guard disk, leveling screws and hold down holes are provided. The 8 inch diameter, 5.75 inch high ventilator weighs 5.5 pounds.
The VEN can be supplied with AC (110 or 220 volts) or DC (12 or 24 volts) fans. Recent research has shown that the VEN will increase the nighttime offset of the Pyranometers as the instrument case will be warmed by the fan. Many researchers have decided to use a 12 VDC (high flow) fan to reduce this offset.