GrowControl Rain Sensor is a high quality optical type rain sensor with no moving parts. The rain gauge senses water hitting its outside surface using beams of infrared light. It uses the same sensing principle used in millions of automotive rain sensing windshield wiper controls. Connect to GC-Pro or GC-Extreme controllers' digital inputs to close vents and windows down to a weather set-point at the first sign of rain. Equipped with arm for mounting to structure or weather station. Includes a built-in heater to allow use in temperatures down to 32?F (0?C). Smart logic prevents false triggers from dust and other slow build-up of accumulation. Adjustable sensitivity allows for four different settings which activate the sensor from the slightest amount of rain to heavy rainfall. Operates on 24Vdc from controller and connects directly to any digital input.