Function of rain sensor - GF82.30-P-4103-02PP

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Function principle

Infrared light is radiated from the infrared transmitter (2) through the lens (1) to the windshield (4). The intensity of the light reflected at the windshield is measured by the IR receiver (3) which is located at the other end of the lens (1). 1

Windshield is dry (figure A)
If the windshield is dry in the vicinity of the reflective surface, almost all of the light is reflected: the IR receiver (3) measures high light intensity.
Windshield is wet (figure B)
If the windshield (4) is wet in the vicinity of the reflective surface a portion of the light escapes from the windshield glass (4). This reduces the intensity of the reflected light, the IR receiver unit (3) measures a lower light intensity.

The light intensity measured by the IR receiver (3) is a measure for the quantity of water on the windshield (4) The smaller the measured intensity the larger the quantity of water on the windshield (4).

Fig 1: Rain Sensor Function Diagram

Reading out rain sensor

The rain sensor is connected to the class B Controller Area Network bus (interior) (CAN-B) via the overhead control panel control module as an interface. The front SAM control unit with fuse and relay module transmits via the CAN-Class B a request to the rain sensor, which then responds to any request by notifying the front SAM control unit with fuse and relay module of the degree of wetness at any given moment.