Basic Principle
Emitted Beam from luminosity diode is reflected entirely against the windshield exterior, and then turn into photo diode. If there is water on the windshield exterior, beam separates optically, and the degree of remained beam is measured in the photo diode.
What there is water in the windshield, it means beam is not reflected all, so the degree of lost beam indicates the degree of glass surface wet.
Note. Rain sensor consist of two luminosity diode, two photo diode, optic fiber and coupling pad.
Contact Influence
The rain sensor can malfunction due to following condition
- Contamination of the measurement surface.
- Air bubbles between the windshield and the coupling pad contact surface.
- The movement of coupling pad by vibration.
- Damaged wiper blade.