How does the rain sensing work ? - PeachParts Mercedes-Benz Forum

syljua · #8 04-21-2009, 09:14 AM

Quote:

Originally Posted by ILUVMILS

The rain sensor works by the principle of refraction (bending light???). Try sticking your finger into a bucket of water. See how your finger appears to bend? That's refraction, at least the way I understand it.

Yes, the sensor has two parts. One LED, light emitting diode, and
a photo sensing diode, located some centimeters apart.

The LED sends light into the windscreen. When there no water on the windscreen, the light is reflected back and forth inside the screen, like in a optical fibre, and reaching the photosensor.

When water comes into contact with the screen, light "escapes", so less light is seen at the photosensor end. That means, that any water (or other contamination that will let the light "escape"), on either side! of the screen, can cause the wiper to wipe.

I think they have some kind of material on the inside, to reflect light, but it will not hurt to clean the inside as well?

Do also remember, that the sensor must be fastened correctly to the inside, or else, the amount of light, going into the screen, and escaping a few centimeters away, will be insufficient to declare the screen as clean:-)

br,
syljua