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Function principle of rain sensor
Fig. 58: Identifying Rain Sensor Principle Function
Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
Infrared light is radiated from the infrared transmitter unit and led to the windshield. The intensity of the
light reflected at the windshield is measured by the infrared receiver unit If the windshield is dry in the area
of the rain/light sensor (picture A), then the light is reflected almost completely and the infrared receiver
unit measures a high light intensity If the windshield is wetted in the area of the rain/light sensor (picture B),
then part of the light is scattered from the windshield glass. As a result the intensity of the reflected light
reduces and the infrared receiver unit measures a lower light intensity.
The light intensity measured by the infrared receiver unit represents a measure for the degree of wetting of
the windshield. The smaller the measured light intensity the greater the degree of wetting of the windshield.
Function principle of light sensor
The light sensor measures the light intensity striking it from outside. The resistance in the light sensor drops
as the light intensity reduces.
The information from the rain/light sensor is passed on to the SAM control unit (N10/10) via the local
interconnect network interior 1 (LIN B).
DATA LINK CONNECTOR COMPONENT DESCRIPTION - GF54.22-P-2200MCC
MODEL 451.3/4
Shown on LHD model
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