Steering Angle Sensor: Testing and Inspection

Function
In the center position of the steering wheel the 8 apertures (b) assume a defined position relative to the 9 light-emitting diodes (a). This center position is recorded by the computer in the steering angle sensor. When the steering wheel is turned the position of the apertures relative to the light-emitting diodes changes (light/dark). This produces a quite specific signal pattern due to the different length apertures and aperture spacings so that the respective steering wheel position can be calculated. Angle values are calculated with the aid of the signal patterns and converted into serial information for the control modules connected.

The signals are recorded in 2.5° steps by light-emitting diodes and photoelectric barriers. The signal recording system is designed for a steering angle of ± 720° (4 steering wheel revolutions). Voltage is supplied via terminal 30 so that the steering angle can be recorded even after "ignition OFF". The steering angle sensor must be re-initialized after the voltage is interrupted (terminal 30). This is achieved by turning the steering wheel from stop to stop