Wheel rpm sensor, component description - GF42.45-P-5134GZ
MODEL 164 up to Model Year 08
Shown on model designation 164.1
The rpm sensors supply the current wheel speeds to the ESP control unit (N47-5). The ESP evaluates these signals corresponding to the direction of rotation, the wheel speed and fault detection
The active sensors consist of a housing and a sensor element which is based on the magnetoresistive measuring principle.
An active rpm sensor during an acceleration phase shows the curve of the current.
Function of the active wheel speed sensor
The strength and direction of an external magnetic field causes a change in the internal resistance inside the sensor. A square wave signal is produced via an electronic analysis system accommodated in the sensor the frequency of which depends on the rpm, the amplitude height remains constant.
This signal is read in and processed by the ESP control unit.
The external magnetic field is produced by a multipole ring. This consists of an elastomer plastic into which metal particles have been incorporated. Using a special magnetization procedure the metal particles are aligned so that magnets occur, the polarities of which change from North to South at the periphery.