GF42.45-P-5134TX Wheel RPM Sensor, Component Description

GF42.45-P-5134TX Wheel rpm sensor, component description

Component Identification:

Location
The left front rpm sensor and right front rpm sensor are mounted on the front axle steering knuckle.

The left rear rpm sensor and right rear rpm sensor are mounted on the rear axle wheel carrier.

Task
Produce a square wave signal from the SBC control unit (A7/3n1) which detects current wheel speeds

Design
Active sensor, consisting of a housing with integral evaluation circuit and a sensor element which is based on the Hall principle.





The presentation shows the current curve through the active speed sensor during an acceleration phase.

Function
Due to the strength and direction of an external magnetic field, a change of internal resistance is caused inside the rpm sensor. Via an electronic analysis system accommodated in the rpm sensor (supplied with voltage by the SBC control unit) a square wave signal is produced the frequency of which depends on the rpm and the amplitude of which is constant. The direction of travel is detected by a different signal representation when the wheel runs to the left or right. This signal is read in by the SBC control unit and by the ESP control unit (N47-5) and placed on the engine compartment CAN.

Furthermore, the rpm sensor can detect a poor installation position and convey this to the SBC control unit.

The external magnetic field is produced by a multipole ring.

This consists of an elastomer plastic containing metallic particles. Via a special magnetization process they have been aligned so that various magnets arise, the polarity of which changes at the circumference from north to south.

Advantages compared with a passive (inductive) rpm sensor:
^ Sensing from low rpm to v = 0 km/h.
^ Improvement in signal quality (digital signal).
^ Signal largely insensitive to vibrations and temperature differences.
^ Lower weight and smaller design than induction-type pulse generator.