4530 Brake system ABS 5.7 - Speed sensor · On the ABS generation 5.7, a new speed

911 Chassis and suspension 4 4530 Brake system ABS 5.7 - Speed sensor On the ABS generation 5.7, a new speed PSM 5.7 sensor generation (DF 11) is introduced with the change of model. This is a active speedThe PSM hydraulic units are adapted in their sensor with Hall element and IC (integratedsoftware to the specific parameters. Also, to circuit).improve the control quality, a new gener a- In comparison to the passive speed sensor,tion of "linear technology" solenoid valves the active speed sensor generates a variable(LMV) is used. pulse width square-wave signal through the internal electronics. This technology not only Functional description of linear technology determines the wheel speed, but also the direction of rotation, wheel stop and the sig- In linear technology, the valves are co n- nal quality. trolled by the flow. Compared to the previ- ous generation, where valves could only be opened and closed, the new valve can adapt intermediate positions or can be opened or closed slowly. Particularly through the "open again slowly" feature, the pressure increase in critical areas (low friction coefficients) can be applied more softly. This technology is of particular benefit when braking on icy road surfaces. Vehicle yawing moments do not build up at all due to the softer pressure increase and the car is easier to keep on track. 2002 Service Information 4 - 5