CLS 550 (219.372) V8-5.5L (273.960) (2007)
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:
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Sensing from low rpm to v = 0 km/h.
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Improvement in signal quality (digital signal).
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Signal largely insensitive to vibrations and temperature differences.
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Lower weight and smaller design than induction-type pulse generator.