A vehicle wheel speed sensor has a rotor 11 provided with a series of circumferentially spaced rotor elements 12 mounted on a wheel axle 10. A sensor 13 mounted on a relatively non-rotatable support is influenced by passage of the rotor elements to output a sine wave signal. The sine wave signal is fed for processing to an interface unit 15 on the vehicle and pulses are generated at at least two predetermined phases of each cycle of the sine wave. A method of producing marker pulses by detecting the zero cross-over points and the peaks and troughs of a sine wave signal, and generating a marker pulse at each zero cross-over point and at each peak and trough of the sine wave signal is also described.

To simplify a field plate effect speed and position sensor, particularly for association with the starter gear of an automotive-type internal combustion engine, four meander-arranged permalloy resistance tracks are located on a substrate at the corners of a rectangle, spaced, in circumferential direction, by about half the pitch distance of the teeth (2) of the starter gear. The resistances can be connected in a voltage divider (FIG. 4) configuration, or in form of a bridge circuit (FIG. 5) supplied from a constant current source (CC) to eliminate temperature variation affects, and providing alternating current output voltages within the wide range of temperature of essentially uniform level as the teeth (2) scan the sensor, a special marker tooth (10) providing an output signal of different level. Preferably, the resistances (5-8) are formed as meander-shaped thin film vapor deposited tracks on a silicon substrate (4), a permanent magnet (9) providing bias magnetization, the direction of which changes with respect to the orientation of the meander tracks--preferably 45.degree. with respect to the direction of rotation (11) to cause the resistance elements to either have high, or low resistances (FIG. 3).

The invention proposes a rotor arrangement for use with an automotive Hall generator for detecting the precise position of a select or predetermined one of a plurality of pistons, or the precise rotational position of the crank shaft, of an Otto cycle engine, by providing a distinct marking on a trigger wheel preferably mounted for rotation with the drive shaft of a distributor for generating a signal in a Hall element which signal is then detected by evaluation or discriminating circuitry.

Position of a rotatable automotive part is sensed with a trio of magnetic field intensity sensors disposed adjacent a ring that rotates with the automotive part, the ring comprising alternating permanent magnet sections with at least one localized magnetic field depression corresponding to a synchronization position of the part wherein the sensors are spaced along the direction of ring rotation so that the relative phase between the output signals of a first pair of the sensors as indicated by the relative output signal magnitude indicates incremental displacement of the part, and so that a significant difference in magnitude between the output signal of a second pair of the sensors indicates the synchronization position.

The present invention relates to a system and method for sensing the angular position of a rotatable member. The system and method employ the use of a composite rotatable member comprising a solidifiable material and a magnetically attractable particulate material. The rotatable member has a major body portion and at least one magnetically detectable reference point. The reference point has a first magnetic property and the major body portion has a second magnetic property, different from the first magnetic property. A magnetic property sensor is fixed relative to the rotatable member to detect the passage of the reference point within the rotatable member. The sensor produces a signal in response to the passage of the reference point. A central processing unit is provided for determining the angular position of the rotatable member in response to the signal generated by the sensor.