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A new type of sensor capable of sensing the direction and velocity of motion of smooth surfaced metallic targets is described. The sensor consists of a small permanent magnet and a magnetic field sensor displaced from each other along the line of motion, each at a small fixed distance from the target surface. Operation is based on the motion dependent location, strength and polarity of magnetic field sources created within proximate target regions via their passage through the field of the magnet. The fields arising from these target regions are detected by the magnetic field sensors, typically Hall effect or magnetoresistive devices. With ferromagnetic targets, a non-volatile memory of the direction of last occurring motion is also provided. Utility of these sensing capabilities is illustrated by descriptions of applications for automatic turn signal canceling and antitheft devices, back-up alarm activation and for engine misfire detection via crankshaft speed variation.

The development of a transducer for sensing the torque on the output shaft of a four speed rear wheel drive automatic transmission is described. Magnetoelastic polarized ring technology was selected based on its independence from shaft properties and its non-contact mode of sensing. The ring and several intermediate sleeves were attached by press fits onto an experimental shaft. The magnetic field arising from the ring with the application of torque was sensed by flux gate sensing elements. Ability to accurately measure the output torque of an engine driven transmission over its full range of torque and speed was demonstrated by dynamometer tests.

The benefits of a magnetoelastic torque sensing system and its application on Formula 1 and CHAMP Car racing driveshafts are identified. In particular, the use of circumferential remanent magnetic bands on the shaft itself has enabled a design that satisfies the application's demanding packaging requirements. The criteria used to determine the suitability of a given shaft material for optimal magnetoelastic characteristics and concurrent mechanical strength are illustrated. Shaft material and geometry are shown to have significant effects on sensor performance. Design considerations for the magnetic field sensor layout and signal conditioning circuit are also presented. The racing driveshaft application is shown to add particular challenges in terms of temperature, packaging, and kinematic tracking. Magnetization and calibration processes associated with field operation of the sensor are discussed.