Precise Rotationally Symmetrical Speed Sensor with Detection of Direction of Rotation

In many applications with magnetic field-based speed sensors and passive target wheels, the rotatability of the sensor due to rotational symmetry is an important application criterion (reduction of the number of variants and thus of costs); likewise, air gap-independent tooth mapping and, increasingly, rotational direction detection are often required. Rotational symmetry can preferably be achieved by a single sensor element on the axis of rotation. A specially designed asymmetrical shape of the teeth of the sensor wheel is then required for the detection of the direction of rotation. In this concept, a suitable evaluation algorithm of the magnetic field over tooth and gaps of the sensor wheel is proposed, so that a precise tooth mapping almost independent of the air gap is possible—at least for one tooth edge (rising or falling edge).