Patent ID: 7183760

Claim:
A rotational speed sensor comprising a rotatable ring, the rotational speed sensor having K magnetic pole pairs distributed angularly over the rotatable ring, K being an integer greater than one, and sensor means positioned relative to the rotatable ring such that a varying magnetic field is detected by the sensor means, the sensor means comprising at least a first pair of magnetic sensors, the first pair of magnetic sensors being positioned 2πL/K radians apart from each other, L being an integer between 1 and K−1, wherein the sensor means comprise at least one second pair of magnetic sensors, the second pair of sensors being positioned 2πM/K radians apart from each other, M being an integer between 1 and K−1, the first pair of sensors and second pair of sensors being positioned at a relative position of (2π/K)*((2n−1)/2) radians, n being an integer greater than one.