Variable Reluctance Speed Sensors

Are also known as Variable Reluctance (VR) speed sensors that consist of a wire wrapped around a permanent magnet and pole piece. This is similar to a coil winding, solenoid or DC motor. The magnetic speed sensor does not require external power and usually has two leads which are power and ground. When used in speed applications, the tooth of a ferrous target (usually a gear) moves within a proximity of the sensor and generates voltage. The frequency of the rotating target can then be translated into a speed for the given application which depends on the diametral pitch, diameter of the target wheel and dimensions of each tooth.