Detecting ferromagnetic tooth in rotation speed sensor e.g. for internal combustion engine, by evaluating changes in inductance of sensor coil

摘要

The method involves evaluating the changes in inductance caused by the tooth (1). The sensor (2) may be a coil. A square wave voltage (8) is applied to the coil and the current in the sensor is detected. The sensor may be a frequency-defining member in an oscillator. The sensor may be arranged in an LC oscillator circuit.