Application of a Crankshaft Position Sensor to Control Engine Timing

The crankshaft position sensor (CPS) is a variable reluctance magnetic sensor which accurately senses the position of four teeth equally spaced 90° apart on a toothed ring attached to the crankshaft. The electronic engine control (EEC) calculates RPM using two adjacent pulses, and with other processed information, calculates spark advance. Actual spark initiation again uses the CPS as a reference position. The properties and environment of the sensor which determine accuracy, noise, and other characteristics important in its interface with the system is discussed.