Crank Angle Sensor
The crank angle sensor is a basic component of the entire computerized ignition system and is built into the distributor. It monitors engine RPM, and piston position and sends this information to the Electronic Control Unit (ECU).
The crank angle sensor has a rotor plate and a wave forming circuit. The rotor plate has 360 slits in one degree increments for engine speed signal and 4 or 6 slits for piston position signal. Light Emitting Diodes (LEDs) and photo diodes are built in the wave forming circuit. When the signal rotor passes between the LED and photo diode, the slits in the rotor plate alternately cuts the light. This is converted into an on-off pulse by the wave forming circuit, which is sent to the ECU. See Fig 1.