If you want a definition of a crank angle sensor, than here is a tech one.
The crank angle sensor is a basic component of the ECCS It monitors engine speed and piston position, and sends signals to the ECU to control fuel injection, ignition timing and other functions. The crank angle sensor has a rotor plate and a wave-forming circuit. The rotor plate has 360 slits for 1 0 signal and 6 slits for 120 0 signal. Light Emitting Diodes (LED) and photo diodes are built in the wave-forming circuit.
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