Crankshaft Position Sensor: Description and Operation

Crank Angle Sensor:

The crank angle sensor, detects engine RPM and crank angle (piston position) and transmits these signals to the control unit. The sensor consists of a signal rotor plate and light emitting diodes (LED) located in the distributor. The signal rotor plate has 360 slits spaced at 1 deg. on it's outer perimeter. It also has six slits at 60 deg. intervals located inboard from the outer slits. The inner slits are used to detect the crank angle position (piston position). The outer slits are used to provide the 1 deg. signal used to control ignition timing and engine RPM's.

Crank Angle Sensor Layout:

Engine RPM is determined by the the 1 deg. signal that is created as each of the 360 slits on the signal rotor plate allow light to pass from LED's 1 and 3 to the photo diodes. When the light from the LED reaches the photo diode, it causes an alternative voltage. Thus, each wave from each diode is compounded. Then, the compound wave is converted into an on-off pulse. this 1 deg. on-off signal is sent to the control unit.

Signal Pickup:

Top dead center (TDC) is detected by the 120 deg. signal created as the 60 deg. slits pass between LED 2 and the photo diode. When the light from the LED reaches the photo diode, it causes an alternative voltage. At this time, a signal on-off pulse is generated. Since engine RPM is twice that of the distributor, the rotor plate has six slits at 60 deg. intervals.