Crank Sensor frequency

[steve-V8s]

Ford use 36 teeth and 1 missing, Vauxhall use 60 with 2 missing (I think). Are these correct and what other combinations are commonly used, also what amplitude pulse is normally expected by the ECU ? It seems that most systems use a magnetic sensor how does this work ? At a guess a coil wound round a magnetised pole piece generates a pulse as the sensor wheel tooth passes the pole piece and changes the field.

[GreenV8S]

The sensor that seems most common is a Magnetic Variable Reluctance (MVR) sensor. This produces a very weak signal which increases with speed. I think the ECUs usually have a variable gain system to accommodate the huge difference in amplitude between minimum and maximum revs.

The other sensor sometimes used is a Hall Effect sensor, which essentially detects a moving magnet.

[steve-V8s]

Thanks Pete

[annodomini2]

There are also optical sensors and the cheap way is to use the unfiltered alternator output.

[350Matt]

Most cranks sensors are the 2 wire inductive pick-up type and they generate a sine wave when they 'see' the toothed wheel blurring past the end of them.

Typical signal strength is 5-12V

Matt

[Pigeon]

annodomini2 said:

the cheap way is to use the unfiltered alternator output.

That's OK for driving a rev counter but not for ignition timing.