Sir,

You may use a trigger wheel and inductive pick up. This is the simplest and cheapest solution.

If you are looking for more precision you may use crank angle encoder.

You may check CA encoder from Kubler, Kistler and AVL. Latter mentioned two are costlier.

Let me know if you need more details.

Dear Kaisan,

the simplest and cheapest solution is the one mentioned by Jubin. You can also increase the resolution of the flying whell by dividing it digitally. However, for the applications regarding combustion analysis, the most used devices are encoders which provide CA resolution up to 0.1 CAD.

The most simple way is to "tap" the tooth sensors (inductive or hall) already installed for the ECU (Engine Control Unit). The toothed wheel (sampled on one edge only) usually gives 60 (-2) teeth per revolutions - equalling to a 6 degrees resolution. Between the tooth edges, the angle can be interpolated with a - usually - high-enough precision.

But it should be clear that other measurement approaches with individual measurement hardware apply as well - starting e.g. with an electrical generator (giving some sine signal) and maybe ending with some optical incremental encoder. Between these two "extremes" is the whole wealth of magnetical, optical or whatever sensors - either incremental or with some kind of continuous (typically sin/cos) signal output.

May be you can use laser diode which is fixed on the rotating shaft and a circular array of of photo diodes which are fixed on static frame around the shaft. By detecting the pulses generated at the detectors one can can get the angle as the diodes can be encoded into angles of position.

Best wishes

The state of the cylinders (position, open or close of the valves) may give you an approach of the position of the ckrank.

In addition to inductive encoders, optical pattern encoder discs with photodiode measurement have also been previously used and allow measurement to 0.1 CAD. Depending on the signal processing and data reduction methods used, you would typically need 0.25 to 0.5 CAD minimum for calculation of AHHR from cylinder pressure measurements. Flywheel tooth measurements, even with a degree of interpolation, would not provide sufficient resolution for combustion analysis.

Define TDC of a single cylinder and use crank angle encoder. AVL and kistler have reliable encoders of 0.1 CAD.

Actual pulse comes in each 0.5 CAD, where you get the reading upto 0.1 optically through software