inductive vs optical

[Michael Fawke]

At 11:43 AM 6/3/1996 S, Andrew wrote:

>Assuming your sensors are ok, the basic idea is to get the most
>information from the minimum number of sensors (hence $$$)
>Missing/short/long pulse detection needs either time or frequency based
>detection. (Any other's I've missed?)
>Car engines run over a relatively wide rpm range, so time-based detection   
>is out.
>Frequency based detection is usually done by a phase or frequency locked   
>loop,
>either analog or digital.
>Either way, you still have a fairly complex filter to design to ensure
>under/over-shoot doesn't cause false (extra or missing) triggering.

I agree on the filtering part, but unless you are running an analogue 
controller there should be no problem with accurate time control when the
input from the sensor in used to generate an interrupt to a processor. I
must admit that the long-pulse system would be a real pain (I know the car
manufacturers use it, but I have no idea how), but a missing or extra pulse
is easy from a programming point of view..... as long as the CPU speed is
adequate.


Michael Fawke
fawkacs at ozemail.com.au