[Gllug] Data sampling problems

[Chris Bell]

On Sat 17 Sep, Tethys wrote:
> 
> 

> 
> Amongst other things, I'm trying to measure the crankshaft RPM,
> using a sensor and some magnets embedded into the flywheel, with
> the time between pulses being used to calculate the RPM. The
> problem I'm having is that the results aren't consistent. Instead
> of the expected RPM, my results are showing oscillating values
> above and below the expected figure:
> 


   I think that the Bosch engine management system on my car looks for
notches in 15 out of 16 positions on the flywheel of my car using a Hall
effect device. My Maplin catalogue only lists one Hall effect device, and
that is only flat to 23KHz, so probably would not be suitable. There is
probably an off-the-shelf sensor that will do the job.
   Whichever way you sense the flywheel position and divide down, would it
be better to generate an IRQ and then read the elapsed time?

-- 
Chris Bell

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