From: John Tserkezis 
Reply-To: Fidonet AVtech Echo 

Bob Lawrence wrote:

>  All this talk has forced me to make some calculations. At 6,000
> rpm in top, the tailshaft is going at 100Hz and this explains the
> problem. I've been talking through my hat, you're wright and I'm
> worng.

>  Shit! That hurt.

  Good, just remember that the next time I'm wrong. :-)

>  1 - 100Hz is the crossover where *nothing* works! If you
> measure a fixed period (Frequency), you need 1 second to get 100
> pulses and that's too slow, and if you measure time between pulses
> (Period), you have to fake it at low speed where the pulses are
> 1-second apart (2kmph).

  You could decrease the resolution where you have excessive jitter, as so to 
reduce the magnitude of fluctuations.

>  The only answer is hardware - either gear the sensor up 5-times, or
> use a multi-slot interruptor.

  From a mass-production point of view, that might cost more.  If it's doable 
in software, they'll do that.

>  As for jitter, that's not a problem... just write it into the
> software - update every fifth of a second.
>  Shit!

  Ah, the coin drops.  It does cost more after all.

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