Paul,

I am working with a 2nd gen CAS and wondered why the calculated
frequency at a given RPM does not match what I am seeing on the
scope?

Maybe I am calculating it wrong;  (RPM X 24teeth)/ 60  Thanks for any
help

Joe Berki


The 2nd gen CAS rotates at half e-shaft speed. So it is only 12 teeth
per revolution.

Paul Lamar


Paul,

E shaft is at 8000 rpm  divide by 2 = 4000 rpm X 24 = 96000 / 60 = 1600
Hz  = .625msec period.

  I measured 3.15msec period = 2857 Hz,

I divided the eshaft rpm by 2 and spun the CAS to half of the eshaft speed.

I measured the output with a scope and calculated freq as i/period.

What am I missing?

Joe Berki


Divide RPM by 60 for CPS (Hertz in the French system :))

Put all your units in the equation. Helps to keep track of what your
doing. Your math teacher may have been a liberal arts major :)

8000 RPM / 2 = 4000 RPM

4000 RPM x 24 teeth = 96000 PPS or teeth per second.

1 / 96000 PPS =  0.00001041666666666667 second for one tooth.

.01041 milli second period.

Are you sure you are looking at the lower sensor?

If so I may be out of adjustment. Not much of a gap there.

Paul Lamar



Paul,
Sorry, 3.15 msec = 1/ .00315 = 3174 Hz

Joe Berki




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