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


Paul,

Does the CAS need to be calibrated?

If so how is it done?

Joe Berki

No but the gap is adjustable. My guess is somewhere
around .020 to .030.

Paul Lamar

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