Measuring motor speed using the encoder

For the encoder on this motor ( which gives 12 counts per revolution if I just count the number of rising edges on one channel, the formula for computing the motor speed is N f (2 M_Pi)/12.0, where N is the number of counts and f is the sampling frequency. However, this seems to be off by a factor of 10. What am I doing wrong.

I know I am missing something because I am getting the max speed of the motor to be ~6000 rpm. It should be slightly under ~600 rpm.


Your calculation seems fine except that you are leaving out the conversion from the motor shaft to the gearbox shaft. The motor you have has a gear ratio of 9.68:1, and the free run speed of the 25D motors without a gearbox is 6200RPM.


Thanks much. This is exactly what I was overlooking.