This question leads on from a question I asked last night, so some people will know it.
I am using an FPGA with a 1000 ppr rotary quadrature encoder counting 4x (counting all edges is 4000ppr) and had planned on counting the number of pulses every 1ms. The motor rpm range is from around 1000 or 2000 up to 4000 rpm with no gearbox. The encoder is coupled straight to the motor.
I had planned to use this equation:
(Hopefully someone can edit this :) RPM = ((Pulses per ms) * 60,000) / Pulses per revolution
However when I run this calculation on a calculator I see a change of 1 pulse per millisecond equates to 15 rpm of the motor.
Does this encoder not have enough ppr for this application, or am I doing something incorrect in my maths?