There is an instrument outputting pwm-like current pulse trains proportional to its rotation speed. I convert the output current pulses to voltage pulses by a shunt resistor to be read by a DAQ hardware. Pulses are sampled with 12kHz. The software detects the rising edges and calculates the frequency for each pulse. Above on the left figure is what I see from the output of the instrument. P is the period, T is the pulse duration. Whatever the rotational speed the pulse duration T remains the same around 80us-120us(between 80 and 120 microseconds). Period P can be between 330us up to 2000us.
I have two questions:
1- As shown in the right side of the above figure, I want to convert these pwm-like pulses to sharper ones. What kind of op-amp configuration would you suggest for this application.
2- Since the frequency is counted between the rising edges what should be the sampling rate? My guess is 2*(1000000/80) = 25kHz. Would you agree?
3- If I cannot reach up to that sampling rate is there work around for lower sampling rates?