Measuring motor speed

[fovea1959]

Hugh, thanks.

We may fall back to the USDigital, but we're trying to see if there are viable alternatives in the single pulse per rev range. Our experiments so far is that the US Digital are noisy and unreliable at these speeds (had a student plotting speed at constant power, flat with spikes of varying size above and below the line). Needed a fair amount of filtration to get something that looked decent.

If I can find something cheaper, less noisy, more robust, and sends sends fewer pulses to the poor cRIO, I want to explorer it. A 10000 rpm shaft on a 250 pulse /rev encoder is over 40000 pulses/s; depending on what numbers you believe, that's close to what the FPGA can handle.