I can only offer minor insights since I have never had to perform Nadcap audit for Ro-tap machine myself. I presume you would use stop-watch to measure the taps/minute and some form of calibrated (i.e. certified) tachometer for the rotation speed. I understand that the timer must also be calibrated/certified. The screens must also be certified (available from manufacture).
Perhaps someone with more Nadcap familiarity can help with this answer.
