Digital Instrumentation for Angular Velocity and Acceleration

An instrument is described for the measurement of angular velocity and angular acceleration of a rotating shaft, based upon an optical angular transducer and an associated operational digital (pulse rate) system. The angular transducer produces a pulse rate directly proportional to the instantaneous angular velocity and this quantity and its rate of change are processed by the pulse rate system and presented as parallel binary-coded decimal representations driving in-line digital displays. The operational digital system comprises essentially an electronic register controlling a variable rate pulse generator that tracks the input pulse rate in a frequency lock loop. Changes of loop frequency are brought about by changing the register contents by positive or negative correction pulses, and the rate at which these are supplied provides an accurate measure of acceleration or deceleration, respectively, provided that the loop is locked on and hence follows the changes of input pulse rate accompanying changes of angular velocity. The error correction pulse rate may be measured in a second frequency lock loop and the registers in the two loops used to control digital in-line decimal displays of angular velocity and acceleration, of ranges up to 10 000 r/min (±1 r/min) and 1000 r/min/s (±1 percent), respectively.