Chapter 20 – Rotational Motion Transducers

This chapter is concerned with the measurement of rotational (angular) movement in the form of displacement, velocity, and acceleration motion. The discussion on measuring rotation displacement starts with circular and helical potentiometers and then looks in turn at the merits of the rotational differential transformer, incremental shaft encoder, coded-disk shaft encoder, resolver, synchro, rotary inductosyn, and both the free and rate-integrating gyroscope. Moving on to the measurement of rotational velocity, the various forms of digital tachometer available are explored before considering stroboscopic methods, analog tachometers and the two forms of gyroscope that measure rotational velocity, the rate gyro and the fiber-optic gyro. Finally, the subject of rotational acceleration measurement is considered. Separate sections during the course of the chapter also consider the calibration techniques used for the various measurement devices covered.