Sinusoidal shaft position encoder

The magnetic design of an analogue sinusoidal output shaft position encoder is described. Two configurations are discussed, each using a rotating permanent magnet and a stator containing Hall sensors. The first of these has a complete annular stator with the sensors in the air-gap; the second, which was the design choice, uses a segmental stator with the sensors positioned between the segments. A practical model is described and it is shown that three-dimensional analysis rather than the simpler two-dimensional analysis is required to model the system accurately. Results showing the measured and practical harmonic spectrum are presented.