Appendix F: Measuring angular velocity with hall encoder
The rotational Hall encoder converts the angular velocity to electrical signal. Hall elements are semiconductor devices which change its conductivity as a function of applied magnetic field. A magnetic disk is coupled to the shaft of an electric motor. Along the disk boundary, there are evenly distributed magnetic pole pairs (N or S). Close to the magnetic disk, there are mounted both Hall elements which generate a logical signal reflecting current polarity (N or S) generating two shifted square pulse waveforms (Figure F.1). Their frequency (2/Timp) is proportional to the angular velocity and phase shift τ depends on the direction of rotation.
