This video demonstrates my experimental shaft encoder made from a 6mm x 3mm neodymium magnet and an MLX90393 3-axis magnetometer.
Two quadrature sinewave outputs appear when the magnet is rotated which allows us to calculate the absolute shaft angle at any instant in time.
The linearity is excellent as a straight line is obtained when the shat angle is plotted over a full revolution off the magnet.
Construction details and test code may be found at https://www.instructables.com/Magnetic-Shaft-Encoder/
