Abstract: A motion transducer for measuring the displacement of, for example, shafts in gas control modules. The shaft 14 carries two magnets 10, 12 each of hollow cylindrical form, the magnet 10 presenting a south pole everywhere over its external cylindrical face and the magnet 12 presenting a north pole everywhere over its external cylindrical face. The shaft 14 moves vertically past an array of Hall-effect sensors 18-24 to produce sinusoidal voltage outputs at the sensors. The outputs are combined in a summing amplifier (FIG. 3). The combined output is not affected by rotation of the shaft and magnets nor by tilting or sideways displacement of the axis 16 of the shaft. That is because no matter what the rotational position is the sensors are always subjected to the same magnetic field and, if the shaft tilts or is displaced sideways an increased field at some sensors is compensated by a decreased field at others.(FIG. 1 is suggested as the accompanying drawing).