Patent ID: 7554527
Filing Date: 2009-06-30
Classification: G01D,G05G,G06F

Abstract:
1. An apparatus for monitoring orientation of a substantially spherical body, the apparatus comprising: a substantially spherical body; at least one resonant circuit fixed relative to the spherical body; a physical mounting for fixing a location of the spherical body relative to the apparatus while allowing rotational movement of the spherical body; a transmit aerial for generating an alternating magnetic field in the location of the spherical body to induce an electric signal in each resonant circuit, the transmit aerial comprising a plurality of excitation windings that are arranged so that the magnetic field generated from each winding is generally spatially orthogonal to the fields from each of the other windings; and a receive aerial for receiving an induced sense signal generated in response to the induced electric signal in each resonant circuit, the receive aerial comprising a sensor winding; wherein an electromagnetic coupling between one or both of i) the transmit aerial and each resonant circuit and ii) each resonant circuit and the receive aerial, varies in accordance with the orientation of the spherical body so that the induced sense signal in the receive aerial varies in accordance with the orientation of the spherical body; and wherein the excitation windings are operable to induce minimal net voltage components in the sensor winding generated by direct electromagnetic coupling between the transmit aerial and the receive aerial.