Abstract: A circular array of equally spaced, interleaved, reference elecrodes or pole pieces are arranged about the center of the array for producing an electric or magnetic field in which the resultant vector representing the maximum field strength rotates as a polyphase current or voltage source is successively applied to successive ones of the electrodes or pole pieces. In a preferred embodiment, each of the electrodes is uniquely and generally crescent shaped such that along any radius from the center of the array passing through a given electrode, the radial width of the electrode varies in proportion to the sine of A.multidot..theta. where A is an arbitrary constant and .theta. is the azimuthal angle of the radius as measured from the initial end of the electrode. The radial cross-section ratio may be achieved by varying the width alone, varying the elevation alone, or by a combination of the two.

Abstract: A rotating electric field is generated in the vicinity of a rotating member, the electric field having an axis of rotation coinciding with the axis of rotation of the member. An electric-field sensing or reading device is positioned at the rotational axis of the electric field and associated therewith for detecting variations therein as the electric field passes the rotating member, and creates an electrical output whose relative phase is dependent upon the angular orientation of the rotating member.