A sensor assembly for sensing radial position and speed of a rotatable member, the member being rotatable about a central axis (A c) and having an outer surface extending circumferentially about the axis, the sensor assembly comprising: a generally annular target body disposed about the rotatable member outer surface or integrally formed with the rotatable member and having a substantially continuous outer circumferential surface; a generally annular angular position indicator having an outer circumferential surface and at least one angular position index corresponding to a particular angular position of the member with respect to the central axis, the angular position indicator being one of integrally formed with the target body and spaced axially from the target body; a plurality of radial position sensors spaced circumferentially about the axis, each sensor being spaced radially outwardly from the target body outer surface and configured to sense radial displacement of the target body with respect to the central axis; a reference sensor disposed circumferentially between two of the radial position sensors, having an inner end spaced radially outwardly from the target body outer surface by a first spacing distance, and configured to detect the target body; and an angular displacement sensor spaced axially from the reference sensor and having an inner end spaced radially outwardly from the angular position indicator outer surface by a second spacing distance, the angular displacement sensor being located such that the second spacing distance is generally equal to the first spacing distance and such that the angular position index passes between the displacement sensor inner end and the central axis during rotation of the rotatable member. a generally annular target body disposed about the rotatable member outer surface or integrally formed with the rotatable member and having a substantially continuous outer circumferential surface; a generally annular angular position indicator having an outer circumferential surface and at least one angular position index corresponding to a particular angular position of the member with respect to the central axis, the angular position indicator being one of integrally formed with the target body and spaced axially from the target body; a plurality of radial position sensors spaced circumferentially about the axis, each sensor being spaced radially outwardly from the target body outer surface and configured to sense radial displacement of the target body with respect to the central axis; a reference sensor disposed circumferentially between two of the radial position sensors, having an inner end spaced radially outwardly from the target body outer surface by a first spacing distance, and configured to detect the target body; and an angular displacement sensor spaced axially from the reference sensor and having an inner end spaced radially outwardly from the angular position indicator outer surface by a second spacing distance, the angular displacement sensor being located such that the second spacing distance is generally equal to the first spacing distance and such that the angular position index passes between the displacement sensor inner end and the central axis during rotation of the rotatable member.