A gear rattle detector is adapted for use with a gear set having meshing drive and driven gears. The gear rattle detector comprises a magnetic pick-up including a base, a first arm extending from the base and defining a north magnetic pole, a second arm extending from the base and defining a south magnetic pole, and a coil wound around the base. The poles are spaced sufficiently such that they span the root circles of the gears.

A magnetic structure including a stator including sensor windings and a field exciter, and a movable armature having a variety of applications, including a synchro resolver and a tachometer. The stator comprises a plurality of planes of oppositely polarized parallel magnetic pole pieces contained in an annular or toroidal structure of rectangular cross-section to circumferentially surround the movable rotor or armature. The parallel pole pieces of opposite polarity form a segment extending radially inward, and are surrounded by a plurality of sense windings, wherein the rotor selectively provides a relatively low reluctance path to one or more of the pole pieces, causing a change in flux and corresponding voltage to be produced in the sense windings. In one embodiment, the pole pieces are energized by a permanent magnet located in the stator to produce a tachometer output voltage upon the sense windings. In that configuration the sense winding signals vary in amplitude according to velocity and position. Alternately, the pole pieces are energized by an electromagnet at an excitation frequency, producing corresponding sense winding signals at the excitation frequency. In this case, the sense winding signals vary in amplitude and phase according to the rotor position relative to the stator. The sense winding signals for the tachometer or synchro resolver are connected to appropriate commutation and signal detection circuits to provide the desired tachometer or synchronous resolver output signals.