Magnetic gain adjustment for axially magnetized linear force motor with outwardly surfaced armature

An axially magnetized linear force motor employs an exteriorly faced armature (4) having a first exterior face (14) and a second exterior face (16), wherein said first face (14) is acted upon by a first axial magnetic field established by a first annular, axially polarized, permanent magnet (22) and said second face (16) is acted upon by a second axial, magnetically opposing, magnetic field established by a second annular, axially polarized, permanent magnet (26). Actuation of a coil (32) affects the first and second fields oppositely causing an imbalance of net magnetic forces. The force imbalance causes the armature (4) to displace to a point where the net magnetic force equals a counter force established by a spring (10). Positionable ferromagnetic slugs (36, 37) alter the ratio of displacement of the armature (4) to the magnitude of a signal used to actuate the coil (32).