Miniaturized magnetoelastic torque transducers

Torque transducers based on circumferentially polarized band technology are shown to be scalable downward to accommodate torque measurements to at least low mN·m ranges. Shaft diameter for any required torque range is determined by material strength, while band width and separation are selected primarily to meet specific field detector requirements. Experiments verify the theoretically based expectation that the fields arising with the application of torque to property scaled mini-shafts are of similar intensity to those from larger shafts. A torque transducer of simple construction with a 0.79 mm diameter alloy steel shaft having a coercivity greater than 60 Oe, together with Hall effect field detectors exhibits suitable characteristics for torque measurement in the ±25 mN·m range