A magnetoelastic torque sensor for providing an output signal indicative of
the torque applied to a member, comprising, a first magnetoelstically
active region in the member, the region being ferromagnetic,
magnetostrictive magnetically polarized in a single circumferential
direction and possessing sufficient magnetic anisotropy to return the
magnetization in the region to the single circumferential direction when
the applied torque is reduced to zero, whereby the ferromagnetic,
magnetostrictive region produces a magnetic field varying with the torque.
Magnetic field sensors are mounted proximate to the ferromagnetic,
magnetostrictive region to sense the magnetic field at the sensors and
provide the output signal in response thereto. The field arising from the
magnetoelastically active region does not magnetize regions of the member
proximate to the magnetoelastically active region to give rise to
parasitic magnetic fields which are of sufficient strength to destroy the
usefulness, for torque sensing purposes, of the net magnetic field seen by
the magnetic field sensor means.