Negative Hysteresis in Magnetoelastic Torque Transducers

Unusual manifestations of magnetomechanical hysteresis often observed in magnetoelastic torque transducers are described. Characterized by a remanent field at zero torque having a polarity opposite to that at the torque peak, this "negative" hysteretic effect is shown to be of magnetic origin and hypothesized to reflect axial magnetization of unpolarized material radially inward of the circumferentially polarized band. The retained portion of this magnetization at zero torque is shown both by analysis and experimental results with an electromagnetic simulator to be a source of magnetic field having opposite polarity to that present at the previous torque peak. When this field becomes larger than the normal positive remanent field it appears as negative hysteresis.