Abstract: A magnetoclastic transducer for sensing a torque in a shaft (150) is formed by circumferentially magnetising a magnetisable, integral portion (156) of the shaft. To assist in the emanation of a flux-dependent torque, the transducer element portion (156) of the shaft may have further circumferentially magnetised portions (154, 158) to each side. These further portions (154, 158) are of opposite polarity magnetisation to that of the transducer element (156). The external magnetic flux emanated by the transducer (156) is a function of torque and is detectable by a magnetic field sensor (160). An alternative means for the same purpose is to provide the transducer element at a portion (172) of the shaft (170) having an integral annular section of raised profile projecting beyond adjoining portions of the shaft. The shaft may be provided with a series of circumferentially magnetised portions of alternating polarity.

Abstract: A circuit for sensing a magnetic field has at least one saturable coil (L1). The circuit includes switches (S1, S2) controlled by a comparator (12) to drive the coil (L1) to saturation by alternating polarities of current. In the absence of an external magnetic field the currents are balanced. An applied external magnetic field causes an unbalance in the coil (L1) in reaching saturation. An unbalance current is applied through a sensing resistor (R2) to an integrator (20) to develop an output voltage (Vo) as a measure of the applied magnetic field. The switches (S1, S2) are implemented by transistor switches. Dual (FIG. 1) and single (FIG. 2) supply rail circuits are disclosed. The circuit finds particular application in torque transducers using magnetoelastic elements.