GB865051A - An electromagnetic torsional transducer - Google Patents

Abstract

865,051. Electric measuring systems. VYZKUMNY A ZKUSEBNI LETECKY USTAV. Aug. 22, 1958 [Aug. 24, 1957], No. 27057/58. Class 40 (1). Apparatus for comparing two forces or torques comprises means for applying the forces to twist a ferromagnetic shaft subjected to a rotating magnetic field, whereby voltages are induced in coils surrounding the shaft, which voltages are compared to obtain the ratio of the applied forces or torques. As shown (Fig. 1), a ferromagnetic rod or tube 5 is centrally located in two ferromagnetic cylindrical casings 8 whose end-plates 9 are secured to the rod 5. The open ends of the casings 8 are fitted with metal flanges 10, separated by an insulator 11. The rod 5 is divided into four equal parts by arms 6, 7 which protrude beyond the casings 8, the two arms 7 being mechanically linked, and the spaces between the rod 5 and the casings 8 are occupied by four similar coils 1, 2, 3, 4. Coils 1, 4 and also coils 2, 3 are connected in series opposition, the two pairs of coils also being connected in series through a potentiometer 16 (Fig. 4), with the outer ends of coils 1, 3 connected to a balancing potentiometer 19. An A.C. voltage is connected to the flanges 10 of the casings 8, producing a rotating magnetic field inside the casings, which is distorted when a first torque MK 1 is applied to arms 7 and a second torque MK 2 , in the opposite direction, is applied to arm 6, producing induced voltages in the coils 1-4 and an unbalance voltage between the sliders of potentiometers 16, 19 which is reduced to zero by moving the slider of potentiometer 19 either manually, or automatically via amplifier 17 and motor 18. It is shown that at balance the distance the slider of potentiometer 19 moves from the centre is proportional to the ratio of the applied torques MK 1 , MK 2 . The torque MK 2 applied to the central arm 6 may have a fixed known value obtained by adjustment of bolts attached to the casings 8.