David Eugene Brandon

A new inductive displacement transducer

A fixed core structure 52 comprises a central bobbin 54 about which its wound a primary coil. Secondary cores 74,76 and 78 embedded in epoxy resin 54 have axes parallel to the primary axis and arranged on an arc concentric with the primary coil with pole faces on the two parallel major faces of the core structure 52. Secondary coils are wound on the three secondary cores. Because the coil axes are all parallel, the coils are poorly coupled. A rotor of ferro-magnetic material has two parallel arms which rotate across the major faces of the core structure 52, having cylindrical extensions which fit into the central aperture 106 of the bobbin. The ends of the arms move across the faces of the secondary cores 74, 76, 78 and the arms provide low reluctance paths bridging the primary to the secondaries selectively. The centre secondary coil 80 is a dummy and, when the arms are centered on the centre core 76, no output is induced in either of the outer secondaries 82 and 84. Movement of the arms to the left and the right produces an increasing signal in the secondaries 82 and 84 respectively, indicative of the amount of rotation away from the centered position in the corresponding sense.