Abstract: A probe (10) for sensing movement of a body of magnetic material comprises a magnetically energisable pole piece (30), a closed loop electrical circuit (20) having a first end (25) which is wound around the pole piece (30) and forms a pole piece coil (25) inductively coupled to the pole piece, the arrangement being such that movement of a body of magnetic material (70) relative to the pole piece (30)induces a current in the closed loop circuit (20), and a second end (45), remote from the pole piece (30), which forms a transformer primary coil. A transformer secondary coil (65) is inductively coupled to the primary coil (45), and terminated by a load resistance and means for measuring an output signal from the secondary coil. The primary (45) and secondary (65) coils form a transformer such that a current in the primary coil induces a voltage across the secondary coil. One or more shorting turns (60) of a conductor are inductively coupled to the primary (45) and secondary (65) coils.

Abstract: A probe (10) for sensing movement of a body of magnetic material comprises a magnetically energisable pole piece (30), a closed loop electrical circuit (20) having a first end (25) which is wound around the pole piece (30) and forms a pole piece coil (25) inductively coupled to the pole piece, the arrangement being such that movement of a body of magnetic material (70) relative to the pole piece (30)induces a current in the closed loop circuit (20), and a second end (45), remote from the pole piece (30), which forms a transformer primary coil. A transformer secondary coil (65) is inductively coupled to the primary coil (45), and terminated by a load resistance and means for measuring an output signal from the secondary coil. The primary (45) and secondary (65) coils form a transformer such that a current in the primary coil induces a voltage across the secondary coil. One or more shorting turns (60) of a conductor are inductively coupled to the primary (45) and secondary (65) coils.

Abstract: A shaft monitoring system for sensing axial movement of a shaft, especially in a gas turbine engine, comprises a toothed wheel attached to and rotatable with the shaft, and a pair of inductive sensors disposed radially of the toothed wheel for sensing the passage of the teeth as the shaft rotates. In one embodiment, the toothed wheel has two axially-spaced sets of teeth, one set straight cut and the other set diagonal cut, so that the phase difference between the respective outputs of the sensors varies with axial movement of the shaft. In another embodiment, the sensors are positioned at opposite axial ends of the toothed wheel, so that axial movement of the shaft causes one sensor output to increase in amplitude while the other decreases.

Abstract: A proximity sensor includes an electrical circuit formed by a slot in an elongate conductive strip. The strip carries a magnet having a pole piece protruding through the strip at one end of the slot. At the other end of the slot pass laminations which magnetically couple the electrical circuit and a multi-turn coil arranged on a form attached to the strip. The coil is terminated at a pair of output leads. A ferrous object passing in the vicinity of the pole piece of the magnet modifies the flux pattern at the pole face. The resultant flux changes, being tightly coupled to the electrical strip, induce a low voltage high current emf into the strip, which forms the primary turn of a current transformer. The secondary of the current transformer is formed by the close-coupled coil, which has multiple turns, dependent upon the output voltage required at the output leads.