Device for measuring linear displacements

A device for measuring linear displacements, which, on being coupled to an object of measurement and connected to a source of a-c voltage, shapes an output signal carrying information on the linear displacement of said object, said device comprising:

• a primary detector comprising:
• a central core shaped as a cylinder provided with a central axial opening, having a longitudinal axis;
• an external core shaped as a cylinder provided with a central axial opening, disposed coaxially to said central core;
• a movable member disposed coaxially with said external and central cores and connected with said object;
• a measuring winding consisting of turns, having a first output and a second output, disposed on said central core along said longitudinal axis so that said turns encompass said central core in a longitudinal direction and induce eddy currents in said movable member as said movable member moves;
• an additional winding consisting of turns, having a first output and a second output, said first output with said additional winding connected to said first output of said measuring winding, said additional winding being disposed on one of said cores so that said turns of said additional winding encompass one of said cores in a longitudinal direction and pass through the corresponding said central axial opening, said additional winding compensating for an additional error caused by external factors with said movable member in any position;
• said device further comprising a measuring amplifier having a first input and a second input, a-c voltage from said source being fed to each of said inputs,
• a third input of said measuring amplifier, connected to said first output of said measuring winding and said first output of said additional winding;
• a fourth input of said measuring amplifier, connected to said second output of said measuring winding;
• a fifth input of said measuring amplifier, connected to said second output of said additional winding;
• an output of said measuring amplifier at which a signal is shaped, carrying information about the linear displacement of said object.