Patent ID: 8164325
Filing Date: 2012-04-24
Classification: G01D

Abstract:
1. A displacement sensor comprising: a cylindrical displacement detector coil; an electric conductor disposed close to an inside or outside of the displacement detector coil in a radial direction thereof, the electric conductor being freely displaceable in an axial direction of the displacement detector coil; an oscillator that outputs an oscillation signal with a frequency corresponding to an inductance of the displacement detector coil, the inductance of the displacement detector coil linearly increasing or linearly decreasing depending on a displacement of the electric conductor from one end to the other; an oscillation cycle meter that outputs a signal corresponding to a cycle of the oscillation signal output from the oscillator, the signal output from the oscillation cycle meter including square root component of a product of inductance and capacitance of the displacement detector coil; and a square calculator that performs a mathematical squaring operation on the signal output from the oscillation cycle meter, and outputs a squared signal corresponding to a square of the signal output from the oscillation cycle meter, the mathematical squaring operation removing the square root component of a product of inductance and capacitance of the displacement detector coil, such that the squared signal output from the square calculator changes generally linearly relative to a displacement of the electric conductor.