Patent ID: 7602175
Filing Date: 2009-10-13
Classification: G01D

Abstract:
1. A non-contacting position measuring system comprising: a sensor that includes a measuring coil which can be energized with alternating current, and wherein the measuring coil comprises at least two voltage taps; an electrically or magnetically conductive object to be measured which comprises a tube having a wall of predetermined thickness and with the tube positioned adjacent the measuring coil so that the measuring coil induces eddy currents which penetrate the wall of the tube when energized; an evaluation circuit connected to the at least two voltage taps, wherein the sensor and the tube can be displaced relative to one another in a longitudinal direction of the measuring coil, wherein the tube includes at least one discontinuity affecting the impedance of the measuring coil between the at least two voltage taps so that the evaluation circuit provides an output signal which correlates the position of the tube in relation to the at least two voltage taps, and wherein the wall thickness of the tube is greater than the penetration depth of the eddy currents induced in the wall of the tube by the measuring coil when energized.