Patent ID: 7495433
Filing Date: 2009-02-24
Classification: G01N

Abstract:
1. A defect detecting device for non-destructively detecting defects in an electrically conductive material, comprising: an exciter device that generates a low-frequency signal for detecting defects in the electrically conductive material; a yoke having a planner surface where the yoke is essentially U-shaped having a first end of the U-shape and a second end of the U-shape connected by a connecting section of the U-shape; first induction coil arranged at the first end of the U-shaped yoke, the first induction coil being connected to the exciter that transmits an electromagnetic signal and induces an eddy current in the material; a second induction coil arranged at the second end of the U-shaped yoke, the second induction coil being connected to the exciter that transmits an electromagnetic signal and induces a further eddy current in the material; and a reception device connected to the exciter device containing magnetoresistive gradiometer magnetic-field sensors with an integrated-bridge circuit having a plurality of chip feed lines, where the reception device extends from the yoke at essentially right angles to and between the first and second induction coils such that no magnetic field component is provided at the reception device, wherein the integrated bridge circuit with chip feed lines is configured to have inductance such that the signal output voltage of the integrated bridge circuit is essentially proportional to the magnetic field of the eddy currents and configured to detect the eddy current induced magnetic fields that indicate defects of the material, and the exciter device is designed and arranged such that when the generated electromagnetic signal is applied to fault-free material, the exciter device does not produce a signal output voltage.