A double-layer mutual inductance coupling planar eddy current inductance sensor

Abstract

This invention discloses a double-layer mutually inducted coupled planar eddy current detection sensor. First, an external excitation source provides AC power input to the detection coil layer, causing the LC resonator, composed of the detection coil and a parallel resonant capacitor, to resonate, generating a sinusoidal current and forming a primary magnetic field. When the test piece is in the primary magnetic field, eddy currents are generated on its surface, creating a mutual inductance effect with the sensing coil. Changes in lift-off or disturbances in the flow direction of eddy currents at defects lead to changes in the mutual inductance coefficient, causing a change in the equivalent inductance of the sensing coil and a change in the resonant frequency. Finally, the resonant frequency is detected and extracted to obtain the detection signal. Similarly, a set of detection signals is also extracted from the reference coil. By comparing the changes in the signals detected by the reference coil and the detection coil, lift-off and defect signals are separated to obtain defect information.

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