Microdefect Detection and Characterization Using Pot-Core Coils and LDC

To address the challenges of high power consumption and limited applicability of current pipeline eddy current detectors in small-diameter and low-pressure pipelines, this article introduces a novel low-power eddy current sensor based on an inductor digital converter (LDC). This sensor is specifically designed to detect minor defects. It employs a pot-cored coil as the sensing probe and can simultaneously output inductance L and parallel impedance <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{p}$ </tex-math></inline-formula> signals to characterize defects jointly. In this study, we establish a theoretical model of resonant eddy current testing (ECT) and investigate, through numerical simulations, the magnetic field distribution, induced eddy current distribution, and detection capabilities for various types of defects in pot-core coils, I-core coils, and air-core coils. Performance tests of the sensor were conducted using flat plates and half tubes with artificial defects as detection objects. The experimental results demonstrate that the sensor exhibits high sensitivity to small defects, successfully detecting a minimum width of 0.2 mm, a minimum diameter of 2 mm, and a minimum depth of 0.5 mm. These findings provide a theoretical foundation for the application of the sensor in detecting small-diameter and long-distance pipelines.