A Simple Multisensor PECT System for Omnidirectional and Small Crack Detection on Medium-Carbon Steel Surfaces

Pulsed eddy current testing (PECT) is a vital non-destructive testing technique for detecting surface and subsurface defects in conductive materials. However, conventional single-sensor probes exhibit limited sensitivity to cracks oriented parallel to the eddy current flow, resulting in directional blind spots. This paper proposes a multi-sensor PECT probe for omnidirectional crack detection in C45 medium-carbon steel, integrating five HW-105A Hall sensors—one central (Hall1) and four peripheral (Hall2–Hall5)—strategically positioned to capture eddy current disruptions in multiple directions. A data fusion and Multivariate Singular Spectrum Analysis (MSSA), analyzes transient responses from all sensors simultaneously for accurate crack characterization regardless of orientation. Experimental results on C45 medium-carbon steel samples with controlled surface cracks (0.25–2 mm deep, 3–14 mm long, 1 mm wide) demonstrate that the multi-sensor approach achieves significant improvements in detection reliability and sensitivity, with signal-to-noise ratio (SNR) gains of up to 9.22 dB from multi-sensor fusion compared to traditional single-sensor probes. The system successfully detects cracks oriented at 0°, 45°, and 90° relative to the scanning direction. These findings highlight the potential of this multi-sensor PECT system to enhance NDT effectiveness for critical structural components, providing a robust solution for quality control and material integrity assessment.