Design of an Underground Metal Pipeline Detector Based on Electromagnetic Induction

To meet the detection requirements of hidden infrastructure in railway systems, this paper designs an excavation-based underground metal pipeline detector using the principle of electromagnetic induction. By establishing a magnetic field model based on the Biot–Savart law, the study innovatively adopts an orthogonal four-coil differential array structure, combined with a zero-value determination logic (∆V = 0), to achieve accurate decoupling of pipeline orientation along the railway (X/Y axes and diagonal directions). A vertical moving peak positioning method is proposed to determine burial depth, and the half-peak method is extended to measure horizontal offset distance (satisfying the d ≈ h relationship with a simulation error of less than 5%). The hardware system employs a differential amplification–band-pass filtering–peak detection circuit, which can effectively extract weak signals even under strong electromagnetic interference near the railway (signal-to-noise ratio improved by ≥ 40%). This solution provides technical support for the precise localization of metal components such as track-bed pipelines and signal cables during railway maintenance, significantly improving maintenance efficiency and excavation safety.