In the field of industrial monitoring and safety inspection, non-contact high-precision detection of weak current signals is a core technology for ensuring the operational reliability of critical equipment. To address the problems of signal distortion, noise interference at high frequencies, and low detection accuracy in traditional methods, this study proposes a non-contact high-precision acquisition and demodulation method for weak induced currents. By combining down-conversion and digital phaselocked detection, the method solves the current monitoring problem ofdevices such as bridge-wire electric detonators, enabling precise measurement of weak currents. The system is optimized through a “down-conversion-filteringdigital phase-locking” architecture, achieving high-precision acquisition of weak currents in the range of 5~200 mA. This approach overcomes the bottleneck of electromagnetic interference inherent in traditional contact-based measurements and establishes an integrated system from physical sensing to digital processing. A TMR sensor is used as front-end sensing unit, leveraging its high sensitivity and wide frequency response to address the technical challenges of high-frequency current measurement. In the signal processing stage, multi-band signals are down-converted to 50 kHz using a mixer; low-pass filtering and ADC are then applied to suppress high-frequency noise. At the back end, a digital phase-locked loop based on million-scale multiply-accumulate operations is implemented using an FPGA, which separates target signals from background noise through cross-correlation detection. Experiments results show that in the frequency range of 50 kHz~10 GHz, the system achieves a detection accuracy of ≤±0.65, with real-time performance ensured by FPGA parallel processing. This non-contact detection method, through the synergy of sensor shielding and digital algorithms, provides a low-cost and highly reliable technical solution for the safety monitoring of electric detonators and current measurement of industrial equipment, with broad application prospects.