The length of the cable between the search coil and the preamplifier circuit has a significant impact on signal transmission. This study conducts a multidisciplinary simulation analysis and experimental verification on search coil magnetometer with long-distance cables. Based on search coil magnetometer prototype targeting a frequency bandwidth of 10Hz-1kHz and a noise level of 30fT/√Hz@1kHz, this study conducts research and establishes a circuit-principle model of the search coil-cable-preamplifier circuit. The role of the cable in search coil magnetometer based on transimpedance preamplifier circuit is analyzed, and theoretical simulation is carried out. The influence of cable length variation on sensitivity and noise frequency distribution is verified through experiments, and the results are basically consistent with the theoretical model, indicating that although the increase in cable length has a significant impact on search coil magnetometer, it can be designed and predicted through theoretical models. An increase in cable length reduces low-frequency sensitivity and low-frequency noise level, but it also significantly raises the level of high-frequency noise. It has little effect on magnetic wave detection at low-frequency, but substantially degrades magnetic field detection performance at high-frequency. For the target search coil, even if the cable length reaches 50 meters, it demonstrates satisfactory response and low noise levels within the 10 Hz–1 kHz frequency band, meeting the requirement of 30fT/√Hz@1kHz.
DownLoad: