Study of synthesized multi-frequency excitation signal and magnetic induction detection method based on Walsh function

Magnetic induction detection technology is a non-contact and non-invasive electrical impedance detection technology. Multi-frequency synchronous detection can simultaneously obtain the impedance information of the tested object at different frequencies.Firstly, the principle of multi-frequency synchronous excitation-detectionis studied. Five-frequency excitation signal is synthesized based on Walsh function. Secondly, the performance of synthesized multi-frequency detection is analyzed, and a synchronous excitation-detection system is designed.Finally, the experiments of NaCl solution with different conductivity were designed. The results show thatthe measurement results of five main harmonics of synthesized five-frequency excitation signal have good linearity. The average sensitivityis 12.356mv.m/s, and the average conductivity resolution is 7.7 x 10(exp -3)s/m, which meets the measurement requirements and provides a multi-frequency synchronous excitation-detection method for magnetic induction signal detection.