A High-Efficiency Excitation and Measurement Scheme for Electromagnetic Tomography

In the electromagnetic induction tomography (EMT/MIT) systems, the conventional method for driving excitation coils involves the combinational use of direct digital synthesizer (sinusoidal signal generator) and power amplifier. Generally, this circuit scheme has limited output current, i.e., several hundred milliamperes, producing relatively low magnetic field intensity within the sensing field and signal-to-noise ratio. This paper introduces an excitation and measurement strategy based on zero voltage switching (ZVS) circuit and phase sensitive detector (PSD), aiming to provide a high-efficient solution for EMT data acquisition system. The performance of ZVS circuit and PSD have been evaluated with numerical simulations and experiments, and compared with the conventional circuits based on the power amplifier. It has been indicated that, the employment of ZVS circuit has significantly increased the excitation voltage across the load and thus the current. In addition, the experimental results have confirmed the feasibility of the proposed excitation measurement scheme presented in this paper.