Digital phase-sensitive demodulation in electrical capacitance tomography system

Electrical capacitance tomography (ECT) techniques have been developed to visualize industrial processes with dielectric materials. Phase-sensitive demodulator (PSD) is a crucial part in ECT system. Different methods of demodulation are demonstrated in this paper, including analogue and digital methods. Analogue demodulator can not overcome shortcomings of analogue devices which have been a bottleneck of imaging precision and speed. A digital demodulator based on FPGA and DSP is designed in this paper, and realizes the full digital quadrature demodulation. Both the systematic speed and precision are improved.