Digital signal processing in electrical capacitance tomography

Abstract

This paper presents the design, implementation and performance of a 16-electrode electrical capacitance tomography in Tianjin University. Currently, electrical capacitance tomography systems are primarily based on analog hardware. However, there are some disadvantages for the analog devices, e.g. relatively narrow bandwidth and long settling time, which place limits to further improvements in both data acquisition rate and precision. With the advances in logic resource, lower cost and flexibility of FPGA, an FPGA based data acquisition scheme was chosen over the traditional analog signal processing method. Improvements in system performance are achieved by implementing most functions in digital rather than analog hardware. Logics realized within the FPGA perform the signal generation, phase-sensitive demodulation, micro-controller and data transfer functions, thus providing effective integration. Preliminary results show that the signal-to-noise ratio could be greater than 76dB. The reconstructed images on the prototype are presented to illustrate the feasibility and potentiality of the FPGA based capacitance measurement system. © 2008 IEEE.