A high-performance EIT system

This paper presents the development of a new electrical impedance tomography system for online measurement of two-phase flows with axial velocities up to 10 ms/sup -1/. The system is designed in a modular fashion and can consist of several data acquisition modules and computing modules. The data acquisition module includes a voltage controlled current source with a direct-current-restoration circuit, an equal-width pulse synthesizer unit and a synchronized digital demodulation unit. A new concept of current switching scheme is developed to enhance the ac coupling speed. The computing module includes a digital signal processor (TMS320C6202/6713) with memory, multichannel buffered serial ports and an IEEE1394 communication interface. Several DSP modules can be pipelined for a series of tasks ranging from measurement control to image reconstruction to flow velocity implementation. The performances have been tested and some trial results are reported. A data acquisition speed of 1164 dual-frames (2.383 million data points) per second has been achieved with a root mean square error less than 0.6% at 80 kHz in static test application. An application in the measurement of vertical oil-in-water pipe flow is reported.

[1]  Mi Wang,et al.  Electrical resistance tomography for process applications , 1996 .

[2]  J. O'm. Bockris,et al.  Electro-chemical science , 1972 .

[3]  C. J. Kotre,et al.  EIT image reconstruction using sensitivity weighted filtered backprojection. , 1994, Physiological measurement.

[4]  Walt Kester,et al.  5 UNDERSAMPLING APPLICATIONS , 1996 .

[5]  A. Plaskowski,et al.  Cross Correlation Flowmeters, Their Design and Application , 1987 .

[6]  Yixin Ma,et al.  Performances of a High-Speed Impedance Camera for Flow Informatics , 2004 .

[7]  T Dudykevych,et al.  Impedance analyser module for EIT and spectroscopy using undersampling. , 2001, Physiological measurement.

[8]  V. Pollak,et al.  An equivalent diagram for the interface impedance of metal needle electrodes , 1974, Medical and biological engineering.

[9]  Mi Wang,et al.  Inverse solutions for electrical impedance tomography based on conjugate gradients methods , 2002 .

[10]  L. Maccone,et al.  Tomography , 1940, British medical journal.

[11]  W. A. Evans,et al.  Hybrid technique in waveform generation and synthesis , 1980 .

[12]  Mi Wang,et al.  A high performance online data processing EIT system , 2003 .

[13]  Brian H. Brown,et al.  Design of a phase-sensitive detector to maximize signal-to-noise ratio in the presence of Gaussian wideband noise , 1992 .

[14]  V. Pollak.  Computation of the impedance characteristic of metal electrodes for biological investigations , 2006, Medical and biological engineering.