High Speed EIT With Multifrequency Excitation Using FPGA and Response Analysis Using FDM

Abstract

The investigation of quickly-evolving flow patterns in high-pressure and high-temperature flow rigs is crucial due to inherent hazards. There is a dire need for a high-speed, non-intrusive imaging technique to identify characteristic flow phenomena to alleviate these hazards. Electrical Impedance Tomography (EIT) enables reconstruction of the admittivity distribution of the flowing medium(s), facilitating the characterisation of its/their flow. The requirement for images at high frame-rates led to simultaneous voltage excitations over electrodes on the periphery of the flow associated to Frequency Division Multiplexing (FDM), doped ONe Excitation for Simultaneous High-speed Operation Tomography (ONE-SHOT) method. In previous studies, we have demonstrated the possibility of the full implementation of simultaneous excitations and measurements strategies for EIT, which maximise the number of measurements for 16 electrodes. This article presents the details of the proposed method and the signal generation/acquisitionfirmware based on a Field Programmable Gate Array (FPGA) data acquisition system focusing on hardware and software integration and the signal processing involved in realising the ONE-SHOT operation of the EIT. It is shown that the simultaneously generated signals are successfully discriminated and used for image reconstruction, at a rate up to 3906 frames per second (fps). The associated signal-to-noise ratio varies in the 55.6 dB-69.1 dB range, depending on the generated frequency in the range of 3.906 kHz-468.7 kHz.

Impedance Imaging of Cells and Tissues: Design and Applications

“…The resolution and robustness of EIT can also be improved by including a priori knowledge about the sample and adjusting image reconstruction algorithms to exclude reconstructed images that are not compatible with the known physical properties of the sample [ 129 , 130 ]. Passive electrode arrays with low numbers of electrodes can be controlled through field-programmable gate arrays (FPGAs), on which efficient postprocessing algorithms can be implemented [ 131 , 132 ]. CMOS HD-MEAs are well suited for performing EIT measurements owing to their small pitch and large number of electrodes.…”

Improving EIT-Based Visualizations of Two-Phase Flows Using an Eigenvalue Correlation Method

“…2(b), employs fast Fourier transform (FFT)-based frequency-division multiplexing instead of the time-consuming time-division multiplexing, and the superimposed signals of the 120 excitation patterns are discriminated by FFT, giving the boundary measurements simultaneously. This system applies constant voltage injection, the currents are obtained from voltages measured across resistors located in series in the voltage excitation circuit, and a detailed representation of the system can be found in [14] and [15]. The voltages are measured against the same ground as the voltage injection electrodes.…”

“…Our EIT system can perform measurements at a frame rate up to 3906 frames/s [15], but, during each experiment, we selected a rate of 100 frames/s over 30 s as we found it is sufficient to capture the characters of the flow for the various phase injection conditions considered. A higher frame rate would not bring additional information while requiring more computational power.…”

A novel neural network-based data acquisition system targeting high-speed electrical tomography systems

“…Nevertheless, Msequence is preferable since it features strong sequence orthogonality, which results in low cross-talk between measurements. However, multi-frequency EIT typically necessitates a high signal bandwidth [14], [15], which means that narrow-band low-pass filters are not permitted, making multi-frequency EIT systems more susceptible to colored noise. In practice, it is difficult to completely eliminate the colored noise, even with well-designed hardware.…”