Electronic hardware design of electrical capacitance tomography systems

Abstract

Electrical tomography techniques for process imaging are very prominent for industrial applications, such as the oil and gas industry and chemical refineries, owing to their ability to provide the flow regime of a flowing fluid within a relatively high throughput. Among the various techniques, electrical capacitance tomography (ECT) is gaining popularity due to its non-invasive nature and its capability to differentiate between different phases based on their permittivity distribution. In recent years, several hardware designs have been provided for ECT systems that have improved its resolution of measurements to be around attofarads (aF, 10(-18) F), or the number of channels, that is required to be large for some applications that require a significant amount of data. In terms of image acquisition time, some recent systems could achieve a throughput of a few hundred frames per second, while data processing time could be achieved in only a few milliseconds per frame. This paper outlines the concept and main features of the most recent front-end and back-end electronic circuits dedicated for ECT systems. In this paper, multiple-excitation capacitance polling, a front-end electronic technique, shows promising results for ECT systems to acquire fast data acquisition speeds. A highly parallel field-programmable gate array (FPGA) based architecture for a fast reconstruction algorithm is also described. This article is part of the themed issue 'Supersensing through industrial process tomography'.

Measurement in opaque flows: a review of measurement techniques for dispersed multiphase flows

“…This process is then repeated sequentially with the other electrodes. The entire process typically takes milliseconds, but this obviously depends on the hardware used [72]. The material distribution is not measured directly, but must be reconstructed by solving an inverse problem using the data obtained from the electrodes [71].…”

“…Simply increasing the number of electrodes is not trivial, as that would reduce their size and thus their sensitivity. Furthermore, it increases the complexity of the electronics hardware and achievable frame rate [72]. Nevertheless, the technique is able to discern flow regimes ('stratified' versus 'churn flow', etc.).…”

Application of Electrical Capacitance Tomography for Imaging Conductive Materials in Industrial Processes

“…Typically, the ECT system contains three parts, an array of electrodes, a data acquisition unit, and a computing device [26]. Assume we have a group of n electrodes, thus, each two formulate a capacitive sensor.…”

FPGA Implementation of ECT Digital System for Imaging Conductive Materials

“…A typical ECT system contains three hardware parts, an array of electrodes mounted around the area of interest, a data acquisition unit including a multiplexer to switch between capacitance sensors, and a computing device (usually a general-purpose computer) to carry out the image reconstruction and the parameters' analysis [24]. Figure 2 is a sketch of the ECT system with all three components [2].…”