Design of electrical capacitance tomography sensors

Abstract

Electrical capacitance tomography (ECT) has been developed since the late 1980s for visualization and measurement of a permittivity distribution in a cross section using a multi-electrode capacitance sensor. While the hardware and image reconstruction algorithms for ECT have been published extensively and the topics have been reviewed, few papers have been published to discuss ECT sensors and the design issues, which are crucial for a specific application. This paper will briefly discuss the principles of ECT sensors, but mostly will address key issues for ECT sensor design, with reference to some existing ECT sensors as a good understanding of the key issues would help optimization of the design of ECT sensors.The key issues to be discussed include the number and length of electrodes, the use of external and internal electrodes, implications of wall thickness, earthed screens (including the outer screen, axial end screens and radial screens), driven guard electrodes, dealing with high temperature and high pressure, twin planes for velocity measurement by cross correlation and limitations in sensor diameter. While conventional ECT sensors are circular with the electrodes in a single plane or in twin planes, some non-conventional ECT sensors, such as square, conical and 3D sensors, will also be discussed. As a practical guidance, the procedure to fabricate an ECT sensor will be given. In the end are summary and discussion on future challenges, including re-engineering of ECT sensors.

Co-operative sensor fusion using time warping in multimodal tomometry for process control

“…Current developments on tomography are largely on 3D image constructions called Electrical Capacitance Volume Tomography (ECVT) and improved image resolutions. But in practice it is still difficult due to computational difficulties (Yang 2010).…”

Comparative Performance Evaluation of Entropic Thresholding Algorithms Based on Shannon, Renyi and Tsallis Entropy Definitions for Electrical Capacitance Tomography Measurement Systems

“…The Electrical Capacitance Tomography (ECT) is one of the imaging system developed for monitoring and measurement of industrial processes [1][2][3][4][5][6]. The system has been extensively evaluated for applications in hydrocarbons multi-phase flow measurement and monitoring [7][8][9][10][11][12][13][14][15].…”

Switch Configuration Effect on Stray Capacitance in Electrical Capacitance Volume Tomography Hardware

“…Various geometry of the sensors have been designed to adapt the ECVT for different application. There are cube, conical, twin-plane cylinder for high pressure and high temperature application [1]; hemisphere for breast scanning [2]; helmet for brain activity scanning [3]; bend, T-shape, half-cylinder for flow imaging [4]; and other geometry designs. The problem in ECVT system is low resolution, hence image reconstruction is not good, ill-posed reconstruction problem, much more artefact, and the image attracted upwards and TELKOMNIKA ISSN: 1693-6930 …”