Electrical Capacitance Volume Tomography: Design and Applications

Abstract

This article reports recent advances and progress in the field of electrical capacitance volume tomography (ECVT). ECVT, developed from the two-dimensional electrical capacitance tomography (ECT), is a promising non-intrusive imaging technology that can provide real-time three-dimensional images of the sensing domain. Images are reconstructed from capacitance measurements acquired by electrodes placed on the outside boundary of the testing vessel. In this article, a review of progress on capacitance sensor design and applications to multi-phase flows is presented. The sensor shape, electrode configuration, and the number of electrodes that comprise three key elements of three-dimensional capacitance sensors are illustrated. The article also highlights applications of ECVT sensors on vessels of various sizes from 1 to 60 inches with complex geometries. Case studies are used to show the capability and validity of ECVT. The studies provide qualitative and quantitative real-time three-dimensional information of the measuring domain under study. Advantages of ECVT render it a favorable tool to be utilized for industrial applications and fundamental multi-phase flow research.

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

“…Subsequently, voltage signal at Op-Amp output is recorded and analyzed, and the result shown on Figure 9. Total current i 4 and voltage signal at Op-Amp output can be calculated with the following equation: Based on graphics on Figure 9, the simulation in ideal condition resulting in low value down to Pico Farad instead of Femto Farad 1 10 , this is due to no noise added in simulation and only parameters in the datasheets used in simulation (blue line). In fact, the circuit in ECVT hardware has noise from other sources such as PCB design, components layout, excitation signal that passes through PCB track, and adjacent track in parallel, which can cause capacitance effect.…”

“…Consequently, current flowing to i 4 decreases to 38.9 nA. In ideal condition when floating mode, current i, i 1 , i 2 , i 3 , i 4 should not flowed into detection circuit, however in fact the currents are still flowing into detection circuit through C soff in switches S 5 and S 4 , hence it causes stray capacitance. The current i 4 based on Table 1 is very small about 38.9 nA for one channel, if some channels are connected together through switches, the current flowing into detection circuit will increases as depicted on Figure 7, hence increases stray capacitance.…”

“…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 …”

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

“…Its goal is to generate instantaneous images of dielectric material component permittivity distributions inside a vessel using external capacitance measurement [41,42]. The imaging technique is capable of distinguishing between different components or phases in a multiphase mixture based on the permittivity distribution in the mixture.…”

Column flotation monitoring based on electrical capacitance volume tomography: A preliminary study

“…ECVT, developed from 2-D electrical capacitance tomography (ECT), is a promising non-intrusive imaging technology that can provide real-time 3-D images of the sensing domain 9 . ECVT is based on the utilizing the nonlinear distribution of electric field lines in the 3-D space to reconstruct a volumetric image of different materials in the sensing domain.…”