Leow Pei Ling

Segmented Capacitance Tomography Electrodes: A Design and Experimental Verifications

A segmented capacitance tomography system for real-time imaging of multiphase flows is developed and presented in this work. The earlier research shows that the electrical tomography (ECT) system is applicable in flow visualization (image reconstruction). The acquired concentration profile obtained from capacitance measurements able to imaged liquid and gas mixture in pipelines meanwhile the system development is designed to attach on a vessel. The electrode plates which act as the sensor previously has been assembled and fixed on the pipeline, thus it causes obscurity for the production to have any new process installation in the future. Therefore, a segmented electrode sensor offers a new design and idea on ECT system which is portable to be assembled in different diameter sizes of pipeline, and it is flexible to apply in any number due to different size of pipeline without the need of redesigning the sensing module. The new approach of this sensing module contains the integration intelligent electrode sensing circuit on every each of electrode sensors. A microcontroller unit and data acquisition (DAQ) system has been integrated on the electrode sensing circuit and USB technology was applied into the data acquisition system making the sensor able to work independently. Other than that the driven guard that usually placed between adjacent measuring electrodes and earth screen has been embedded on the segmented electrode sensor plates. This eliminates the cable noise and the electrode, so the signal conditioning board can be expanded according to pipe diameter.

Comparison of single and segmented excitation of electrical capacitance tomography

Electrical Capacitance Tomography is a modality which enables users to visualize and monitor the process flow in a closed pipe. It is a non-invasive and non-intrusive technique, yet, it suffers from soft-field effect which produces low resolution images. Segmented excitation is proposed in this paper to overcome the problem faced by ECT single excitation. The comparison between single and segmented excitation are presented in form of images and electrical potential value. From the 1st switching, segmented excitation recorded 315% higher electrical potential compared to single excitation at the center of the pipe. From simulations, sensitivity maps are generated and compared between both excitation methods. The electrical potential for segmented excitation is well-distributed and produces 164% higher of average electrical potential compared to single excitation method.