Electrical Capacitance Volume Tomograph EVT4

K. Krzewska, Ł. Dałko, M. Stosio, B. Radzik, M. Kłos, T. Olszewski, J. Kryszyn, W. T. Smolik, R. Szabatin

Institute of Radioelectronics, Warsaw University of Technology, Poland

Abstract

The paper presents the progress in the development of a new generation electrical capacitance tomograph being designed by our group. The modular device consists of 32 channels for capacitance measurements. The development of sensing electronics increases sensitivity of capacitance measurement and enables application of three dimensional sensor. The electrodes can be arranged in different 3D setups enabling different modes of work e.g. two planes by 16 electrodes or 3D configuration with 32 electrodes. The elaborated electronics modifications allow a high speed of measurement. The capacitance measurement time is about 5 µs using the modified charge-discharge circuit what gives high frame rate equal to 5250 frames/s. The modular electronics consists of 8 measurement boards with 4 channels each, read-out boards and a control board. Each analogue board is extended by the read-out board that transmits data from ADCs to the control board. All control electronics is designed using Xilinx programmable devices. The control board is equipped with Xilinx FPGA (Spartan) and 32 bit (ARM CORTEX) processor. The control board and readout boards are connected using a point-to- point Multi-Gigabit Transceivers. The physical LVDS standard is used only. The data are transferred using a custom data transmission protocol. The clock data recovery is used for synchronization of the boards. The hardware is connected to the host computer by the Ethernet interface. The applied digital technology enables high data transmission speed.

Keywords: electrical capacitance tomography; image reconstruction; inverse problem solver