Date of Award

1-1-2019

Language

English

Document Type

Master's Thesis

Degree Name

Master of Science (MS)

College/School/Department

Department of Electrical and Computer Engineering

Content Description

1 online resource (viii, 81 pages) : color illustrations.

Dissertation/Thesis Chair

Gary J. Saulnier

Committee Members

Mohammed Agamy, Jonathan Muckell

Keywords

Electrical impedance tomography, Voltage regulators, Electric current converters

Subject Categories

Computer Engineering | Electrical and Electronics

Abstract

Electrical impedance tomography (EIT) is a simple, non-invasive and ionizing radiation-free imaging technology with potential application to medical diagnostics such as lung function, cardiac output, breast cancer, and cysts. Of the above imaging techniques, lung imaging has developed into the prime application for EIT. Because it presents an ill-posed inverse problem, EIT requires high-precision instrumentation and this thesis studies a new method for obtaining a high-precision current source and voltmeter for EIT. This thesis describes various simulation studies performed on the voltage-controlled current source (VCCS). The output impedance (Zo) of various types of Howland current source (HCS) including the basic Howland current source (BHCS), the improved Howland current source (IHCS), and variations these sources that prevent the generation of a DC current, are characterized in terms of the parallel components of output resistance (Ro) and output capacitance (Co). We further analyze the voltage compliance, gain, and noise power density (NPD) of the system. A complete single electrode system of EIT system was simulated in which a sinusoidal signal is generated using an FPGA and passes through a 16-bit digital-to-analog converter (DAC), difference amplifier, HCS, load impedance, buffer, instrumentation amplifier (IA), an 18-bit analog-to-digital converter (ADC) before returning to the FPGA for voltage measurement. These studies were performed over the frequency range of 1 Hz to 100 MHz. The results indicate that the BHCS maintains high Zo over a wider frequency bandwidth compared to the IHCS, making it better suited for our proposed system, despite that fact that the IHCS has better voltage compliance and less power dissipation. Finally, the NPD demonstrates that the system is well-designed from a noise perspective. For hardware implementation as a test bench, we designed the printed circuit board (PCB) for single electrode current source out of thirty-two channel current sources for the new EIT system.

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