Yinan Wang, Nan Li, Hui Xu, Hongqi Yu, Xin Xu, Zhaolin Sun, Husheng Liu
Electrical Impedance Tomography; Voltage ControlledCurrent Source; Direct Digital Synthesizer; ImprovedHowland
Electrical Impedance Tomography (EIT) is applied to acquire the impedance characteristic, which is correlative with the physiological and pathological status of a body, and reconstruct the images of impedance distribution. Current injection with voltage measurement phantom is widely adopted in the application of biomedical detection. Voltage controlled current source (VCCS) develops an important part and its performance directly affects the precision of EIT system. In this paper, we design and realize a VCCS using a direct digital synthesizer (DDS) and an improved Howland current source. The detailed simulation and test results and performance analysis are presented. The simulated maxim output impedance achieves 103.41Mohm under frequency from 1KHz to 100KHz and the current source provides broad -3dB bandwidth. In the practical experiment, the driving capability and dynamic performance are tested and analyzed. The actual results show that the VCCS performs stably and provides great output impedance and fine dynamic performance, which are suitable for EIT application.
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