Wilson A J, Milnes P, Waterworth A R, Smallwood R H, Brown B H
Department of Medical Physics and Clinical Engineering, Royal Hallamshire Hospital, Sheffield, UK.
Physiol Meas. 2001 Feb;22(1):49-54. doi: 10.1088/0967-3334/22/1/307.
This paper describes the Sheffield Mk3.5 EIT/EIS system which measures both the real and imaginary part of impedance at 30 frequencies between 2 kHz and 1.6 MHz. The system uses eight electrodes with an adjacent drive/receive electrode data acquisition protocol. The system is modular, containing eight identical data acquisition boards, which contain DSPs to generate the drive frequencies and to perform the FFT used for demodulation. The current drive is in three sequentially applied packets, where each packet contains ten summed sine waves. The data acquisition system is interfaced to a host PC through an optically isolated high speed serial link (RS485) running at 2 Mbaud (2 Mbits s(-1)). Measurements on a saline filled tank show that the average signal to noise performance of the system is 40 dB measured across all frequencies and that this figure is independent of frequency of measurement. These results suggest that the current system is 10 dB better in absolute terms than the previous Sheffield (Mk3a) system.
本文介绍了谢菲尔德Mk3.5电阻抗断层成像/电阻抗光谱（EIT/EIS）系统，该系统可在2 kHz至1.6 MHz之间的30个频率下测量阻抗的实部和虚部。该系统采用八个电极，采用相邻驱动/接收电极数据采集协议。该系统是模块化的，包含八个相同的数据采集板，这些数据采集板包含数字信号处理器（DSP），用于生成驱动频率并执行用于解调的快速傅里叶变换（FFT）。电流驱动以三个顺序施加的数据包形式进行，每个数据包包含十个叠加的正弦波。数据采集系统通过运行速度为2兆波特（2 Mbits s(-1)）的光隔离高速串行链路（RS485）与主机PC相连。在充满盐水的水箱上进行的测量表明，该系统在所有频率上测得的平均信噪比性能为40 dB，并且该数值与测量频率无关。这些结果表明，当前系统在绝对性能上比之前的谢菲尔德（Mk3a）系统高出10 dB。
