中文摘要：

针对电阻抗断层成像技术对电阻抗信号采集精度的要求，建立了一个高精度的数据采集系统。该系统主要由一个基于数字合成技术的可编程激励电流源和一个基于正交序列数字解调法的边界电压采集模块共同构成。系统可以在1～190kHz之间编程选择激励电流的频率，并可在0～1．25mA之间编程设定输出幅度以满足人体测量的安全要求。系统可同时检测出边界电压的幅值和相位信息。工作频率范周内，系统的共模抑制比高于75dB，相对测量精度优于o．02％。

英文摘要：

To provide electrical impedance information with the high accuracy for the electrical impedance tomography, a high precision data acquisition system is developed. The system is mainly composed of a programmable driving current source based on digital synthesis technique and a boundary voltage measurement module based on orthogonal sequential digital demodulation method. The frequency of the driving current can be programmed among 1-190 kHz. The amplitude of the output current can be programmed among 0-1.25 mA to meet the safety requirement on the human body. When data acquiring, both the amplitude and the phase shift of the boundary voltages can be simdtaneously extracted. In the bandwidth, the common mode rejection ratio（CMRR） of the system is more than 75 dB, and the relative measurement precision is higher than 0.02 %. Comparison results show that the system is superior to some other systems in main aspects.