【摘要】 本文设计了一种基于DSP的主从式人体电阻抗断层成像系统,频率范围从10kHz到1MHz。系统采用PC机作为主控机,DSP控制激励信号、电极选通、数据采集并与上位机通讯。采用直接数字合成(DDS)技术构建正弦波发生器,加入反馈环节,有效提高了压控电流源的线性度和稳定性;采用低导通电阻的多路开关;基于测量有效值和相位差实现相敏解调,获取人体复阻抗信息;采用16位AD转换器,提高测量信号的分辨率。试验测试与成像结果表明,该系统能够在较宽的频带范围保证测量精度和图像分辨率。更多还原

【Abstract】 A master-slave Electrical Impedance Tomography system for body complex impedance based on DSP is designed in this paper. The frequency covers the range from 10kHz to 1MHz. A PC is used as a master computer, which performs the image reconstruction and display on time, while DSP carries out the tasks,such as electrode selection, data acquisition and data communication with the master. Some methods were taken to improve the measurement accuracy. Based on DDS technique and with a feedback unit, the voltage-controlled current source has the perfect linearity and stability. The multiplexers with very low on-resistance are used; To achieve the body complex impedance information, a novel phase sensitive demodulation circuit is adopted through measuring the RMS and phase of the signal. A 16 bit AD converter is used to improve the resolution. Experimental results show that this system improved the data acquisition precision and the image resolution in a wider frequency range.更多还原