STUDY ON A DATA ACQUISITION SYSTEM FOR BIO-ELECTRICAL IMPEDANCE PARAMETERS MEASUREMENT
生物电阻抗特征参数测量数据采集系统的研究

In order to establish electrical impedance parameter tomography (EIPT),we have accomplished a rapid, precise acquisition system for bio-electrical impedance characteristic parameters measurement, and the sweeping frequency technique combined with mixing frequency technique, which can collect impedance information at different frequencies simultaneously, was employed. Also, a new demodulation method, named by us as “orthogonal sequential digital demodulation”, was chosen to improve system precision. The results showed that this system could select frequencies from 1.6kHz to 380kHz with a minimum frequency interval between any two frequencies less than 100Hz. It could collect impedance information at four different frequencies at the same time. The noise level of the signal source was about -80DB. And if 64 points per period was sampled, the signal to noise ratio could be improved by more then 5.6 times by demodulate algorithm.