Bioelectrical Impedance Measuring Platform Based On Virtual Instrument

Bioelectrical Impedance Measuring Technology (BIMT) is a new technologydeveloped in recent years. Due to the feature of non-invasive, low-cost, safety,nontoxic and harmless, it has extensive application perspective. The special attentionis paid to the BIMT technique by the researchers in biomedical engineering andclinical medicine areas.Not only for fundamental research but also for clinical application, it is notsatisfied that only the magnitude or real part of the impedance is measured at singlefrequency. A new measurement technology should be studied with multi-frequencymeasurement and extraction the complex impedance information. In order to collectthe bioelectrical impedance information in different frequencies at the same time, thebioelectrical impedance measuring platform based on virtual instrument is designed.This platform can set the frequency, amplitude and phase of the extraction signal, andit can realize the self-adapting amplification and anti-aliasing filtering of the signal.Using virtual instrument technology, the impedance information analysis platform isconstructed on PC and its open structure made the research and realization of differentimpedance extraction method easier. To solve the problem of phase shifting in thepractice measuring, a virtual reference point method is presented. According to theresearch on the information extraction method in the mixing frequency excitationmode, orthogonal digital demodulation method and Fourier transfer method based onthe virtual reference point are designed, moreover, these two methods are realized andproved on the platform.Resistor, R-C network and human body respectively are measured on theplatform. The experimental tests compared with the Agilent4294A analyzer show thatthe method is feasible.