Study On Technology Of Human Bioelectricity Impendance Detection

Bioelectrical impedance is an important electric parameters in the human body biological signals, it contains abundant physiological and pathological information,and measures the bioelectrical impedance has important research and application value.Bio-impedance Measuring Technology is no damage and it has became very important research subject in the biomedical field and attracted a lot of attention among domestic and foreign scholars.It is of great importance about how to extract the modulus value and phase angle of bioelectrical impedance signal effectively in recent yeas.In this article,based on the bioelectricity impedance detection technology,used the four-electrode measuring method, designed a set of bioelectrical impedance detection circuit, measured bioelectrical impedance signal modulus and phase angle accurately by multi-frequency excitation and IQ demodulation.Firstly, comparative analysis the four kinds of commonly used principle of bioelectrical impedance detection.Secondly,identified four electrode method as the research object of this system.Using the four electrode method is not only make hardware circuit simply but also reduce the contact resistance between the electrodes and skin, and then reduce the measurement error.The article makes particular research on the four electrodemethod, deduces calculation formula about electrical impedance ’ s modulus and phase angle,and then designs a kind of bioelectricity impedance calculation method basis on the chip of AFE4300,came up with a bioelectrical impedance measurement circuit built on multi-frequency excitation.In the hardware circuit, the AFE4300 plays the role of measured impedance,the STM32 act a part of central controlled,then made more detailed analysis about the calibration circuit and power circuit,finally design development board circuit.Using the development board do some experiments which contains pure resistance and R-C network then comparing with theoretical model,we can draw the conclusion that actual test results and the theoretical calculation results are identical with each other;After that do test with human body, the measurement result is consistent with the relevant documents.The test results show that as to the chip of AFE4300 the bigger of excitation current source frequency the little of modulus value measurement error.On the contrary, the bigger excitation current source frequency increases the bigger of phase angle measurement error.