Analog demodulation mode type frequency-mixing bio-impedance testing system

Abstract

A frequency-mixed biologic resistance measuring system working in analog demodulation mode is composed of an upper position unit for setting up the amplitude and frequency of sine current stimulating signals and transmits them to lower position unit which uses the digital signal processor as its main controller. A signal generating unit can generate the frequency-mixed stimulating voltage signals and reference signal. Said voltage signals are converted to current ones by control current source and connected via analog switch and electrode drive to stimulating electrode. The measuring electrode is connected via electrode buffer to switch array. The voltage signals from measuring electrode are amplified by differential amplifier and filtered by demodulation filter to obtain the DC signals relative to biologic resistance. Its advantage is no error caused by phase shift.

Description

technical field [0001] The invention belongs to the field of biological information detection, and in particular relates to a system for measuring biological electrical impedance in an analog demodulation mode under a frequency mixing excitation mode. Background technique [0002] Bioelectrical impedance measurement technology is a non-destructive detection technology that uses the electrical properties (impedance, admittance, dielectric constant, etc.) and changes of biological tissues and organs to extract biomedical information related to human physiological and pathological conditions. In the early days, the single-frequency excitation mode was mainly used. According to the frequency impedance characteristics of biological tissues, the cell membrane capacitance is basically stable in the β dispersion range. As the frequency increases, the capacitive reactance of the membrane capacitance decreases, and the applied current bypasses the cell mem...

AI Technical Summary

Problems solved by technology

In order to obtain intracellular information, it is necessary to use the characteristics of high-frequency current flowing through the intracellular and extracellular fluids, so the electrical impedance information of biological tissues measured at a single excitation frequency cannot fully reflect the status of organisms

At present, the multi-frequency excitation mode is mostly used, that is, signals of different frequencies are used for excitation, and the biological impedance of this frequency is measured, but the human body is dynamic, and this method cannot analyze the information of the same life activity under different excitation frequencies, and different When the measurement frequency point is switched, the establishment time of the bioelectrical impedance information measurement at the new frequency is longer, so the data provided by this time-sharing measurement method cannot accurately reflect the electrical impedance information of the organism at a certain moment

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