Měření bioimpedance v širokém pásmu frekvencí

Abstract

This thesis is dedicated to the design of module for measuring bioimpedance spectroscopy. The aim was to design a device, which is capable of measuring bioelectrical impedance in a wide range of frequencies, specifically from 1 kHz to 1 MHz. In order to measure bioelectrical impedance Magnitude Ratio and Phase Difference Detection method was used, which is based on comparison of two signals – one sensed on reference resistor R of known value and the second on unknown impedance load Zx. The tetrapolar connection of electrodes was used - the connection of four electrodes, which eliminates influence of additional parasitive electrode impedance. The device is connected to evaluation board with microcontroller HCS08, which provides programming frequency of signal generator and measurement of data by AD converter. The measurement cycle is controlled by a personal computer using WPF application. The device measures impedance in range from 100 Ω to 2 kΩ, that covers an impedance of a human body. The calibration of device was performed, but only for resistivity measurements.