A high accuracy broadband measurement system for time resolved complex bioimpedance measurements

Abstract

Bioimpedance measurements are useful tools in biomedical engineering and life science. Bioimpedance is the electrical impedance of living tissue and can be used in the analysis of various physiological parameters. Bioimpedance is commonly measured by injecting a small well known alternating current via surface electrodes into an object under test and measuring the resultant surface voltages. It is non-invasive, painless and has no known hazards. This work presents a field programmable gate array based high accuracy broadband bioimpedance measurement system for time resolved bioimpedance measurements. The system is able to measure magnitude and phase of complex impedances under test in a frequency range of about 10-500 kHz with excitation currents from 10 µA to 5 mA. The overall measurement uncertainties stay below 1% for the impedance magnitude and below 0.5° for the phase in most measurement ranges. Furthermore, the described system has a sample rate of up to 3840 impedance spectra per second. The performance of the bioimpedance measurement system is demonstrated with a resistor based system calibration and with measurements on biological samples.

Galvanically Decoupled Current Source Modules for Multi-Channel Bioimpedance Measurement Systems

“…To measure the velocity of the pulse wave within the arteries, at least two simultaneous bioimpedance measurements are necessary. Kaufmann et al [9] have shown that the usage of measurement frequencies of up to 390 kHz do almost not affect the morphology of the detected pulse wave and lead to similar results. The second intended application is the electrical impedance myography for detecting muscle contractions.…”

“…Afterwards, the remaining DC offset voltage is removed by a passive 1st-order high-pass filter with a cut-off frequency of f c = 200 Hz. A voltage-controlled current source (VCCS), which is based on the AD8130 (Analog Devices Inc., Norwood, MA, USA) [9,20], converts the voltage signal into an AC current. This current flows via the electrodes through the bioimpedance (Z Bio ) and a shunt resistor (R S = 69.8 Ω).…”

“…The filtered signal is afterwards buffered by an OPA2134 (from Texas Instruments). The circuit diagram of the subsequent voltage-controlled current source, based on the published circuits of Zhao et al [20] and Kaufmann et al [9], is shown in Figure 4. Its transfer function is given in Equation (1).…”

“…Additionally, in some applications, such as the electrical impedance tomography (EIT) imaging technique [7,8], multi-channel measurement devices are required. One further application is the detection of the arterial pulse wave at different positions of the human body to obtain information about its velocity and changes in pulse morphology [1,[9][10][11].…”

A Bioimpedance-Based Cardiovascular Measurement System

“…It is mostly used to estimate the composition of the human body. Further applications are monitoring of the respiration and the cardiac output as well as the detection of arterial pulse waves and muscle contractions [2,3,4,5,6]. For these purposes, several specific bioimpedance measurement systems have been developed and published in the past [3,5,7].…”