  Bioimpedance measurements are a non-invasive method to determine the
composition of organic tissue. For measuring the complex bioimpedance between
two electrodes, an alternating current with a constant amplitude is injected
into the tissue. The developed voltage drop is used to calculate the real and
imaginary part of the impedance under test. Measurements in the past indicated
that it could be possible that the beating of the heart has an effect on the
measured phase shift of the impedance under test. In this work a hardware
system is developed, capable of measuring changes of the bioimpedance phase
shift with high resolution. Two different measurement methods are used. The
first method is an analog circuit, which has been developed in a previous
project. The other method uses the integrated circuit AFE4300 (Texas
Instruments) [1]. The results of both methods are transmitted with a
microcontroller (Xmega256A3BU from Atmel Corp.) via the USB interface to a host
PC. On the host PC the visualization of the measurements and the control of the
embedded system is achieved with a developed LabView program. The work includes
the development of the hardware and software, as well as a comparison of the
accuracy of the two measurement methods. The result of a verification of the
systems is that both measurement methods have an effective resolution of about
0.3{\deg}.
