  Pulse wave analysis is an important method used to gather information about
the cardiovascular system. Instead of detecting the pulse wave via pressure
sensors, bioimpedance measurements can be performed to acquire minuscule
changes in the conductivity of the tissue, caused by the pulse wave. This work
presents a microcontroller-based bioimpedance measurement system, which has the
capability to acquire impedance measurements from up to four independent
channels simultaneously. By combining a problem-specific analog measurement
circuit with a 24 bits analog-to-digital converter, the system is capable of
acquiring 1000 impedances per second with a signal-to-noise ratio in a range
from 92 to 96 dB. For data storage and analysis, the digitized data are sent
via universal serial bus to a host PC. A graphical user interface filters and
plots the data of all channels in real-time. The performance of the system
regarding measuring constant impedances, as well as impedance changes over time
is demonstrated. Two different applications for pulse wave analysis via
multichannel bioimpedance measurements are presented. Additionally, first
measurement results from a human subject are shown to demonstrate the system's
applicability of analyzing the pulse wave morphology as well as the aortic
pulse wave velocity.
