CompanyName: Dartmouth College
Abstract: Preliminary evaluation of a DSP-based 10MHz EIT system
Alex Hartov, Mariana Markova, Nirmal
Soni, Keith Paulsen
Thayer School of Engineering, Dartmouth College, Hanover, NH, 03766, USA
In this presentation we describe
a DSP-based system and its performance.
This latest design has been conceived around a per-electrode module complete
with a direct digital synthesis waveform generator, two A/D converters, a
field-programmable gate array and a SHARC DSP chip. The system was built for
maximum flexibility and also for improved acquisition speed. Channel modules
are grouped in sets of 32, which are supervised by a microcontroller. This
processor's task is to communicate with the system computer via a USB link.
Any number of channel is realizable with this architecture. We present results
regarding the accuracy of the waveform generator, as well as the measurements.
The DSP chip produces three quantities: voltage magnitude, current magnitude
and current phase, based on a continuous sampling of the output waveform. The
data acquisition is performed using a pair of 16-bits A/D converters across a
sensing resistor. Up to 100 frames per second can be acquired, each frame
consisting of a full data set from 32 electrodes. We present tests of
absolute accuracy compared to a bench-top impedance analyzer, as well as
measurements made on known impedances.