Geodesic Sensor Net - Subject Wearing an HCGSN; Functional Block Diagram of a Typical GES

1: GSN Introduction
25
Geodesic Sensor Net Technical Manual S-MAN-200-GSNR-001 • January 31, 2007
Geodesic Sensor Net
During EEG recordings, subjects wear a GSN. It
consists of an array of sensors that tessellates the
surface of the head. Small sponges wetted with
electrolyte rest against the head. A subject wearing
a 128-channel child-sized HCGSN is shown in
Figure 1-3.
Amplifier
A 32-, 64-, or 128-channel Net is connected to an amplifier. The 256-channel Net
connects to two Net Amps 200 amplifiers or to one Net Amps 300 amplifier.
The amplifiers filter and measure the EEG signals that are picked up by the Net and
sample them at millisecond intervals.
The digitized samples are transferred to the data-acquisition computer in real time.
Acquisition Computer and Software
Packets of data containing digitized EEG samples are sent from the amplifiers to the
data-acquisition computer so that the acquisition software can collect them for display
and storage to disk.
A functional diagram is shown in Figure 1-4.
Figure 1-4. Functional block diagram of a typical GES
Figure 1-3. Subject wearing
an HCGSN
Mouse
Keyboard
Monitor
Amplifier
GSN sensor array
Data acquisition
computer running
EEG acquisition
software