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The GSR Amp
The GSR Amp provides a fully subject-isolated amplifier for measurement of skin
conductivity, in particular the change in skin conductivity in response to stress or
anxiety known as the galvanic skin response (GSR). This gives a general measure of
autonomic nervous system activity.
Measurement is displayed in SI conductance units (siemens), and absolute conductivity
of up to 100 µS (microsiemens) can be measured. Low, constant-voltage AC excitation
allows enhanced safety and the use of dry electrodes, with no special electrolytes
needed.
The rest of this chapter contains general information about the features, connections
and indications of the GSR Amp. It also looks at signal measurement for GSR. There is
more detailed information in the technical section.
The Front Panel
The front panel of the GSR Amp is simple, with a pair of input connectors for bipolar
electrodes and a small indicator light.
Figure 3–1
The front panel of
the GSR Amp
Status Indicator
Input sockets
The Status Indicator
The status indicator light is at the bottom left of the front panel. When an ADInstruments
program opens, the status indicator flashes briefly and then remains green, indicating
that the program has found the front-end, checked and selected it, and it is ready for
use. If it does not light up when the program is open, this indicates a problem with the
connection, the soft ware or the hardware.
The GSR Amp Input Sockets
Connections are made to the GSR Amp using two 4 mm shrouded banana sockets,
similar to sockets found on many digital multimeters, and are designed to be used with
shrouded male 4 mm plugs. A cable with these plugs is supplied with the GSR Amp.
These provide very low-voltage and low-current AC excitation to measure conductance.
As the GSR Amp uses AC excitation, polarity of the connections is not important. The
input connections are isolated internally by circuitry.
Owner's Guide
19
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