USER MANUAL SAGA
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6
OPERATIONAL PRINCIPLES
SAGA Device
SAGA is an amplifier for electrophysiological measurements designed for optimal
signal quality. The SAGA amplifier is characterized by low input noise, high input
impedance and high common mode rejection. It is a true DC reference amplifier with
high resolution and uses active signal shielding to minimize electrode cable
capacitance and thereby minimizes cable movement artefacts and sensitivity to
mains interference (50/60 Hz).
The SAGA Device consists of a Data Recorder and Docking Station. The Data
Recorder’s main function is to capture and digitize electrophysiological signals
and/or sensor data. The Docking Station acts as the receiver of the data and relays
it to the data acquisition PC.
SAGA is an all-in-one solution for research applications that can be used as
stationary, portable and ambulatory measurement device.
The unipolar channels of SAGA are configured as an Average Reference amplifier
but can also be configured as a Common Reference amplifier. The device is also
equipped with two dual bipolar inputs for supplementary measurements and three
triple auxiliary inputs to connect sensors and a digital input.
Application software installed on the computer controls the SAGA measurement
functions.
Unipolar input channels
The input stage for measuring unipolar electrophysiological signals is configured as
an Average Reference amplifier. All signals are amplified against the average of all
connected unipolar inputs. Inputs that are not connected to an electrode are
automatically switched off. These channels will show a flat line signal.
Reference
In case the device is configured for Common Reference measurement, the unipolar
inputs are referenced against that electrode. In case the connection of that reference
input is lost, the device will continue on as an Average Reference amplifier.
An Average Reference is recommended to use, as it does not depend on a separate
reference electrode and location of a reference electrode. However, for some
applications the Common Reference configuration could be preferred. This decision
is left to the researcher/clinician.
Active signal shielding
All electrode cables are shielded with the electrode signal itself (active shielding).
The active shielding ensures that disturbances such as cable movement artefacts
and mains interference (50/60 Hz) are reduced to a minimum. No filters that can
cause a significant or frequency dependent behaviour within the analogue bandwidth
are present in the device. There are no notch filters built into the device.
