A-M Systems
131 Business Park Loop, P.O. Box 850 Carlsborg, Wa 98324
Telophone: 800-426-1306 * 360-683-8300 * FAX: 360-683-3525
E-mail: [email protected] * Website: http://www.a-msystems.com
4
Operating Instructions
Typical Set-Up Procedure
The Head Stage Probe is used to connect the extracellular electrodes to the amplifier. The
4 inch Connector Cables can be used to connect the Probe inputs to electrodes which
have standard gold male pin connectors. The
GND
connector on the front panel of the
amplifier should be used as the system ground in the particular recording medium (e.g.
bath or animal ground).
Note: Either the Head Stage
PROBE GND
or the
GND
on the front
panel must be connected to provide a return current path. If neither ground is
connected the Head Stage Amplifier will saturate and no signal will be measured.
Care should be taken to keep the power cables from all instruments as far away as
possible from the recording set-up.
Proper grounding and shielding techniques
should be used to insure a minimum of interference.
Recording
The
MODE
switch should be placed in the
REC
position. The
LOW CUT-OFF
Filter,
HIGH CUT-
OFF
Filter, and
NOTCH
Filter should be set according to the frequency content of the signal
to be recorded. The
GAIN
Switch should be set so that the signal at the
OUTPUT
connector
is less than ±10 V, otherwise higher and/or lower portions of the signal may appear cut-off
or flattened.
Stimulating
The
MODE
switch should be placed in the
STIM
position. Stimulation current (I) is
monitored by measuring the voltage (V) across an internal, fixed resistor (R = 1 k
) in
series with the electrodes. Since I=V/R and R is known, the voltage is a measure of the
stimulus current. The internal resistor is in series with the indifferent lead (
PROBE-
) so that
excessive voltages do not appear at the Probe Amplifier inputs. Therefore, to insure that
the current in the indifferent lead is equal to and opposite of that in the active lead, only
isolated stimulus sources should be used. An added benefit of isolated stimulus sources
is that they produce less stimulus artifact than ground referenced sources. The Positive
Conductor of the Stimulus connector (Pin A; upper left; red wire in the stimulation cable) is
connected through the Probe to the active electrode lead, while the Negative Conductor
(Pin B; upper right; blue wire in the stimulation cable) is connected to the indifferent
electrode lead. The shield of the stimulation cable is not internally grounded in the
amplifier and needs to be grounded at the connection to the stimulator. When an isolated
stimulator is used the
PROBE-
connector must be grounded to function properly.
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