EXT-10C User Manual
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3.5.
Headstage
Figure 3: electrode holder (optional) and headstage of the EXT-10C
Headstage Elements
1
BNC connector for the electrode holder
2
REF: reference electrode connector
3
GND: ground connector
4
holding bar
On request, P
EL
can be implemented using 1 mm or 2 mm banana jacks or using SMC
SUBCLIC connectors.
3.6.
Operation
Extracellular measurements are mostly done in slices or
in vivo
, where distortions of the
signal caused by other instruments and the animal itself are very common. Additionally,
extracellular signals are very small and have to be amplified enormously. The drawback is
that noise is amplified as well. Therefore, the headstage of the EXT-10C is equipped with a
differential input that minimizes noise pick-up. Differential means, that the signal for the
amplifier is the difference between the positive (+) (P
EL
) and negative (-) (REF.) input of the
headstage. This results in canceling of all signals which both electrodes record, e.g. noise.
For differential measurements, both inputs of the headstage (REF. and P
EL
) are connected to
microelectrodes using cables with grounded enclosure or electrode holders. P
EL
is connected
to the measuring electrode and REF. to the reference electrode. The experimental chamber is
grounded by an Ag-AgCl pellet (or an AGAR bridge) connected to GND of the headstage
(see Figure 4).
If differential measurement is not required (single-ended measurement configuration, see
Figure 4), the REF input must be connected to ground (GND). The amplifier is in an
undefined state, if the REF is left open, and can go into saturation making reliable
measurements impossible.
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version 1.5
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