EXT-02F User Manual
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version 4.2
page 10
3. Operation
The EXT-02F can be operated either using the inputs of the front panel (#16, Figure 1) or
using a headstage.
Very Important: You must not use inputs at the front panel and a headstage for one channel
simultaneously!! If the BNC connectors are used the headstage must be disconnected.
Also Important: If you encounter noise when operating the EXT-02F try to place the amplifier
as far away as possible from the power supply!! This will avoid magnetic coupling of the
power supply to the amplifier!
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, each channel of the EXT-02F is equipped with
differential input that minimizes noise pick-up. Differential means, that the signal for the
amplifier is the difference between the positive (+) (P
EL
at the headstage) and negative (-)
(REF. at the headstage) input of the amplifier. This results in canceling of all signals which
both electrodes record, e.g. noise.
For differential measurements, both inputs are connected to electrodes using cables with
grounded enclosure or electrode holders. + (P
EL
) is connected to the measuring electrode and –
(REF.) to the reference electrode. If no headstage is used, the switches #14, Figure 1 have to
be in the same position, i.e. both set to ON. The experimental chamber is grounded by an Ag-
AgCl pellet (or an AGAR bridge) connected to GND of the headstage (see Figure 4).
Important: If differential measurement is not required (single-ended measurement
configuration), the REF input must be connected to ground (GND at the headstage, see Figure
4) or the –IN switch (#14, Figure 1) must be set to OFF.
If no headstage is used, the switch corresponding to the unused INPUT (+ or -) has to be set to
OFF (see #14, Figure 1).
The amplifier is in an undefined state, if the REF is left open, and can go into saturation
making reliable measurements impossible.
