ELC-01MX User Manual
version 2.6
page 22
7 Introduction into Experiments
The ELC-01MX is capable to perform several types of experiments that are briefly introduced
in the following. It is assumed that the capacity of the electrode is compensated, the offset of
the electrode is cancelled and, for intracellular recordings in BRIDGE mode, electrode artifact
is eliminated using the bridge balance circuit.
7.1 Recordings with the Differential Headstage (optional)
Extracellular measurements are mostly done in slices or in vivo, in noisy environments, where
distortions of the recorded 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
ELC-01MX can be 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 common
mode signals (i.e. 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 10).
Important: For reliable measurements the experimental chamber or animal, respectively, must
be grounded.
Also Very Important: When operating in VC mode, the reference electrode must not have a
resistance of more than 1 k
Ω
!! CC mode is not affected.
If differential measurement is not required (single-ended measurement configuration, see
Figure 10), 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 (for more details see Lalley et al., 1999).
