Multichannel Systems MPA32I Manual - Manual (Page 10)

32-Channel Miniature Preamplifier Manual
4
3 Setting Up and Connecting the MPA
3.1 General Setup Recommendations
In the following, you find general recommendations for the installation.
Important: It is important that the complete setup refers to a single common ground. The
reference input has always to be connected. It is recommended to use a reference electrode.
However, if you are not using a reference electrode, connect the reference input to ground
(GND). Otherwise, noise picked up by the reference input will be subtracted from the recording
signals. This will either lead to signal loss or to a very high noise level.
1. Ground the animal with a ground electrode of large surface area, for example, a liquid gel
adhesive electrode, that is connected to the ground of the setup, for example, a large metal
table or a Faraday cage, to avoid pickup of noise from the environment. The ground electrode
is best positioned in an electrically inactive region (not near muscle, nor heart), for example, at
the belly.
2. Connect the GND input or the metal case of the miniature preamplifier to the common
ground of the setup. (The GND input is internally connected to the metal case.)
3. Connect the reference electrode to the reference input of the miniature preamplifier.
Generally, a reference electrode is inserted into non-active tissue of the experimental model.
The reference electrode should be identical to the recording electrode so that both electrodes
see the same background noise. This is necessary because despite the grounding, the animal’s
body often has not exactly a potential of zero, due to the electrode impedance, for example.
The background noise is then subtracted from the recording signal, increasing the signal to
noise ratio. Please note that this may not work if the complete setup is not properly grounded.
4. (Optional) If two reference electrodes are used, connect the second electrode to the free
reference input. Otherwise, leave it free. It is generally not necessary to use a second reference
electrode. It can be used to enlarge the surface area of the reference, though.
5. Connect the recording electrodes to the recording channels of the miniature preamplifier.
You can either use single electrodes or multitrodes with the miniature preamplifier. MCS provides
adapters for standard probes.