Multichannel Systems MPA8I Manual - Manual (Page 10)

8-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. If you are using NeuroNexus
probe adapters available from MCS, please refer to the following chapters for more information.
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.
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.
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.
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.
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.
Connect all unused recording channels to the GND input or to the reference electrode if the
reference and ground electrode of the amplifier are short circuited, to avoid noise pickup. As the
total amplifier gain generally lies in the range of 1000, even very small noise signals may generate
high noise signals.