Details of operation
38
The diagram on the left shows a multi-channel 1902 setup
where each channel has separate +ve and −ve electrodes. Each
channel produces an independent measurement of the potential
difference between the electrodes associated with that channel.
There is one common electrode providing the bias current
return path. This type of arrangement is appropriate for
measurement of parameters such as EMG where individual
muscle sites are being examined.
The diagram on the right shows the configuration with a buffer
circuit in operation. One electrode (the reference electrode) is
taken to the buffer input, and the output of the buffer is fed in
parallel to the −ve inputs of all the channels. In this
arrangement, each channel produces a measurement of the
potential difference between its own electrode and the shared
reference electrode. Each electrode sees the same input
capacitance load.
If you are using either the CED1902-10 Active Head Stage or
one of the CED1902-11 Electrode Boxes, note that the
Common inputs of all 1902s are connected together inside the
box and brought to a single input socket.
Independent
electrode pairs
Multi-channel with
independent electrode pairs
Multi-channel with
shared buffered reference
Electrodes with
shared reference
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