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Maximum number of channels for EEG

If you are using a single MP100/MP150 system, the maximum number of EEG amplifiers you can have is 16.  If more channels are required, it is possible to link acquisitions from more than one MP150.  However, the modular design of MP150 systems does not lend itself well to high density EEG recording, so BIOPAC does not strongly recommend this solution.
The Mobita System 32-channel wireless EEG system is a better solution for multi-channel applications.
Unipolar recording:
For unipolar recording you need as many amplifiers as you have sites to record from. For example, for 16 sites you would need 16 EEG amplifiers.  To perform this recording you would need 16 active electrodes, 1 reference (linked via 15 jumper cables to connect all amplifiers), and 1 ground.
Bipolar recording:
For bipolar recording the number of EEG amplifiers will be the same as the number of pairs of electrode sites for which you want to calculate the potential difference. Therefore, if you want to look at all possible pairs, you can calculate the combinations without repetition: n!/(r!(n-r)!) where n is the number of electrode sites and r is 2. For example, for a bipolar recording on 5 sites you would need 5!/(2!3!) = 10 EEG amplifiers. This assumes that you want to look at the potential difference between all possible combinations of electrode sites. This is the maximum number of EEG amplifiers that would be required.
Here is a reference for the number of EEG amplifiers required if you need to look at all electrode pair potential differences:
2 electrodes: 1 amplifier
3 electrodes: 3 amplifiers
4 electrodes: 6 amplifiers
5 electrodes: 10 amplifiers
6 electrodes: 15 amplifiers
Page last modified 30Dec2014

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