Combing 10-20 and ABCD electrodes for recording 128 electrodes

[BolgerDee76]

Hello,

This question is somewhat related to a question posed on the forum earlier today.
Our lab wants to record EEG with 128 electrodes. We already have the C and D electrode sets (P32-ABC-C and P32-ABC-D) and I was told that it would be fine to use two electrode sets corresponding to the 10-20 system for the A and B sets (i.e. P32-1020-32A and P32-1020-32B) .
However, when I plug all four electrode sets into the AD box, the CM is indicated as being out of range (flashing blue light).

All electrode sets appear to function so I am wondering if, for some reason, the problem is due to the fact that we cannot combine electrodes from the 10-20 and ABCD systems or if there is another possible reason for this problem?

Many thanks in advance for any insights.
Deirdre

[Coen]

You can only use the channels that are actually installed in the AD-box.

To check: inspect the offsets with no electrodes connected to the AD-box, installed channels are maximally negative, uninstalled channels are zero.

You will probably find that only channels 1-64 are installed. In order to use more channels, you will have to purchase additional amplifier/ADC modules.

The electrode sets themselves only differ with respect to the labeling (and sometimes extra integrated CMS/DRL for an A set)

Best regards, Coen (BioSemi)

[BolgerDee76]

Thank you very much for taking the time to reply and so quickly.
This is very clear.
I kind of feared that would be the case; the budget for extra electrodes sets is not the same as that for the extra amplifiers.
I think we will contacting you soon for a purchase.

Kind regards,
Deirdre