CM out of range with more than 64 electrodes
Posted: Wed Sep 22, 2021 6:13 am
Hello,
For a study in our lab, we've created custom EEG caps with the standard 64-electrode 10-20 system layout plus additional electrodes to oversample a particular region of interest. However, we've found that when adding a third band of electrodes in the C slot on our Biosemi amplifier, the blue light starts blinking, indicating a CM out of range issue. I've tested it using the bucket test and it's not a bad electrode issue - it happens with multiple strips whenever we plug in a third one.
Looking into this, I thought it may be because of the electrodes we're using - we're using the pin type P32-1020-64A and B, which say they can be used in 64 channel head caps. It might also be that we don't have a true C strip - we're using an extra P32-1020-64A or B in the C slot on the AD box, and the same thing seems to happen when we plug our A strip into the B slot.
Can anyone shed some light on this issue, and (if it really is one of the potential issues outlined above) let me know what electrodes we'd need to order to correct this? Would we need to order just a P32-ABC-C strip or the P32-ABC-A and B as well?
Thanks very much!
For a study in our lab, we've created custom EEG caps with the standard 64-electrode 10-20 system layout plus additional electrodes to oversample a particular region of interest. However, we've found that when adding a third band of electrodes in the C slot on our Biosemi amplifier, the blue light starts blinking, indicating a CM out of range issue. I've tested it using the bucket test and it's not a bad electrode issue - it happens with multiple strips whenever we plug in a third one.
Looking into this, I thought it may be because of the electrodes we're using - we're using the pin type P32-1020-64A and B, which say they can be used in 64 channel head caps. It might also be that we don't have a true C strip - we're using an extra P32-1020-64A or B in the C slot on the AD box, and the same thing seems to happen when we plug our A strip into the B slot.
Can anyone shed some light on this issue, and (if it really is one of the potential issues outlined above) let me know what electrodes we'd need to order to correct this? Would we need to order just a P32-ABC-C strip or the P32-ABC-A and B as well?
Thanks very much!