a possible DRL problem
Posted: Thu Jun 11, 2009 9:09 pm
Dear Coen
I would like to consult about a possible problem with CMS-DRL "pin-type" electrodes that may not be explained by a gel bridge.
When mounting the 64 channel cap we get in most cases very high noise levels (actually a no-signal) in one or two electrodes adjacent to the DRL (in P2 and/or PO4), while electrode offset is in normal range. The problem is not related to these 2 channels but rather to the specific location, because switching their location with other channels dislocates the noise to the new channel positioned next to the DRL.
We are well aware of a possible gel bridge between the DRL/CMS and the near-by data electrodes (I also read your correspondence with Juan at viewtopic.php?t=392), but we tried several times to carefully administer low quantities of gel under these channels, as we also do for all the other channels. In addition, when we switch the CMS and the DRL between them, the problem passes to the other side (P1 and PO3). Therefore I thought more about a DRL problem rather than a gel bridge in a specific place.
Lastly, when we use the flat DRL-CMS, data are more noisy overall. My second question would be whether this happens because we located the DRL and CMS far from each other (e.g. near the 2 ears)?
Many thanks!
bo
I would like to consult about a possible problem with CMS-DRL "pin-type" electrodes that may not be explained by a gel bridge.
When mounting the 64 channel cap we get in most cases very high noise levels (actually a no-signal) in one or two electrodes adjacent to the DRL (in P2 and/or PO4), while electrode offset is in normal range. The problem is not related to these 2 channels but rather to the specific location, because switching their location with other channels dislocates the noise to the new channel positioned next to the DRL.
We are well aware of a possible gel bridge between the DRL/CMS and the near-by data electrodes (I also read your correspondence with Juan at viewtopic.php?t=392), but we tried several times to carefully administer low quantities of gel under these channels, as we also do for all the other channels. In addition, when we switch the CMS and the DRL between them, the problem passes to the other side (P1 and PO3). Therefore I thought more about a DRL problem rather than a gel bridge in a specific place.
Lastly, when we use the flat DRL-CMS, data are more noisy overall. My second question would be whether this happens because we located the DRL and CMS far from each other (e.g. near the 2 ears)?
Many thanks!
bo