No SSVEPs using Dry Passive and Active electrodes
lucasbaldezzari
Uruguay
Hello everyone, how are you?
I'm looking for some suggestions about how I can improve the signal quality coming from the Dry passive and active electrodes in order to get SSVEPs.
When I use the electrode cap kit with the gel cap I have SSVEPs, in some cases the SSVEPs are very nice, and in other cases the signals are just nice, but are enough to recognize them. But when I use the Cyton or Ganglion with the Passive or Active electrodes, the signals are very noisy.
I was reading at the forum that the gel electrodes perform better than the dry electrodes, but, does this mean that I can not use dry electrodes to get SSVEPs? I was trying some strategies, like averaging some trials before looking for the SSVEPs in the EEG signal, but unfortunately with bad results.
So any kind of help will be welcame.
Regards from Uruguay.
Lucas
Comments
Lucas, hi.
It appears you have already proved your question / point. ;-)
A kind of 'half-way' solution between gel or paste electrodes, and dry electrodes -- is using a small absorbent 'pad' (wet with water or saline solution), between the 'dry' electrode and the skin. This will give the advantage of the increased signal amplitude / quality, without any messy cleanup required.
And the new gel-free cap in the shop uses the same idea. Inside each sponge / electrode assembly is a silver chloride electrode termination.
https://shop.openbci.com/collections/frontpage/products/gelfree-bci-cap-kit?variant=40785117249694
This page covers some other saline headset types, both commercial and DIY:
https://sites.google.com/site/biofeedbackpages/velcro-saline-sensors/commercial-saline-sensors?authuser=0
William
Hello @wjcroft, how are you? Like always, thank you so much for your fast reply.
I will try what you said. I remember working with an absorbent pad and your idea is great, I didn't realize. I will try to get some sponges like you shared in your post, or perhaps make some and I will share the results with you and the forum.
Regards!
Lucas