Lower SNR after first day of use
smanne
Stanford, CA
Hi,
I'm using the electrode gel cap with the Cyton Board and while I got good SNR on the first day of use, it has dropped significantly on subsequent days and I can't seem to recover it. After the first day of use I brushed off all remaining gel but didn't soak in water. I soaked in non-distilled water AND brushed on all subsequent days. How likely is it that the problem is because of dried gel / mineral build up on electrodes (even though I've only been using them for a couple days)? Or is it more likely the problem is with low-signal REF/BIAS pins? Impedance seems to be fine according to checks in the GUI.
In the GUI Cyton Signal widget under "Live" the signal ranges from 0.2%-5% across channels. When I take the electrode cap off my head and keep streaming data, the signal shoots up to between 10-100%.
I also see much stronger and sensitive signal when I connect SRB2 to AGND on Cyton Board instead of to my REF electrode.
I would appreciate advice on why this happened, what I can do, and what tests I can carry out to evaluate the cause.
Comments
Hi SManne,
Since your cap is a new purchase, have you tried emailing Customer Support (contact at openbci.com) and mentioning your degradation issue? As you suggest, the issue might be related to your first day of use allowing the remaining gel to dry on the electrodes.
https://docs.openbci.com/AddOns/Headwear/ElectrodeCap/#electrode-cap-care-and-cleaning-guide
As recommended above, it is also a good idea to finish up the cleaning process with distilled or deionized water, as this apparently helps clean the sintered metal better, removing any potential ionic content of the water.
With the cap off your head, differential amplifiers tend to pickup large amounts of ambient room EMF noise. The electrodes, reference, and Bias (Ground) need to be connected to skin to get valid readings.
Do not connect SRB2 to AGND. The ground connection for the Cyton is labeled 'Bias'. AGND is for another application (powered 'active electrodes' such as the ThinkPulse.) In that case AGND is part of the power supply leads to the actives.
William