All electrodes railed (Daisy device)
In our company we conduct biosensing experiments, mainly with regards to workload estimation.
We use the EEG Daisy device and now a problem occured with it:
All signals are railed, although the impedance test is confirming low resistivity.
The device was applied to further experiments and studies before and worked error-free until now. I haven't changed any settings on the board and cannot retrace why all signals are suddenly not getting any voltage. Has anyone experienced similiar problems or has an idea what could have caused this misfunction? I would be happy about all hints, which could help finding a solution.
Comments
This is the result of using the 'Advanced Search' button at upper right:
https://www.google.com/search?as_q=railed&as_sitesearch=openbci.com
Another area to look at is the electrical environment, in terms of EMF Electromagnetic Fields. EEG is very sensitive to environmental noise.
https://www.google.com/search?as_q=emf&as_sitesearch=openbci.com
There are meters that can measure this, and also some phone apps, if your higher end model has a built in magnetometer.
https://www.amazon.com/s?k=emf+meter&ref=nb_sb_noss
William
Hi William,
thank you very much for your response. Of course, I have already completed the "getting derailed" steps and also tried different filters, hardware settings, and locations. In my opinion, it has nothing to do with the EMF or the hardware settings. All channels are 100 percent railed, and there is no effect when removing or re-applying the ear clips.
However, it wasn't always this flattened. A few weeks ago, the signals were derailed and seemed to measure something, although the visible signal reactions to clenching the teeth were very small. Now, I am barely able to recreate any signal except for 100 percent railed, and I really have not changed anything. Should I write to the Open BCI support, or do you have other ideas on what I could check further?
Best, Leonie.
Yes, send an email to (contact at openbci.com), which will open a ticket.
What electrodes / electrolyte are you using? Could the issue have something to do with poor skin contact?
I'm using dry electrodes. They definitely often have poor skin contact, but I already tested them on a person without any hair and had the same outcome at one point. Also, the impedance test is working quite well, as electrodes directly on the skin have lower impedance than electrodes on hairy areas or with less direct contact. And wouldn't the electrodes normally measure the EMF field around them anyway?
I'll contact support, thank you!
You are using the Ultracortex headset? Or some other type of cap?
The silver chloride, dry, combs used with Ultracortex, can wear out over time. Check the tips of the combs, they should be the same grey as the body of the comb. If you see any other color, it could be a sign that combs need replacing.
These combs are a plastic base, then plated with silver, then chlorided. If the chloride wears off, you might see the silver below or even the plastic base. Silver chloride electrodes only have excellent performance when the chloride layer is functional.
Sorry for my late response; I was on holiday. We use the UltraCortex with the standard silver chloride dry combs, but they do not seem to have changed in color. Additionally, the headset is only nearly two years old and has been used approximately 50 times. Can it wear out that quickly?
The only element on the headset that can 'wear' are the electrode tips. Did you get any useful info from your emails with customer service? I assume when you said "...but they do not seem to have changed in color", that you were examining the TIPS of the combs, correct? The rest of the comb experiences no wear thus will still be grey.
Did you see my suggestion on the EMF fields around your lab environment? I suggest using a phone app or dedicated meter to check. Avoid all: extension cords, power bricks, LED lighting, wireless gear, conduits in walls floors ceilings, avionics (you are at AirBus, correct), etc.