Very limited data over Data Stream
Hello,
I got my Ultracortex Mark 4 pre assembled last week and set it up over the weekend. I now wanted to try it out using the OpenBCI Gui. This also works, to a degree. A link is established and data is clearly sent (Accelerometer data is very responsive). But the "Head Plot" stays almost completely red, with very little movement and the actual EEG data transferred seems to be lacking in quality (of to be honest flat out none existent exist.
I used different positions for the electrodes (not the yellow markings in the picture below, there the picture on your sales site seems to be faulty), but I assume that shouldn't impact the Head Plot in this way. I wear both ear clips and off course the headset with it being adjusted to my head size and all electrodes having contact to my skull. There are also no major electronic interferences, aside from usual office noise.
What am I doing wrong with the setup? Is there any software error?
I installed the FTDI driver use the newest Version of the Open BCI Gui on a up to date PC.
Pictures that show setup and error:
Comments
Georg, hi.
See this thread on suggestions for getting 'unrailed'.
https://openbci.com/forum/index.php?p=/discussion/1481/how-to-become-de-railed
HOWEVER, because virtually ALL of your channels are railing, this points to something they all share in common: the reference electrode on the ear lobe. So it is likely that something is amiss with that ear clip or its contact with the skin. As one test you could try moistening the ear lobe with some water before attaching the clip, but normally that is not needed. You can also swap clips between Bias and Reference.
William
Hi William, thanks for the help. I used some water and changed the ear lobes and that did definitely improve the signal quality. I can now definitely detect when i clench my jaw muscles. But closing my eyes does not change the alpha waves in a meaningful way. So great improvement so far but probably still a little way to go.
I have 2 more potential suspects where your recommendations may help. I have three types of electrodes here, that as far as I know are for different hair lengths/densities. I have ones with no prongs (I suspect they are for bare skin (forehead... which in my case extends upward quiet a bit), lets call them "A". Short spikey pronged ones (feel pretty uncomfortable, therefore Im currently not using them) lets call them "B". and lastly Ones with longer blunt prongs which is suspect are for longer hair (that I dont have) but still use for most electrodes, since they are the most comfortable ones, lets call them "C". There are also various other electrodes in the package, but they have no screw hole in the middle but nob instead. I guess they are for the wet electrodes, so not currently in use. Is there a guide for which of those electrodes to use when or can you give me recommendations?
Another thing that may help could be a short (1 meter) usb extension for the usb dongle, so I can really move it away from the PC and everything that could cause noise. Is this a good idea? I dont know if the extension would cause more issues or help. Again I dont suspect major noise to be present at the moment, but every bit of improvement I can get is appreciated (as is your help ).
Your FFT above shows lots of jagged noise-like appearance. This was likely a jaw clench? Your Time Series plot max scale is at 200uV, yet most valid EEG is below 100uV. So changing scale can help. You can't say anything about your true EEG from the screenshot since it contains noise spikes at -3.5 etc. Best place to check alpha eyes closed is in occipital lobe or parietal. Might be easier to have a friend look while you close your eyes.
Yes you show the 3 types commonly used with the headset.
It appears you have a combination kit which includes the velcro headband. Electrodes shown with the rear posts mate with the female ECG connectors provided.
https://shop.openbci.com/products/openbci-eeg-headband-kit
Yes, a common technique is to put the dongle on an extension, then drape over something on your desk like the top of a monitor. So it is free in the air but off the table top and computer.
Hi, thanks for the feedback.
My wife checked my the graph while I closed my eyes, but I tried seeing it myself very hard as well She assured my there was no change, you can argue with her about that... if you are brave enough, I sure wont
But jokes aside, as for the 3 types of electrode/measuring tips, any recommendation which to use for which hair type or are there any generaly better in regards to signal quality?
Electrodes with rear posts are then out for this case (we wont use the headband).
Perfect, so my fixes for now would be to change the scale to 100uV and buy an extension for the dongle and use lube on the ear connectors. Thats great.
Are there any more recommendations to improve signal quality? Or asked the other way around, in your experience/opinion whats the most common reason for low signal quality?
Since the Cyton to dongle connection seems to be part of the problem would it be advisable to save the data directly to an SD card in the Cyton?
Remember that eyes closed alpha is most pronounced in the occipital and parietal electrodes. If she was watching ALL 16 channels for changes, that might have slipped by. You need to watch those particular channel colors in the FFT graph around 10 Hz.
Finally, eyes closed increases alpha, but you get the maximum increase when you are relaxed and not actively worrying or planning your next actions. In other words a quiet / meditative state, just relaxing.
The 5mm combs work well on areas with hair, the 'cone' electrodes on bare skin. But those combs are usable on skin areas as well since the tips are blunt. The 'spikey' / pointy electrodes can work on short hair. But are painful on bare skin.
You could try the headband and ear clips with just one occipital channel (O1 or O2) with your wife as the subject.
I'm not sure what you are referring to as 'lube'. Normally NO wetness is needed on the ear clips. I only recommended that because you were seeing such universally bad / railing on most channels. Signaling that you have some issue with the SRB2 reference clip. Only use a little bit of water if you want to wet. Other substances may damage the sliver chloride plating on the clip. Water also requires no cleanup, whereas other things leave gunk on the electrode.
If you are continuing to have low quality, then email customer service at (contact at openbci.com) for advice.
No that should not be necessary.