freqamp
freqamp
About
- Username
- freqamp
- Location
- Australia
- Joined
- Visits
- 40
- Last Active
- Roles
- Member
- Location
- Australia
Comments
-
@celticharp said: Now that you are talking about DC noise, I must also say that I had to place Ganglion about 1 meter away from my laptop because the noise was clear in the GUI when not 1 meter away. Also, I noticed that if my feet were not o…
-
Yes, William mentioned a technique for troubleshooting that may help: "With clean, 'new' electrodes, you can use a glob of paste to connect a test channel, reference, and ground (bias) together. This should always produce a channel signal of very…
-
Hi celticharp, The constant positive/negative value you mention is the result of the galvanic effect that William mentioned. I also had this issue (discussed earlier in this thread, neg 3000-4000!), and was able to mostly rectify it with new electr…
-
https://brainflow.org It'll take a little coding, but the community is supportive
-
I don't think you can infer the impedance from the raw values. Judging by my recent experiments, the chemistry of the electrodes offset it a lot more than the connection quality. I've been reading papers trying to better understand it, but chemistry…
-
Hi Do you mean the raw output into the text files? If its the text file output, it seems depending on the chemistry of your electrodes, offsets can occur. My outputs above had offsets of about -3800, but that didn't affect the graph in the GUI (on…
-
Emotiv is also an option for more affordable (than research grade) hardware https://www.emotiv.com/product/epoc-flex-gel-sensor-kit/
-
Hi William, that is exactly the state of the gold cup electrodes and the ear clips. These aren't new electrodes, so I'm not sure how they were treated previously. I generally clean them with a paper towel or a soft toothbrush. Occasionally I use c…
-
So regarding my original question. Does anyone know what units output are to the txt file as raw output? Why are there negative values in the raw output, are they set from bestline from ref electrodes? @wjcroft
-
-
Good idea, Ive actually never checked baseline noise
-
"13.2.1.1 Equipment An MRI-compatible EEG recording system is needed. The electrodes and wires need to be non-magnetic, which is the case for Ag/AgCl or gold electrodes. It is possible to use whole-head caps or single electrodes. Using caps reduces…
-
Cool, this would be interesting. You would need MR safe hardware however, and I'm not sure that the OpenBCI boards are that. I suppose you could use very long leads...
-
Wow, sorry for duplicate posts above. Cant seem to delete them.
-
Regarding impedance, the values I stated earlier were checked live before recording. The accelerometer data is a funny one. The playback above does have some accelerometer data toward the beginning, then all goes zero.
-
-
Your GUI looks good. The poor text drawing on mine hasn't concerned me much, and figured it would get fixed with a future update. Unfortunately the forum won't let me post a text file.
-
@Billh I think you're onto something. I'll look into that. I know what my matlab values are, but I wouldn't know how to get that info from the GUI
-
This is GUI 5.0.8 on Mac. Text has been drawing that way for the last few updates. I don't normally use the accelerometer widget so I don't notice it much. When I do it seems to work. The board was laying flat on a table in this session, so could th…
-
OpenBCI GUI should be µV, matlab will be the same. But I don't know if the raw output from the GUI adjusts for the reference data. It must not as how could I get -7.23 for example. And if it was a straight conversion why do I get 0.5422 as the pea…
-
Thats a good price. Interesting stuff the gel. Looks like there are a number of salts in it like the ten20 paste. Ultrasound gel is much simpler. Thanks for clarifying.
-
According to the matlab forums the fft absolute amplitude should be in the same units as the input data. So I don't know what's going on. Perhaps it's my code, although, I followed the matlab fft example and it gives the same result...
-
Oh, I have read about those. Sounds a lot more convenient, and the paste can be difficult to remove from the hair. Would ultrasound gel be suitable? That is certainly easy enough to come by.
-
Anyone have any insight? @wjcroft @retiutut
-
Hi rainegu, I use Ten20 paste with good results with gold cup electrodes. Perhaps it could suit your cap. A little goes a long way... https://www.neurotherapy.com.au/product/ten20-conductive-paste-4oz-single/
-
Here is a sample of the same data, Raw, after the Matlab filters applied, FFT:
-
Hi Bill, No, that's part of my issue. I would assume its Volts. But if that's the case, the amplitude is 542000 uV. If its mV, the amplitude is 542 uV. We are expecting about 4 or 5 uV.