Search found 5 matches

by marohde
10 Feb 2011, 21:39
Forum: BCI Systems - Brain Signals
Topic: covariance matrix estimation
Replies: 2
Views: 3869

thanks, jhill, a few seconds of EEG should give you an R that is sane, if not especially robust. A few minutes should give you something fairly stable. it should be stable enough, in that case (ca. 200x1s) I didn't realize that CAR means loosing one channel but it makes sense - so maybe i just chuck...
by marohde
10 Feb 2011, 16:05
Forum: BCI Systems - Brain Signals
Topic: covariance matrix estimation
Replies: 2
Views: 3869

covariance matrix estimation

Hello everyone, I ran into problems implementing a CSP filter when I realized that none of the covariance matrices estimated from my data were positive definite (i.e., alwyas one negative eigenvalue). I estimate the covariance R in one trial by R = (X X')/ trace(X X') and then average across trials ...
by marohde
04 Feb 2011, 11:02
Forum: Known Issues
Topic: which hardware to use with BCI2000
Replies: 5
Views: 3053

I do not think you can principally measure impedance with any active electrodes system, regardless what manufacturer.
...there seem to be systems that indicate a good connection with an LED directly on the electrode.
by marohde
04 Feb 2011, 10:42
Forum: Known Issues
Topic: which hardware to use with BCI2000
Replies: 5
Views: 3053

thanks Gerv! I should have mentioned that we use their active electrodes - does this make a difference to what you said about the skin impedence measurement? We need to work with those as there is lots of noise in the set-up room. We called the company a number of times and send them pictures of the...
by marohde
03 Feb 2011, 15:40
Forum: Known Issues
Topic: which hardware to use with BCI2000
Replies: 5
Views: 3053

which hardware to use with BCI2000

hello, i wondered which EEG hardware works best with BCI2000. i have worked on 1 project so far with BCI2000 and a gtec system. I really liked the software and how well it works together with the hardware. however, there are some things i dislike about the gtec system - strange artifacts, flimsy cab...