Understanding the GUI in Action

nicholas10nicholas10 south carolina
edited August 2016 in OpenBCI_GUI
Hi friends,

Can anyone either explain what I am looking at when I stream data on the GUI, make a tutorial doing so, or point me towards something comparable?

I need to know what I am looking at when I get data from the GUI. Some of my question include but are not limited to:

1) What is the FFT Plot and how do I read it?
2) What are Uvms?
3) What do the blue and red colors on the head diagram represent as well as their varying intensities?

Thanks everyone,

Nicholas

Comments

  • wjcroftwjcroft Mount Shasta, CA
    edited June 2015
    Nicholas, hi. Checkout some of these,

    http://openbci.com/forum/index.php?p=/discussion/97/recommended-books

    (1) the FFT Fast Fourier Transform, is just a plot of amplitude in microvolts (uV), versus frequency in hertz. That is, how big is the frequency component at each part of the spectrum contained in the EEG. For example the alpha band is centered at 10 hz. Typically from 8 to 12 hz.

    (2) uV rms = microvolts root mean square, a measure of amplitude.

    (3) head diagram lights up with a rough estimate of the amplitude coming in at that numbered channel. Note the channel to 10-20 location assignments shown are not necessarily what you have used yourself.

    Also make use of the Search box at lower right of forum.


  • aleksabaleksab Norway
    Hi,

    Is there any documentation or tutorial that covers the options in the OpenBCI GUI?
    I mean, what 'BP filt' do? What does 'smooth 0.75' mean? What should be expected when putting a input type to 'MVDD'
    All these options are probably quite clear for someone educated in signal processing, but it's not that straight forward for a regular data science guy.
  • wjcroftwjcroft Mount Shasta, CA
    @aleksab, I merged your question into this existing thread.

    EEG programs use DSP digital signal processing algorithms. BP Filt is the the Bandpass Filter being applied, it is selectable between different ranges of hertz. Similarly the signal can have various 'smoothing' time averages applied. Some of these are covered in the tutorial doc,


    Regarding MVDD, you may be referring to the detailed SDK command codes, normally you don't need to work with these in most cases. Some of these settings are for applying test signals to the channels instead of the actual EEG scalp readings. Just let those default to power up settings.


  • harithasreeviharharithasreevihar
    Hi,

    What is the significance of the red and blue coloured sensors in openbci gui headplot?

  • wjcroftwjcroft Mount Shasta, CA
    "What do the blue and red colors on the head diagram represent as well as their varying intensities?"

    Some info on the head plot colors in this thread,

    http://openbci.com/forum/index.php?p=/discussion/comment/4158/#Comment_4158

    The head map contour algorithm is here,


    This is Chip @chipaudette 's code. I believe dark red is indicating RAILED or out of range. And the working electrodes are "averaged" into a kind of "heat map" using a color scale ranging in shades from blue to white to red. So depending on the overall range of your channel amplitudes, you could see any shade in that range.
  • wjcroftwjcroft Mount Shasta, CA
    @harithasreevihar, hi.

    I merged your question about the head plot colors into this existing thread.

  • togumetogume United States
    We are also wondering how to interpret the head plot, and did not find any further information on the docs site or forums. Reading the HeadPlot source file helped understand a bit more, but I still don't have a clear picture of how it works or how to interpret it.

    > Chip might comment here. I think it would be helpful to have a sentence on how the colors are interpreted on the docs site.

    Chip hasn't commented... yet.

    As far as I can tell, the brightness of the color (i.e. light red vs. bright red) indicated the intensity of the signal. However, what do the different colors mean? Are they associated with different scales of intensity or bands? What controls the dispersion of a color (i.e. light red can be spread wide and similarly with bright red)?

    I'm happy to write/PR something for the Docs on this once I understand it better.

    Here's a couple GIFs of this in action:
    image
    image
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