recording impedance values and voltage values at the same time

adaradar
edited August 2016 in OpenBCI_GUI
I want to record the voltage and impedance values at the same time is it possible?
or
Recording one channel's impedance value and other channels' voltage value?

Comments

  • wjcroftwjcroft Mount Shasta, CA
    edited June 2019
    Adar, hi.

    You should be able to modify the OpenBCI_GUI Processing code to write the impedance values to the CSV file. So you could record all the channels and their impedances if you want.

    https://github.com/OpenBCI/OpenBCI_Processing

    Note there is a slight degradation in performance of the ADS1299 when recording impedance. The input impedance of the amp drops from 1Gohm to 500 Mohms. Generally with a high impedance amp like this you don't need to be that concerned about skin impedance.

    http://wwe.eeginfo.com/research/ElectrodeImpedance.pdf
    http://openbci.com/forum/index.php?p=/discussion/165/measuring-electrode-impedance

    William

  • adaradar
    Hi again,

    I have downloaded processing and openbci_gui master. However in compiler whenever I press play button it gives `cannot find anything named surface`. What am I doing wrong?
  • wjcroftwjcroft Mount Shasta, CA
    Are you sure the libraries are setup as outlined in step 2?

    https://github.com/OpenBCI/OpenBCI_Processing

    If the external libraries are not in the right folders, you'll be missing various graphics objects.

  • adaradar
    Yes I think It was the version problem thanks a lot. Where can i find the totorials for source codes to change recording type of a channel.

  • wjcroftwjcroft Mount Shasta, CA
    I'm not aware of any "tutorials for source codes". You'll have to navigate yourself based on what comments are in the code. Look for how the impedances are calculated and displayed when the GUI checkboxes are turned on to display them on the screen.

    "to change recording type of a channel": I don't think you want to change the channel output, but rather output both the channel uV and the impedance in your new CSV format, for example output the channels in pairs, uV followed by impedance.
  • adaradar
    Yes actually i want to output both impedance and uV in csv format. 
  • biomurphbiomurph Brooklyn, NY
    @adar
    We don't currently record the impedance values in the saved file. That's a good idea!
  • adaradar
    I would like to record the impedance values the ones showing when you press ''P'' or ''N'' button on the gui.
  • wjcroftwjcroft Mount Shasta, CA
    Hi, @adar. See the previous answers here, you just need to modify the source code. See where the values are being placed in the screen buffer, and copy those to your print buffer.

  • adaradar
    I think that is exact solution that I need. However I could not find the exact place for those because I am not good at ''processing''. 
  • wjcroftwjcroft Mount Shasta, CA
    https://processing.org/tutorials/

  • kitokito
    We want to record electrode impedance with the open bci. We can already
    observe them on screen but the data is not recorded into the csv file.
    So my questions is: How do I get the impedance values into the csv file?
    Maybe there are specific lines in the source code which one could alter
    in order to record impedance values. I should mention that I am not an
    expert programmer but come from psychology. Any help much appreciated!
  • wjcroftwjcroft Mount Shasta, CA
    Hi, @kito. I merged your question into this existing thread. Please see some of the previous posts.

    Regards,

    William

  • biomurphbiomurph Brooklyn, NY
    Right now we don't have a way of recording the actual impedance values, however, you can 'run' the file and compute them as you replay.
    Alternatively, you could modify the GUI so that when it is actively measuring the impedance it would write the ohms value into the saved file.
    That would take some poking around to figure out how to pull off, but I'm sure it's doable.
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