Measuring electrode impedance w/ GUI

edited August 2016 in OpenBCI_GUI
What's the correct way to measure electrode impedance w/ GUI?
Do I need to have Data Collection ON or OFF?
Do I need BOTH BIAS and SRB connected?

Sometimes, when turning impedance measuring ON I can see a BIG signal increase (looks like a square wave) on SOME electrodes (e.g., 1), but not on others (e.g., 8). Is this normal?

Thx,
David

Comments

  • biomurphbiomurph Brooklyn, NY
    You need to have the SRB connected for sure, and the data needs to be streaming in order to detect the impedance
  • wjcroftwjcroft Mount Shasta, CA
    There is a bit written about the firmware command bytes here,

    http://docs.openbci.com/software/01-OpenBCI_SDK#openbci-sdk-command-set-leadoff-impedance-commands

    Turning on the ADS1299 impedance signal injection does degrade the amplifier input impedance from the normal value of 1 gigohm to 500 megohms. So it should be disabled when not actively measuring the impedance. If you are using the default firmware setup of SRB2 and the IN*N channels, then you should turn on/off the 'N' column impedance checkbox(s).

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