What is the Max Voltage I can input into Ganglion Channel?


Doing some tests on the ganglion board to check its accuracy in capturing signals from a waveform generator.
Just want to make sure first that I'm not damaging the board.
Can I pass a signal that it roughly 1V peak to peak into the openBCI? 



  • This is an interesting question.

    @biomurph may know!
  • biomurphbiomurph Brooklyn, NY
    That's a good question. The Ganglion uses 3.0V for it's analog supply AVDD. 
    the 'AGND' is generated by a voltage follower that outputs 1.5V (AVDD/2).

    There are Instrumentation amplifiers on the front end that have a set gain of 51, so if you insert a signal into the Ganglion differential inputs that is 1V peak to peak in reference to AGND, then your signal will clip for sure.

    Might be best to use a Voltage divider to drop the signal amplitude down to a level that won't clip? A rough calc would be 30mV peak to peak as absolute maximum, but it's untested and there are other things to consider. 
  • biomurph:  The AFE chip's AGND is Ganglion's GNDA which is Ganglion's ground.  Maybe you were referring to D_G which a person could think of as analog ground for the patient.

    Xp0:  Yes, need to divide that signal down ... certainly to be able to see a decent waveform, and possibly to avoid damaging the AFE on the board.  See today's post at http://openbci.com/forum/index.php?p=/discussion/1396/internal-signal-test-for-ganglion#latest.

         -- Bruce P.

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