Leadoff detection in bipolar EEG
Has anyone attempted to detect whether there is skin electrode contacts in a bipolar EEG setup? Since I'm not interested in measuring skin electrode impedance, I imagine this would look something like turning one of electrodes channels (+ or -) on to output a DC current and detecting this on the opposite polarity of all the channels, any channel that didn't detect it would not be making contact with the skin. The process could then be repeated by having one channel of the opposite polarity inject a current and checking the response of the remainder of the channels to make sure all are making contact. This would not need to be done continuously, just used to check connections periodically.
Has anyone done something like this before? I've found some resources on the OpenBCI forums checking skin electrode impedance, but nothing on how to do leadoff detection.
I also saw in the Cyton SDK documentation: (http://docs.openbci.com/OpenBCI Software/04-OpenBCI_Cyton_SDK) that there is support for leadoff commands, however the command seems only to send a test signal, and doesn't return any response. I assume that means that it's intended to be used in a manner somewhat similar to what I described above. Am I missing something?
Has anyone done something like this before? I've found some resources on the OpenBCI forums checking skin electrode impedance, but nothing on how to do leadoff detection.
I also saw in the Cyton SDK documentation: (http://docs.openbci.com/OpenBCI Software/04-OpenBCI_Cyton_SDK) that there is support for leadoff commands, however the command seems only to send a test signal, and doesn't return any response. I assume that means that it's intended to be used in a manner somewhat similar to what I described above. Am I missing something?
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which also notes that the board doesn't have the capability to output a DC current (at least likely not as a current source), but does have the ability to output an AC current at 7.8Hz, 31.2Hz and Fs/4.
I should note that since my use case doesn't require me to constantly check for connection or impedance, I can output a test signal in the same frequency range as an EEG (7.8 and 31.2 Hz frequencies).
Links to any other helpful threads (or even better, Git repositories) would be really appreciated!