This is a screenshot taken whilst using the calibration output of the analogue openEEG board connected to channel 1 and with channel 2 grounded. The calibration signal is a square-wave at around 14 Hz.Note that the analogue boards have coupling capacitors forming high-pass filters cutting off at about 0.1 Hz. This means that it can take up to around 10 seconds for the output data to settle down and become meaningful after changing the input connections. So you need to be patient!
The grounded channel seems to float towards the negative saturation level and stay there with occasional "noise" spikes. I'm not sure yet why it does this but it seems consistent from board to board.
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