Direct signal injection from function generator for EEG BCI calibration

Question

I have seen several topics related to calibration of BCI and most of them use a "head phantom". But I want to know, is it possible to test the openBCI hardware directly using function generator? And I am curious about the connection, like where I should connect the VCC and GND of function generator to OpenBCI (like Cython)

If I want to build a signal generator for EEG calibration, what should I consider? such as impedance, etc

Thank you

Answer 1

How about something like this

^{simulate this circuit – Schematic created using CircuitLab}