I am building a heart rate monitor using the INA122. In these cases, my electrodes are attached directly to the skin, meaning that above 1mA of output current, I could feel pain from electrical current.
I know that the INA 122 has an input bias of 10 nA for its inputs, but I would like to calculate the current running into its reference terminal. The reference terminal is a 3rd electrode also attached to the skin that aids in noise reduction -- if you've never done biomedical workbefore, think of it as a floating offset voltage. What is the best way for me to calculate, on paper, the current flowing into the reference terminal? Specifically, the current flowing into my reference electrode? The reference terminal appears as "ground" for the single supply case being considered here.
One of my problems in just doing this by hand is that the positive supply voltage isnt connected to the rest of the circuit? Or rather, it's connected only by a 0.1 uF capacitor. I know this must be a noob question, but how can I calculate the current flowing from the battery to the reference terminal/electrode, since this is likely the bulk of the current entering? Is this even safe to do in the INA's single supply case, where reference and the negative terminal of the battery are shared?