Grey is virtual ground that sits at 2.5 V. A 50K potmeter is used as gain set resistor. The Arduino is connected to a laptop disconnected from mains. The analog signal is converted and sent through serial so it can be read on the laptop.

Next steps:

1. Change the circuit so the full range of the Arduino input can be used to read values. Currently it cannot since the AD620 is not rail-to-rail.

   According to the datasheet the output van go about 1.5 V close to either rail. So optimally the supply voltage would be +/- 4V.

   I will continue this research in a new page (ad620-rail-to-rail).

2. Experiment with the potmeter to see what gain is maximum. Also, what happens when the gain set resistor is zero?

   The gain formula is G = 1 + (49.4 k/RG), so at RG 0 the gain would be infinity. Except the datasheet lists 10000 at the gain range maximum.

3. Look up what the assumed voltage is that is readable on the human skin, to figure out what amplification is needed.

   Upper limit of normal amplitude is 2.5 - 3.0 mV (source)