Hello Beirut. 😃
In the circuit schematic attached previously I didnt use the driven right leg circuit but now I am after my teacher recommended it. I have attached the schematic of the driven right leg circuit from Saksit's thesis. He used an INA 2128 instrumentation amplifer but in your case i think the AD620 u are using is fine.
The value of the EMG voltage before going into the instrumentation amplifer is around 1-5milivolts i think. Depending on the muscle type and strength of muscle contraction. Biceps and trapezius are stronger than forearm muscles.
If ur interested in constructing a driven right leg circuit with shielding:
Basically in Figure 1, I sliced off the red and white banana plugs and replaced them with crocodile clips (to clip onto the AgCl electrodes). When we remove the insulation of the left and right wires, we can see inside the left wire there is one smaller insulated wire (white or red insulation) and another shield wire with no insulation. Similarly we can see inside the right wire, there is one smaller insulated wire (white or red insulation) and another shield wire. Strip off the insulation of both the white and red smaller wires and solder these wires to crocodile clips to be connected to AgCl electrodes. The shield wire is left alone but make sure it does not accidentally touch the crocodile clips or other parts.
The green stereo audio jack of the RCA to stereo audio cable is connected to a female connector (I dont have a picture at the moment). This female connector has 3 parts which can be soldered (positive,negative and shield). The positive and negative parts of the female connector are wired to inputs 2 and 3 of the instrumentation amplifier. In Figure 2, at the 'phone plug' 1 and 3 represent the positive and negative parts of the female connector whereas 2 represents the shield. 1 and 3 are connected to the instrumentation amplifier, 3 is connected to the driven right leg part which begins with the inverting pin of U2A.
