Hey,

The Uno has 6 analog inputs, labeled A0 through A5, each of which provide 10 bits of resolution (i.e. 1024 different values). The important part is that the ADC is 10 bits, which means 2^10, which is 1024 (0-1023).

The other important part is that Arduino UNO works at 5V.

So:

1. You need to make sure to set SHIELD-EKG-EMG to 5V mode of operation.

2. To calculate voltage per unit:

5 volts / 1024 units = 0.0049 volts (4.9 mV) per unit.

Other boards have other ADC resolution (for example, 12-bit or 16-bit). Other boards can work at 3.3V too. That is why I needed to know the board to be able to calculate it.

Best regards,

Lub/OLIMEX