If Ra = 1M ohm
Rb = 111K ohm ( I used this resistor to calibrate the Vout. Because all components are slightly different, use a meter to get Vout right)
Vin = Whatever input you are measuring
Vout = Vin * Rb/(Ra+Rb)
The decoder in this circuit is used to represent the Arduino inputs.
The batteries represent my inputs.
This info is borrowed from Instructables.com Make mini arduino programmable 4 channel DC-DVM
Have fun
