I'm trying to measure very small signals (under 500mV) with the ADC of my Duemilanove board and I need precision around 0.1mV.
So that means I need a small ADC reference. With 2 resistive dividers I obtained 120mV and 60mV. 120mV is the AREF input and 60mV is the ADC input. Logically that should mean I always read 512 from the ADC pin but no mn the reference.
What did I do wrong ?
What is the lowest AREF value I can use ? Documentation says between 0 and 5V, 120mV is in that interval last time I checked
Here is the code:
#define inputPin A0
LiquidCrystal lcd(7, 6, 5, 4, 3, 2);
int adInput = 0;
adInput = analogRead(inputPin);
And these are my resistive dividers