AREF pin

1) If 3.3V supply is used for an analog device, the arduino's analog to digital convertor should be informed about this change.

2) This is done by connecting the line to 3.3V supply to AREF pin

5) This can sometimes give more accurate reading because the 5V supply, when supplied through computers USB is often noisy because of the CPU operations

In the sketch

In the setup, set :


Example of a thermistor using 3.3V supply