Electrical – Arduino mega 2560 Analog max reference voltage


Each time I power up the Arduino, the max reference voltage which is represented by 1023 changes. I observed this by measuring the voltage from the Aref pin each time. Is there any internal function or way to find this max voltage? Because, the voltage reading from the analog input pins of a constant voltage source keeps changing every time as a result of varying max reference voltage.

Best Answer

The default reference should be 5V, fed from Vcc to Aref by way of an internal reference select multiplexer. If might be less than 5V if the board is powered from USB.

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Measure your 5V source - is that varying as well?