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Arduino link 3.3v for ADC

I have an Arduino UNO. I have a sensor that has a 3.3V output. To maximize the accuracy of the ADC, I moved the 3.4v pin of the Arduino to AREF and in settings

analogReference(EXTERNAL);

I have a timer set. When this happens, the ADC is read from A1 through

analogRead(1)

So, to check the link, I moved 3.3v to A1 input. Since the ADC is 10 bits, I expected to get values ​​at or near 1023. Instead, they range between 870-880. Any thoughts?

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The AREF pin has an internal 32k resistor. So you must put a resistor on the AREF pin to give it 3.3V ideal input. You can simply use a resistor along with a 32 kHz resistor and provide a perfect 3.3V.



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