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I need some help because I did not understand the configuration analogReference(INTERNAL). I would measure the intensity of a Laser beam passing through a filter. This is the circuit I would implement, using the 3.3 V power supply: figura In order to rise up the resolution of the system, I would use the 1.1 V power supply (Arduino Uno) to feed the sensor, keeping the Laser power supply at 5 V. In the analogReference(EXTERNAL) configuration shown in the schematic, the sensor is powered by the 3V3 pin, which is connected to the AREF pin. How should I change the circuit in analogReference(INTERNAL) configuration?

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    What exactly is the sensor? – Majenko Mar 11 at 15:56
  • If you use the internal reference voltage, you must remove the wire from 3.3v to AREF. So it's not connected to anything. – Gerben Mar 11 at 16:11
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Changing the analog reference does not change the resolution. All it does is change the measurement range. It compresses the existing resolution into a smaller voltage range.

If you then compress the voltage range of your signal in the same way to fit into the now compressed analog reference voltage range (for example by reducing the supply voltage to 1.1V) you end up achieving absolutely nothing.

The only time you would use the 1.1V internal reference is if your incoming signal is already between 0V and 1.1V and you would otherwise be wasting the resolution above the highest voltage the sensor gives out.

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