Hello there,
Here is a quick comparison of the ADC in the Atmega 328 chip in an Arduino Uno and a 16 bit ADC separate chip. It would be nice to hear about other people's uses too, as to any comparisons they performed.
The Uno uses the +5v reference available on the board, which is not as stable as the 16 bit ADC internal reference, so the difference in readings is often more off by about 3 or 4 millivolts, and as high as 5 millivolts. The only calibration for the 328 chip ADC is done by measuring the +5v supply and using that measurement as a factor in the conversion from the ADC code to the voltage displayed.
There is no calibration for the 16 bit ADC, which is found to be very close to a measurement with an expensive meter, although some calibration would help there too.
The attachment shows three readings, although the top 'red' display should really be ignored because that was taken with the ground lead on a different point in the circuit.
The top reading in the blue display is the 16 bit ADC, and the bottom reading is the 328 chip ADC, and the number to the right on the bottom in the blue display is just the sample count.
The conclusion was that the 328 chip differs from the 16 bit ADC by up to 5 millivolts, but the power supply on the Arduino board was found to vary, so a better reference voltage would probably help there. In any case the +5v has to be measured in order to set the factor in the code correctly, or at least close. If a different reference is used that would have to be measured.
Here is a quick comparison of the ADC in the Atmega 328 chip in an Arduino Uno and a 16 bit ADC separate chip. It would be nice to hear about other people's uses too, as to any comparisons they performed.
The Uno uses the +5v reference available on the board, which is not as stable as the 16 bit ADC internal reference, so the difference in readings is often more off by about 3 or 4 millivolts, and as high as 5 millivolts. The only calibration for the 328 chip ADC is done by measuring the +5v supply and using that measurement as a factor in the conversion from the ADC code to the voltage displayed.
There is no calibration for the 16 bit ADC, which is found to be very close to a measurement with an expensive meter, although some calibration would help there too.
The attachment shows three readings, although the top 'red' display should really be ignored because that was taken with the ground lead on a different point in the circuit.
The top reading in the blue display is the 16 bit ADC, and the bottom reading is the 328 chip ADC, and the number to the right on the bottom in the blue display is just the sample count.
The conclusion was that the 328 chip differs from the 16 bit ADC by up to 5 millivolts, but the power supply on the Arduino board was found to vary, so a better reference voltage would probably help there. In any case the +5v has to be measured in order to set the factor in the code correctly, or at least close. If a different reference is used that would have to be measured.