Hi people, at this moment I am trying to measere the pH with the analog inputs. We first converted the 4-20mA signal to 0.66-3.3V with a 165 ohm resistor. The values from the analog input mostly fluctuate about 4 to 6 points, but sometimes more than 20 points. I am using the standard 10bit ADC. Does somebody know what could be the cause for these fluctuations? I was thinking about an unstable reference voltage of the Aref pin. Ore are there other possibilities for the fluctuations? I was thinking about appluing an external reference voltage. Does somebody know if this is possible? And if it is possible, how to do this? Thank you already for replies. Alex
