I want to read two voltages of different ranges with an ATmega328P ADC with the highest resolution possible:
The 1st signal varies from 0 to 1V. It's the output of an LM35DZ Temperature Sensor. I wanted to use the internal 1V analog reference to get the highest ADC resolution possible.
The 2nd signal is the battery voltage, that varies from 0 to 5V. I feed it to this Over-Discharge Protection circuit that Russell McMahon proposed and based on that reading, it will turn off the circuit if battery levels are too low. To read this signal, I have to use the ADC 5V voltage reference.
My questions are:
Is it ok if I keep changing the ADC voltage reference from the internal 1V to the 5V reference to make one read then the other?
When I switch to 1V internal reference, will the other 5V signal damage the other analog input? I got the impression that the 1V reference would be a limit for the ADC and the 5V on the other input would somehow violate this.
I actually tried to switch between 1V and 5V reference, but when I do it, the reading of the 1st signal (with 0 to 1V range) starts fluctuating. Why is that? I tried giving the ADC time to settle (10 to 50 ms), but that didn't work. How do I get a stable reading after switching the analog reference?