Drift in Read Voltage

[kmarxx]

I was using the TinyDuino to read in a voltage value (20 readings / sec) which fluctuated between ~2 - ~4 volts over about 12 hours. I noticed what appeared to be drift over the course of the 12 hour test and after some troubleshooting I realized that even when the voltage being read by the duino was constant (was using pin A5 to read voltage), the data that the duino would save to my SD was drifting... tried to replicate the issue with an Arduino Uno but it saved constant voltage values without drift?

Any thoughts on what could cause this? Is this a known problem with the TinyDuino platform?

Thanks!

[patiencenye]

The TinyDuino uses an ATmega328P chip, while the Arduino Uno uses the same chip. Slight variations in the ADC hardware and internal voltage reference could contribute to the observed drift.