I have a UNO board. The 5 V reference / 1023 gives +_ 5 Degree between steps of the 1023 divisor since the output of the Temp device is mv = Deg F. 140 mv = 140 deg F. I'm looking for the difference between 130 deg and 140 deg F, which is about the error of the decoded Analog. steps. I could amplify the signal to V = Degrees, or use a 1 volt reference instead of 5 V.. I see the MEGA has 1.1 V ref. Are those two the only options?
Carl
The LM34 has a scaling factor of 10 mV per °F. 3V (3000 mV) = 300°F
With a 5V reference you get precision of 0.488 °F.
With an external 3.3V reference you get a precision of 0.322 °F.
With the internal reference of 1.1V you get a precision of about 0.11 °F but a top limit of 110 °F.
With the internal 2.56V reference you get precision of exactly 0.25 °F and upper limit of 256 °F so that might be your best bet for measuring 130 to 140 °F.