I've setup four thermistors and a known resistor in series and connected them to the 3.3V output (as I've heard it's cleaner than the 5V) of an Arduino Uno (with the 3.3V also connected to ARef to increase accuracy), with the four analog inputs testing the voltage drop across each thermistor to determine its resistance, and hence temperature.
But even with no change in the thermistor temperatures, the voltages I get from the arduino vary significantly. See below an example readout of the four arduino inputs (with thermistor temperatures/resistances same throughout):
230 424 634 849
212 412 597 819
241 415 611 857
204 413 654 845
The accuracy I come out with is around 5-10 degrees - way more than I expected. Why is this? And what can I do to get it down to less than one degree? Many thanks
UPDATE: A MASSIVE THANKYOU to all those who helped me on this, particularly @NickGammon, @Talk2 and most of all @JRobert for the brilliantly clear and simple to follow circuit instructions to follow, all of which helped to thoroughly solve my problem! The sensor works great now, many thanks!!