There is also the problem of calibration, A Wheatstone Bridge's output is bi polar in nature and depending on the actual values on either half... Extremely sensitive, Typically used for making matched pairs of resistors... to .001% or more. A Wheatstone Bridge isn't a really great idea unless you are after 10th's of a degree accuracy over a narrow range of temperatures
Use a current source fed from a constant voltage source... Independent of the Arduino's Vcc.
I usually use a pot and a TIL431 reference diode (read Variable Zener Diode) fed from a clean 9 to 12V source. I use a 10K 1% MF or better, use a stable one with a low tempco (10PPM/deg C.).
There is a "Table" of values for calibration by PH Anderson and a formula for doing the same thing "On the Fly" available freely on the Internet for final calibration. Don't forget 2 really important things... Bypass the regulated voltage source well and really important use a star grounding layout... 5 or 10 mV of combined ground drop voltage can destroy any real accuracy however if you pay attention to detail you can easily make a nearly "Traceable" and very accurate thermometer... for a few dollars extra... IMO
Doc