Suppose you solve all your problems and build a system with 0.1 C accuracy. Now you compare it with the Fluke (which has perhaps 0.3 C accuracy), and your circuit says 20.1 C but the Fluke says 20.3 C. You know your circuit is good, so you try a different Fluke and it says 19.9 C. You could recalibrate your circuit to read 20.3 or 19.9, but not both! If you really need 0.1 C accuracy you had better find a meter that's calibrated and accurate to 0.01 C.