@dc42 So, if I understand correctly, for the Duet Wifi, the figures are approx. double i.e. 1.2C for 12bit resolution with the PT1000 and 0.3C for 14bit.
If, as you say, noise has a certain probability of being directional, that means that if I'm printing ABS at a nominal 260C I might, in fact, be at a 12 bit version of 260C, in other words somewhere in the range 258.8-261.2C.
The PID controller would kick in at the limit of that range (when the ADC increments/decrements) and tend to steer the hotend back into it, though presumably there will be some overshoot relating to the physical separation of thermistor, heater and meltzone.
Since the duet will in any case display 4 significant figures (260.3C), derived from the possiblity of 14 bit accuracy, what I observe in DWC will actually be an oscillation in the range 260 +/- 0.3C (if no overshoot occurs and is registered). Or perhaps eg. 260 - 1.2C +/-0.3C ?? Hmmm