Searched several topics, but in particular have not found how I'm thinking about this.Intuition suggests:- Each P, I, D should be minimized to tighten the control.
- P (proportional gain - potential height of oscillations) should require a minimum multiple of the precision of measurement (if input measurement has 1 decimal of precision eg- 35.3°c, then P could be +/- 2.0°c or something, but if precision is no decimal eg- 35°c, then 2° P would not be reasonable and should be bigger. Of course P would also need a minimum based on the potential rate of change and ability to control the set point.
** Edited to add: My particular application is automotive electric fan controller for radiator. I will measure 0.1° precision and I have not yet datalogged to determine latency of change to temp based on change from fan.