Overall
Some observations:
- If I tried to run it too slow, the pump would stall, so the lowest rate turned out to be around 20 - 30 mL/hr
- the high-end rate was very high 6000+ mL/hr was the max this particular pump could achieve
- at low rates the scale would not detect fluid rate changes so the data was not terribly accurate. i.e. running at control value 49 vs 50 showed no difference in the fluid rate.
- I did not test it for long periods of time; what happens when the tubing in the pump head wears out or becomes more pliable? What is the effect on the overall accuracy
- I did not test it with back pressure. The system would simply drip water into a jar on the scale, i.e. without any obstructions or constrictions to the fluid flow. Would having constrictions (e.g. a needle, or a narrowing of the tubing) cause any significant change to the actual fluid rate?
- I did not test it against more than one pump. There could be a substantial impact from pump to pump based on mechanical & manufacturing differences for the rollers, case, tubing, etc.
I believe that more data, and specifically more accurate data, would have calculated a much better set of coefficients and I would expect the error to come down substantially.
Adding a motor encoder would make the system substantially more accurate as well as allowing for error detection (e.g. stalling).