[bigben2k]

I admire your persistance, Jay.

1) that would work, but we really want to keep the flow rates to a somewhat typical rig, so 0.5 and 1 gpm are a must.

2) Possible. You could do that without any heat power applied, as a comparison point, to account for heat induced by the pump and pumping action.

3) That might work too. You'd need a good measurable temp increase which means a long time sample; if you can do that without frying the CPU, then all is well. I have a mercury thermometer with 0.1 deg C graduations, ranged from 19C to 27C that would be perfect for this. I think I prefer #2 though.