I think that Milwaukee intended for the numbers on the controller to just be for reference and not to be exactly correct. I fine tune my controller by setting the CO2 so it’s always on (put the controller at a really low pH like 6.0) then I wait until the reading on the digital readout says the exact pH that I am aiming for. After it has the pH on the screen I then turn the controller dial very slowly until the warning light goes off. This gives a pretty accurate setting but it may take a few more slight adjustments before it gets exactly where you want it. HTH |