I may have found another 'issue' with calibration that may need a look - the pH calib fluids that came with my unit are 7.0 and 9.0, the default calib points are 4.0 and 7.0, so when using keypad to change calib fluid 1 to 7.0 it says points to close as calib fluid 2 is defaulted to 7.0 as well. So I bypassed changing fluid 1 and changed fluid 2 to 9.0, it doesn't seem to have a way to backup and now change point 1 nor does it save the new calib fluid 2 setting so next time I come back I have 4 and 9 which I could then set to 7 and 9....