Hi, i created pH meter, like there, withour adjust. http://www.sparkyswidgets.com/portfolio-item/ph-probe-interface/ But its nor working, on exit i am always getting around 4.5V, even with connected pH probe or not. i am using TL072CP, all resistors chosen as written there ( not in schematic but below). There is negative voltage, i for it i used ICL 7660. Any suggestion, plz need fast help
Is there difference if i am using 0.25W resistors. Should i uses 0.5W or 1W resistors. Or there is no difference?
The wattage of the resistors does not matter.
Are you using both +5v and -5V with the common 0v from each supply connected as the ground reference. When you measure between the +5v and the -5v rails do you get 10 volts. If not then you have your supplies incorrectly connected.
The description of that circuit doesn't seem to correspond to the diagram very well.