You may also be interested in a Walchem Controller.
The Liquitron DR5000 is a dual-channel ORP (redox) controller providing either relay or proportional pulse outputs to drive chemical metering pumps. A custom backlit display provides constant information regarding controller and system conditions.
High and low alarm points, delay and limit timers, and other user programmable features make the DR5000 the most adaptive ORP (redox) controller available.
To see the complete range of LMI Liquitron Controllers, visit our LMI Controllers page.
You may also be interested in a comparable product from Walchem, the WPH600 Series of pH and ORP controllers.