The application of programmable logic controller on pH control.

The control of pH plays an important role in wastewater treatment, cell growth rate in biological processes and other chemical processes. Despite the difficulties encountered in controlling pH due to its highly non-linear behavior, it is very necessary to control this in order to cope with the increasing demands of product quality, process productivity and environmental impact. This study deals with the application of Programmable Logic Controller on the control of pH. The PLC was programmed through the use of Allen Bradley software in the computer. A circuit was added to the system for the adjustment and comparison between the set point of the pH and actual pH due to incapability of PLC to compare the actual pH with the set pH. A pH-voltage calibration curve was plotted to determine the equivalent voltage of a specific pH. The experiment consists of two parts. The first is the continuous process and the second is the batch process. The experimentation is done by changing the percent maximum flow of the metering pump, the kind of controller and by introducing an impulse disturbance. The results of the experiment showed that the PLC used can not effectively control the pH