A multichannel pH controller for solution culture systems

A multichannelled, computer-controlled system has been developed for maintaining near-constant pH in nutrient solutions. This system will monitor, record and individually maintain pH in up to seven solutions continuously. All components except the software and pump controller were available commercially.In an experiment for which the system was developed, in which six individual solutions were controlled for 20 days, the pH was generally maintained within 0.1 pH unit of the set value. Drift outside this range was generally due to addition of nutrients required to maintain adequate levels. Such drifts were quickly and automatically corrected.This equipment has been subsequently used in several experiments in which it was imperative to maintain pH at a constant level in several solutions simultaneously with actively growing plants over a long period of time.