Development of a microprocessor-controlled coulometric system for stable ph control

The coulometric pH control system utilizes a programmable coulostat for controlling the pH of a certain volume of unbuffered solution. Based on theoretical considerations, conditions are established which guarantee stable operation with maximum suppression of disturbances from the dissolution of carbon dioxide, for example. It is shown that the dynamic properties of the control system depend greatly on the response time of the pH sensor which measures the actual pH. The best results are therefore obtained by using an ISFET as pH sensor