The theory and practice of pH measurement

By Rosemount Analytical

DETERMINATION of pH is one of the most common process chemical measurements made today. This White Paper covers the basic mechanism of pH measurement, the structure of the sensor and its fundamental limitations, and also provides installation, maintenance and troubleshooting guidance. The paper also discusses industrial ORP (oxidation-reduction potential) measurements.

This booklet has five major sections. The first section discusses the construction and features of the electrochemical cell used for measuring pH. The second section discusses how the pH analyzer converts the measured cell voltage into pH. The third section discusses some fundamental limitations to pH measurements. The fourth section discusses industrial ORP measurements. Because ORP measurement cells have much in common with pH cells, much of the information in the pH cell section applies to ORP measurements. The fifth section deals with installation, maintenance, and troubleshooting of pH systems.