Basics of pH Measurement

pH Scale
pH of Common Items
(image courtesy of
pH is a numeric scale used to designate the acidity or alkalinity of an aqueous solution. Solutions with a pH below 7 are acidic and solutions with a pH higher than 7 are basic. Pure water is considered neutral and are neither an acid nor a base.

pH measurement is very important in many industries including medicine, chemistry, agriculture, food science, environmental science, chemical engineering, water & wastewater treatment, and many others.

pH electrodes and sensors are the sensing portions of a pH measurement. Various installation options including retractable, flow thru, immersion, and direct insertion. Proper pH electrode/sensor selection is critical for optimal measurement results.

2 wire analyzer
2 wire transmitter (Yokogawa)
pH meters, analyzers and transmitters are used for continuous process monitoring of pH to ensure water/product quality, monitor effluent discharge, batch neutralization, pulp stock, scrubbers, cooling towers, chemical, water/wastewater treatment and many other applications.

Four Wire Analyzers: 4-wire analyzers separate the power supply from the measurement output. As a minimum we need two wires for the power supply and two wires for the current output of the analyzer.

Two Wire Analyzers: 2-wire analyzers combine the wires for current output, power supply, and digital communication.

The document below (courtesy of Yokogawa) provides a comprehensive understanding of pH/ORP measurement and how to achieve reliable results. Basic information on the principles of measuring pH/ORP, the construction of the sensing elements and their basic use in process applications are provided.

For more information, contact:
Power Specialties, Inc.
9118 E. 72nd Terrace
Raytown, MO 64133
Toll Free: (800) 432-6550
Phone: (816) 353-6550
Fax: (816) 353-1740