pH Measurement and Instrumentation

pH Measurement - A sample chapter from the title Practical Analytical Instrumentation in On-Line Applications - This chapter shows the need for pH measurement, Describes the properties of water, Defines pH, Demonstrates the principle of both the measuring and reference electrodes and their relationship to each other, Explains the Nernst equation and its dependence on temperature, Lists the various sources of error in the measurement of pH and shows how calibration is carried out - Thanks to IDC.

Guide to pH Measurement - the Theory and Practice of pH Applications - The aim of this book is to give a representative description of pH measurement in the process industries. The actual sensor, the pH electrode, is therefore the main focus of the text. Correct sensor use is fundamental for a meaningful pH measurement. Accordingly, both practical and theoretical requirements are discussed in depth so that the measuring principle is understood and an accurate measurement made possible - from Mettler - Toledo AG.

pH Measurement - Some super information thanks to Cole Palmer.

Typical Problems in Industrial pH Measurement & Control - Tips and solutions to Industrial pH problems from EUTECH Instruments.

The Easy Guide to pH Measurement - Thanks to ABB Automation.

The ABB Guide to Fast pH Measurement - Used for a host of applications across a variety of industries, getting the best from pH equipment requires consideration of a range of factors to achieve optimum efficiency and cost effectiveness.

pH Theory and Practice 

pH Measurement Basics

The following articles are compliments of Digital Analysis Corporation:

pH Probe Architecture - A description of how a pH electrode functions. Sample calibration procedures are also included in this discussion.

pH Probe Calibrations - Fundamental procedure for cleaning and calibrating the most common pH electrodes used in industry today which are also the most common probes that we use on our systems.

pH Adjustment, a Primer - A review of the meaning of pH, covering the pH scale, acids and bases, acidity and alkalinity, and the definition of pH. Also covered are the two basic system designs used in industry Continuous Batch (Flow Through) and Batch pH adjustment systems. Also discussed, but only briefly, is a proprietary design known as "Optimized Batch" pH adjustment / neutralization systems.

Limestone for pH Adjustment - This article clears up many misgivings regarding the use of limestone of for pH Adjustment. So you are thinking about using limestone? Better read this article first.

Chemicals used for pH Adjustment - The various choices for acid and base neutralizing chemicals are discussed here. If you are wondering which acid or base you should use as a neutralization agent then this discussion may be of help.

The following technical papers are from Emerson Process Management:

Theory and Practice of pH Measurement - An excellent 43 page handbook.

Theory of pH Measurement - pH is a measure of the acidity or alkalinity of a water solution. The acidity or alkalinity of a water solution is determined by the relative number of hydrogen ions (H+) or hydroxyl ions (OH-) present. Acidic solutions have a higher relative number of hydrogen ions, while alkaline (also called basic) solutions have a higher relative number of hydroxyl ions. Acids are substances which either dissociate (split apart) to release hydrogen ions or react with water to form hydrogen ions. Bases are substances that dissociate to release hydroxyl ions or react with water to form hydroxyl ions.

pH made Easy, Reliable - Jonas Berge - Water and wastewater treatment plants, as well as other industries, use several types of liquid analyzers to monitor quality in terms of many different properties. The pH meter is one of the most important. Analyzers communicate digitally using protocols such as HART®, Foundation® fieldbus, and WirelessHART. Maintaining this mix of analyzers can be a challenge. This is a result of analyzer probes being in direct contact with the process and subject to various different problems depending on the process conditions. However, modern pH analyzers diagnose themselves, the glass, and reference electrodes in the sensor, as well as the temperature sensor. This allows for more effective maintenance schemes that help keep the loop and plant running with minimum downtime. Recent enhancements to the EDDL (Electronic Device Description Language) IEC 61804-3 standards have helped improve calibration and advanced diagnosis of high-end pH analysers.

Advances in pH Modeling and Control - Gregory K. McMillan (Emerson) and Mark S. Sowell (Solutia Inc) - Many chemical and biological processes have pH control loops. Good pH control can be important for product quality as well as environmental compliance. The extraordinary rangeability and sensitivity of pH as a concentration measurement poses exceptional challenges in many aspects of pH design and implementation.

Virtual Control of Real pH - Virtual Design reduces the hassles of pH control.

Smart pH loops for Plug-n-Play Installation Reduce Calibration Time - Linda Meyers - New technology enhances pH sensors usage because of the Smart software that's implemented in advanced pH sensors and instruments. Never before has it been so easy to calibrate, plug-n-play, and evaluate pH monitoring. Before the Smart technology emerged, the only way to calibrate the pH sensor was to carry all of the calibration equipment into the field. In many facilities, this meant carrying at least two buffer solution bottles, two beakers and one rinse bottle to the various installation sites. Then, the calibration was done on-site at a location closest to the sensor installation. So come rain or shine, sleet or snow, hot or cold weather conditions, the technician had to maintain the sensor in even the worst environmental conditions.Smart technology changes all that. Smart pH sensors have a memory which holds calibration information, so there is no need to carry equipment to field - from PaceToday.

Bringing pH Measurement Systems Up to Date - George Pence and Richard Baril - Improvements in sensor life and range of applications can move liquid analysis from one of the most “cursed” functions in the plant, to one that requires only modest attention - Thanks to ISA and InTech.

pH Instrumentation Maintenance

pH Sensors: Know whether to Calibrate the Sensor, Clean the Sensor, Perform a Calibration Check or ...? - Fred Kohlmann - This paper addresses knowing when to do a pH sensor calibration versus a calibration check, how to properly clean a pH sensor, how to perform a pH sensor calibration and a decision tree for step by step guidance - from the ISA and Endress+Hauser.

pH Probe Maintenance - from the Digital Analysis Corporation.

Probe Cleaning

A common issue with pH meters is contamination and fouling of the probe, the following links provide some good information on cleaners available, including ultrasonic, bushing, chemical and self cleaning methods.

http://www.analyticon.com/analyticon/products/process/pH_cleaningdevices_immersionhc7.htm
http://www.wq.hii.horiba.com/pdf/k8.pdf
http://www.endress.com/eh/home.nsf/?Open&DirectURL=4E3EC3004B14A5F5C1256D4A002C6B7B

Other pH Instrumentation Accessories

Redundant probes

http://www.phneutralizing.com/products/redundant_probe.htm