pH sensors and transmitters

How to select pH electrodes

pH sensors and transmitters are used in many industries such as chemicals, water & wastewater, food & beverage, pharmaceuticals, power plants, primaries and oil & gas. The selection of the sensor depends on the application. Choose the glass sensor's diaphragm and reference system according to your needs. Use ISFET sensors where glass breakage is intolerable or media contain high amounts of organic solvents. Apply enamel sensors when long-term stability and lowest maintenance are required.

pH measurement with glass electrodes and enamel electrodes

The pH value is used as a unit of measurement for the acidity or alkalinity of a liquid medium. The pH-sensitive element of glass electrodes is a glass bulb that supplies an electrochemical potential which is dependent upon the pH value of the medium. This potential is generated because small H+ ions penetrate through the outer layer of the membrane while the larger negatively charged ions remain in the solution.

Glass pH probes contain an integrated Ag/AgCl reference system that serves as the required reference electrode. The pH value is calculated from the potential difference between the reference system and the measuring system using the Nernst equation. Our pH sensors and transmitters achieve outstanding linear measuring performance over an extremely wide pH range!

The measuring principle of enamel pH electrodes corresponds to that of glass pH sensors, however, the pH-sensitive element is enamel.

pH measurement with ISFET electrodes

The pH value is measured with an ion-selective field effect transistor (ISFET). It is a simple transistor with a source and drain that are separated from the base by a semiconductor. Hydrogen ions from the medium may accumulate here. The resulting positive charge on the outside is 'mirrored' on the inside of the base where a negative charge occurs. This makes the semiconductor channel conductive. The more H+ ions accumulate on the base, the more current can flow between the source and drain.

Benefits

• Our pH sensors and transmitters meet all requirements from basic functionality up to multichannel and multiparameter measurement.
• We offer pH buffers, pH solutions and pH standards for pH calibration to ultimate precision. They are produced in our own permanent calibration laboratory that has successfully passed the DAkkS accreditation (German accreditation authority).
• The different types of electrodes cover all kinds of diaphragms and reference systems, from dirt-repellent PTFE junctions over highly sensitive ceramic diaphragms to blocking-resistant open apertures.
• We offer pH assemblies for all fields of applications: fixed installation assemblies, immersion assemblies, flow assemblies and retractable assemblies.
• Automated systems for calibration, adjustment and cleaning ensure optimum performance of the pH sensors and transmitters in chemical processes, pharmaceuticals production or hygienic applications.