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pH measurement is usually done with the use of a combination electrode. The combination electrode is an electrode system formed by a glass sensing half-cell and an internal reference half-cell. As the reference junction acts as the medium of conductor between the reference electrolyte and the sample to be measured, it must allow free movement of electrons through the junction and into the sample.
A potential develops on the membrane surface when a pH electrode comes into contact with a sample and its value varies with the pH of the sample. This variation in potential is measured in mV by a meter and is converted to direct pH values.
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Stable reference systems are the heart of reliably functioning, long-lasting electrodes. In pH measurement up till now, the user was not spared the need for frequent calibration. The reason for this lies in shifting reference potentials due to chloride loss in the reference electrolyte. However, contaminated and partially clogged diaphragms also contribute considerably to changing properties in pH electrodes, which can only be resolved with a fresh calibration. For pH measurements where a very high degree of accuracy is required, it should therefore be sufficient if the pH sensor is calibrated just before measuring. But in industrial applications - especially in the case of online pH measurement - this is possible only with a great deal of effort, if at all. What is even worse: even if a calibration with certified pH buffers is correctly carried out, the very next measurement will not necessarily be accurate! Depending on the age of the electrode or, more precisely, the state of the diaphragm and the chloride content in the reference electrolyte, different diffusion potentials may occur in buffers and measurement medium. Technically speaking, it is impossible to eliminate this source of error entirely, but with pHeasy technology it is possible to detect it online!
Hamilton, with its pH glasses and the ingenious inner buffer, has built true long term stability into pHeasy electrodes.
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pH sensor
- Low alcaline error
- Higher life expectancy, given that refillable
- Blocking resitant
description
The Kuntze AH-300-K-2-1 is a combination electrode with ceramic junction for pH measurement. The sensor is liquid filled, thus blocking resistant and particulary suitable for lightly polluted media.
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pH Sensor
The Pico pH sensor is a robust epoxy bodied pH electrode ideal for educational use. The pH sensor consists of a standard electrode capable of measuring the full to 0 to 14 pH range. The electrode comes complete with a small bottle of storage solution to help prevent it drying out. Output is via a BNC connector.
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