What is a pH meter?
A pH meter is a scientific instrument used to measure the hydrogen-ion activity in water-based solutions and it indicates the acidity or alkalinity expressed as pH using a scale of 0 to 14. A pH meter. The pH of a substance indicates the proportion of hydrogen ions formed in a certain volume of water.
How does a pH meter work?
The pH meter has a moving-coil meter or a digital meter that has to be inserted into the solution. A circuit is created when two electrodes are put into it. Electrodes are based on different materials: the glass electrode (based on a silver electrical wire) and the reference electrode (which has a potassium chloride wire). The pH meter measures the voltage between these two electrodes and it is converted into a pH value.
How to calibrate a pH meter?
The pH meter calibration depends on solutions of known pH, before the use. The electrodes are used as probes and dipped into the test solution, long enough for the hydrogen ions to equilibrate with the ions on the surface of the glass electrode.
The first, Nobel-Prize winning chemist Fritz Haber (1868–1934) and his student Zygmunt Klemensiewicz (1886–1963) designed the glass electrode idea in 1909, but the use of electrodes for pH measurement started in 1920. The first patent for a complete instrument was registered in 1934 by Arnold Orville Beckman (1900–2004). He introduced many modifications until in 1936 was the first year of real sale of the instrument. Since then this instrument has made important changes in the level of performance, but it is still based on the same principle.
Types of pH meters
There are different types of pH meters. Models vary from simple and inexpensive pen-like devices to complex and expensive laboratory instruments that include computer interfaces, inputs to indicate temperature and determined pH variation according to temperature and a digital (digital pH meter) or analogue output. The electric input can be battery-powered or rely on line power. There are many types of pH meters, some of them are:
Portable pH meter. This device is very functional and it can be used in the laboratory or in the field. Depending on the model, it might have a digital output, temperature control
Benchtop pH meter. It is ideally used in laboratories, industry and manufactory. There is a wide range from economical to expensive, with a wide variety of features. Some models include the standard and the dissolved oxygen meter.
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