As a measuring instrument, the acidity meter includes an electrometer part and electrodes. It is classified in four ways:
① Classification according to the accuracy of the instrument: it can be divided into 0.2, 0.1, 0.02, 0.01 and 0.001. The smaller the number, the higher the accuracy.
② Classification according to the reading indication: it can be divided into two types: pointer type and digital display type. Pointer pH meters are rarely used now, but pointer meters can display the continuous change process of data, so they are still used in titration analysis.
③ Classification by component type: can be divided into transistor type, integrated circuit type and single-chip microcomputer type. Now more microcomputer chips are used, which greatly reduces the size of the instrument and the cost of a single machine; but the development cost of the chip is very expensive.
④ Classification by application: It can be divided into pen type pH meter, portable pH meter, laboratory pH meter and industrial pH meter, etc. The pen-type pH meter is mainly used to replace the function of pH test paper, and has the characteristics of low precision and convenient use. Portable pH meters are mainly used for on-site and field testing, requiring high precision and perfect functions. The laboratory pH meter is a desktop high-precision analytical instrument, used for experimental teaching and scientific research, requiring high precision and full functions, including printout, data processing and so on. Industrial pH meters are used for continuous measurement of industrial processes, not only with measurement and display functions, but also with alarm and control functions.
For more details, please refer to the full text of "Use and Maintenance of Acidity Meter" (Zhao Xiang, Zhao Bing, Wang Guiyan, Liu Jingying, Wang Shaoning, Wang Guoqing)
