Classification of pH meters_Function of pH meters
Also known as pH meter, acid-base detector, it is an instrument that uses a pH indicating electrode to measure the pH value of a solution by potentiometric method. It is a precision electronic millivolt meter designed for use with ion selective electrodes. Since the potential of the pH indicating electrode changes with the change of the pH value of the solution, when the pH indicating electrode (such as pH glass electrode) and reference electrode (such as saturated calomel electrode) are immersed in the solution to form a measurement battery, the electromotive force generated Depends on the pH value of the solution. The pH meter converts the electromotive force output into a pH reading. Each pH interval is equivalent to 2.303RT/F volts. This value changes with the temperature of the solution in the measurement battery. Therefore, the pH meter is equipped with a temperature compensation knob. Adjust it to make The change in electromotive force at each pH interval is exactly equivalent to the change in measured temperature. The pH meter is also equipped with a positioning regulator, whose function is to add an appropriate voltage to the battery electromotive force to make the pH meter reading consistent with the standard pH value. In this way, the pH value of the solution is displayed directly on the meter. The general measurement range of a pH meter is pH 0 ~ 14, and it is equipped with a ±mV block to expand the range of use.
Classification of pH meters
1. Classification of meters
(1) Classification according to 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 acid-base test paper. It has the characteristics of low accuracy and easy use. Portable pH meters are mainly used for on-site and field measurement methods, which require high accuracy and complete functions.
(2) According to the classification of instrument accuracy: it can be divided into level 0.2, level 0.1, level 0.02, level 0.01 and level 0.001. The smaller the number, the higher the accuracy.
(3) Classification according to reading indication: it can be divided into two types: pointer type and digital display type. Pointer pH meters are rarely used nowadays, but pointer meters can display the continuous change process of data, so they are still used in titration analysis.
(4) Classification according to component type: it can be divided into transistor type, integrated circuit type and single-chip microcomputer type. Nowadays, more microcomputer chips are used, which greatly reduces the instrument volume and stand-alone cost; but the development cost of the chip is very expensive.
2. Laboratory pH meter: The laboratory pH meter is a desktop high-precision analytical instrument that requires high precision and full functions, including printout, data processing, etc.
3. Industrial pH meter: Industrial pH meter is used for continuous measurement of industrial processes. It must not only have measurement and display functions, but also alarm and control functions, as well as considerations for installation, cleaning, anti-interference and other issues.
