Industrial PH meter definition, working principle and structure introduction Industrial PH meter is a kind of commonly used industrial instrument testing equipment, mainly used for research and development of pollution source online monitoring, manufacturing, sales, on-site installation and commissioning, technical support and operation management. The comprehensive entity of the service, the pH meter is widely used in the industry as an analytical instrument for measuring the hydrogen ion concentration of the roughness meter in the solution.
1, PH value definition roughness meter
2, the principle and structure of the PH meter 2.1 Principle of the PH meter The potentiometric method to determine the p H value of the solution is the most basic method. The principle of potential measurement p H is derived from the Nernst formula. For example, a counter electrode with a reversible hydrogen ion and a reference electrode are placed in a solution to form a primary battery. Since the potential of the reference electrode in the primary battery is constant under certain conditions, the value of the electromotive force of the primary battery changes with the activity of the hydrogen ions in the measured solution. Therefore, the p H value in the solution can be calculated by measuring the electromotive force of the primary battery. According to the Nernst equation, the electrode potential is:
The first constant ( 9. 649 × 10 4 mo l-1 ); aH is the activity of hydrogen ions. 2. 3026 RT / F is called the electro-conductivity conversion coefficient of the electron-electron balance that is reversible for hydrogen ions. When the p H value of the measured solution changes by one potential, since both R and F are constant, the electrode potential is a function of temperature [ 2 ]. A single potential cannot be measured. Only the reference electrode can be measured at a certain temperature to measure the p H value of the solution to be tested.
2. Structure of 2 p H meter
The composition of the PH meter is shown in Figure 1. It is generally divided into two parts: the measuring part (inverter) and the p H electrode (sensor).
The measuring part of the acidity meter is a general potentiometer or bridge. Because the requirement for the measurement circuit is that when the entire system is turned on, the battery under test (ie, the electromotive force generated by the electrode pair) must be performed without current passing through. Otherwise, it will cause electrolysis and polarization of the electrodes, resulting in measurement errors. Therefore, this is why the compensation method is used to measure the potential.
In addition, a deep negative feedback amplifier circuit is used in the measurement section to further increase the input impedance and reduce the output impedance, thereby greatly improving system stability.
This article is mainly excerpted from Wang Lin's "Overview of Industrial PH Meters"
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