The principle and maintenance method of online pH meter

On-line pH meter is one of the more chemical analysis instruments currently on the market. It has strong environmental adaptability, clear display, simple operation and excellent test performance. It has high cost performance and can measure the pH value and temperature of the solution. The principle of PH electrical measurement is electrochemical method and the principle of primary battery. A primary battery is a system whose function is to convert chemical energy into electrical energy. The voltage of this battery is called electromotive force (EMF). This electromotive force (EMF) is formed by two half-cells. One of the half-cells is called a measuring cell, and its potential is related to a specific ion activity; the other half-cell is a reference half-cell, usually called a reference cell, which is generally connected to the measuring solution and connected to the measuring instrument . The potential difference generated by the internal galvanic battery reaction is transmitted to the pH controller, and the corresponding algorithm is sent to display the pH value. (1) Internal reference electricity: silver/silver chloride electricity, the main function is to lead out the electric potential, which requires stable potential and small temperature coefficient. (2) Internal reference solution: the internal reference solution whose zero potential is 7pH is a neutral phosphate and mixed solution. Glass electricity and reference electricity constitute the pH value of the zero potential of the battery, which mainly depends on the pH value of the internal reference solution and the concentration of chloride ions. A ph value, the glass electricity will produce a potential change of 59.16mv. But in fact, all glass electricity cannot reach the theoretical value. Generally, the electric slope is more than 98% (percentage slope) of the theoretical value. In addition, the mv difference corresponding to each unit of pH value at different temperatures has a certain change. Precautions for electrical use and maintenance of the online pH meter: 1. The electrical lead wire is a special 6-core shielded wire. It is forbidden for customers to cut and connect the lead wires without permission, and they will not be responsible for the consequences. 2. When measuring, it should be washed in distilled water (or deionized water) first, and dry the water with filter paper to prevent impurities from entering the measured liquid. The electric bulb and liquid junction should be completely immersed in the measured liquid. 3. When the power is not in use, it should be washed and inserted into the protective cover with saturated lvhuajia solution. 4. Check whether the terminal is dry. If it is stained, please wipe it with absolute alcohol and dry it before use. 5. Long-term immersion in distilled water or protein solution should be avoided, and contact with silicone grease should be avoided. 6. If the electricity is used for a long time, its glass film may become transparent or have deposits. At this time, it can be washed with dilute hydrochloric acid and rinsed with water. 7. It is recommended that users regularly clean the glass bulb and liquid junction in front of the battery, and regularly cooperate with instrument calibration. 8. When you use the above methods to maintain and maintain the battery, you still cannot perform the calibration procedure and normal measurement, indicating that the battery can no longer restore the response, please replace the battery. The online pH meter is an intelligent upgraded product of the acidity meter, which can continuously measure and control the pH value of the liquid. The meter itself has a relay control output, which can be used to realize the functional requirements of industrial site control acid-base pump adding acid and alkali. Standard configuration The 4-20mA analog output can realize the real-time connection with the paperless recorder, PLC, etc. In addition, the communication function can realize the real-time connection with the computer, and the free upper computer software can also realize the system monitoring function of multiple PH controllers online . This instrument is suitable for various fields such as urban sewage treatment plants, chemical industry, printing and dyeing, papermaking, pharmaceuticals, electroplating and environmental protection.