What causes the pH meter's zero drift and how to fix it!
What is the zero drift of the pH meter and how to solve it! The problem of the zero drift of the pH meter must first understand the zero drift. There are many factors affecting the zero drift of the electric meter, especially the direct coupled amplifier, which is difficult to completely overcome the serious influence of the zero drift. When the power supply voltage fluctuates, the operating state of the amplifying element characteristics changes, and the parameters of the circuit elements change with the ambient temperature and the working time. When the input is zero, the output fluctuates, that is, the zero point drift. Again, it is necessary to find the problem. The problems on the pH electrode will be more prominent. For example, electrode scaling will cause the resistance between the electrodes to be unbalanced and cause drift. Long-term electromagnetic interference will also cause problems. The polarization of the electrodes is also the same. will also affect. 1. Several ways to reduce the impression brought by zero drift: 1. Use regulated power supply, 2. Use AC amplifier circuit. 3. Dynamic input impedance. Industrial pH meter and laboratory pH meter stability and zero drift solution.
1. Application of negative feedback circuit. In order to reduce zero drift and improve stability, the amplifiers used in pH meters all use negative feedback circuits. Using DC negative feedback can not only effectively increase the input impedance of the electric meter, but also improve the stability of the electric meter The sensitivity and range of the instrument are not affected by the parameter changes of electronic components.
2. Selection and maintenance of pH electrode. The composite electrode of pH meter is the key accessory to ensure the correct measurement of the instrument. Excellent electrodes should be selected to resist the influence of various chemical, temperature, mechanical vibration and other factors to maintain stability. After the test in the sample, it should be cleaned repeatedly to remove the residual liquid of the sample on the electrode, so as to avoid the bulb conjunctiva of the electrode from reducing the sensitivity and eventually lead to measurement failure.
