What is the zero point drift of the pH meter and how to solve it!
What is the zero point drift of the pH meter and how to solve it! To solve the problem of zero point drift of the pH meter, you must first understand the zero point drift. There are many factors that affect the zero point drift of the meter, especially the direct coupling amplifier, which is difficult to completely overcome the serious impact of the zero point drift. When the power supply voltage fluctuates, the working state of the amplifying element characteristics changes, and the circuit element parameters change with the surrounding temperature and working time. When the input is zero, the output fluctuates, that is, zero point drift. Again, we need to find the problem. There will be many problems on the PH electrode. For example, electrode fouling will cause an imbalance in resistance between the electrodes, causing drift. Long-term electromagnetic interference will also cause problems. The polarization of the electrodes will also cause problems. will also be affected. 1. Several ways to reduce the impression caused by zero point drift: 1. Use a regulated power supply, 2. Use an AC amplifier circuit. 3. Dynamic input impedance. Solutions to the stability and zero point drift of industrial pH meters and laboratory pH meters.
1. Apply negative feedback circuit. In order to reduce zero drift and improve stability, the amplifiers used in pH meters all apply negative feedback circuits. Using DC negative feedback can not only effectively increase the input impedance of the meter, but also improve the stability of the meter. degree, so that the sensitivity and range of the instrument are not affected by changes in electronic component parameters.
2. Selection and maintenance of pH electrode. The pH meter composite electrode is a key accessory to ensure that the instrument can measure correctly. Excellent electrodes should be selected to resist the influence of various chemical, temperature, mechanical vibration and other factors to maintain stability, such as in adhesive After testing in the sample, it should be cleaned repeatedly to remove the residual sample liquid on the electrode to avoid the bulb conjunctiva of the electrode, which will reduce the sensitivity and ultimately lead to measurement failure.
