What is the zero drift of a pH meter and how to solve it!
What is the zero drift of a pH meter and how to solve it! The problem of zero drift in pH meters first requires an understanding of zero drift. There are many factors that affect zero drift in electrical meters, especially in directly coupled amplifiers, which are difficult to completely overcome the serious impact of zero drift. When the power supply voltage fluctuates, the working state of the amplification component changes, and the circuit component parameters continue to vary with the surrounding temperature and working time. When the input is zero, there is a fluctuation in the output, that is, zero drift. Once again, it is important to identify the root of the problem. There are many prominent issues on the pH electrode, such as electrode scaling causing an imbalance in resistance between the electrodes, resulting in drift, long-term electromagnetic interference, and polarization of the electrodes.
Several ways to alleviate the impression caused by zero drift:
1. Adopting a regulated power supply,
2. Adopt AC amplification circuit
3. Dynamic input impedance
Solution for stability and zero 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 use negative feedback circuits. Adopting DC negative feedback can not only effectively improve the input impedance of the meter, but also enhance its stability, so that the sensitivity and range of the instrument are not affected by changes in electronic component parameters.
2. Selection and maintenance of pH electrodes. The pH meter composite electrode is a key component 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. For example, after testing in adhesive samples, repeated cleaning should be carried out to remove residual sample liquid adhering to the electrode and avoid the reduction of sensitivity caused by the electrode's bubble film, which may ultimately lead to measurement failure.
