In the field of industrial automation and water quality monitoring, online pH electrodes are the core equipment for real-time detection of solution acidity and alkalinity. Their accuracy and stability are directly related to production safety and environmental compliance. This article will delve into its working principle and summarize key usage precautions to help you efficiently master this technological tool.

　　1、 Working principle of online pH electrode

The core of an online pH electrode is the synergistic effect of a glass sensitive membrane and a reference electrode. The glass membrane is made of special lithium glass, and the surface is covered with a layer of hydrated gel. When the electrode is immersed in the solution, the difference of H+concentration inside and outside the membrane drives the ion exchange to form the membrane potential. According to the Nernst equation, the potential difference is linearly related to the pH value of the solution, and the electrical signal is converted into a pH reading through a high impedance input pH meter. The reference electrode (such as Ag/AgCl) provides a stable potential reference to ensure measurement accuracy.

　　2、 Usage precautions: Details determine success or failure

1. Installation environment

Avoid strong acids and bases (pH 0-2 or 12-14), high temperatures (>80 ℃), or high-pressure environments to prevent glass film aging or reference liquid leakage. It is recommended to install it in pipelines with stable flow rate and no bubbles, away from mixers or pump ports, to reduce mechanical impact.

2. Regular calibration and maintenance

Using two-point calibration method (pH 4.01 and 7.00 standard solutions), the frequency depends on the intensity of use (usually once a week). After use, the electrode should be soaked in 3M KCl solution to prevent membrane dehydration; If it is not used for a long time, it is recommended to install a protective cap and regularly replace the filling fluid.

3. Cleaning and Pollution Treatment

Oil or protein contamination can be cleaned with mild detergent, and inorganic salt crystals can be soaked in dilute hydrochloric acid. Avoid using hard objects to scratch the glass film to prevent scratches from affecting response speed.

4. Signal interference prevention

Ensure that the electrode cable is kept away from strong electromagnetic fields (such as frequency converters), using shielded cables and single ended grounding. Regularly check if the connector is oxidized to ensure stable signal transmission.

5. Life management and replacement

The lifespan of a regular electrode is about 1-2 years. If there is a slow response, slope below 90%, or increased drift, it should be replaced in a timely manner. High temperature, high salt, or fluorine-containing environments can accelerate electrode aging and require shorter maintenance cycles.

Conclusion

The precise operation of online pH electrodes stems from a deep understanding of the principles and rigorous operational standards. Through scientific selection, standardized installation, and proactive maintenance, not only can equipment lifespan be extended, but reliable data support can also be provided for process control and environmental monitoring. Mastering these key points makes pH electrodes the "smart eye" in your production process.