Introduction to pH meter for Hongjie Water

PH meter is a commonly used instrument and equipment, mainly used to accurately measure the pH of liquid media. If equipped with corresponding ion selective electrodes, it can also be used to measure the potential value of ion electrodes, and is widely used in industries, agriculture, scientific research, and environmental protection fields.

Classification of pH meters

According to different measurement methods, pH can be divided into indicator method, hydrogen electrode method, hydroquinone electrode method, antimony electrode method, and glass electrode method.

At present, the most widely used method is the glass electrode method, which is mainly divided into two forms: traditional glass electrode, reference electrode, and composite electrode that combines the two.

Here is a brief introduction to the principle of a glass electrode pH meter: if there is a glass film between two solutions with different pH, a potential difference will be generated across the glass film, which is proportional to the pH difference between the two solutions.

When measuring the pH of the solution, a set of glass electrodes and a reference electrode are simultaneously placed in the tested solution. The glass electrode is sensitive to pH, while the potential of the reference electrode is stable. The two form a galvanic cell in the measured solution, and the potential of the galvanic cell is the algebraic sum of the potentials of the glass electrode and the reference electrode.

Therefore, while the temperature remains stable, the potential change of the primary battery is only related to the potential of the glass electrode, while the potential of the glass electrode depends on the pH of the measured solution.

So by measuring the changes in potential, the pH value of the pH solution can be obtained.

Nowadays, composite electrodes are commonly used, some of which come with temperature compensation, making the measurement results more accurate.

Selection and precautions of pH meter

Currently, there are commonly used glass electrode pH meters and differential electrode pH meters (pH/ORP).

The glass electrode pH meter is divided into portable glass electrode pH meters and online glass pH meters, which are suitable for corresponding needs.

The following precautions should be taken when using a glass electrode pH meter:

1. The glass electrode socket should be kept dry and clean, and it is strictly prohibited to come into contact with harmful gases such as acid mist and salt mist. It is strictly prohibited to get stuck with aqueous solutions to ensure the high input impedance of the instrument;
2. New or unused electrodes must be soaked in distilled water for several hours before use. Reduce the asymmetric potential of the electrode to achieve stability and reduce the internal resistance of the electrode;
3. During measurement, all electrode bubbles should be immersed in the measured solution;
4. When using, the reference electrode should be removed and the rubber stopper at the dispensing port should be clicked to maintain a certain flow rate of the reference electrolyte (salt bridge) through gravity and communicate with the measured solution to avoid reading drift.

Differential pH/ORP adopts differential electrode measurement technology (such as American Hash), using three measuring electrodes to replace the double electrodes in traditional pH sensors. The measured value is obtained through two glass electrodes, relative to the differential value of the third metal electrode. Reduced contamination of the reference electrode connection and improved accuracy.

The above is a brief introduction about pH meters introduced by Hongjie Water. You can refer to the corresponding pH meter manual and operation manual for specific information.