Definition and function of pH meter
A pH meter, also known as an acidity meter, is a commonly used physical and chemical analytical instrument specifically designed to measure the pH value of a solution.
The pH value is the negative logarithm of the concentration of H ions in a solution (pH=- lg (H ⁺)), which intuitively reflects the acidity or alkalinity of the solution.
A pH meter can not only accurately measure the pH value of a solution, but also partially measure the potential difference between two electrodes.
In many fields such as environmental protection, hygiene and epidemic prevention, quality control, safety protection, as well as scientific research and production, pH meters play an irreplaceable and critical role, ensuring the accuracy requirements for measuring the acidity and alkalinity of solutions in various work.
Working principle of pH meter
The pH meter operates based on the principle of primary batteries. Its core components include a reference electrode, a glass electrode (pH sensitive electrode), and a measuring device.
The reference electrode can maintain a constant potential, providing a stable reference for measurement; The potential of a glass electrode will change with the activity of hydrogen ions in the solution.
When these two electrodes are immersed together in the test solution, a primary battery is formed.
The potential generated by the battery is the algebraic sum of the potentials of the glass electrode and the reference electrode, i.e. E-battery=E-reference+E-glass. Under constant temperature conditions, the potential of the battery will change correspondingly with the pH value of the test solution.
The generated small potential difference signal is amplified and processed to drive the display instrument, presenting the corresponding pH value in the form of pointer deflection or digital display.
Classification of pH meters(Divided by measurement accuracy)
Level 0.2: The division value is 0.2pH, suitable for scenarios where measurement accuracy is relatively low and only a rough understanding of the pH range of the solution is needed, such as some general industrial production preliminary testing stages.
0.1 level: The division value reaches 0.1pH, which can meet the accuracy requirements for pH measurement in common industrial production, ordinary experiments, and other scenarios, such as controlling the pH of raw materials or intermediate products in some food processing processes.
0.01 level or higher accuracy: With a division value of 0.01 pH or even smaller, it is commonly used in fields such as scientific research experiments, high-end pharmaceuticals, and precision chemical engineering that require extremely high accuracy in pH measurement. Even tiny changes in pH can have a significant impact on experimental results or product quality.