A pH meter is an instrument that measures the acidity or alkalinity of a solution, expressed as the pH value. The working mechanism of a pH meter involves measuring the electrical potential difference between a pH-sensitive electrode and a reference electrode.
The pH-sensitive electrode is usually a glass electrode that contains a special type of glass that is sensitive to hydrogen ions (H+). When the electrode comes into contact with a solution, the H+ ions in the solution interact with the glass, generating a small electrical potential difference that is proportional to the pH of the solution.
The reference electrode, on the other hand, is a half-cell that contains a stable reference solution, usually a saturated solution of potassium chloride (KCl) in water. The reference electrode provides a stable reference potential against which the pH-sensitive electrode can be measured.
When the pH-sensitive electrode and the reference electrode are both immersed in the solution, the potential difference between the two electrodes is measured by the pH meter, which then converts the voltage into a pH value using a calibration curve.
In summary, the pH meter measures the electrical potential difference between a pH-sensitive electrode and a reference electrode to determine the pH of a solution.