A pH meter is an important tool for measuring and reacting the acidity and alkalinity of a solution. There are various models and products of pH meters, and there are two display modes to choose from: pointer display and digital display. However, regardless of how the type of pH meter changes, its working principle is the same, and its main body is a precision potentiometer.

Chinese name PH detector, foreign name PH meter

　　The working principle of pH detector

A pH meter is used to measure the pH value of a solution using the potentiometric method. Therefore, the working mode of a pH meter is not only to measure the pH value of the solution, but also to measure the electromotive force of the battery. PH, in Latin, is the abbreviation for Pondus hydrogeni, which is the activity of hydrogen ions in a substance. PH is the negative logarithm of the concentration of hydrogen ions.

The main measuring components of a pH meter are a glass electrode and a reference electrode. The glass electrode is sensitive to pH, while the potential of the reference electrode is stable. Putting the two electrodes of the pH meter together into the same solution forms a primary cell, and the potential of this primary cell is the algebraic sum of the potentials of the glass electrode and the reference electrode.

The reference electrode potential of a pH meter is stable, so under stable temperature conditions, the potential change of the original battery composed of solution and electrode is only related to the potential of the glass electrode, which depends on the pH value of the solution being measured. Therefore, by measuring the potential change, the pH value of the pH solution can be obtained.