what is ph meter

A pH meter is a scientific instrument used to measure the hydrogen-ion activity in water-based solutions, indicating its acidity or alkalinity expressed as pH. The pH meter measures the difference in voltage between pH-sensitive glass electrode and a reference electrode, which is usually a silver–silver chloride electrode or a mercury–mercurous chloride electrode. The glass electrode develops an electric potential that is directly related to the hydrogen-ion activity in the solution, and the voltmeter measures the potential difference between the glass and reference electrodes. The pH measurements are made by comparing the pH reading of a sample solution to that of a reference solution with defined pH, such as buffers. Therefore, it is important to calibrate the instrument with appropriate buffer solutions before making any measurements. pH meters range from simple and inexpensive pen-like devices to complex and expensive laboratory instruments. pH meters are used in various fields, including chemical laboratory analyses, soil measurements in agriculture, water quality for municipal water supplies, swimming pools, environmental remediation, brewing of wine or beer, and many more. In-line or in situ pH meters, also called pH analyzers, are used to measure pH continuously in a process and can stand-alone or be connected to a higher-level information system for process control.