A pH meter is an electronic device used for measuring the pH of a liquid to know how acidic or basic (alkaline) the liquid is. A typical pH meter consists of a special measuring glass probe (made up of two electrodes) connected to an electronic meter that measures and displays the pH reading. Principle of pH meter, operation of pH meter, calibration, and storage of the glass probes are also covered in this chapter. The basic principle of pH meter is to measure the concentration of hydrogen ions. A pH value of 7 indicates a neutral solution. pH values less than 7 indicates an acidic solution while a pH value greater than 7 will indicate an alkaline solution.