A PH Meter works through an electrochemical cell mechanism, where the H + in the chemical reaction allow determining the concentration of them in solution. When determining pH with a pH meter, a reference electrode and a measurement electrode are used, which are sensitive to analytes.
In other words, a PH Meter is a high impedance amplifier that accurately measures the minimum electrode voltages and displays the results directly in pH units on an analog or digital display. In some cases, the voltages can also be interpreted for special applications or use with ion selective or oxidation / reduction potential electrodes.