One of the Most Important Quantities in Industrial Units is pH. pH Parameter is an Abbreviation of the (Potential of Hydrogen Ion) which is Directly Related to Hydrogen Ions and Hydroxyl Ions in Solution. The Amount of These Two Ions in the Solution Specifies the Solution Acidity, Alkalinity or Neutrality. This Parameter Graded in the Range of 0 to 14.
If the Amount of Hydrogen Ions is High, the Solution is More Acidic, and if This Amount is Less, the Solution will be More Basic. pH Measurement Method is Potentiometric which is Done with an Electrochemical Sensor. One Type of the Fluid Analyzer is pH Controller that Includes a Probe to Measure the pH of Chemicals, and a Digital Panel that is Connected to the Sensor or Probe.
The Accuracy of the pH Displayed by the Electrode Depends on the Continuous Stability of the Factors such as Temperature, Freshness of Buffer Solutions and Sample Condition.
The Most Convenient Method of Measuring pH is Based on the Potential Difference Between Two Half-Cells (Reference) Consists of a Conductor Through a Conductive Glass Membrane Immersed in a Suitable Electrolyte Solution. The Voltage Between the Half Cells, according to the Nernst Equation, is as Follows:

V=V_0+2.3 RT/nF log ([H_m^+])/([H_ref^+])

V0: Half Cell Reference Voltage

R: Global Constant of Gases

T: Absolute Temperature

n: Capacity

F: Faraday Constant at 25°