ApH meteris an instrument used to measure acidity or alkalinity of a solution - also know as pH.
Why is pH measurement and control a problem? pH electrodes have been around long enough to be well understood and readily applied. The problem is since pH is a logarithmic function, a change of one pH unit represents a ten-fold change in hydrogen ion concentration.
The term pH is derived from "p,the mathematical symbol for negative logarithm, and "H, the chemical symbol for Hydrogen.
pH is a unit of measure which describes the degree of acidity or alkalinity of a solution. It is measured on a scale of 0 to 14.