Process variable

This article is about the engineering indicator. For the mathematical concept used in thermodynamics, see process function.

A process variable, process value or process parameter is the current status of a process under control. An example of this would be the temperature of a furnace. The current temperature is called the process variable, while the desired temperature is known as the set-point.

Measurement of process variables are important in controlling a process. The process variable is a dynamic feature of the process which may change rapidly. Accurate measurement of process variables is important for the maintenance of accuracy in a process. There are three commonly measured variables which affect chemical and physical process: pressure, temperature, and composition.