Temperature & Process (PID) Control
Proportional–integral–derivative controllers (PID controller) are widely used in industrial control systems for feedback and appropriate system control. Temperature Controllers control the temperature in a system to a very tight tolerance. A Thermocouple or RTD Sensor typically provides the input to the Temperature Controller. The output is typically a discrete on/off output to a contactor controlling a furnace, heater, or cooler by cycling its power on and off. Alternatively, a continuously variable analog output can be used to control the heating or cooling element.
A Process Controller is just like a Temperature Controller, except that it senses and controls system variables other than temperature, such as pressure, humidity, or flow rate.
Temperature Controllers and Process Controllers are often referred to as PID Controllers, because they use the mathematical concepts of Proportion, Integral, and Derivative to dynamically control a system variable.