Process control is the regulation of process parameters such as pressure, temperature, flow etc. to within a specified target range or to a set target value called the set point. Process control is most often used in manufacturing and process plants, because many parameters, such as color, composition, and density, must be accurate for a product or process to be as desired. Therefore, to implement a quality product, a controller(PLC) through its Input and Output interfaces, regulates these variables by analyzing its deviation from the target and actuating the needed corrections on the system.
Proportional-Integral-Derivative (PID) control is the most common control algorithm used for control systems and has been universally accepted in industrial control..
The basic idea behind a PID controller is to read a sensor (whose parameter is known as the PROCESS VARIABLE-PV) then compute its deviation (ERROR) from the desired target value called the SET POINT. The controller then makes use of this information to produce a required OUTPUT (CV) which makes an attempt to correct the ERROR by bringing the PROCESS VARIABLE (PV) close to the SET POINT as much as possible. PID controllers do this using three different calculations and actions namely, PROPORTIONAL, INTEGRAL and DERIVATIVE actions. It then sums this to provide the desired response (output).
In the video available on this page, we take you through a process control demonstration in our laboratory where the level of liquid in a tank is regulated by a simple PID program.