Process control is a statistical and engineering discipline that deals with architectures, mechanisms and algorithms for maintaining certain process outcomes within desired ranges.
Process control – First we need to understand what Process Control is and what are the important technical terms and parameters involved in this process. Process control is a statistical and engineering discipline that deals with architectures, mechanisms and algorithms for maintaining certain process outcomes within desired ranges.
Example of Process Control
An example of process control is heating to room temperature which is a process that has the specific result desired to reach and maintain the temperature (eg 20 ° C) that is set by you or the person in the room and must be kept constant over time.
You can always change the settings from time to time depending on what your body wants. We can use the remote control and adjust the settings to the temperature we want.
In the example above, temperature is a process variable (PV). At the same time, it is an input variable because it is measured with a thermometer and is used to decide whether or not to heat the room the way you want it. The desired temperature (20 ° C) is the setpoint (SP).
The state of the heater, for example a valve arrangement that allows hot water to flow through it or in the case of simple on-off control, turning the heater off and on is called a manipulated variable (MV).
The first example is an example of Proportional control because the valve opening is proportional to the user’s room requirements. There are other types of control such as Derivatives and Integral or a combination of both combined with Proportional or what we call PID. These are all common in controlling other parameters such as pressure, flow and level of a material (liquid or solid).
A commonly used control device called a Programmable Logic Controller, or PLC, is used to read a set of digital and analog inputs, apply a series of logic statements, and produce a series of analog and digital outputs.
Using the example in the previous paragraph, room temperature will be the input to the PLC. The logical statement will compare the setpoint with the input temperature and determine whether more or less heating is required to maintain a constant temperature.
The PLC output will then open or close the hot water valve. depending on whether more or less hot water is required or simply turn off the heater when the desired temperature is reached and turn it back on when certain hysteresis is met.
Larger and more complex systems can be controlled by a Distributed Control System (DCS) or a SCADA system.
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