A control loop is the physical/schematical representation of the control of a process variable. In other words, a control loop is the way in which you perform the control of a process/equipment.
The aim of a control loop is to maintain the selected process variable as close to its set-point as possible which in turn we may interpret as the optimum conditions.
How do you recognize a control loop?
First of all, a control loop always have 4 components. These are
- a process/equipment,
- a sensor,
- a controller and
- a final element of control.
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| The four key components of a control loop. |
All these components are tied to each other as in a chain. Let us dig a little deep into each of these components.
A process/equipment
This is the location or the source of the current where the process variable is measured. The control loop aims to keep the process variable closely to its desired value.
A sensor
Another way of referring to this component is: instrument. You need a device capable of taking readings of the process variable in real-time. This is important so that you may know how far the measurements are from the desired value.
A controller
The controller is at the heart of the control loop. It takes the real-time measurements made by the sensor (instrument) and performs a comparison of these with the set-point (desired value). From this comparison the controller decides if a correction in the process/equipment needs to be done and how intense this action should be.
The final element of control
The final element of control in the scheme above is a control valve but it can also be an electric motor or other device. This component adjusts itself according to an output coming from the controller so that the process changes towards the optimum conditions.
Any question? Write in the comments and I shall try to help.
Other stuff of interest
- LE01 - AC and DC voltage measurement and continuity test
- LE 02 - Start and stop push button installation 24V DC
- LE 03 - Turn on/off an 24V DC pilot light with a push button
- LE 04 - Latch contact with encapsulated relay for turning on/off an AC bulb light
- What is a process variable?
- What are the most important process variables?
- Time dependence of process variables
- A list of process variables
Ildebrando.
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