One of the primary difference between PLC (Programmable Logic Controller) and SCADA (Supervisory Control and Data Acquisition) is that PLC is hardware and SCADA is (usually) a software, however, some would argue SCADA is a plant’s overall control system that uses both hardware and software elements. Regardless of semantics, both can be used in an industrial setting, and usually, they are used together but still are very different from each other.
To get a better understanding, let us first understand what both this equipment stand for.
What is a PLC software?
They are designed with the objective of controlling complex industrial processes like running machines and motors. PLC is fairly easy to program and can be fully scalable to an operation’s requirements. You can use it to collect data from systems they are in control of. PLC is an upgrade of old relays and timers previously used to control industrial machinery as they are capable of performing much more complex tasks.
What is SCADA?
To begin with, SCADA is a central system which is used to monitor and run plant processes. Usually, the software is installed on a computer and one its most prominent function is that it acts as an interface with industrial machines ( or Human-Machine Interface, or HMI). In simpler terms, it will give you the freedom to track information that is coming from the equipment, make changes to the programming (if required), etc.
SCADA systems more often than not are used in conjunction with PLCs and other devices (in fact, some would say that PLC could be part of a SCADA system). Data that you get from PLCs and Remote Terminal Units (RTUs) are relayed to the system, and then you enter the commands into the HMI to make adjustments to the processes they control.
Now, what exactly is the relationship between PLCs and SCADA?
When they are used together, SCADA and PLCs form an automatic system for prescribing tasks and then formulate the core of a predictive maintenance program. It functions something like this:
The data extracted from sensors on individual assets is transmitted to the PLC
Then the PLC translates the data into a format that can be used by the software
You will then get to access the data through the HMI on the software
In case the data crosses certain thresholds, a maintenance work order is created
Now let us see an example, if a turbine is showcasing too much vibration, sensors then transmit the data through the system, and the readouts that are present on the user end would trigger a work order. In this situation, SCADA software controls the entire system while PLCs act as a relay and controllers for certain assets.