If we are discussing process automation and advanced system design such as SCADA, PLCs, and HMI, they play a crucial role. To begin with, PLC is a hardware-based device, then SCADA is a system that works well in conjunction when combined with PLC. Moreover, HMI, at the same time, works beautifully with PLC. 

You might know that both SCADA and HMI have more or less the same functions; it is only vital that you know the difference between the two. If you are still a little confused as to how all of them function, the following article will provide you with a better understanding. Also, cover points such as how they work together in a coherent manner. 

First, let us focus on the SCADA software, which stands for Supervisory Control and Data Acquisition. As mentioned above, the system is an amalgamation of both software and hardware elements and can be used for an array of things such as:

  • You will be in control of various processes from anywhere, be it a remote location or locally.
  • You will be able to interact with pumps, motors, sensors, and valves with the help of HMI (Human-Machine Interface) software.
  • Easily monitor, process and access real-time data
  • Recording the events into a file.

Now let us focus on PLCs. It stands for Programmable Logic Controller and is an industrial computer that is used for industrial automation. It comes under various sizes and capabilities, depending upon the nature of the company and its requirements. It is a powerful computer that 24*7 keeps on monitoring the condition of input devices and therefore makes the required decision about how to control the state of output devices. 

An added advantage that comes with PLC is that they have the power to control vast chunks of the production line, with the whole production line itself.

Now comes the part where we try to understand how they function. 

Much more straightforward than you might think. The first and foremost step is called an input scan; it detects the state and condition of the input devices that are chained to the PLC. Then comes the second step that is called the program scan, which helps scan the program that the consumer-created and then executes it. Let’s move on to the next step, which is called the output scan. As the name suggests, it scans the output devices that are attached to the PLC, and it energizes or de-energize them.

Last but not least- HMI

The reason why are covering this topic, in the end, is that they first communicate with PLC, and as such, the whole system is completed. Whereas, you might be knowing that SCADA systems represents a remote system that is used to collect and communicate data. However, HMI is capable of doing the same, but the only difference here is that they are local machines. It is a user interface that helps connect the operator to a device or a machine.

One of the most significant examples of HMI is a tablet. If you have your TV connected via Bluetooth, with the help of HMI, you can control it. HMIs comes in an array of shapes and sizes – computer monitors and machines with built-in screens.

So, in conclusion, SCADA and HMI systems are used to collect and display specific data. PLC, as an industrial computer, acts as a bridge between the process and its control. Moreover, PLC is often used with SCADA systems and HMIs. Furthermore, HMI is something that is omnipresent in every kind of industry or even our homes.

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