HMIs versus SCADA
It is very common for people, even experienced automation engineers, to confuse HMIs with SCADA systems. SCADA stands for Supervisory Control And Data Acquisition. When a person correctly refers to SCADA, they are referring to systems that include sensors, PLCs, RTUs, control software such as HMIs, and so on. SCADA systems are more for larger systems, for example, systems that will supervise whole plants.
In contrast, an HMI is designed to control a single machine. A machine’s HMI will usually be placed near the machine, and it exists to operate that machine or a very limited group of related machines. Depending on the system you used to develop the HMI, you can network HMIs to a SCADA system. To do this, you will need to have a SCADA system that can support this type of functionality.
As such, the best way to think of the differences between HMIs and SCADA systems are as follows: