PLCs are designed to control complex industrial processes, such as running machines and motors. They are simple to program and fully scalable to an operation’s requirements. They’re also used to collect data from the systems they control.

They’re an upgrade over the old relays and timers previously used to control industrial machinery since PLCs are capable of performing much more complex tasks.

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SCADA is a central system used to monitor and run plant processes. It’s typically software installed on a computer, and one of its major functions is to act as an interface with industrial machines (or Human-Machine Interface, or HMI). In other words, it allows users to track information coming in from equipment, enter commands, make changes to their programming, etc.

SCADA systems are often used in conjunction with PLCs and other devices (in fact, some would say that a PLC would be part of a SCADA system). Data from PLCs and Remote Terminal Units (RTUs) are relayed to the system, and commands are entered into the HMI to make adjustments to the processes they control.