Are PLCs dependent on external devices for operation?

Programmable Logic Controllers (PLCs) fundamentally rely on external devices to fulfill their operational role in automation and control systems. These external devices, such as sensors, switches, and actuators, play an essential part in providing the PLC with the necessary input signals, which the PLC processes to execute control commands. For instance, sensors detect physical parameters like temperature, pressure, and position, sending this data to the PLC so that it can make decisions and control outputs accordingly.

While some PLCs may have integrated components, like in-built processing units and memory, they still need to interact with the environment to perform their functions effectively. The external devices allow the PLC to monitor real-world conditions and respond to them in real-time, an essential aspect of automation. Therefore, the correct understanding is that PLCs do indeed rely on external sensors and actuators to operate properly in a control system.