When selecting a PLC (Programmable Logic Controller), you must prioritize I/O capacity (Digital/Analog), CPU processing speed, and memory size to ensure it can handle your specific logic complexity. It is critical to verify communication protocol compatibility (such as Modbus, Profibus, EtherCAT, or PROFINET) to ensure seamless integration with existing HMI and SCADA systems. Additionally, check for expandability options and environmental ruggedness, specifically looking for IP ratings and operating temperature ranges suitable for your factory floor.