Industrial Maintenance Technician Practice Test

When checking an input/output card on a PLC (Programmable Logic Controller), it's essential to focus on the input card because it is responsible for receiving signals from various sensors and switches in the system. This card converts the physical signals into digital signals that the PLC can process. If there is an issue with the input signals, it could lead to a malfunction in the entire control system, as the PLC may not receive the necessary information to make decisions or execute commands.

In contrast, the output card is responsible for sending signals to actuators or other devices based on the processed information from the input card. While it is important to check the output card, understanding the root cause of any issues often starts with examining the inputs. The control card, which may refer to the main processing module, handles the logic and processing but does not directly interact with input/output signals. Similarly, the power supply card provides the necessary power to the PLC system but does not manage data input or output operations directly. Therefore, focusing on the input card allows for a more effective diagnosis of any issues related to the PLC’s input/output functionality.