Glossary · Electrical engineering and control panels
I/O module
Also known as: Input/output module, I/O card, Signal module
German: I/O-Modul
In industrial control, an I/O module is a hardware module that connects field signals, such as sensor inputs and actuator outputs, to a controller, converting them between electrical signals and data in the controller's process image.
- Control panels
In one sentence
An I/O module connects sensor and actuator signals to a controller, converting between electrical signals and process data.
Example
The PLC rack contains a 16-channel digital input module, an 8-channel relay output module and a 4-channel analog input module.
How it applies
- Engineering: I/O modules are chosen by signal type, channel count, diagnostics, isolation and whether they sit in the controller rack or in remote I/O stations on a fieldbus. Channel-level diagnostics (wire break, short circuit) simplify troubleshooting.
- Maintenance: Many modules can be replaced with removable terminal connectors without rewiring; some systems support hot swap. Check the manufacturer's rules before removing modules under power.
- Documentation: The I/O list and circuit diagram map each channel to its field device and tag. Keep module types and firmware versions in the configuration documentation.
I/O module vs. I/O system
An I/O module handles a set of channels. The I/O system is the whole arrangement of modules, head stations, backplane and communication that connects them to the controller.