IO-Link – the communication system for sensors and actuators

A prerequisite for successful automation  is the availability of efficient communication systems. A standardized communication system is available which organizes the communication of the higher-level controller with several sensors and actuators more efficiently via a master unit in the form of IO-Link.

How does IO-Link work?

The IO-Link technology was developed to make the communication from the PLC to field devices possible or simplify it on the basis of standardized 3-wire cabling technology of sensors and actuators.

An IO-Link system consists of a master, a sensor hub and connected sensors and actuators.

    • The master communicates with the PLC and is attached to it with a bus-specific cable. There is now an IO-Link master for many different bus systems such as PROFIBUS, PROFINET, AS-i, CANopen, CC-Link, DeviceNet, EtherNet, EtherNet/IP, INTERBUS S, Powerlink and Sercos III, therefore making universal deployment possible.
    • The sensor hub gathers status information and measurement data from up to 16 binary sensors via conventional 3-wire cables and transmits parameter data and switch commands to sensors and actuators.
  • IO-Link - Network design

Because the sensor hub and the master are positioned close too the sensors and actuators, parallel wiring is prevented and the cost of cabling is significantly reduced.

Advantages of IO-Link

Seamless and uncomplicated communication between near all production-related devices to the lowest level of sensors and actuators is one of the requirements for companies who wish to fulfill the requirements of Industry 4.0. The standardized IO-Link system is a solution for this and bridges the gap to the terminal devices for the Internet of Things.


  • Compatibility between the devices of an industrial system, which frequently originate from different manufacturers, is made considerably easier by the IO protocol due to the standardization of the wide range of different parameters.

    The IO protocol also makes it possible to modify the parameters even during operation, which lowers maintenance costs considerably – having to stop production to adapt the system is therefore a thing of the past.

  • IO-Link - Compatibility

Easy wiring and parameterization

  • The cost of materials and implementation is also comparatively low with IO-Link because conventional, unshielded 3-wire cables up to 20 meters long can be used. In addition to having this simplified cabling, parameterization is automatic.

    Intelligent master

    The IO-Link technology is also highly functional. The user is able to choose data packages with different file sizes, from 2 bytes to 32 bytes of process data per cycle. When devices are replaced, parameters from the previous device can be transferred directly to the new device, regardless of the manufacturer.

  • IO-Link - Wiring and parameterization

Device-specific IODD configuration files

Handling of IO-Link devices is also extremely simple, since every remote station in the system has an IODD (IO device description).All relevant data is contained within these device-specific description files, from the manufacturer to the tasks and the functionality. Every device is therefore clearly identifiable and does not need to be elaborately equipped, but can be parameterized from the PLC.

IO-Link and technical translations

PRODOC customers from the industrial automation sector have been offering an increasing number of IO-Link products over the last few years, both master or sensor hubs and also IO-Link capable sensors and actuators.

Similarly to PROFIBUS or PROFINET, IO-Link also has XML-based configuration files.

These configuration files are IODD files, as was previously mentioned, and contain device-specific data. This data could be display texts from intelligent sensors, among other things.

This plays a part as far as technical translation into several languages is concerned, since you can enter display texts and messages for the control panel at the controller in a central location. At least German – English translation is often required.