IO-Link and the role of the IO-Link Master

While it is true that IO-Link is plug-and-play from a hardware perspective, it pays to do your homework on the software.

IO-Link is a digital communication protocol that enables the exchange of data between sensors, actuators and automation systems. It was developed under the direction of the IO-Link Consortium, and since 2009 has been standardised as IEC 61131-9. Today, IO-Link is supported by hundreds of device manufacturers and used in countless industrial applications worldwide.

Components of an IO-Link system

IO-Link is a standardised, bi-directional communication protocol supported on sensors or actuators. It is not another fieldbus, but instead was developed to be as simple and universal as possible.

An IO-Link system consists of the following components:

• IO-Link devices: Intelligent sensors and actuators that communicate via the IO-Link protocol, and can send and receive detailed information about their status, performance and environment.
• IO-Link Master: The heart of an IO-Link system, it is a central device that acts as a gateway between the IO-Link devices and the upper-level control system — such as a PLC or DCS — and coordinates the communication and provides data integration with the main control system.
• Standardised cables: Standard, unshielded, 3-, 4- or 5-wire cables M12, M8 or M5 cables, making it easy to integrate into existing systems.
• Device description files: Each IO-Link device is provided with an IODD (I/O Device Description) file, which contains information about the device’s capabilities, parameters and diagnostics. The IODD file allows the IO-Link Master to correctly identify and configure the device.

Benefits of IO-Link

IO-Link offers numerous benefits for industrial automation, particularly in sectors such as manufacturing, food and beverage, pharmaceuticals, and packaging, where real-time monitoring, diagnostics and flexible communication are essential.

Device diagnostics and monitoring

IO-Link allows for detailed diagnostics at the sensor or actuator level. This means that in addition to basic process data, the device can also transmit health and status information, such as temperature, or operating hours. This real-time diagnostic data is invaluable for predictive maintenance and reducing downtime.

Remote configuration

One of the most significant features of IO-Link is the ability to configure devices remotely. This capability is especially useful in environments where sensors and actuators are difficult to access, such as in hazardous locations or in systems with a large number of devices. Users can change device parameters without physical intervention, which reduces setup time and enhances system flexibility.

Standardisation

Since IO-Link is an open standard it is vendor independent. This means devices from different manufacturers can be integrated into the same system as long as they adhere to the IO-Link standard. This interoperability allows you to choose the best devices for your specific needs without worrying about compatibility issues.

Cost effectiveness

By using standard, unshielded cables for IO-Link communication, without individual wiring back to the PLC, you can save on wiring costs. Additionally, the enhanced diagnostics and remote configuration capabilities help reduce maintenance costs by minimising downtime and manual intervention.

In greenfield sites considering digitalisation, IO-Link provides high functionality, with a good price/performance ratio. For brownfield sites, IO-Link can be an effective way to add digitalisation to improve efficiency and lower maintenance costs: Total cost of ownership is improved with efficiency improvements and cost savings during the lifecycle of a project.

But wait: there’s a catch…

Perhaps the greatest advantage of IO-Link is that you can mix and match sensors and actuators from any vendor to meet the needs of your process and your project budget, as long as they are IO-Link compatible. But there’s a catch: software compatibility.

The fact that IO-Link hardware is standardised allows for flexibility in device selection, but many users do not know that the software environment surrounding IO-Link systems often requires careful planning.

While the hardware aspect of IO-Link is standardised — and users can mix and match sensors, actuators and masters from different vendors — there is one important thing to be aware of: the software used to configure, manage and diagnose IO-Link devices is dependent on the vendor of the IO-Link Master.

Each vendor typically provides its own configuration tools, integration methods and device management software. This is applicable to both the IO-Link masters and the field devices. This creates a situation where the choice of the IO-Link Master dictates the software available to configure the devices in the field, and the data that is available to the controller. The inverse may also be true where the higher-level software in use at the control system dictates the types of IO-Link Master that can be used.

Often, users will purchase IO-Link Masters from a vendor offering the best price, which will work fine with the end devices; however, they may run into difficulties configuring and commissioning end devices and the master itself.

Vendor-specific software tools

Different vendors of IO-Link Master hardware offer their own configuration tools that are used to set up and manage the IO-Link system. For example, companies like Siemens, Rockwell Automation, Balluff and IFM provide specialised tools that are tailored for their IO-Link Masters. These tools enable users to import IODD files for the connected devices, configure parameters and monitor device status; however, the interfaces and functionality of these tools can vary significantly, and the tool from one IO-Link Master vendor will not be fully compatible with another.

The software used with the IO-Link Master must also integrate with the fieldbus or industrial Ethernet system used at the higher levels of the control system. For example, if the control network is communicating over EtherNet/IP, then the IO-Link Master must be able to handle communication with the control system via EtherNet/IP. This can be as a single protocol available on the master, or as part of a multiprotocol software suite.

In many cases, IO-Link Masters are integrated into vendor-specific platforms, providing a unified interface for configuring the entire automation system, including IO-Link devices. This further emphasises the need to align the choice of IO-Link Master with the software in use at the higher levels of the system.

Additionally, while IODD files for IO-Link devices are standardised and available for all compliant devices, the quality, interpretation and display of these files within the configuration software can also vary from vendor to vendor.

Conclusion: do your research

The most discussed benefit of IO-Link is that it is plug-and-play. And while this is true from a hardware perspective — with standardised interfaces, IO-Link Hubs, IO-Link Masters, cabling and connectors — it is not necessarily true from a software perspective. As a user it is important to be careful to select an IO-Link Master that is compatible with your software environment.

So if you are planning on taking advantage of the many benefits of IO-Link, it pays to do your research before selecting your IO-Link Master device.

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