IO-Link: making the automation environment smarter

14 July 2020

Industrial environments are generating more data than ever. Whether for production volume, downtime or serial numbers, this information can offer insight into processes and productivity, as Svenja Litz and Kate Zimmerman explain.

Many plants already rely on this data for tracking purposes but it can offer much more – it can help improve operations, expand go-to-market strategies, streamline maintenance, boost uptime and increase yield. But, to see these benefits it is first necessary to find a way to collect, analyse and display the data in an appropriate format.

Using plug-and-play smart sensors powered by IO-Link can help achieve this, allowing engineers to take full advantage of data generated by the plant. 

IO-Link history
Within the last decade, the industry has experienced a few big changes. To be used in things like robots or attached to hard-to-reach equipment, sensors needed to become smaller as mechanical components were shrinking. This made it difficult to integrate fieldbus interfaces into sensors due to size limitations. 

Manufacturing and automation equipment became more complicated which created the need to gather and control data beyond basic ‘on/off’ or ‘high/low’ capabilities. Further, it was becoming more difficult to keep up with the various types of cables used for digital and analog sensors. Each required a different installation configuration and needed to be stocked in case of performance problems.

These factors resulted in the creation of IO-Link technology. As a standardised interface, it works in even the smallest of devices. IO-Link devices can be easily integrated via an IO-Link master to different fieldbus environments or automation systems.

For easy installation, a single cable is run from an IO-Link device (such as a sensor or actuator) to an IO-Link master, which controls communication with devices and links to networks like EtherNet IP or Profinet to share information with the control system. Data is then transmitted from the IO-Link master via a high-level fieldbus communications protocol to a PLC or computer. 

What is IO-Link?
IO-Link is a simple point-to-point communications protocol used to link sensors and actuators to the fieldbus or industrial Ethernet. 

It was created to make sensors smart. Without it, simple sensors can communicate one parameter: on/off, no object/object present, high/low, etc. With IO-Link, even small sensors can communicate much more data – and can translate data into actual values. Instead of telling you whether a temperature level is ‘high’ or ‘low’, for example, smart sensors utilising IO-Link can provide current temperature readings. 

The value of IO-Link
In addition to facilitating fast, cost-effective communication among devices to reduce downtime, IO-Link offers other benefits: 

• Data storage: IO-Link masters have the capability to store up to 2 KB of the parameters that impact how a sensor or actuator functions. When a device connects to the IO-Link master, the correct parameters are automatically uploaded. This makes things like sensor replacement quick and easy, with no need for manual intervention once the device is installed.

• Remote configuration and monitoring: Device and sensor parameters can be changed remotely as needed, saving time in the manufacturing process to accommodate things such as product changeovers (shifting from small bottles to large bottles on a production line, for example). This also makes it easier to reconfigure devices in hard-to-reach locations. Sensor outputs and status alerts can be monitored remotely in real time to help you quickly identify and resolve problems before they cause downtime. 

• Diagnostic capabilities: Smart sensors equipped with IO-Link can communicate about their own status via the IO-Link master to the PLC. Before processes come to a halt, you’ll know immediately if a sensor needs to be replaced, requires maintenance or is experiencing an error. This gives the ability to optimise machine maintenance schedules and diagnose problems with a specific sensor without shutting down the entire line or a piece of equipment.

Technology limitations 
While IO-Link has the capability to streamline manufacturing processes and save valuable time, it does have some limitations:

• The cable that runs between the IO-Link device and IO-Link master has a 20 m distance limit.
• IO-Link devices can transmit up to 32 bytes per cycle, which means that it can’t transmit megabytes of data, for example.
• IO-Link is designed for integrated automation applications; if you manage simple, standalone applications, you may not see a great benefit.

Belden has worked to overcome these limitations. With the addition of IO-Link hubs to Belden’s LioN-Power IO-Link System, for example sensor and actuator connectivity can be improved. 

LioN-Power IO-Link hubs connect up to 16 standard digital I/O signals on one end and transmit them to the controller via IO-Link. When combined with LioN-Power IO-Link masters, up to 136 digital I/O signals can be cost-effectively transmitted up to 20m from the IO-Link masters. 

Svenja Litz is product manager at Belden Deutschland GmbH and Kate Zimmerman is marketing communications manager – Industrial Markets at Belden Inc.

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