IO-Link: The Last Meter to the Internet of Things

by: Shannon Foos and Kevin Zomchek, Rockwell Automation

A significant hurdle stands in the way of industrial operations attempting to realize the full benefits of the Internet of Things (IoT). That hurdle is comprised of the billions of sensors, actuators and other instrumentation that lie beyond the reach of the Internet Protocol (IP). But two innovative technologies can support that vital connection, extending the increased operational data, enhanced productivity and improved reliability that come with the IoT.

The last meter to the IoT is being bridged by IO-Link® for discrete applications and HART®, together with WirelessHART® for process applications. Both of these communication protocols work with EtherNet/IPnetworks to connect sensors to control systems and business-level enterprise systems.

With instrument data available on EtherNet/IP, industrial operations can capture the real-time, actionable information they need to achieve operational efficiencies, increase productivity and achieve the full benefits of the IoT.

IO-Link for Discrete Applications

In an evolving IoT world, companies are looking to get more intelligence from every device. But in discrete applications, such as packaging or automotive facilities that use large amounts of sensors, it is simply not cost effective to replace existing instrumentation with IP-enabled devices. IO-Link was developed to create a cost-effective, last-meter connection between sensors and control systems for seamless data flow.

There have been attempts in the past to get these sensors enabled on different communication protocols, such as PROFIBUS® or DeviceNet, which required a different network to connect to the devices. However, many sensor users pushed back on those efforts because it doubled the number of products (networked and non-networked) they had to support on their machines. It also involved learning a new protocol – even if only a subset of the total sensors on a given machine required more than on/off information, which was often the case.

IO-Link has become a suitable compromise for this dilemma – offering access to a wealth of information cost effectively, while operating in conjunction with existing IP networks.

This access to device-level data means industrial operations don’t have to delay their needs for smarter machines while waiting for all sensors to have IP accessibility. IO-Link offers a simple solution to increase connectivity throughout discrete applications. IO-Link communicates over the same three-wire conductors and can use the same configuration software currently used with EtherNet/IP networks, so getting the sensor data to IP is relatively seamless. Therefore, all sensors installed on a machine can support IO-Link, but only those connected to an IO-Link master interface will take advantage of the technology with diagnostics. This eliminates the need to learn a new protocol and limits the additional expenses to those sensors that are actively using the IO-Link technology.

To access the IO-Link functionality utilizing existing technology already in the plant, manufacturers simply remove the discrete card and install an IO-Link card, the aforementioned IO-Link master. Many sensors featuring embedded IO-Link cost and act the same as the standard I/O sensors that manufacturers are already using until connected to a master. But interfacing these sensors with an IO-Link master “wakes up” the advanced functionality in the sensor, giving the user access to all the data and configuration capabilities IO-Link has to offer. This means users have the flexibility to install IO-Link sensors as standard IO today and activate IO-Link functionality later – whenever and wherever they want – without having to install costly new wiring or sensors. Ultimately, this makes IO-Link an excellent forward- and backward-compatible solution for sensor suppliers and users. 

Additionally, the flexibility to interchange “standard” and IO-Link enabled sensors allows users to be selective – not all machines or sensors need additional diagnostics. With the IO-Link master, users can choose which sensors to enable with IO-Link – gaining benefits without information overload. Although all machines can benefit from IO-Link, it’s not needed throughout the machine. In fact, less than 20 percent of the sensors on a machine are typically at risk of physical damage – these are the areas where the additional diagnostics offered by IO-Link would be most beneficial. 

With IO-Link, users have access to new information that flows from the devices through IP to higher levels of the system. This could include diagnostics about sensors that are broken or not performing at optimal levels. An example might be the monitoring of a photoelectric sensor located near a cutting operation where there is significant debris that can accumulate on the sensor lens. Currently, most machine builders use compressed air to periodically blow debris off the sensors regardless of how dirty the sensor might be. The IO-Link sensor can inform the control system to initiate compressed air or send a maintenance person to clean the sensor only when necessary. Not only does this reduce downtime on a machine, since it optimizes predictive maintenance, but it can also be used to save compressed air usage, reducing the operational expense of the machine.

In another example, consider how proximity sensors are used to detect objects moving along a conveyor belt. If a machine gets out of alignment and shears off the head of a standard sensor, the controller no longer receives updates from the device that there are products being sensed. Yet the machine will continue to operate, and operators often have no way of knowing that critical data is not being collected until production is interrupted. But if that proximity sensor is IO-Link enabled, an alarm will trip and tell the control system that the sensor head has failed. The diagnostic is not a direct measurement, but it alerts the system that the data is no longer valid. Additionally, the damaged sensor could more easily be pinpointed for quick replacement.

HART – Wired and Wireless – for Process Applications

The promise of instrument data throughout the enterprise has been around for many years in process applications with HART. However for many installations, hardwiring devices can be an arduous process. In applications, such as tank farms or mining operations, that span many miles, hardwiring devices through point-to-point connections is difficult, time-consuming and expensive – even more so for systems that need the extra reliability of redundancy.

Those geographic and environmental complications have led to the need for technology with a broader reach. WirelessHART has been the solution to these challenges, offering wireless connections to sensors that measure pressure, temperature and volume in process applications.

Now, the WirelessHART gateway is IP-enabled in multiple variants including EtherNet/IP. Similar to other wireless networks, existing devices can be converted to WirelessHART to create a robust infrastructure that allows greater connectivity and generates a wealth of new data.

WirelessHART offers greater flexibility for the variety of applications, offering device monitoring and diagnostics. For example, if a pipe is empty when it should be transporting a product, the sensor will alert the operator to the situation, rather than simply showing an erroneous flow measurement. This helps the operator classify the plant deviation as an operations issue rather than a maintenance issue.

Similar to IO-Link, the diagnostics are not direct measurements. Sensors enabled in HART devices give an inside view into the equipment with device information that can be used for predictive maintenance. This not only improves the reliability of the process, plant safety and data security, but can also reduce the cost of maintenance and unplanned downtime.

HART devices also work seamlessly with EtherNet/IP on standard IP networks offering complete connectivity. Before, device data was limited to the control system, but now data from the process floor can travel throughout the entire plant, offering operators access to additional valuable data.

The availability of this granular data optimizes every aspect of the operation – from troubleshooting problems on the plant floor to inventory or production capacity decisions on the business side. The more asset knowledge operators have allows for increased auditing and verification – that leads to both increased process safety and data security. 

The IP connectivity from the industrial control system through the gateway – either IO-Link or HART – closes the last meter to provide connectivity to devices that are sitting in the field. These two networks allow industrial operations to bridge to an IP network as seamlessly as possible, making today’s plants more future-ready for the industrial IoT.

DeviceNet and EtherNet/IP are trademarks of ODVA Inc.

HART and WirelessHART are trademarks of the HART Communication Foundation.

IO-Link and PROFIBUS are trademarks of PROFIBUS & PROFINET International (PI).