Is IO-Link with Single Pair Ethernet the Future?

20 meters.

That is the maximum distance between an IO-Link master port and an IO-Link device using a standard prox cable.  Can this length be extended?  Sure, there are IO-Link repeaters you can use   to lengthen the distance, but is there an advantage and is it worth the headache?

I hope you like doing some math, because the maximum distance is based on the baud rate of the IO-Link device, the current consumption of the IO-Link device and finally the cross section of the conductors in the cabling.  Now throw all that into a formula and you can determine the maximum distance you can achieve.  Once that is calculated, are you done? No.  Longer cables and repeaters add latency to the IO-Link data transfer, so you may need to slow down the IO-Link master’s port cycle time due to the delay.

Luckily, there is a better and easier solution than repeaters and the sacrifice of the data update rate — Single Pair Ethernet (SPE).

SPE is being discussed in all the major communication special interest groups, so it makes sense that its being discussed within the IO-Link Consortium.  Why?  A couple of key factors: cable lengths and updated speeds.  By using SPE, we gain the Ethernet cable length advantage. So, instead of being limited to 20 meters, your IO-Link cabling could stretch to 100 meters!  Imagine the opportunities that opens in industrial applications.  It is possible that even longer runs will be achievable.  With 10 Mbit/s speed, to start, the update rate between IO-Link devices and the IO-Link master could be less than 0.1 millisecond.

Latency has been the Achilles heal in using IO-Link in high-speed applications, but this could eliminate that argument. It will still be IO-Link, the point-to-point communication protocol (master-to-device), but the delivery method would change. Using SPE would require new versions of IO-Links masters, with either all SPE ports or a combination of SPE and standard IO-Link ports. The cabling would also change from our standard prox cables to hybrid cables, containing a single twist Ethernet pair with two additional conductors for 24 volts DC.  We may even see some single channel converts, that convert standard IO-Link to SPE and vice versa.

There likely would have been pushback if this was discussed just five or ten years ago, but today, with new technology being released regularly, I doubt we see much resistance. We consumers are ready for this. We are already asking for the benefits of SPE and IO-Link SPE may be able to provide those advantages.

For more information, visit www.balluff.com.

John Harmon has experience and knowledge of the industrial automation industry with Balluff. With his product and industry knowledge, he is sharing his passion for automation with Automation Insights.

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