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How Ethernet APL Will Impact Field Device Functionality

by Paul Rubens

The Ethernet APL protocol provides impressive network speeds and power output that will potentially pave the way for a new category of field devices.  

There's a new 10MBps (80Mbps) Ethernet standard on the block that's making waves right now. So the obvious question to ask is this: what's the big deal? After all, Ethernet has sped up considerably since it was introduced in 1980 at just 2.94Mbps, and the latest data transfer rates go as high as 400 Gbps. 

The answer is that the 10MBps in question is the culmination of a decade's worth of work to create a protocol-neutral advanced physical layer (APL) to provide connectivity to two-wire, loop-powered field level devices in potentially hazardous environments. It's called Ethernet APL.

What we're talking about here are factories, processing facilities and other industrial sites. The field level devices in question are sensors and other devices that collect data such as temperature, pressure, motor speeds and so on, and convert that data to signals, which are then transmitted to the control or supervisory levels for monitoring and analysis. These devices may also include actuators which take signals from the control level and then turn valves, pumps, motors and other devices on or off, or adjust them, to control industrial processes.

Faster Network Speeds 

Now 10MBps may not sound very impressive, but in industrial networks that may be located in dangerous, potentially explosive environments, those sorts of network speeds are impressive. To get an idea how impressive, 10MBps is about 300 times faster than FOUNDATION Fieldbus H1, a popular factory automation communication system, and more than 8,000 times faster than the original Highway Addressable Remote Transducer (HART) protocol from the mid '80s.

Getting down to the nitty gritty, Ethernet APL is based in the new 10BASE-T1L (IEEE802.3cg-2019) Ethernet physical layer standard, which was approved in November 2019. It can support any higher-level Ethernet protocol including PROFINET, an industry technical standard for data communication over Industrial Ethernet. (PROFINET is derived from the words Process Field Net.)

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What's particularly notable is that older industrial Ethernet physical layer technologies were limited to a range of just 100 metres, which means that control processors have to be very close to the factory floor. By contrast,  Ethernet APL allows field-level devices and their control systems to be situated up to 1000 metres apart.

Getting signals down a kilometre of single twisted pair is quite an achievement, and Ethernet APL uses two amplitude modes: a 2.4V peak amplitude for the full 1000-metre range, and a lesser 1.0V amplitude mode with reduced range for use in explosion-proof systems environments, which are subject to stringent energy restrictions. 

APL’s Power

Ethernet APL can also deliver power, and it turns out it can deliver quite a lot of it. Up to 500mW to Zone 0 (intrinsically safe) applications, which is more than ten times what is possible using other technologies. And for non-intrinsically safe applications it can deliver a whopping 60W.

That's pretty exciting because it should enable the introduction of a whole new category of field devices with new features and functionality. Think enhanced edge processing of data, and higher performance measurements. Or perhaps web servers running on field-level devices offering a whole range of information in real time that could be used to optimize process flows. Or perhaps field to cloud process automation installations. Who says Ethernet can't be sexy?

Also read: Why eBPF is the Future of Linux and Cloud Native Networking

This article was originally published on Monday Dec 21st 2020