Key highlights
- With APL field switches already launched and deployed, process engineers can begin integrating modern Ethernet-based solutions even before all APL-compatible instruments are widely available.
- Ethernet-APL can run multiple protocols on the same physical layer, helping engineers design more adaptable and future-proof systems.
While several types of Ethernet-Advanced Physical Layer (APL) devices are in various stages of development, field switches appear to be making the most progress. They have the most launched and deployed components so far, which are paving the way for other Ethernet-APL solutions and systems.
“We’re still at the early adoption phase, but interest in APL is growing. It isn’t where we want to be with available instruments yet, but it’s gaining traction, and there will be more devices it can connect to soon,” says Bernd Schuessler, global major accounts manager and global APL sales lead at Pepperl+Fuchs. “We’re continuing to reach out to end users globally, and collaborate with manufacturers like Endress+Hauser. This included several recent, well-attended summits with Endress+Hauser and Samsung—some with live demos—in Houston, Italy, Australia and Belgium. They’re continuing this year with a October event in the Carolinas, which we’re hosting with our distributor Carotek, and will continue with a September summit in Calgary. We’re also planning similar events in Europe and South America.”
For instance, Pepperl+Fuchs’ Ethernet-APL field switch features a built-in PA proxy to help Profibus-PA instruments like communicate with Profinet protocol control systems. “APL is already available for Profibus-PA and Profinet. In fact, our APL switch features a built-in PA Proxy to allow connecting existing Profibus-PA devices, and some end users are deploying it,” says Schuessler. “We don’t have EtherNet/IP instruments with APL yet, but they’ll probably be available in 12-18 months.”
In the installer’s shoes
In a recent demonstration at Hannover Fair 2025 in Germany, Pepperl+Fuchs showed how its FieldConnex Ethernet-APL Ex-ia intrinsically safe (IS) rail field switch with eight, 16 or 24 APL ports and its web-based interface work with Endress+Hauser’s Cerabar PMC 71B transmitter and Samson’s Trovis 3797 valve positioner, which both have the interface built in to communicate via Ethernet-APL utilizing hardened industrial protocols such as Profinet and Ethernet IP (Figure 1).
“We put ourselves in the installer’s shoes, who connects remote I/O and DCS. Our APL field switch and web interface means no DCS or configuration is required to perform preliminary field testing,” says Andreas Hennecke, product marketing management head in Pepperl+Fuchs’ process automation division. “Other installation tasks are still needed, but what’s new is this switch and interface work like an app on a smart phone, and use standard Ethernet techniques to identify the other APL devices they’re working with no matter which supplier they’re from. In this case, we’re using linked layer discovery protocol (LLDP), which queries any transmitter or other field components to deliver their electronic identity.”
Because Ethernet-APL complies with IEEE 802.3 standard Ethernet, users can now choose Ethernet from the control room all the way to the field, including in hazardous areas. Switches and installation provide a seamless infrastructure. “Having a built-in APL interface gives users Ethernet all the way from field devices to controllers and asset management systems, which creates a seamless network infrastructure that can just use a switch, and doesn’t need a gateway to translate protocols. Ethernet is like having a common road to drive on,” explains Hennecke. “The highway doesn’t care what cars, trucks or other vehicle travel on it, so we suppliers can still compete car-to-car, each with our own field devices and features, but they can all use the same path. Ethernet-APL is the asphalt that gets that common road into hazardous areas.”
Hennecke reports Ethernet-APLs also makes it easier for installers to check their work, document at shift change what the network is showing about what’s connected where, and provide snapshots and reports their bosses can sign off on. “And all of this can now happen during the installation phase where the DCS and other tools are not present yet. The end user is ensured, that signals are stable and the installation is of good quality,” explains Hennecke.
“This lets remote I/O and switches connect any type of digital communications from the field to control systems and asset management systems, which we couldn’t do before with the detail that’s possible now. Conversely, APL also lets the IT level back into even old, as-built processes and facilities, and allows software to ask any device linked to the network about its status, performance and needed changes. Where this used to require configurating, programming and connecting devices in the field, APL makes this seamless because instruments can deploy updated configurations residing in the asset management system, and even perform configuration automatically, which saves time and labor, and reduces human error.”
Plus, where 4-20 mA’s single analog signal can indicate little more than a wire break or short-circuit situation, Ethernet-APL’s bandwidth can relay all of an instrument’s internal diagnostics. “A vibration sensor may know when something happens, but traditionally there was no way for it to tell what it knows,” adds Hennecke. “APL gives sensors a communication channel for subsequent diagnostics and possible alarms, and even let devices generate notifications when they need adjustments or repairs.”
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Promulgating protocols
Thanks to prior development efforts, Schuessler reports that Ethernet-APL for the process industries has already been deployed in several process applications.
“Ethernet-APL’s organizers have been working on it behind the scenes for about eight years. However, our APL switch is only three years old, and it needs other devices to connect to, so we can prove that it and Ethernet-APL’s physical layer can run multiple protocols safely and successfully in hazardous areas,” explains Schuessler. “This will let users use EtherNet/IP protocol for their drives, for example, run Profinet somewhere else, and generally run whichever protocol they prefer."
Whatever protocols they decide to run on APL, users will gain Ethernet-APL’s big speed advantage of 10 Mbps that can accommodate the data streams from more and smarter instruments, and seamlessly transport all that information from the field via APL switches to control systems and cloud-computing services.
“Ethernet-APL also makes it much easier for users to replace instruments in the field than it is with traditional fieldbuses,” says Schuessler. “While working with fieldbuses requires users to discover and add drivers and configuration files for instruments, Ethernet-APL doesn’t require them to look elsewhere because the devices themselves have the latest documentation, and can make configuration much easier.”
Even though different protocols run on the same the same physical space layer on Ethernet and Ethernet-APL, devices using those protocols can’t directly interoperate, but they may be able to find some better ways to communicate.
“If data is brought to a controller, it doesn’t necessarily care if it’s delivered via 4-20 mA or one of the fieldbus protocols. A controller could receive inputs via Profinet, and use its network interface card (NIC) to send it out using a different protocol,” says Schuessler. “For example, APL could be used to plug into field devices running HART-IP, Profinet, EtherNet/IP—and soon Foundation Fieldbus—and their backends could relay information to a controller via Profinet, EtherNet/IP or Modbus TCP/IP. In addition, a controller that can talk to field devices using different Ethernet protocols also lets users coordinate them more easily, and gain more and better diagnostics, analytics and performance.
“Hooking up Foundation Fieldbus to APL is a big deal because it helps users who already have it installed,” explains Schuessler. “Foundation Fieldbus is 15-20 years old in many locations, so users are seeking upgrades, replacements or other new technologies. Consequently, it can be helpful to show fieldbus users a migration path to APL. We all know about Ethernet’s advantages in mainstream networking. Well, Ethernet-APL’s greater speed, larger bandwidth and greater distances brings those benefits to more heavily industrial and hazardous locations.”
