Ethernet APL – data transmission in the process industry

Continuous use of Ethernet in the process industry

Ethernet APL – Empowering the digitalization in process automation

Ethernet communication to field level

Ethernet APL enables the direct two-wire Ethernet connection of devices and sensors in the Ex zones of process technology applications (“Ethernet in the field”). In this way, the communication infrastructure enables the continuous use of Ethernet in the process industry. This makes it possible to implement applications from the Industrial Internet of Things (IIoT) and Industry 4.0 sectors, which have become an integral part of the manufacturing industry.

What exactly is Ethernet APL?

Prototype of the Ethernet APL switch with the connected sensor  

Simple Ethernet connection of sensors by means of the APL field switch

The abbreviation APL stands for Advanced Physical Layer and describes a further development of physical data transmission in Ethernet networks. This physical layer makes it possible to exchange Ethernet data via only two wires, instead of the previously required four or eight wires.

Aside from pure communication, the technology also optionally enables the supply of power to connected devices on the same pair of wires.

Ethernet APL therefore is one of several manifestations of the Single Pair Ethernet (SPE) and enables the direct connection of sensors, thereby making possible a continuous communication to the last few meters in the field.

What is the difference between SPE and Ethernet APL?

The Single Pair Ethernet technology is comprised of various standards which support different data rates and cable lengths and which therefore are suitable for various applications. A distinction is drawn between the standards 10BASE-T1S, 10BASE-T1L, 100BASE-T1, and 1000BASE-T1.

Advanced Physical Layer uses the 10BASE-T1-L standard of the IEEE 802.3cg along with the IEC TS 60079-47, 2021-03 (2-WISE) standard (2-WISE = 2-Wire Intrinsically Safe Ethernet), and supports explosion protection methods including intrinsic safety. Thus Ethernet APL enables use in potentially explosive areas and the bridging of great distances up to 1,000 m at 10 Mbps.

Ethernet APL features

The APL technology offers the following features:

  • Bridging large distances: Trunk lengths of up to 1,000 m, spurs up to 200 m
  • Use in explosion-protected areas is possible (zones 0, 1, and 2)
  • Interoperability of the devices and systems of different manufacturers
  • Capture and analysis of huge amounts of additional data is possible (big data) – new solutions such as predictive maintenance can be realized to increase availability
  • Cost-efficient modernization of systems thanks to use of existing cabling and proven Ethernet protocols such as EtherNet/IP™, HART IP, OPC UA, and PROFINET

Where is Ethernet APL used?

Figure of a processing plant and an indicated network  

Ethernet APL in processing plants

Advanced Physical Layer enables the direct connection of devices and sensors in the Ex areas of process technology applications.Due to the direct Ethernet integration, complex gateway solutions can be dispensed with if data is to be accessed from the field. Therefore, Ethernet APL is the economic basis, and an empowering factor, for the IIoT in process automation. At the same time, it enables new concepts, such as the NAMUR Open Architecture (NOA) or the Open Process Automation standard (O-PAS™). Consequently, different user groups can profit from this new technology:

  • Operators and users
  • Control system suppliers
  • EPCs and system integrators
  • Device manufacturers

Setup of an APL network

Ethernet APL can be used both in compact plants (e.g., pharmaceutical or chemical plants) and in extensive plants in the process industry. The trunk and spur topology is used for greater range.

The Ethernet APL switches installed in the field are intended for use in potentially explosive areas (zones 1 and 2 or division 2), such that all increased demands regarding explosion protection can be met with the degrees of protection of increased safety or intrinsic safety.

Setup of an APL network for extensive plants in the process industry which uses the trunk and spur topology
Field switch
Trunk cables
Power switch
Field devices
Spur cables

In addition, the network topology can be flexibly designed so that even compact layouts can be realized. It is possible to dispense with the trunk by using the APL switches to connect the APL spur ports directly to the standard Ethernet.

Setup of an APL network for compact plants in which APL switches directly connect the spur ports to the Ethernet
Field devices
Field switch
Spur cables

Our commitment to Ethernet APL

Logo of the Ethernet APL project, in which Phoenix Contact and other leading suppliers of process technology are working on creating a two-wire Ethernet solution  

Ethernet APL logo

Within the scope of the Ethernet APL project, Phoenix Contact and other leading suppliers of the process technology are working on the realization of a two-wire Ethernet solution that meets user demands. Together with the standardization organizations PROFIBUS & PROFINET International, FieldComm Group, ODVA, and OPC Foundation, the industrial partners are establishing an open standard based on a new physical layer for use in process automation.

Phoenix Contact presented first working prototypes of Ethernet APL switches in demonstrators during the NAMUR General Meeting in late 2019 and the ARC Forum in February 2020. The NAMUR installation with the APL project partners ABB, Endress+Hauser, KROHNE, and SAMSON used the PROFINET protocol to connect data via the Ethernet APL switch and PLCnext Technology to an HMI and the Cloud.At the ARC Forum, we were able, together with ABB, to demonstrate the connection via OPC UA.

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