【Guide】Ethernet APL (Advanced Physical Layer) specifies relevant information on the application of Ethernet communication in sensors and actuators in the process industry, and will be published according to IEC standards. It is based on the new 10BASE-T1L (IEEE802.3cg-2019) Ethernet physical layer standard approved on November 7, 2019, and specifies explosion protection methods for implementation and use in hazardous locations. Leading process automation companies have worked together under the standards framework of PROFIBUS and PROFINET International (PI), ODVA, Inc., and FieldComm Group® to enable Ethernet APL to be used across industrial Ethernet protocols and accelerate its deployment.

The Ethernet APL (Advanced Physical Layer) specifies information related to the application of Ethernet communication in sensors and actuators in the process industry and will be published according to IEC standards. It is based on the new 10BASE-T1L (IEEE802.3cg-2019) Ethernet physical layer standard approved on November 7, 2019, and specifies explosion protection methods for implementation and use in hazardous locations. Leading process automation companies have worked together under the standards framework of PROFIBUS and PROFINET International (PI), ODVA, Inc., and FieldComm Group® to enable Ethernet APL to be used across industrial Ethernet protocols and accelerate its deployment.

Why is Ethernet APL important? Ethernet APL will change the field of process automation by enabling high-bandwidth, seamless Ethernet connections to field devices. It addresses challenges that have until now limited the use of Ethernet in the field. These challenges include power, bandwidth, cabling, distance, and use in hazardous locations. By addressing these associated challenges for brownfield upgrades and new greenfield installations, Ethernet APL will help gain new insights that were previously unobtainable, such as combining process variables, auxiliary parameters, asset health feedback, and linking them seamlessly. sent to the control layer. These new insights will enable data analytics, operational insights and productivity improvements through a converged Ethernet network from the field to the cloud (see Figure 1).

Figure 1. Using Ethernet APL in process automation for seamless Ethernet connectivity.

In process automation applications, the goal of replacing 4 mA to 20 mA devices or fieldbus communications (Foundation Fieldbus or PROFIBUS Pa) with Ethernet APL requires simultaneous power and data supply to sensors and actuators. In process automation applications, the distance between field-level devices and control systems has been a huge challenge for existing industrial Ethernet physical layer technologies, which typically require cable lengths limited to 100 m. However, process automation applications require a distance of up to 1 km and require low-power field devices suitable for Zone 0 (intrinsically safe) applications with stable and reliable performance. Therefore, process automation requires a new method that can implement Ethernet physical layer technology. This new approach is Ethernet APL.

Ethernet APL is based on the 10BASE-T1L physical layer functionality of a full-duplex, DC-balanced, point-to-point communication scheme with PAM 3 modulation at 7.5 MBd symbol rate and 4B3T coding. It supports two amplitude modes: 2.4 V peak for up to 1000 m of cable and 1.0 V peak for shorter distances. The 1.0 V peak amplitude mode means that this new physical layer technology can also be used in explosion-proof (Ex) environments and meets strict maximum energy limit requirements. 10BASE-T1L supports long-distance transmission using twisted pair technology, and simultaneously transmits power and data through a single shielded twisted pair.

In terms of powering field devices, Ethernet APLs can deliver up to 500 mW in Zone 0 applications, whereas today’s 4 mA to 20 mA systems can only deliver about 36 mW. In non-intrinsically safe applications, the power can be up to 60 W, depending on the cable used. As higher power is available at the edge of the network, new field devices with enhanced features and capabilities are available, while 4 mA to 20 mA devices have power limitations and fieldbuses are no longer applicable. For example, the extra power is now available to enable higher measurement performance and enhanced data processing at the edge. This will unearth valuable insights about process variables, which can now be accessed through web servers running on field-level devices (field assets), ultimately driving improvement and optimization of process flow and asset management.

Leveraging the rich data sets containing these valuable new insights requires higher bandwidth communication links to transport data sets from these new field devices across process installations to plant-level infrastructure or the cloud for processing. Ethernet APL enables converged Ethernet networks across information technology (IT) and operational technology (OT) domains without the need for complex, power-hungry gateways. This converged network simplifies installation and component replacement, and speeds up network commissioning and configuration. This will ultimately speed up software updates and simplify root cause analysis and field-level device maintenance.

Advantages of the Ethernet APL Solution

By converging based on Ethernet APL, power-hungry, costly and complex gateways are no longer required. This enables the transition from highly fragmented fieldbus infrastructures that create data islands that restrict access to data internal to field-level devices. By removing these gateways, the installation cost and complexity of these legacy devices is significantly reduced and the data islands they create are eliminated.

Until now, process automation applications have used the legacy communication standards shown in Table 1, and the new 10BASET1L Ethernet standard overcomes several limitations of legacy standards. 10BASE-T1L promises to reuse existing installed cabling, creating opportunities for brownfield upgrades of process automation installations through Ethernet APL based on the 10BASE-T1L physical layer.

Table 1. Comparison of 4 mA to 20 mA, Fieldbus, 10BASE-T1L Communication Technologies Using HART®

To communicate with devices that support Ethernet APL, a host processor with integrated media access control (MAC) or a switch with 10BASE-T1L ports is required (see Figure 2).

Figure 2. Ethernet APL field-level device data connection with 10BASE-T1L PHY.

Ethernet APL Cabling and Network Topology

The 10BASE-T1L standard does not define a specific transmission medium (cable), but rather a channel model (return loss and insertion loss requirements). This channel model is well suited to the Type A fieldbus cables currently used for PROFIBUS PA and Foundation Fieldbus; therefore some installed 4 mA to 20 mA cables can be reused with Ethernet APL. Advantages of single twisted pair cabling are lower cost, smaller size and easier installation compared to more complex cabling.

Figure 3 shows the proposed network topology for Ethernet APL, referred to as trunk and drop network topology. Trunk cables can be up to 1 km long with a PHY peak amplitude of 2.4 V in Zone 1, Division 2. The drop cable can be up to 200 m long with a PHY peak amplitude of 1.0 V in Zone 0, Division 1. The power switch is located at the control level, provides the Ethernet switch functionality, and supplies power to the cable (via the data line). The field switches are located at the field level in hazardous areas and are powered by cables. Field switches provide Ethernet switch functionality, connect field-level devices on drop cables to trunk cables, and provide power to field-level devices.

Connecting multiple field switches on one trunk cable allows more field-level devices to be connected to the network.

Figure 3. Future edge-to-cloud seamless connectivity technologies using Ethernet APL and 10BASE-T1L.

New Ethernet APL Devices Create New Opportunities

Ethernet APL will facilitate the transition to process automation installations with seamless field-to-cloud connectivity, including hazardous locations for food and beverage, pharmaceutical, and oil and gas installations. New Ethernet APL field devices with enhanced features and functionality can be supported due to the increased power available. These new devices will leverage powerful data analytics capabilities to unlock rich data sets for cloud implementations and drive automation with actionable insights. It will also be possible now to introduce new business models for the process industry to deliver more complex process manufacturing processes and create greater value from the greater number of new insights gained today.

Learn more about Analog Devices’ Chronous™ Ethernet solutions portfolio and how it is accelerating the transition to real-world Industrial Ethernet networks.

(Source: Analog Devices)