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10BASE-T1L solves the challenges that have limited the use of Ethernet in process automation so far.
How can the electronics industry help manufacturers embark on the journey of digitalization and industrial automation? What is the role of sensors in IIoT and how can manufacturers ensure the cyber security of their industrial control systems? This month's In Focus looks at the challenges and progress of manufacturers' transition to smarter factories.
10BASE-T1L is a new Ethernet physical layer standard (IEEE 802.3cg-2019), which was approved internally by IEEE on November 7, 2019. It will significantly improve the efficiency of plant operations through a seamless Ethernet connection to the field level, thereby greatly changing the process automation industry equipment (sensors and actuators).
10BASE-T1L solves the challenges that have limited the use of Ethernet in process automation so far. These challenges include power, bandwidth, wiring, distance, data islands, and intrinsically safe zone 0 (hazardous area) applications. By solving these challenges of brownfield upgrades and new greenfield installations, 10BASE-T1L will achieve new insights that were previously unavailable, such as combining process variables, secondary parameters, asset health feedback, and seamlessly communicating them to the control layer and cloud These new insights will bring new possibilities for data analysis, operational insights, and productivity improvements through converged Ethernet from the field to the cloud (see Figure 1).
Figure 1: Seamless Ethernet connection with process automation field sensors and actuators.
To replace 4mA to 20mA or fieldbus communication (Foundation Fieldbus or PROFIBUS PA) with Ethernet in process automation applications, it is necessary to provide power and data to the sensor or actuator through a shielded single twisted pair cable. Compared with more complicated wiring, single-twisted-pair wiring has the advantages of lower cost, smaller size and easier installation. The distance between field-level devices in process automation applications has always been a major challenge, and the existing industrial Ethernet physical layer technology is limited to 100 m. Since process automation applications require distances of up to 1 kilometer, and require extremely low power consumption and rugged field devices for Zone 0 (intrinsically safe) applications, a new method is needed to implement Ethernet physical layer technology for process automation . 10BASE-T1L is this new method.
The core function of 10BASE-T1L is a full-duplex, DC balanced, point-to-point communication scheme, using PAM 3 modulation, symbol rate 7.5MBd, and 4B3T encoding. It supports two amplitude modes: 2.4V peak-to-peak up to 1km cable and 1.0V peak-to-peak to shorten the distance. The 1.0V peak-to-peak amplitude mode means that this new physical layer technology can also be used in an Ex-proof system environment to meet the strict maximum energy limit. It can realize long-distance transmission on 2-wire technology. Power and data are all on a twisted-pair cable. It belongs to the single-pair Ethernet (SPE) media series.
10BASE-T1L can significantly improve the power supply capacity of field devices; up to 500mW in zone 0 (intrinsically safe) applications. In contrast, the power consumption of 4mA to 20mA devices is about 36mW. In non-intrinsically safe applications, depending on the cable used, the power can reach up to 60W. As the available power at the edge of the network has increased significantly, new field devices with enhanced features and functions can be enabled because the 4mA to 20mA and fieldbus power limits no longer apply. For example, with additional functions, higher performance measurements and enhanced data edge processing can now be achieved. This will open up valuable insights about process variables, which can now be accessed through web servers running on field-level equipment (field assets), and ultimately drive the improvement and optimization of process and asset management.
In order to take advantage of the rich data sets containing these valuable new insights, a higher bandwidth communication link is required to transfer the data sets from field devices across process installations to plant-level infrastructure or the cloud for processing. 10BASE-T1L eliminates the need for complex, power-hungry gateways and supports converged Ethernet across information technology (IT) and operational technology (OT) networks. This converged network provides simplified installation, easy device replacement, and faster network debugging and configuration. This can speed up software updates through simplified root cause analysis and field-level equipment maintenance.
Advantages of Ethernet-based solutions
By converging Ethernet as a communication method at the enterprise, control level and field level in process automation, the need for complex and power-consuming gateways is eliminated. This also realizes the transition from a very decentralized fieldbus infrastructure, which creates data islands and restricts data access within field-level devices. By removing these gateways, the cost and complexity of these traditional installations are significantly reduced, and the data islands they create are also removed.
So far, process automation applications have used the traditional communication standards shown in Table 1, and the new 10BASE-T1L standard overcomes these limitations. There are also knowledge base challenges in process automation. After retirement, technicians and engineers will leave the workforce and carry detailed knowledge on how to deploy, debug, and maintain 4mA to 20mA installations using HART or fieldbus communication systems. University graduates are not familiar with these traditional technologies, but are very familiar with Ethernet-based technologies and can quickly upgrade Ethernet-based network solutions.
Table 1: 4 mA to 20 mA, using HART and fieldbus and 10BASE-T1L
The Ethernet standard ensures that all higher protocol layers of 10BASE-T1L work exactly like 10BASE-T, 100BASE-TX and 1000BASE-T, without the need for complex gateways. IEEE 802.3 is where all the physical layers in the ISO 7-layer model are defined for Ethernet: 10BASE-T1L (see Figure 2). This means that devices can now use PROFINET, EtherNetTM/IP, HART/IP, OPC UATM or MODBUS/TCP and support IoT protocols such as MQTT, which provides a simple and powerful way to connect field devices to the cloud. Ethernet also supports simple, centralized control of software updates up to the terminal node, enabling faster network debugging.
Figure 2: 10BASE-T1L in the ISO 7-layer model.
To communicate with devices that support 10BASE-T1L, a host processor with integrated media access control (MAC), a passive media converter, or a switch with a 10BASE-T1L port is required. No additional software is required, no customized TCP/IP stack, and no special drivers are required (see Figure 3). This brings obvious advantages to 10BASE-T1L equipment:
Although the 10BASE-T1L connection requires a media converter, it only converts the physical code, not the content of the Ethernet packet. From the perspective of software and communication protocols, it is transparent.
Through the Ethernet connection, the sensor can be configured using a laptop or mobile phone, regardless of whether the sensor is on a desk or deployed in a manufacturing plant. For example, today's temperature transmitters have an additional interface (for example, in the form of USB) in order to be able to configure the converter. Depending on the manufacturer, there are more than 100 adjustment options. Today, these parameters are simply not accessible via 4 mA to 20 mA. HART allows access, but is usually not available due to cost reasons. Therefore, if an error occurs during the desktop setup process, the 4 mA to 20 mA sensor needs to be reconfigured after the on-site installation. Sensors connected to 10BASE-T1L can be accessed via the network and can be updated remotely anytime and anywhere.
4mA to 20mA devices can only transmit one process value. Ethernet can not only directly access process values, but also all equipment parameters, such as asset management, life cycle management, predictive maintenance, configuration, and parameterization.
Figure 3: Connection between field-level equipment and 10BASE-T1L PHY.
Access advanced Ethernet network diagnostic tools to simplify root cause analysis.
Process automation wiring and network deployment
In process automation, unlike machine manufacturing or factory automation, these sensors and actuators (flow, level, pressure, and temperature) are not close to the controller. A distance of 200 m between the sensor and the I/O is not uncommon, and from there, the distance between field switches can reach 1000 m. Process automation uses Type A fieldbus cable because it is used today for PROFIBUS PA and Foundation fieldbus installations.
The 10BASE-T1L standard does not define a specific transmission medium (cable); instead, it defines a channel model (return loss and insertion loss requirements). The 10BASE-T1L channel model is very suitable for fieldbus type A cables, so some installed 4 mA to 20 mA cables may be reused with 10BASE-T1L, creating important opportunities for brownfield upgrades for process automation installations.
Since 10BASE-T1L allows the signal amplitude voltage to be reduced to 1 V on a line up to about 200 m, 10BASE-T1L can be used in an explosion-proof system environment and meets the strict maximum energy limit of 500 mW in hazardous areas.
Compared with 4mA to 20mA (500mW to ~36mW), the power is significantly increased. Today's 4-wire devices that require an external power supply due to the limited power of 4mA to 20mA can now be replaced by 10BASE-enabled 2-wire devices-T1L, which eliminates the need for external The demand for power supply provides greater installation flexibility for new equipment.
Figure 4 shows the proposed network topology for the process industry, called the trunk and branch network topology. The trunk cable can be up to 1 km long, with a PHY amplitude of 2.4 V peak-to-peak, located in Zone 1 and Zone 2. The branch cable can be up to 200 m long, and the PHY amplitude is 1.0 V peak-to-peak and resides in zone 0 and zone 1. The power switch is located at the control level and provides the function of an Ethernet switch and supplies power to the cable (via the data line). The field switch is located at the field level of the hazardous area and is powered by the cable. The field switch provides the Ethernet switch function, connects the field-level equipment on the branch line to the main line, and transfers the power to the field-level equipment. Multiple field switches are connected to the backbone cable to provide a large number of field-level devices to connect to the network.
Field switches can be connected through a ring topology to achieve redundancy. At the edge, up to 10Mbps is a major advancement for most applications, which were previously limited to data rates below 30 kbps. Since Ethernet is now used to connect field-level terminal node devices, IT and OT have successfully merged into a seamless Ethernet network to achieve IP addressing capabilities for any terminal node device anywhere in the world.
Figure 4: The 10BASE-T1L network topology of the process industry.
Ethernet-APL (Advanced Physical Layer) specifies the application details of Ethernet communication in process industry sensors and actuators, and will be published under IEC. It is based on the 10BASE-T1L Ethernet physical layer standard and specifies the implementation and explosion-proof methods for use in hazardous locations. Leading companies in the field of process automation are collaborating under the umbrella of PROFIBUS and PROFINET International (PI), ODVA, Inc., and FieldComm Group® to make Ethernet-APL work across the industrial Ethernet protocol and accelerate its deployment.
Process automation: the transition to a seamless Ethernet connection in the future
The 4 mA to 20 mA connection to HART has been successfully deployed in process automation applications for many years and is a proven and robust solution that will not disappear overnight. The existing large-scale installation base of 4 mA to 20 mA is equipped with HART-enabled instruments. ADI is investing in software configurable I/O to provide greater installation flexibility for these existing devices by allowing any industrial I/O function. Access on any pin allows the channel to be configured at any time in the remote I/O application. This means that it can be customized at the time of installation, thereby shortening time to market, reducing design resources, and universal products that can be widely used between projects and customers. Examples of ADI's software programmable I/O circuits are AD74413 and AD4110-1.
Figure 5: Traditional discrete wiring will gradually become an intelligent Ethernet network for all sensors and actuators.
Figure 5 shows the transition from traditional 4 mA to 20 mA connected instruments to brownfield Ethernet, where new instruments that support 10BASE-T1L will coexist with traditional 4 mA to 20 mA instruments. Software configurable I/O connects these traditional instruments, where remote I/O provides aggregation point to 10 Mb Ethernet uplink to PLC.
A seamless edge-to-cloud connection will be realized in process automation through 10BASE-T1L technology. 10BASE-T1L eliminates the need for gateways and I/O, and supports Ethernet connections from field devices to the control level and ultimately to the cloud. Unlocking field devices will generate rich data sets for advanced data analysis.
10BASE-T1L applications beyond process automation
10BASE-T1L is now gaining huge traction in building automation, factory automation, energy supply, monitoring, water plant and wastewater treatment automation, and finally elevators. All these applications require a higher bandwidth, seamless Ethernet connection to the sensor (no gateway) on a single twisted pair cable that supports power and data. Table 2 compares 10BASE-T1L with the existing wired technology used today. Application examples include RS-485 used in building automation and I/O links used in factory automation.
10BASE-T1L equipment creates actionable insights to drive process optimization
By adding 10BASE-T1L physical layer products to ADI's ChronousTM industrial Ethernet solution portfolio, ADI will realize the transition to field-to-cloud-connected process automation installations, including food and beverage, pharmaceutical, oil and gas installations. The new 10BASE-T1L physical layer transceiver will provide a physical layer interface to unleash the many advantages of Ethernet-connected factories. With 10BASE-T1L, Ethernet data packets move from the field layer to the control layer, and finally to the cloud, without the need for a gateway, to achieve the goal of a unified IT/OT network for Industry 4.0. As the available power increases significantly, new field devices with enhanced features and functions can be enabled. The transparent IP addressing capability of each field-level device will greatly simplify the installation, configuration and maintenance of 10BASE-T1L connected instruments. 10BASE-T1L will unlock new field equipment, rich data sets for cloud computing, and advanced data analysis. The efficiency of plant operations will be improved by gaining actionable insights from its processes, thereby accelerating the deployment of more complex process automation production facilities in the future.
For more information on the ADI Chronous industrial Ethernet solution portfolio and how they can accelerate the transition to real-world industrial Ethernet networks, please visit analog.com/chronous.
Table 2. Comparison of existing communication standards and 10BASE-T1L
Maurice O'Brien is the Strategic Marketing Manager for Industrial Connectivity at Analog Devices. He is responsible for developing strategies to support industrial Ethernet connectivity solutions for industrial applications. Prior to this, Maurice worked in ADI's power management applications and marketing positions for 15 years. He holds a bachelor's degree in electrical engineering from the University of Limerick in Ireland. You can contact him at maurice.obrien@analog.com.
Volker E. Goller is a system application engineer at ADI. He has more than 30 years of experience in various industrial applications, from complex motion control and embedded sensors to time-sensitive network technologies. As a software developer, Volker has developed a variety of communication protocols and stacks for wireless and wired applications, and actively participates in the formulation of new communication standards by participating in leading industry organizations. You can contact him at volker.goller@analog.com.
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