Introduction to Single-Pair Ethernet | What You Need to Know

Single-Pair Ethernet, or SPE, is a new Ethernet communication standard for factory, process, and building automation that will enable a more rapid deployment of integrated strategies, such as the Industrial Internet of Things.

In this article, we will introduce you to the basics of Single-Pair Ethernet and will explore what you need to know to be ready to consider SPE for your plant or facility.

1: Transmission using one pair of copper wires

The first concept you need to know is that Single-Pair Ethernet describes the transmission of Ethernet using only one pair of copper wires.

Until now, two pairs of copper wires were necessary for Fast Ethernet operating at 100Mb or four pairs of copper wires for Gigabit Ethernet.

SPE is a game changer, especially for connection of field devices and sensors. This simple two-wire system is able to deliver data rates of up to 1 Gigabits/second.

2: Power supply delivery using PoDL

The next important concept is that Single-Pair Ethernet can also deliver a simultaneous power supply to end devices using what is called PoDL, or Power over Data Line.

Special cables and connectors allow both power and data to be transmitted over a single cable. Various cable configurations and power capacities are available to deliver up to 16A to connected devices.

3: IEEE 802.3 standards

Single-Pair Ethernet is represented by a new group of IEEE 802.3 standards.

The IEEE 802.3cg standard is most important for the process industries. This standard describes 10Base-T1 or 10 Megabits/second Ethernet which can be run over a single twisted pair cable up to 100 meters with no loss of signal.

IEEE 802.3bp is most important for factory automation. It is the standard with a higher data rate of 1 Gigabits/second but with shorter lengths of up to 40 meters allowed.

4: Industrial Ethernet protocols

Single-Pair Ethernet communicates across the common industrial Ethernet protocols available today, such as Ethernet/IP, Profinet, and EtherCAT.

This allows existing control devices, such as PLCs, which operate on these industrial ethernet protocols to interface to Single-Pair Ethernet subnetworks via the use of SPE Field Switches.

5: Benefits of Single-Pair Ethernet

The use of SPE Field Switches and Ethernet-connected devices means IP communication can be brought down to the lowest automation level, offering full transparency from sensors and actuators all the way up to the cloud.

Other benefits of Single-Pair Ethernet include reduced wiring costs, reduced node costs, reduced power consumption, and data communications via a single pair of wires.

IP technologies are very familiar to engineers, technicians, and operators alike.

Being able to use a single network type for all plant-level communication will flatten learning curves and eliminate the need to learn the nuances of many types of networks.

6: PoDL vs. PoE

Single-Pair Ethernet using Power over Data Line is not the same as Power over Ethernet, often referred to as PoE. Power over Ethernet is described by IEEE Standards 802.3af, 802.3at, and 802.3bt.

PoE requires a special network switch with one device connected to each port using a CAT5 cable. For IEEE 802.3af, power is limited to 350 milliamps. For IEEE 802.3bt, power is limited to 960 milliamps.

PoE has been useful for connection of devices such as wireless access points, voice-over-internet phones, and monitoring cameras.

The physical network limitations of Power over Ethernet limits its usefulness for the integration of plant-level sensors or field devices.

7: Ethernet APL vs. SPE

Single-Pair Ethernet and Ethernet APL are not interchangeable terms. As mentioned before, there are several IEEE Standards that define the different versions of Single-Pair Ethernet.

Ethernet APL, for Advances Physical Layer, is a specific version of Single-Pair Ethernet.

Ethernet APL operates at 10 Megabits/second, defined as 10Base-T1L, where the designation of L indicates a long distance, in this case, 1000 meters.

Being able to extend Ethernet to these distances will allow Ethernet to be employed where it has not been able to previously in manufacturing plants.

8: Cables and connectors

Conventional CAT5E and CAT6 cables cannot be used to connect Single-Pair Ethernet devices.

Cables as defined by Standards IEC 63171-6 and IEC 63171-7 have been developed for SPE to ensure interconnectivity between SPE devices.

Automation suppliers, such as TE Connectivity, are engineering and manufacturing these new cable and connector configurations to support SPE networks.

Power and data are delivered to the devices over a single cable using 4-pin M8 connectors or 6-pin M12 connectors.

These quick-connect cables eliminate the need for cable glands, removing the sensor housing, and making screw terminations.

9: Topologies

Single-Pair Ethernet networks can be constructed to connect devices and sensors in a number of different topologies, including point-to-point (from an SPE switch to device using a dedicated cable) and multi-drop for connecting up to eight separate devices.

A multi-drop topology requires a terminating resistor at each end of the segment, the same as ProfibusDP and Foundation Fieldbus field networks.

Hybrid multi-drop connection technology will enable single-point network connections to standalone machines, robots, and portable process tanks, just as a few examples.

10: SPE devices and sensors

While several manufacturers have SPE field network switches available, SPE-enabled sensors and devices are not yet being marketed.

Major automation suppliers, such as Endress + Hauser and Siemens, have developed SPE interfaces for many of their sensors, and many are currently in the testing stages prior to release.

The Single-Pair Ethernet Industrial Partner Network is composed of a number of very reputable automation suppliers and growing. These partner networks will help drive the release of SPE products to the marketplace over the next several years.

11: Hazardous areas

Electrically-classified areas pose additional burdens on automation engineers in the design of systems that are safe for use in hazardous areas.

Single-Pair Ethernet, along with advances in intrinsically-safe barrier technology for communication networks, provides an opportunity to extend Ethernet to these plant-level areas.

Therefore, a single network strategy can be employed from the field to the cloud, by changing only the physical installation details to match the process environment.

Conclusion

Single-Pair Ethernet holds the promise of providing high-speed, safe, secure, and robust communication from the plant floor to the cloud using IEEE 802.3 Ethernet.

The benefits are numerous, from lower-cost, simplified installation, consistent configuration across devices, and simplified maintenance of instruments and automation technology.

We invite you to become a RealPars Pro Member so that you have access to our full course on Single-Pair Ethernet. Join us to experience the future of automation through this course in Single-Pair Ethernet.

Upon successful completion of the course, you will receive a certificate signed by TE Connectivity.

Whether you are a technician, a new automation engineer, or a seasoned professional, you will benefit from this opportunity to learn about this new, innovative technology.

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