Single Pair Ethernet (SPE) is the buzzword when it comes to the network infrastructure for the Industrial Internet of Things (IIoT). Users hope it will allow them to implement a consistent communication architecture in all applications where data is present. The concept is extension of an Ethernet connection down to sensor level, i.e. where there are no data highways but where users need compact data transmission with a long reach.

Industrial-Ethernet networking is used in industrial applications and offers a range of benefits thanks to its real-time transmission. However, it is too complex for simple sensor applications. “At sensor level, we are still using bus architectures. We now want to create an IP-based communication infrastructure with a uniform communication protocol, reaching from the sensor to the cloud”, explains Simon Seereiner, Head of Product Management SAI & IE at Weidmüller.


Adjusting data transmission rates

SPE does not require excessive data-transmission rates and can span larger distances, while also having a more compact design. Unlike cabled Ethernet connections, it requires just one pair of wires rather than two or four pairs. This was originally developed in the automotive sector, where space and weight savings are of utmost importance, to have an infrastructure that has minimal cables, yet deliver the high performance required for the increasing autonomous driving demand. Automotive companies started to develop a protocol for SPE with the IEEE standards in 2012. 

Likewise, in the industrial sector sensors increasingly need to be integrated into machines and systems, so the cabling needs to be compact and designed for industrial use. SPE is the key technology that makes it possible to implement IoT applications in industrial sectors: transfer rates of 10 Mbit/s with a transfer length of 1000 m and up to 1 Gbit/s with a transfer length of 40 m are adequate even for complex sensor systems. Scanners and cameras for monitoring or for detecting a component’s type and location can also be integrated into the network via Ethernet.


Data and power supply in one

Power over Data Line (PoDL) technology means that SPE can also ensure the power supply to connected components. Up to 60 W can be guided to an interface during simultaneous data transmission of 100 Mbit/s. “This makes it possible to supply a sensor with both power and data using just one two-wire cable. And this is all done with a small and compact design”, Seereiner explains. There is no need for an additional power supply cable, which is beneficial when spatial conditions are tight.

Power supply with simultaneous data transmission is set out in the relevant standards. The IEEE has defined a classification into different power classes for this purpose. Classes 1–9 are assigned to Power over Ethernet (PoE), the power classes for PoDL start at 10.

Weidmüller’s product range includes two plug-in connectors for SPE technology; one variation in protection class IP20 and the other in IP67. Both variations are part of the series of standards IEC 63171. Due to the sturdy locking mechanism, the extraction force of at least 50 N and an industrial dielectric strength of 2.25 kV DC, the new SPE plug-in connectors have the perfect properties for industrial use. The high density means that up to 50% less space is required compared to RJ45 plug-in connectors in the IP20 environment. Furthermore, the SPE plug-in connectors can be quickly and easily assembled in the field. 


Pooling experience and expertise

To promote the development of SPE for industrial applications, many experts from the fields of plug-in-connector technology, connection systems, automation technology, and the cable industry, have developed internationally applicable standards for this technology. “Weidmüller has been involved in this type of technology partnership from the start. everyone is working together to pool their competences and exchange information”, says Seereiner about the partnership. The experience of other companies can prove really beneficial, such as in the implementation of new products”, says Seereiner. “The aim of this technology partnership is to guarantee a coordinated infrastructure for devices, plug-in connectors, cables and measurement technology”. 

This type of uniform and consistent infrastructure is based on international standardisation. With a technology of this importance, this involves an extremely wide range of organisations such as the IEEE. For the IEEE 802.3 cg project, plug-in connectors and their electrical properties were defined for the first time in the IEEE environment. All plug-in connectors can be used if they meet the electrical properties set out in the standard. 

Weidmüller’s SPE plug-in connectors are examples of IEC 63171-2 variations for the IP20 environment and IEC 63171-5 variations for the IP67 environment.


Weidmuller will be shortly introducing two new connector solutions for SPE where the two mating faces, ie. for IP20 and IP67, are mutually compatible. This is particularly beneficial in field measurement technology, where users can easily connect devices with IP67 interfaces using an IP20 measurement connector and vice versa. There are plans for a 4-chamber version to allow for the cabling of four SPE systems via a single interface and with a compact design: the housing is smaller than conventional RJ45 housing. Weidmüller is developing additional solutions to create an infrastructure for Single Pair Ethernet technology.

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