Using High-Speed, Ruggedized Ethernet Connectors for Industrial Communications Networks | ELE Times

The Industrial Internet of Things (IIoT), or Industry 4.0, is driving demand for Communications Networks that are able to operate in challenging environments. Often, the weak link in these networks are the connectors as industrial environments are hot, dirty and typically incorporate vibrating machinery, all of which puts continual stress on mechanical connections and undermines reliability. Exacerbating the situation are the consequences of a connection failure in a modern factory. While it can be financially catastrophic with lost production quickly adding up to a large dollar loss, a failed safety connection can cause serious injury. As such, an alternative to the standard RJ45 connector is required.

Designers require Ethernet connectors rugged enough to meet current industrial standards and Ingress Protection (IP) codes, regardless of where they are to be placed initially. They must be able to perform reliably at Cat 6A Ethernet speeds up to 10 gigabits per second (Gbps), support Power-over-Ethernet (PoE), and be as “future proof” as possible, all while meeting often tight design budgets.

This article examines the requirements for industrial communications systems and the appropriate IP levels. It then describes how the features of industrial Ethernet connectors meet these demands before introducing real-world solutions from Amphenol as examples to show engineers how to use the connectors for new projects.

Industrial network requirements

Modern industry has widely embraced wired networking to power “Industry 4.0” (described as the “digitizing of manufacturing”) and build on the computerization of the sector that occurred back in the late 70s and through the 80s. For managers, Industry 4.0 promises increased productivity, higher quality product, lower prices, and improved safety. For engineers, the task is to build the robust networks that support modern manufacturing.

The infrastructure for domestic and commercial Ethernet networks is generally based on inexpensive cables and standard RJ45 connectors, but those components are not designed for factory applications. The factory environment is more challenging, and the selection of cables and connectors must take into consideration the following stress factors:

• Mechanical: shock, vibration, crushing, bending, twisting
• Chemical: water, oils, solvents, corrosive gases
• Environmental: temperature extremes, humidity, solar radiation
• Electrical: electrostatic discharge (ESD), electromagnetic interference (EMI), high voltage transients

Industrial cabling and connectors must be specified to stand up to the most severe conditions anticipated across the network’s entire life. For example, it’s not much use if a cable is specified for normal ambient temperatures if later the factory is rearranged such that the cable now runs near process ovens where the temperature is much higher.

Industrial cables are available with high-grade polyurethane insulation, which is resistant to abrasion, chemicals (including oil) and fire. While insulators such as polyvinyl chloride (PVC) are cheaper, the plastic can be attacked by oils and chemicals, and becomes brittle and cracks at low temperatures.

Building an industrial Ethernet network

In low electrical noise environments, unshielded twisted pair cables might be acceptable. However, industrial devices like arc welders or factory electrical equipment such as switching relays, AC drives or solenoids may cause interference and data disruption in unshielded cables. When in doubt, the engineer should err on the side of caution and use shielded cable to prevent potential costly system errors later. As factories grow, it is common for control and power cables to use ducts that were previously dedicated to Ethernet communications. This could generate data corruption if unshielded Ethernet cables were originally specified.

A double-shielding design, using both foil and a copper braid, is the most effective solution for preventing data corruption. To ensure the shielding works properly, the engineer must also use shielded connectors and terminate the shield to ground. If a shield is left unterminated, it can actually exacerbate interference problems by acting as an antenna.

Even with shielded cables, signals degrade as they travel along long lengths. Cables with solid conductors perform better and can provide a maximum run of up to 100 meters (m), but they are more prone to damage from bending or twisting. Stranded cables handle twisting and bending better but shouldn’t be used for runs greater than 85 m (Figure 1).

Figure 1: Solid conductor Ethernet cables should be limited to 100 m in length, while stranded cable versions should be limited to 85 m. (Image source: Amphenol)

When constructing the network, the minimum static bend radius is four times the cable outside diameter (OD). This applies to stranded or solid, shielded or unshielded cables. Where flexing is required, solid conductor cables should not be used. The data sheets for stranded cables typically specify the maximum flex cycles, which is typically between one million and 10 million, depending on the bend radius.

The cables should be secured with cable ties that are left loose enough for the cables to move freely under the tie. Overtightening will create stress points that can cause conductor failure. The cables should also be kept loose within the cable ties when several cables are bundled together.

Because the vast majority of commissioning errors occur due to field wiring (because maintaining the twisted pairs and correctly terminating the shield is a difficult and time-consuming job), the use of factory-fitted molded connectors is advised.

Designing for the future

While wired networks bring key advantages (such as speed, signal integrity and security), they are expensive to install and maintain. The designer tasked with specifying the network should therefore have one eye on the future to ensure the infrastructure will last as long as possible and require minimal repairs.

The history of Ethernet has seen network speeds rise inexorably. In the future, industrial networks are likely to be dominated by optical infrastructure offering rates of 400 Gbps or even terabits per second (Tbps). For today’s copper wire installations, careful selection of high-grade twisted-pair cable and connectors should see the network cope not only with current 1 Gbps rates, but upcoming 10 Gbps connections (Table 1).

Table 1: Ethernet cable speeds and the associated Ethernet operating frequency, which is generally proportional to throughput. (Image source: Digi-Key Electronics)

Factory networks are also starting to take advantage of PoE, a technology that uses Ethernet cabling to deliver power to connected equipment. PoE uses a single standard Ethernet infrastructure while handling power in the tens of watts. The centralized and flexible nature of the technology eliminates the need for a local power supply for each powered device on the network, allowing powered devices to be placed anywhere and be easily relocated later if required.

An enhanced form of PoE, called PoE+, can supply up to 25.5 watts DC to the connected device and allows connection of high power draw equipment such as security cameras. (See Digi-Key’s technical article, “Power-over-Ethernet Adapts to Meet Higher Demand”.)

Just as cables and connectors should be matched for equal resistance against mechanical, chemical, environmental and electrical stress, so too should they be matched for functional performance. Maximum operational characteristics will be dictated by the least capable component in the network; for example, if Cat 6a cables are matched with Cat 6 connectors, the system will have a maximum throughput of 1 Gbps rather than the cables’ nominal maximum throughput of 10 Gbps.

Connectors for industrial networks

While it is important that the designer carefully considers cable choice, routing, and Ethernet frequency when building industrial networks, the connectors are the greatest design challenge within an Ethernet network. This is because they represent the weakest link; not only do connectors offer potential ingress to water and dirt but they also include short runs where Ethernet pairs are untwisted and are therefore more susceptible to electrical noise.

The designer needs to consider where the connectors will be used as factory environments vary considerably. For example, the IP code—determined by IEC standard 60529—classifies the degree of protection provided by the mechanical casings and electrical enclosures forming the connector. The first digit of the code indicates the degree of solid particle protection (ranging from 0 (no protection) to 6 (dust tight)), while the second indicates the degree of protection against liquid ingress (ranging from 0 (no protection) to 9K (powerful, high-temperature water jets)).

A rating of IP20 (protection against fingers and similar objects, no protection against moisture) for connectors used in clean, dry factory environments is common for many industrial connectors. For example, Amphenol’s ix Industrial IP20 connectors are high-speed, ruggedized, 10-position components that come in a package 70 percent smaller than a typical RJ45.

Connector makers typically provide options for higher protection for use in progressively dirtier and wetter environments, and Amphenol is no exception. The ix Industrial IP20 line extends from IP20 for the standard product up to IP67 (dust tight, immersion up to 1 m depth) for non-standard products.

The network designer should aim to minimize the number of connections, particularly cord sets with male connectors on both ends. These are too easy for non-engineering personnel to extend—with detrimental consequences for the performance of the rest of the network. Moreover, it is standard practice for all fixed connectors to be of the female type.

In common with other manufacturers, the Amphenol connectors are available in male form factors for cables, and three types of female form factors for fixed installations: vertical receptacles for bulkheads, right-angle vertical (ND9AS1200), and horizontal (ND9BS3200) receptacles for pc board mounting (Figure 2). The pc board mount versions come in surface mount technology (SMT) or through-hole form factors for easy soldering to the substrate.

Figure 2: Amphenol’s ix Industrial connectors are available in a variety of plugs and receptacles for cable, bulkhead and pc board applications. (Image source: Amphenol)

The male version can be supplied individually (ND9AP5200) or as part of a cable set (ND9ACB250A) measuring in length from 500 to 2000 millimeters (mm).

A useful guide as to the quality of a connector is to check if it meets the requirements of standards such as IEC 60512 and IEC 61076. IEC 60512 details the mechanical and electrical tests, as well as the thresholds a connector should meet when used with electrical and electronic equipment. The standard covers mechanical factors such as insertion and withdrawal force, vibration resistance, and the maximum number of mating cycles, as well as electrical factors such as resistance due to contact, shielding, and insulation.

The Amphenol ix Industrial connectors are designed to provide a robust, miniaturized Ethernet interface (compliant with the relevant IEC standards) with up to 75% space savings compared to standard RJ45 connectors. With 10 mm connector pitch and robust two-point metal latching, the connectors offer Cat 6a performance for up to 10 Gbps Ethernet communication, PoE/PoE+ capability, and 360° shielding for EMI immunity.

The pc board connectors feature heavy-duty solder tabs to secure them and are robust enough to endure shock and vibration while maintaining a reliable connection. They can withstand up to 5000 mating cycles.

Tables 2 and 3 detail how the ix Industrial series perform against key aspects of the IEC 60512 standard.

Table 2: From an electrical standpoint, the ix Industrial Ethernet connectors can handle currents up to 1.5 A and meet IEC 60512 requirements. (Image source: Digi-Key Electronics)

Table 3: The ix Industrial connector’s mechanical performance allows them to meet IEC 60512 and 60068 requirements. (Image source: Digi-Key Electronics)

IEC 61076 is more focused, covering 10-way, shielded, free and fixed rectangular connectors for data transmission with frequencies up to 500 megahertz (MHz). The document specifies the common dimensions, the mechanical, electrical and transmission characteristics, as well as the environmental requirements for industrial networks.

In particular, IEC 61076 identifies the codings that determine the position of the connectors’ polarization key and keyway. Type A connectors are intended for 100 megabit per second (Mbps) to 10 Gbps Ethernet communication. Type B connectors are intended for all other non-Ethernet applications such as signaling, serial or other industrial bus communication systems (Figures 3(a) and (b)).

Figure 3: IEC 61076 specifies the polarization and keyway for connectors for data transmission. Type A (a) uses a 45° corner located on the lower right of the receptor (viewed into mating face). For Type B (b) the 45° cut corner is located on the upper left corner of the receptor. (Image source: Amphenol)

Conclusion

Modern factories are being built with communications networks to digitize manufacturing for greater productivity and lower costs. The connectors and cables making up these networks not only need to be robust enough to stand up to harsh industrial environments, but also cope with future high-speed communication and PoE demands.

There are solutions from companies such as Amphenol that offer industrial grade cables and connectors designed to precisely meet these challenges and factory budgets. They adhere to exacting industrial connector standards and include features that support high network performance, extended life, and require minimal maintenance. However, as shown, designers need to understand the applicable standards and both the electrical and mechanical limitations of the connectors in order to apply them appropriately toward a successful IIoT or Industry 4.0 network design.

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