Electronic Products & Technology


Selecting cabling and connectors for industrial Ethernet applications

There are several important considerations to take into account when deciding on which type of cables and connectors to use for any specific application.

This article will help you make the proper selections to meet the needs of your application.

The first step is to define the environmental conditions of each area of the application. Will the cables and connectors be subject to any of the following?

• Shock and vibration
• Metallic shavings and filings
• Crushing, pulling
• Humidity
• Bending or twisting
• Solar radiation
• Dust and dirt
• Electrostatic discharge
• Water, oils, chemicals
• Radiated RF
• Corrosive gasses
• Temperature extremes
• Electrical transients

The Ethernet cabling must meet the most severe conditions at any point along its length. For example, if a cable traverses through an area with process ovens where the ambient temperature is greater than 60 degrees Celsius, you must use cabling with a rating that covers the temperature range. Another alternative is to consider re-routing the cabling around the area.

The following key explains their construction: X – Specifies if shielding is under the jacket (U-Unshielded,
S-Screen Shield, or F-Foil); Y – Specifies if shielding is around the individual pairs within the cable.

Always refer to the manufacturer’s specification information for the cable type and connectors that you are considering to determine if it meets your applications requirements.

Consider using high-grade jacket materials, like polyurethane (PUR). PUR is resistant to harsh conditions, such as abrasion, chemical, oil and fire. Lower grade jacket materials, such as PVC, while less expensive, may degrade if exposed to oils and chemicals. PVC also becomes brittle and will crack at low temperatures.

Cat5e 2-pair twisted cabling has a maximum data transmission rate of 100 Mbps over a maximum cable length of 100 m. Typically 2-pair cabling is used for industrial applications and uses either 4-position M12 D-Coded connectors or RJ45 Connectors. For applications where gigabit speeds are required, 4-pair twisted cabling and 8-position connectors are used.

Ethernet data pair conductors are either solid or stranded. Solid conductor Ethernet cabling (one single wire per data conductor) is intended for fixed applications where the cable will not be exposed to frequent repositioning or flexing.
If the cables will be subjected to flexing, be certain that the cable specification on “bend cycles” meets the application requirements. Cables used in applications with a lot of movement will have stranded data conductors, typically seven wires per data conductor. High-flex cabling is used for robotic and cat track applications and uses stranded data pairs with a minimum of 19 wires per data conductor. The number of bend cycles for high-flex cables is into the millions. Again, check the cable specifications for those details.

The most commonly installed Ethernet cabling in the U.S. is UTP (unshielded twisted pair). UTP cables provide sufficient noise immunity for many applications. However, if a noise source is strong enough or close enough, it can interfere with the data signals. If your cabling will run near equipment such as arc welders, switching relays, AC drives, solenoid valves and other noise sources, consider shielded cabling.

There are several types of cabling, such as UTP, STP, S/UTP, S/STP, and S/FTP.

When using shielded cabling, you must use shielded connectors.

Do you need Cat5, Cat6 or Cat7 cabling and connectors? That depends on the bandwidth requirements of the equipment connected to the network. If you are planning on installing a new Cat6 or Cat7 network, or upgrading an existing network, you will need to be certain that all network components support that Category level. If upgrading, that would mean replacing all cabling and connectors with new components that meet the Ethernet Category Level requirements.

You should not mix Cat5, Cat6 or Cat7 cables and connectors on the same network, as network performance may be degraded.

When using shielded cabling, you must use shielded connectors.

Match the connector with the environment where it will be used. In most industrial applications, a connector with an Ingress Protection Rating of IP65 or IP67 is desired to protect against contaminants entering the connector and degrading performance.

The RJ45 connector designed for industrial applications is typically a larger connector with a locking mechanism. It has an IP67 sealing gasket system to protect against contaminants and vibration. A smaller IP20 version is used in clean areas or inside of control cabinets.

The M12 connector is a smaller connector (12 mm) that is available in both four and eight positions. It is a very popular replacement for the RJ45, mainly because of its size and robustness. It is available in male and female, as well as angled and straight versions.

ODVA, an international association comprising members from the world’s leading automation companies, has adopted the M12 Ethernet Standard specifying the M12 as a 4-position, D-coded connector for industrial Ethernet applications. The M12 protects against dirt, water, vibration/shock and temperature extremes, making it well suited for industrial environments.

Fibre-optic cabling for industrial applications is becoming more popular as an option over copper-based solutions. There are several advantages to using fiber-optic cabling and connectors:

• High transmission rates
• No shielding protection is required
• Suitable for Gigabit Ethernet in accordance to IEC 11801
There are several different fiber types to select from:
• Plastic Optical Fiber (POF) has the same transmission characteristics as Cat5e cabling: 100 mbps over a maximum cable length of 100 m, and it’s easy to install.
• Hard Clad Silica (HCS) is a type of glass fiber with a polymer coating. It provides a higher data transmission rate, but is more complicated to terminate and install.
• Glass Optical Fiber (GOF) provides the highest data transmission rate capability, but requires special tools and training to learn how to terminate and install the cabling. The maximum length of GOF can be up to several kilometers.
Industrial fibre optic connectors include SC, ST, FSMA, SCRJ and several others.

When choosing the proper cabling and connectors for an Industrial Ethernet application, there are many issues to consider.

However, it does not have to be a complicated process. Throughout the process, adhere to the ANSI/TIA/EIA-568-C standards and consult the manufacturer’s specifications to ensure that the selected cabling and connector types meet the design and installation standards.

This article was excerpted from a White Paper presented by Chuck Dawson, Product Marketing Lead Specialist -PLUSCON, Phoenix Contact.

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