Electrical Encyclopedia: Industrial Ethernet cabling knowledge overview

Industrial environments are harsher than the average environment, at least in the vibration, humidity, temperature worse than the average environment, Industrial Ethernet requires more professional knowledge and practical experience. If you are installing or using an Industrial Ethernet (Industrial Ethernet Switch), you need to be aware of the five elements of cabling, signal quality, ground loops, switches, and communications. Failure to do so can result in increased maintenance costs.


1, wiring problems

As with all networks, the merits of cables directly affect the pros and cons of Industrial Ethernet. And in addition to high electromagnetic interference (EMI), there is often some level of temperature, dust, humidity, and other uncommon factors in industrial environments that are not commonly found in home and office environments.

So, how to choose the cable? In the office, commercial-grade cables, such as Category 5 cables, are more suitable for 10MB networks and Category 5e cables for 100MB networks. According to the ANSI / TIA-1005 standard, Category 6 or better cables can be used for host or device connections in industrial environments.

Category 6 cable to achieve 1GB network within the range of 100 meters, 10GB network within 55 meters. Category 6e cable can achieve 10GB network within 100 meters.

Category 6 cables are less susceptible to crosstalk and external EMI noise than Category 5 and Category 5e cables. Industrial Ethernet cables are designed to withstand the physical erosion of cables in tougher industrial environments. When installing Category 6 cables, make sure that the RJ45 connectors and sockets also achieve Class 6 rating. The best way to use it is to use pre-assembled patch cables for short-range wiring and to install the connectors in the factory. Socket for long distance wiring.


2, cable, shielding, grounding circuit

Some applications need to be shielded, but it can be counterproductive if shielded cables are not installed properly.

Shielded Ethernet cables perform better in EMI environments when the protective sleeve is exceeded. Good grounding is the key to using shielded cables. A ground reference point is the key of the key. Multiple ground connections form a ground return loop and different potentials at different ground connections introduce noise into the cable.

In order to solve this problem, the grounding circuit will bring huge damage to your network. Use only the grounding RJ45 connector on one end of the cable and the insulated RJ45 connector on the other end to eliminate the possibility of grounding loops.

If the Ethernet cable crosses the power cable, the crossover angle is quite specific. Keep parallel Ethernet cables and power cables separated by at least 8 to 12 inches. This should be greater if the voltage is higher or if the juxtaposed distances are longer. If the Ethernet cable is routed inside a metal trench or bushing, adjacent trenches or bushing must be connected together for electrical continuity.

In general, Ethernet cables should be as far as possible from devices that generate EMI, such as motors, motor control equipment, lighting equipment, live conductors, and more. On the panel, the Ethernet cable and connector are separated by at least 2 inches. Follow the recommended cable bend radius when the cable is far away from EMI sources.


3, switch VS hub

In short, do not use a hub in an industrial Ethernet environment. Hub is just a multi-port repeater. If the hub is left out, the only options left are managed switches and unmanaged switches. The managed switch is better, of course, its price is more expensive than unmanaged switches.

Each device on the network has a unique identifier, which we call the MAC address, which is the key to the switch's ability to recognize better than a hub.

When the switch was first powered on, it initially behaved in the same way as a hub broadcasts all traffic, but as the devices on the network transmit information on different ports of the switch, the switch begins to monitor traffic and identifies Which one port is associated with a MAC address, and then identify the MAC address table. Once the switch discovers that the device's MAC address is connected to a particular port, it monitors the information that points to that MAC address and sends it to that particular address only.

Industrial Ethernet networks have three types of communication. Peer-to-peer unicast communication, one-to-many multicast communication, and a bit of broadcast communication to all nodes.

When the switch's MAC address table is set up, managed switches and unmanaged switches handle unicast and broadcast traffic in the same manner. In general, under the 100MB bandwidth, the broadcast frequency is controlled at 100 broadcasts per second. For any network, there will be more or less broadcast communications. One example is that the print server periodically broadcast announcements over the network.


4, snooping: not just listening

One of the major differences between managed and unmanaged switches is how they handle multicast traffic. Multicast traffic typically comes from smart devices that are piggybacked on the factory process network, using connection-oriented vendor / user model-based technologies. The connection in this case is simply the relationship between two or more nodes on the network.

To be able to receive in-group information, the device must join the multicast communication group and all members of the group can receive the data. If you're just sending data to your team, you do not need to be a team member. In the manufacturer / user model, the main problem with multicast communication is that as the number of team members increases, the amount of communication information increases exponentially. At this point, you need to use a managed switch.

Managed switches open Internet Group Management Protocol (IGMP) snooping. It does this, and when IGMP snooping is turned on, it sends a broadcast to determine the members of any multicast group. Using this information, along with the already-built MAC address table, managed switches are able to send multicast traffic only to members of the multicast group. Unmanaged switches handle multicast data and broadcast data in the same way that data is sent to each node.

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