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10 Tips of Industrial Ethernet Technology (Tip 1 - 5)

[Abstract]:
With the development of Ethernet Technology and the showing up of high-speed Ethernet, the Ethernet has overcame its weakness and been able into industrial circle as the Industrial Ethernet Technology

With the development of Ethernet Technology and the showing up of high-speed Ethernet, the Ethernet has overcame its weakness and been able into industrial circle as the Industrial Ethernet Technology. If you are follow up with this technology, you should know about below aspects.

 

1. Topology Structure

Topology is the layout of the cables in network. As all know, EIA-485/ CAN adopts the Bus Topology. But it is common using hub or switch in Industrial Ethernet, so the usual topology structure is “Star”  style or “Dispersed Star” style.

 

2. Wiring

There are STP cable (Shielded Twisted Pair), UTP cable (Unshielded Twisted Pair) and single/ dual mode cable used in industrial Ethernet network.

 

There isn’t much requirement to the cable in 10Mbps network, while in 100Mbps network, it is recommended to use Cat.5 or better cable. For connection with fiber, it requires a pair of cable. The common wavelengths of dual mode fiber are 62.5/12.5μm or 50/125μm. Compared with inner core of dual mode fiber, the inner core of single mode fiber is thinner, which is only 10μm. Frankly speaking, it commonly uses dual mode fiber in 10Mbps network, while both single mode and dual mode fiber in 100Mbps network.

 

3. Connectors and Connection

There are two pairs of wire in twisted pair RJ45 cable, one pair is for sending and the other is for receiving. The definition mark of the these for signals in MDI are RD+, RD-, TD+ and TD-. 

A complete communication link consists of DTE (Such as workstation) and DCE(Such as extender or switch).  The port of hub, marked with MDI-X, indicates that it can connect DTE and DCE with straight-through cable.  But if connecting with two DTEs or two DCEs, it can be achieved through crossover cable or directly through the Uplink port in the hub.

 

There are ST and SC connectors. The ST connector is used in 10Mbps/100Mbps while SC connector is used in 100Mbps. And the single mode fiber is commonly using SC connector. The connection between DTE and DCE requires only the TX and RX identification of the port.

 

4. Industrial Ethernet Products and Commercial Ethernet Products

What is industrial Ethernet? It is compatible with IEEE802.3 in the technology and with the application requirement of industrial and commercial in the design and package.

 

The designers of the industrial site aims to adopt the Ethernet chips and media that can be found in the market, considering the special requirements of the industrial site. The first thing to be considered is heat, humidity and vibration. Second is if it can be conveniently installed in the control cabinet. The third one is the power requirement. Many control cabinets provide low voltage ac or dc power, but the wall mounted power supply sometimes can't adapt. And the safety standards at the scene are completely different from those in the office, the EMC requirements keep changing depending on the industry environment for EMI and ESD requirements and sometimes it is the rating of the bad environment. The industrial control cabinet standards may be used in factories, and the building systems often use smoke standards. Obviously low-cost commercial Ethernet hubs and switches can't meet these requirements.

 

5. Speed and Distance

Discuss the distance of the Shared Ethernet, and you can't ignore the Collision Domain concept.

Media access to a Shared Ethernet or half duplex Ethernet is determined by the CSMA (Carrier Sense Multiple Access)/ CD (collision detection).

 

In a half-duplex mode of communication, the sending and receiving cannot occur simultaneously, otherwise the data will collide. Before the site is sent, it depends on whether there is a free channel. When sent, the site will be tuned for a period of time to ensure that no other site is being delivered synchronously and eventually the site is successful. Conversely, a collision occurs when the source site sends a blocking signal to reinforce the collision. Retry after the competition site is delayed (the delay time is determined by the algorithm, it is random). Under this mechanism, all sites and all hubs must be within the same collision domain.

 

For industrial Ethernet, 10Mbps and 100Mbps are the most commonly used. In 10Mbps, there are two concepts associated with distance, namely the Segment (Segment) and Network Diameter. The former refers to the distance between two devices (hub, switch, or host). The rest one refers to the distance between the two farthest devices in the network. Whether it's 10Mbps or 100Mbps, the maximum distance from the segment can't exceed 100 meters. The most useful rule for extending the network is the 5-4-3 rule (only for the 10Mbps repeater). The rules are as follows: a network with up to five web segments, four Repeaters, and no more than three hybrid segments. The hybrid segment refers to the coaxial bus network segment (obsolete). The maximum distance from the double stranded wire segment is 100 meters, and the maximum network (network range) is 500 meters.

 

The longest distance between the fiber network segment can be up to 2 km, but to IEEE802.3 standard regulation, cascade cannot exceed the maximum number of three in the use of fiber, the end of the network needs to use twisted pair cable,  and in the middle of the two uses the fiber network segment to ensure that each segment is less than 1 km. Thus, the length of the entire fiber network is limited to two kilometers. As the 5-4-3 rule does not apply to 100Mbps, a 100Mbps switch is recommended.