When the Ethernet standard (IEE802.3) was first adopted in the mid-1980s it was considered unsuitable for industrial automation networks because of its non-deterministic nature. Networks using RS-485 and RS-232 ruled the industry.
That has changed. Advances in switching technologies have made it possible to design deterministic, inexpensive industrial networks, thus making Ethernet a well-accepted, if not the de facto networking interface for industrial automation. The industrial Ethernet market is expected to continue growing by 10% annually.
Ethernet networking has progressed to the point that if you are on a network, there is a 90% chance it will be Ethernet. If you are installing into a new network, there is a 98% chance that it will be Ethernet.
Beyond the fact that major industry players such as Rockwell Automation and Siemens manufacture a majority percent of their products to network via Ethernet, there are additional solid reasons for adopting it in an industrial setting.
- Ethernet is fast. Speeds of 100 Mbps are standard for industrial automation applications using CAT5/CAT6, coaxial cable or optical fiber. Speeds of 1 Gbps are available and 10 Gbps is around the corner.
- Ethernet is easy and cheap. Ethernet uses readily available hardware such as cabling, access points, switches and routers. This infrastructure is far less expensive than the equivalent serial port devices.
- Ethernet is stable. Earlier networking protocols such as RS-485 are prone to errors from data collisions, reduced cycle time as nodes increase, limited number of nodes and the challenges presented by networking devices. Ethernet on the other hand features collision detection, cycle times relatively unaffected by attached devices, built in check-summing and virtually unlimited nodes.
For all of the above reasons the industrial automation market has evolved to the point that Ethernet connectivity is practically a requirement for automation products.
The major question now becomes: “What protocol is to be used to allow the devices to communicate with one another?” The next posting will discuss the major protocols used in industrial Ethernet.