From time to time we have looked at one of the great divides of industrial automation, that of extending Ethernet connectivity below the PLC barrier. While extending Ethernet to a PLC or DCS I/O block is very commonCONTROL ENGINEERING China版权所有, the idea of using it to connect to individual process or discrete sensing devices is relatively rare. But is that assessment changing?
　　Some suppliers see demand based on customers that are tired of multiple platforms. “The most frequent demand from users is to implement one netw

ork for everything in the facility,” says Brian Oulton, director of networks business for Rockwell Automation. “When evaluating device-level networks, customers and instrument vendors frequently question and consider many attributesCONTROL ENGINEERING China版权所有, including cost, use in hazardous areasCONTROL ENGINEERING China版权所有, choices for media and topologies, and the protocol's robustness. The popularity and volumes of standard, commercial Ethernet, as well as its application into broader industrial application spaces have dramatically driven down the cost of embedding EtherNet/IP into instruments. Now, EtherNet/IP nears the cost levels of traditional process networks such as Foundation Fieldbus or Profibus PA.”
　　Carl Henning, deputy directorwww.cechina.cn, Profibus Trade Organization, has typically suggested using multiple tools for networking applications. Is Ethernet driven instrumentation coming? “The cost does nothing but go down as usage goes upCONTROL ENGINEERING China版权所有,” he says. “It's going to become less expensive and therefore more practical to put industrial Ethernet into more devices. The limits you run up against are either environmental, such as the need for intrinsically safe instruments, or when the overhead associated with Ethernet is simply too much. It's nonsensical to use it to carry a one bit data load.”
　　The question remains, will enough customers demand Ethernet connectivity to motivate instrumentation suppliers to produce it? While Ethernet networking and power over Ethernet (PoE) have spread to end devices in home, office, and commercial envir