Ethernet use grows, but runs side-by-side with analog and early digital technology. Network infrastructure still a mixed bag in U.S. plants.

Networking infrastructure continues to operate as a collection of old and new; digital and analog; connected and isolated; throughout U.S. plants. So say the findings from a new Control Engineering and Reed Corporate Research study on CE subscribers use of and plans for industrial networks and communications.

The results were taken from 213 respondents involved in specifying, recommending and/or buying industrial network products. Given the nature of the responses, networking takes many forms and exists in a wide variety of ways. Communication can be as simple as a sensor and display tied via 4-20 mA, or an Ethernet platform spanning several levels from enterprise to plant floor.

Most companies (61%) use network driven SCADA (supervisory control and data acquisition) systems and most (51%) extend that to include diagnostics, testing, and maintenance. Additional answers suggest divisions between discrete and process manufacturing needs.

The nature of frequently used protocols reflects typical applications. Analog techniques, such as 4-20 mA and 0-10 V, are still common enough to make the top 10, but have few uses outside of simple instrument-to-I/O connection. Ethernet platforms, Ethernet TCP/IP and EtherNet/IP, appear in 84% and 66% of plants, respectively, implying wider networking between higher level devices. Older serial protocols, RS-232 and RS-485 persist as platforms for smaller simple or multi-node networks.

Commercial Ethernet and fieldbus platform families are strong, led by ODVA group with EtherNet/IP, DeviceNet, and ControlNet all showing in the top 10. Modbus and Modbus/TCP placed second with the Profibus and Foundation fieldbus protocol groups named third and fourth.

Technology use changes slowly, which makes trends hard to spot, but wireless, especially WiFi (IEEE 802.11b) shows the most movement, with 40% saying they use it currently, up from a statistical dead heat at 34% in 2006, and 35% in 2005. Other wireless technologies (including RFID) are positioned for growth, with the following the highest cited for new use in the next 12 months:

RFID, +17%;
ZigBee (IEEE 802.11g), +16%;
WiFi (IEEE 802.11b), + 14%; and,
Bluetooth (IEEE 802.15), +13%.

At the same time, the extensive amount of hardware that is not yet networked is also telling. While PLCs, and Ethernet devices (hubs, switches, routers, etc.) are integral parts of larger networks, other types of devices can go either way. In fact, on average, slightly more than half of installed instrumentation and sensors are currently not networked, although if plans to connect them over the next 12 months pan out, the balance will shift pushing most process and discrete sensors, switches, and valves over the 50% mark.

Networking requires both hardware and software to maintain and expand. Respondents report extensive plans to enlarge and upgrade their infrastructure. I/O devices and connectors top budget lists year after year, followed by cabling and controllers. The figure shown in the graph is an average of all respondents for their specific company in the given product class.

Peter Welander, Control Engineering
Control Engineering -- April 1, 2007