Electronic Design

Working Without Wires

Plant managers are adding a powerful tool in their efforts to gather more data and keep equipment running smoothly— wireless networking. It lets them locate sensors anywhere, move equipment without routing wires, and perform tasks that would have been difficult or even impossible.

A range of wireless technologies is seeing increased usage as engineers gain confidence that they will work flawlessly in harsh industrial networks. In fact, acceptance of these technologies is following the path experienced by Ethernet.

After a period of skepticism, clever designers came up with techniques that proved effective, bringing increased acceptance. Now it’s growing rapidly, albeit from a small base. IMS Research forecasts unit shipment growth of nearly 30% through 2010.

System integrators can choose from a number of different options. Wi-Fi provides compatibility with Ethernet backbones. Wireless Hart leverages the popular Hart protocol. Emerging standards, including ISA SP-100.11 and ZigBee, are challenging a number of proprietary mesh technologies.

Vendors representing these technologies have banded together within the Wireless Industrial Networking Alliance. This consortium includes suppliers as well as equipment makers like Honeywell and Emerson.

Many protocols are getting more play as engineers use them to install sensors and other gear in spots that would be difficult to wire. Sometimes those installations will be temporary, giving managers a way to zero in on a piece of equipment, adding sensors and diagnostic equipment to gather data for a short time. These systems can be used to rectify problems, then move to other areas to facilitate further performance enhancements.

Wireless links are also seeing use in permanent installations. Sensors can be added in hard-to-reach spots, letting managers perform tasks like monitoring vibration to determine when equipment should be shut down for repairs before failures arise. They can also be used for ancillary tasks like the addition of security sensors, which can boost productivity by preventing sabotage or theft.

The common thread for these applications is that wireless extends networks into hardto- reach areas. “The next wave of adoption will be to the last foot, putting sensors here and there to collect data,” says Paul Daugherty, wireless products manager for GE Fanuc.

Though wireless networks make it simpler to implement equipment in these locations, such installations can’t be done without planning. Industrial environments are extremely noisy environments that are constantly changing as equipment is moved and changed. Maintaining signal integrity is still a challenge.

“There’s no question that reliability is the number one thing,” says Cliff Whitehead, strategic applications manager at Rockwell Automation. “You need to spend more time planning than when you install a wired network. You need to understand that the factory is dynamic.”

Suppliers are attempting to simplify these installations by providing complete systems. For example, Phoenix Contact’s RAD-SYSNEMA4X- 900 includes a 24-V dc power supply, a uninterruptible power-supply (UPS) system, surge protection, and an antenna adapter. The radio-ready package, housed in a NEMA 4X enclosure, simplifies the installation of industrial wireless radio modems and small remote-thermal-unit (RTU) devices.

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