Wireless: Why now for sensors, field instrumentation?


Orlando, FL —Some industrial network advocates contend now's the time to consider or reconsider using wireless for sensors and field instrumentation. Technologies have advanced to make wireless more reliable, less power hungry, and easier to install, according to several speakers at the ABB Automation World 2007 Users' Conference and Exhibition in March. Here's how and why.

A convergence of wireless standards efforts, efficiency demands, and technology advances now available for instrumentation and sensing applications, says Joy Weiss, CEO Dust Networks , a strong proponent for wireless sensor networks (WSNs). It's not about installing more wireless devices, Weiss contends; it's about getting needed information to and from field devices and the control system for greater efficiencies.

Organizations like HART Communications Foundation , ISA , and Wireless Industrial Networking Alliance (WINA) are working on and promoting various wireless standards. Sensors and self-organizing low-power wireless technology, like other microprocessors, are riding Moore's Law (processing power doubles about every 18 months) at the same time the cost of installation of wired field devices is increasing dramatically, Weiss says. The promise is lower-cost communications without sacrificing reliability.

The industrial WSN challenge has been to get wire-like reliability in hard and dynamic RF (radio-frequency) environments with wireless economics, more points, higher efficiency, and greater ease of installation. Weiss says that upon completing a WSN installation, the instrumentation technician should say, "That was easier to install than wires." The process engineer should say, "That looks just like it's wired." IT personnel should say, "It plays nice like other IT programs." And the plant manager should say, "The installed cost is 90% less than wired and that just paid for itself many times over by avoiding a plant shutdown."

In her comments, Weiss cited BP's Dave Lafferty as saying, wireless mesh "enables us to do things we simply could not do before, either because of cost or physical wiring obstacles." BP's five-node installation could have taken weeks to run 700 ft of conduit and 3,000 ft of wire; instead it took two people about two days of labor, without a site survey.

Upside is to use wireless sensors for predictive, rather than scheduled maintenance of machinery and key plant assets. More than $20 billion or nearly 5% of total annual production is lost in North America due to unscheduled downtime, she says, citing ARC Advisory Group numbers from 2002. Potential is large across many industries.

Harbor Research noted in 2005 that among 153,000 U.S. electrical substations, just 10-15% is automated. And for one energy management installation, a wired installation would have taken an estimated four weeks instead of the 2 hours for a wireless solution—a 97% reduction in cost. Self-organizing wireless mesh is an easy retrofit for almost any application, Weiss contends.

A Dust Networks white paper, " Technical Overview of Time Synchronized Mesh Protocol (TSMP) ," offers more advice on technologies, topologies, methodologies, and applications.

" Wireless: Simple, Safe, Secure, Successful ," from Control Engineering also provides guidance.

Mark T. Hoske , editor in chief,
Control Engineering Weekly News
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