Wireless Starts to Mesh

Plants are taking a broader view of the role of the technology

By C. Kenna Amos, contributing editor

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What do end-users desire in wireless? “They want to see reliable, easy-to-use equipment. They want reliable signals. They want easy-to-install, meaning: ‘Can they keep the plant running when they connect the adaptor for wireless?’ They want something that is easy to maintain, where they can install and forget. They want equipment that won’t interfere with the current process signal,” Schosker says.

Plants are looking for more integration with wired devices and the control system, believes Kagan. “They would like to be able to integrate server-based applications and wireless data. They would also like to enable mobile plant personnel to connect wirelessly to the server to interact with control and enterprise applications.”
A Complication
One massive challenge may be getting the WirelessHART specification (see www.ChemicalProcessing.com/articles/2008/071.html) of the HART Communication Foundation (HCF), Austin, Texas, and the ISA100.11a protocols of ISA (the Instrumentation, Systems and Automation Society), Research Triangle Park, N.C., reconciled and compatible with other protocols, as well as device-enabled.
Currently, HCF, through its Wireless Cooperation Team, is aiming to develop an interface specification for a gateway to Foundation Fieldbus and Profibus’ ProfiNet. That team also is working to establish a common set of compliance guidelines for incorporation into the respective product-registration procedures.

Meanwhile, in June, Honeywell unveiled an updated version of its OneWireless industrial-wireless-network equipment that is designed to be compatible with ISA100.11a, notes Becker.

Then, at the end of September, Emerson announced release and shipment of its first wireless pH transmitter, the Rosemount Analytical Model 6081-P. It’s compatible with a WirelessHART Model 1420 gateway.
Essentially, though, no other commercially available WirelessHART products exist now. “However, several manufacturers are in the late stages of testing and will have products ready for registration and compliance testing at HCF in the next two to three months,” noted HCF executive director Ron Helson in late September.
Johnston believes that by January or February a number of WirelessHART-enabled and HART-certified instruments will be available. Those, he forecasts, will include “self-powered instruments, WirelessHART gateways and adapters.” Implementation of WirelessHART won’t be difficult, says Johnson, but will require a site walkthrough to identify possible issues and how they can be avoided. “In actual fact, there is little difference between planning a 4–20 mA installation and a wireless one, apart from the wire,” he notes.
P+F plans to release products in the first quarter of 2009. “These will be WirelessHART gateways and adapters for making instruments wireless,” Schosker says, adding that P+F also will produce ISA100.11a-enabled devices. “It’s kind of like VHS versus Betamax [video tape formats]: You supply both until one wins.”

Interoperability Issues
End users certainly want to avoid the frustration that arose with the eight-headed IEC 61138 fieldbus standard of the International Electrotechnical Commission (IEC), Geneva, Switzerland. It doesn’t specify a particular approach but instead provides an umbrella for rival ones.

“If they [WirelessHART and ISA100.11a] continue on separate paths, they both will meet end-user requirements — much like a Chevy and a Ford,” Kagan suggests. “We believe that the end-user community will be best served with one standard — ISA100 — because that standard has the flexibility to support many other functions in the future. ISA100 is a family of standards architected to work well together.”

Interoperability surely is the key to avoiding frustration of end users, but achieving it can be a elusive goal. “WirelessHART and ISA100 are working on the best way to achieve convergence, i.e., one standard. How that develops remains to be seen,” notes Kagan, who chairs ISA100’s Working Group 6, Interoperability. “We’re just getting going, but the intent is to understand the mechanism for any other standard, as well as the family of ISA100, to have some degree of interoperability. The devil is in the details — and definition of terms.”

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