For over a year, an ISA subcommittee has been working on a plan that would converge the wireless ISA-100.11a specification, approved as an ISA standard last month, and the WirelessHART specification. But a battle between the two industrial automation wireless specs has been under way for some time, with vendors camping out on one side or the other and end users forced to carefully choose the look of their wireless landscape. What manufacturers really need is a way for the two to interoperate. Unfortunately, despite the ISA-100.12 WirelessHART Convergence Subcommittee’s best efforts, that’s not going to happen. “ISA-100.11a and WirelessHART are inherently incompatible from a standards viewpoint,” said Dick Caro, co-chair of the ISA-100.12 subcommittee. “In other words, to write a single standard from which you could pick a menu [of options] and come up with either 100.11 or WirelessHART from the same standard will never happen.” After a detailed review of the technical differences between the two approaches, including protocol suite, system management, gateway, and security specifications, Caro said, it’s clear they are not compatible. “They are so different in detail that I don’t know of anybody who is interested in writing a document that puts them together.” Meanwhile, ISA-100.11a and WirelessHART have both been pushed to the International Electrotechnical Committee for consideration as international standards. It could be that the IEC will demand a unified approach for wireless industrial automation networks. But it’s not likely. “The IEC was responsible for the eight-headed monster that was fieldbus,” Caro said. “I think a two-headed monster for wireless will emerge from IEC.” With that in mind, the ISA convergence subcommittee is redirecting its efforts toward a practice document that recommends a “dual boot” approach that would require a vendor to have both the ISA-100.11a and the WirelessHART network stacks on a device so that a user could choose one or the other during the provisioning stage. The question is, how? Enter Nivis, LLC, a designer of wireless sensor and control networks, which is working on a chipset that accommodates both stacks. While there are currently no commercially available products using the Nivis dual boot system, manufacturers can expect to see demonstrations of this technology in action at ISA Expo 2009, in October in Houston. And, industry experts predict that vendors such as Honeywell, which has been promoting the dual-boot idea within its own OneWireless network, and Yokogawa, a HART supplier active in the ISA-100.12 subcommittee, will bring out products that support both approaches. If that happens, it’s only a matter of time before the rest of the vendor community follows. But, this, too, will depend on what IEC does with ISA-100.11a and WirelessHART. Only time will tell. “We’ll have a good picture of the IEC standard by this time next year,” Caro said.