Distributed Control

Wireless Spotlight Moves to Orlando...

By Andrew Bond, Industrial Automation Insider

Mar 16, 2010

One of the more entertaining side-shows at ARC's Orlando Forum in February may well have been the four-day meeting of the ISA100.12 subcommittee to address the key issue of long-term convergence of WirelessHART with the ISA-100.11a standard. Set against the background of the latter's ongoing problems with ANSI and the apparent disagreement on objectives and deliverables between the sub-committee's co-chairs, the issue at the top of the agenda for many observers, if not for the sub-committee itself, is whether true convergence as understood by the wider user community can actually be achieved and, hence, whether the ultimate objective really is convergence or simply peaceful co-existence.

The press release from ISA which flagged up the meeting adopts what some might interpret as a more conciliatory tone, explaining that the sub-committee is "chartered" with completing a series of tasks that will "provide developers with meaningful information to achieve convergence and end users with educational materials to allow for successful installations of both WirelessHART and ISA-100.11a systems in a pre-converged environment." Among those tasks, it adds, is "the development of a phased convergence specification to converge WirelessHART and ISA-100.11a."

Recommended practice

Two recommended practice documents are scheduled for completion before the end of 2010. The first, due in the next few months, will define how a single wireless field device might be able to run either ISA-100.11a or WirelessHART -- the so-called "dual boot" solution -- while the second, which is being prepared in conjunction with the ISA100 Co-Existence working group, will describe how users should achieve best performance for WirelessHART and ISA-100.11a networks implemented in the same facility and in overlapping radio space.

Arguably more significant in the longer term and also described as "nearing completion" is the comparison document outlining the differences between ISA-100.11a and WirelessHART. This, says ISA, will "serve as an official ISA100.12 technical comparison document for end users." What must be of concern to those hoping for early progress on convergence, however, is that its second purpose will be to "provide a starting point to begin the process of converging ISA-100.11a and WirelessHART," (our italics) nearly two and a half years after the sub-committee was set up with that express intention. Small wonder that there are those, including, one suspects, some backing the "Boyes appeal" which ANSI has insisted that ISA must now hear, who doubt whether there is or ever was a genuine intention to converge the two standards at all.