Editorial: WirelessHART moves into its next stage. Should it?

By Control Engineering Staff September 20, 2007

On September 7, the HART Communication Foundation board voted on and passed the HART 7.0 specification which includes the wireless protocol which has been dubbed WirelessHART. This in itself is not surprising, except for the fact that Jack Bolick, president of Honeywell Process Solutions and member of the HART board, made a last-minute call for his colleagues to vote “no” on the proposal. He suggested they support ISA SP-100 , which is still being formulated, as a better alternative. Bolick’s appeal and a response from Ron Helson, executive director of HART Foundation, were published by Control Engineering .

The two arguments are both compelling. WirelessHART has set out to create a wireless version of its wired protocol, down to ensuring backward compatibility with wired devices, and the same capabilities, tools, and practices users know from their wired instruments. This is certainly a worthy objective for HART to pursue, at least from their perspective and for anyone who uses and appreciates that platform.

However, Honeywell sees this as an approach that is far too limited. In his letter to Control Engineering, Bolick compared WirelessHART to a pager and SP-100 to a cell phone. He wrote, “A pager is a single purpose device dedicated to one function, like WirelessHART is dedicated only to the HART protocol. However, a cell phone is a more universal device designed to efficiently and effectively perform many functions while also providing the paging function.”

He has an interesting point, and many would be wise to follow it. But it won’t apply to everyone. Consider HART in the wired world. For all the millions of HART-enabled instruments installed, fewer than one in five uses the diagnostic functions and secondary variables. Returning to the earlier analogy, if HART is like a pager, a whole lot of users choose not to turn it on and are still writing messages on pink pads that say “while you were out.” To those users, who could easily represent 50% of our process plants, adding the most basic HART functions would be high-tech. For them having the capabilities of WirelessHART will be a huge advance and support all the instrumentation-level wireless applications they could imagine.

On the other hand, Bolick’s advice is sound for plants at the higher end of the technical spectrum. Companies with more sophisticated networking, and those used to more sophisticated diagnostics available from platforms like Profibus or Foundation Fieldbus, find HART slow and old-tech. They might want to wait for Honeywell’s vision of SP-100 and wireless instrumentation with greater ambitions. HART is not the platform they should build on, although it would be wrong to suggest that they shouldn’t use the protocol for specific groups of instruments in a larger environment.

But there is still one big unanswered question: What will SP-100 look like? Will it be the comprehensive standard that includes Honeywell’s vision?

After spending a week at the Emerson Global Users Exchange, the picture that John Berra, president of Emerson Process Management , paints of where SP-100 is going, or where he hopes it goes, is much different than Bolick’s. In an interview at the event, Berra said, “It’s our fervent hope, since the same people that worked on WirelessHART are working on SP-100, that the WirelessHART technology will be adopted by SP-100 as the sensor level standard. That would be the best thing for the industry, and we’ll work towards that direction.” Emerson

Honeywell hopes the same people will come to a different conclusion. “We support HART Foundation 1000%,” says Bolick, “but the underlying issue is the best use of bandwidth.” Jeff Becker, director of Honeywell’s global wireless business adds, “There’s no need for WirelessHART at this time. It doesn’t help anyone to have multiple single purpose protocols when there is already one universal standard being worked on that can support all of these protocols, all at the same time. There’s nothing that the WirelessHART protocol can do that you won’t be able to do with SP-100, and do it more efficiently. At our user group, we demonstrated an Emerson AMS system, completely unmodified, talking to our transmitter over HART. We can handle Foundation Fieldbus or Profibus protocols, all at the same time.

Becker continued: “There’s an obvious path here we could take to unify these two standards into one universal standard under SP-100. We’re trying to make other vendors and particularly customers aware of the choice they’re about to face and the consequences to the industry as a whole if they choose a fragmented rather than unified standard.”

So, where do we go from here? There is little doubt that WirelessHART will proceed, with or without SP-100. There are too many manufacturers behind it, and too many customers will see the benefits of its simplicity and interoperability. On the other hand, Honeywell will probably continue to champion its universal standard concept for SP-100. Bolick says he wants to follow SP-100, so he is pegging his hopes on the group creating the right kind of standard. The most probable outcome is that both will advance in parallel and users will have at least two major platforms to consider. Honeywell will likely stick to its guns and create the best product it can in an effort to bring its customers the most sophisticated approach. It may even be successful in convincing other vendors to join it.

The analogy going forward may be more like the PC and Mac comparison. WirelessHART will trade on its universality. Honeywell will push the versatility of its platform and probably even include all the same HART functionality. Its job will be to convince customers that the advantages are indeed worth having. Customers will then be able to make their choice. While one standard would be best, having two (assuming it’s only two) might not be a bad thing in the long run, as long as there is enough difference to matter.

—Peter Welander, process industries editor, PWelander@cfemedia.com ,
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