Commentary: Are you using wireless for control?

If you aren't, you're already behind. Wireless for control applications is in widespread use today.

By Control Engineering Staff March 3, 2009

Listening to the presentation, I could hardly believe my ears. “30% of wireless devices are being used in control applications.” Did he really say that? The “he” in this case is Bob Karschnia, VP of wireless business for Emerson Process Management , arguably one of the largest suppliers of wireless process instrumentation and control systems today. He made that comment at the ARC Advisory Group forum in Orlando last month, and said it in a very offhand way, like everybody already knew it.

I had to ask if he really meant what he said. “Sales seem to be following the same ratios we see with our wired products for control vs. monitoring applications,” Karschnia explained. “People immediately associate control with high speed flow control loops. With most loops, the fastest ones are flow, followed by pressure, then typically temperature and level. Sure, people use wireless for monitoring applications, but about 30% of our wireless devices are in control applications. Some are open-loop control, meaning an operator will take an intervention, but they use it as a control point. Others are built into control strategies, but they’re things that have longer time constants, like supervisory control applications, tank levels, temperature control of heated jackets, and things like that with slower time constants.

“The larger point is that control requires multiple pieces. Only one of those is high speed, and that is really only for a small subset of applications. What control really needs is repeatable results, high confidence in the measurements themselves, and high reliability to your communication. If communication is sporadic, you find yourself in a situation where you’re chasing after old data. Emerson is in control because we have high-quality measurement devices, and reliable communications.”

All control applications aren’t critical, in the sense that the process will blow up or do something terrible if it gets out of hand. Karschnia went on to point out that these applications have nothing faster than a five-second update rate, which is the shortest period for Emerson’s Smart Wireless devices, pre-WirelessHART. There are users trying faster loops with newer devices, but that’s still considered experimental.

Coming away from that presentation, I wondered if other companies are having similar experiences. Maybe there’s more of this going on than I know about. I asked Jeff Becker, director of global wireless business for Honeywell Process Solutions , if he found the same thing. Honeywell is also one of the largest players in the wireless instrumentation and process control fields. He wasn’t sure he could give a specific percentage, but he also believes it’s already happening.

“End-users have moved past the‘is it secure enough?’ question,” says Becker. “They’re using wireless more for control purposes, everything from temperature regulation to blending and movement. At Honeywell, we built our second-generation platform as a control-ready network, with the latency, updaterates, redundancy, and scalability that is required for control. Honeywell believes that nearly all industrial wireless networks will eventually be used for some element of control, which is why it is important to select a control-ready architecture from the beginning.”

The picture is already emerging: Many customers are not waiting for wireless instrumentation to be pronounced officially “ready” by some monarch or governing body. They’ve concluded that it works, and they aren’t holding back on what they consider to be appropriate applications—monitoring, control, or whatever.

—Peter Welander, process industries editor, , Control Engineering Process & Advanced Control Monthly eNewsletter Register here to select your choice of free eNewsletters .