HCF's Ed Ladd Responds to Wireless Control Questions

Feb. 8, 2010
As part of our research for our February 2010 feature on wireless control, Automation World submitted a list of e-mail questions on the topic to Ed T. Ladd, director of technology programs at the Hart Communication Foundation (HCF), which oversees the WirelessHart standard. Following are Ladd's responses:
Automation World: Given that you've got white papers up on the topic, is HCF making a push to promote WirelessHart for control applications? Ed T. Ladd: WirelessHart is designed for control applications. It is up to the user to decide whether or not wireless should be used for control. My personal recommendation is to stick with noncritical control applications. If the process you are working with can kill someone or it is critical to your process, wire it, but not even that is infallible. The Hart protocol does not eliminate one for the other. With Hart, you can go wired, wireless or both—users' choice. AW: How is the interest level running among both vendors and end-users regarding use of wireless for control? Are any or many end-users actually using or experimenting with wireless control? What kind of success/results have they reported?Ladd: There are people experimenting with control, but we live in a risk-averse industry, and wireless technology is not the “state of the art with 20 years of proven reliability” that our industry typically wants.AW: What are the major considerations for users when looking at possible wireless control applications? Sampling intervals? Latency and Jitter? Battery life? Reliability? Security?Ladd: With the security and reliability built into WirelessHart, the considerations for control via a wireless signal are pretty much the same as wired. It has been proven even with longer sampling intervals, control via a wireless signal can be accomplished satisfactorily. Like any other control application, the users will have to tune the PID (proportional integral derivative) function to provide the appropriate response.AW: What are some of the major concerns of users and how can they be overcome? Is redundancy the key?Ladd:  The industry has been using wireless for years in plants and in SCADA (supervisory control and data acquisition) applications. The unknown is the greatest concern for applying wireless in process control applications.  AW: What kinds of applications will ultimately make sense for wireless control? Ladd:  This is truly up to the user and the application. Water may be a good application for control until it is cooling a nuclear reactor. Air may be a good application for control until it is critical to your combustion process…AW: What are the potential benefits to users of using wireless technology for control?Ladd: In essence they are the same as monitoring applications. Wireless opens the door to providing new monitoring and control points in areas previously inaccessible. Systems previously controlled open loop or through a purely manual process can be automated without the need for wiring new I/O (input/output) points.AW: How do you see the whole wireless control scenario unfolding across industry, and how long will it be before wireless becomes commonplace for control of critical processes?Ladd: Does an airplane fly using wireless controls?  No, not even the most advanced aircraft fly without wires. Critical processes may never be completely wireless, but having the option allows the user to choose what is right for their application. Picking the right wireless standard is important and I believe Hart Communication has the advantage of providing a simple, reliable and secure solution, whether wired or wireless.Related Feature - Wireless Control in the Process Industries: Blasphemy or Common Sense?To read the feature article relating to this story, go towww.automationworld.com/feature-6558.

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