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The Ask Control Engineering blog covers all aspects of automation, including motors, drives, sensors, motion control, machine control and embedded systems. Control Engineering answers questions from readers of Control Engineering's print and online magazines, newsletters and other publications. To comment on any blog posting, click on the post's highlighted question and scroll to the "Post a Comment" box at the bottom. Submit questions as comments to any existing post.
Fieldbus Foundation now certifies hosts?
April 22, 2011
Dear Control Engineering: Looking at the article about the Fieldbus Foundation registering hosts, I was trying to figure out what that means. Are the device manufacturers now telling the control platforms how to communicate? Isn’t it usually the other way around?
There’s more to effective communication than simply providing a channel. You could have the finest telephone system ever built, but if the two people talking don’t speak the same language, speech may be exchanged, but there will be no communication. The same applies with field devices and control systems.
Foundation fieldbus is a communication channel. It provides an infrastructure for efficient communication between field devices and a host, which is normally some type of control system, but as the article points out, a host can be an HMI, alarm panel, recorder, or whatever. It isn’t difficult to get the device and host exchanging basic information such as process variables, but sometimes the more sophisticated stuff can be a greater challenge.
One area that has been particularly problematic is asset management. Trying to get a field device to deliver meaningful diagnostic information to a host is complicated because the device may not be sending it in the way the asset management system wants to receive it. Companies that want to use the diagnostic capabilities of FF don’t like it when they have to find ways to get incompatible things to speak the same language and communicate.
Industry consultant Herman Storey characterizes the situation and the latest development this way: “There were two big problems. First, devices had configuration elements that were not standardized well enough that a host could easily download all configuration parameters. The basic stuff worked, but there was always something that didn’t work. Second, device diagnostics were not interoperable. Devices had information that hosts were not prepared to accept. These problems resulted in a lot of proprietary workarounds that were costing a lot of money on the project side, and limiting payback to end users by limiting achievement of full functionality unless the host and device came from the same vendor. These problems are system-level problems that require system-level solutions, but this is difficult in many organizations because only device guys are involved. The FF team has been attacking these problems at a system level, and the announcement just made is a major step in resolving these problems and making systems behave properly in general.”
This host profile is a significant advance in that it is creating a mechanism for greater interoperability between manufacturers and simplifying the work of end users working on new installations. As more companies implement it, there will be more platforms and devices from a variety of sources that will interact seamlessly via Foundation fieldbus.
Read Device Diagnostics and Asset Management by Herman Storey
Peter Welander, firstname.lastname@example.org
Saturday, 05-11-11 09:20
There are many advantages in Foundation fieldbus technology but why are oil fields are using both smart type instruments as well as FF? Emergency shutdown (ESD) PLCs require only analog signals. Why are digital signals not accepted?