Reviewed resource: Fieldbus Foundation also provides comparison

Profibus spoke first, now Fielbus Foundation replys in the process fieldbus competition.
By Control Engineering Staff March 5, 2008

Last month we offered a paper produced by Siemens comparing Profibus PA and Foundation Fieldbus . Call me naïve, but I was surprised at how controversial that proved to be. This month, FF gets its turn.

Rich Timony, president and CEO of the Fieldbus Foundation, has written a paper entitled, “Choosing the Right Technology for a Digital Automation Architecture.” (You may need to register for our Resource Center to download the paper.) This work is rather longer than the one from Profibus and goes into greater detail on a wider variety of topics. It covers some of the same ground in that it also makes one of the same key differentiations we discussed last month: FF’s ability to perform PID control at the device level vs. Profibus’ suite of networks and its ability to integrate more types of devices across those platforms.

Timony cites more statistics of market share, revenues, and even historical precedents to assert some dominance over Profibus PA. There are also discussions of operational issues, such as adding devices to a hot segment and device addressing, that are identified as functional advantages.

Just as the Profibus paper says that FF is more expensive due to those control functions, Timony says Profibus has its own cost downsides. The paper warns, “Profibus PA requires a gateway to Profibus DP before it can be brought into a control system. This increases cost, reduces performance, and adds failure points to the solution. It also increases engineering time, drawing complexity, and configuration effort.”

For those trying to make an informed and rational decision whether to adopt fieldbus architecture for process instrumentation, the value proposition may still be difficult to see. A company has to decide what it expects to gain from adopting fieldbus networking for process applications. Ultimately the choice typically boils down to a mix of the following:

  • Lower wiring costs;

  • Improved ability to use diagnostics for asset management;

  • Ability to move control functions down to individual devices; and,

  • Improved maintenance and troubleshooting functions.

Some of these are available by other means (e.g., diagnostics capabilities with HART ) and others cannot be realized in a retrofit situation (e.g., lower wiring costs) so the picture is not always completely clear. If you find yourself in that evaluation phase, this paper is worth reading ( as is the one from Profibus ). Also watch for a larger article, “Fieldbus: Growing Globally” in the March issue of Control Engineering .

—Peter Welander, process industries editor, PWelander@cfemedia.com ,
Process & Advanced Control Monthly
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