Well, another Friday, another airport (O’Hare this time, returning from the PROFINET one-day training event in Bur Ridge). And with some time to catch up on comments about the article at ControlGlobal.com: “Fieldbus Wars continue.”
Tim Sweet of Honeywell is quoted saying that use of Foundation fieldbus, HART and Profibus DP has soared in the past three years: “These technologies are now readily accepted and readily deployed. We think these fieldbus protocols are here to stay and are adding significant value to the adopters.” I can’t speak to the non-PROFIBUS protocols, but we certainly see PROFIBUS soaring. There were 30% more PROFIBUS nodes installed in 2005 than in 2004. He’s silent on PROFIBUS PA, but we see continuing growth there, too. I absolutely agree that fieldbuses are adding value to their users. “Adding value” is key here; it’s not just about saving them money.
Speaking of nodes installed, there were well over 15 million PROFIBUS nodes at the end of 2005. That’s about double the nodes of the number two fieldbus – Interbus… and about four times number three DeviceNet. How do we know the exact node count for PROFIBUS? Each node uses a chip available from several suppliers. We count the chips.
This contradicts GE Fanuc’s Bill Black: “GE Fanuc sees DeviceNet fading and Profibus flattening out,” at least from the PROFIBUS side. He’s right about Ethernet increasing though. I just don’t think it’s to the point of flattening out PROFIBUS.
The author says: “Some people claim that HART isn’t a fieldbus, but we beg to differ.” HART is a communications protocol superimposed on point-to-point wiring. Point-to-point wiring is the opposite of a bus. Therefore, HART is not a fieldbus. It’s useful, it can fit neatly into a fieldbus system, but it is not a fieldbus… by the very definition of the word “bus.”
Dave Appleby of Rockwell: “The value of open standards like Ethernet is that they give people a common format to work from. The trick can be determining which standards are truly open.” Actually, Rockwell’s trick is trying to make users believe that theirs is the only “truly open standard.” Hogwash. Look at the IEC standards cited by almost all the major Industrial Ethernets – they’re the same. Yes, even Rockwell’s. Don’t fall for the Rockwell trick.
Scott Saunders of Moore Industries: “Interoperability between vendors has been and always will be a bit of an art.” I’ve heard rumors of interoperability problems with other fieldbuses, but not with PROFIBUS or PROFINET.
Now there were two opposing views stated. The first was espoused by Charles Piper and Eric Marcelo:
“[Charles] Piper, of Invensys, says it really doesn’t matter which fieldbus you choose.”
“Marcelo, of Nestle, doesn’t care which fieldbus he buys, as long as it works.”
The opposing view was from Patrick Rossi: “The splintered state of fieldbus has left end users unable to decide which buses to embrace. With no clear choice to inexpensively deploy to address analog and discrete instrumentation and motors, our choice is not to choose. We’ll just wait for the next ‘breakthrough’ technology to emerge to reduce initial and residual costs.”
First, some comments on the pro-fieldbus viewpoint. FOR GOODNESS’ SAKES, YES, USE A FIELDBUS! I can’t agree that it doesn’t matter which one you choose, of course. PROFIBUS and PROFINET are clearly superior. But use a fieldbus; even those other fieldbuses are better than no fieldbus (probably).
Some comments on the anti-fieldbus viewpoint: FOR GOODNESS’ SAKES, USE A FIELDBUS! Just pick one! Unless your company does not need to save money in installation and maintenance, have greater flexibility in manufacturing, need more uptime, … It’s like you are being offered money, but you can’t decide whether to take a bank check or a cashier’s check. Yep, I’ll just sit here and wait for something better. Great plan.
The author concludes with: “While they waffle, at least two 800-lb gorillas are lurking in the weeds, threatening to upset the fieldbus apple cart—Ethernet and wireless.” I’m sure he must mean that RS-232 serial cables will upset the apple cart. Oh, wait a minute, RS-232 is just the physical connection, not the protocol that allows various pieces of equipment to talk to each other. Uh-oh, Ethernet is the same thing… and actually so is wireless. I guess Ethernet and wireless won’t be upsetting any fieldbus apple carts.
Finally to conclude on a positive note (from the plane now, but to post in the office later), I wholeheartedly agree with Randy Bradford, of Concept Systems: “People running plants aren’t interested in technology for technology’s sake. They view technology as nothing more than a tool, and need to know that the technology will help them achieve their goals without getting in the way of smooth, productive plant operation.”