Standardizing the way manufacturers describe their devices’ functionalities is the goal behind the electronic device description language (EDDL) standard, now out for vote under the ISA-SP104 Electronic Device Description Language committee.
The committee’s charter is to adopt the IEC 61804 standard for electronic device description said Terry Blevins, principle technologist, engineering, at Emerson in Austin, Tex., and chair of ISA-SP104. “We’re not changing [the IEC standard] in any way; we’re just adopting it,” he said. The committee voted to distribute the IEC standard for vote as an ISA standard in their first meeting.
Since some companies are not familiar with the IEC standards even though they are the international standard followed by all countries, and more people in the U.S. and North America and other countries are more familiar with the ISA and ANSI standards, the committee decided to just adopt the IEC standard. By merely adopting the IEC standard and also making it an ISA/ANSI standard, “we’re hoping more people will become aware of it, within the U.S. especially, and will take more interest in that technology,” Blevins said. “That will help the industry because the awareness of that language and technology is important; it’s the facilitator for them being able to easily work with field devices.”
The EDDL standard has two parts, Blevins said. “We’re adopting the part that addresses the [EDDL],” Blevins said. EDDL is a formal language that manufacturers can use to describe the functionality provided by their device. “If you purchase a pressure transmitter, it has all sorts of capabilities in terms of calibration and diagnostics built into it,” he said. “But to express and sh ow that functionality, you need a human interface that looks at information within the device. So you need somehow to describe the information within the device.”
In a way, the application program can show users that information in multiple languages. It can allow manufacturers to show things like trends, groupings of infor-
mation, tabs, and other things. “One approach some companies have used is to create a programming language like visual basic and some other programming language—to program all that language into the application by hard code,” Blevins said. “That’s a fairly quick way of doing it. But it has terrible ramifications for end users because the code now has to be installed in the engineering system. When a company may have 50 to 60 kinds of devices from multiple manufacturers, installing code into something as important as the engineering system is something most people are reluctant to do.”
Another approach, the EDDL approach,
allow you to clip on the wire and talk to a device and calibrate for diagnostic information. “If you think about hundreds of different devices in a plant, these handhelds have device description languages for devices,” Blevins said. “So you can work with any devices. If you get a new device a manufacturer has just introduced, all you have to do is go to a Web site, get device description, and load it into your handheld or engineering system. And you now can work with the new device without having installed any new software. You’ve brought in the device description file, but there’s no loading software so you can now have all the features of a new field device you’ve
means manufacturers can have a formal language to describe a device, but that language is only interpreted, “so you’re really not putting programming into the system,” he said. One application in the system is provided by the manufacturer in most cases, and it can interpret the information the EDDL language provides. This device description is called an electronic device description (EDD). The application can then use the EDD, interpreting the language and providing “all the functionality you’d have with hard code,” Blevins said. “But you don’t have to install software from multiple manufacturers in your engineering system.”
Another important aspect about the standard is “three of the major consortia of the world are all based upon EDDL,” Blevins said. Those are HART Communication Foundation, Fieldbus Foundation, and Profibus International.
just installed without having to install software in a system.”
People may not have heard of EDDL, but they have heard of competing technologies because they were better marketed or promoted. “This technology is sort of hidden in terms of it isn’t a thing a person sees. He sees the end result, but he doesn’t really see or isn’t aware of how the handheld does all its magic,” Blevins said. How does an engineering station know how to display this information in other languages and do trends? Building awareness gives the user better buying decisions about capabilities in his engineering system and handhelds for the future. “So that’s the main reason we’re doing it, for education and making people more aware,” he said. Within the current working group, the committee has proposed establishing six different team leads, some of which have already been filled.
Real-world applications Often a person needs to go into the field and work on a device, check calibration, and service the device. Some handhelds
ABOUT THE AUTHOR
Ellen Fussell Policastro is assistant editor of In Tech. Her e-mail is efussellpolicastro@isa.org.
References:
Archives