The Complete Beginner’s Guide to Device Descriptions
By Walt Boyes
What do you need to know about HART® Communicator device descriptions? We have the answer! Read on to learn what device descriptions are, why you should keep them current, and the simple process to update them.
What are device descriptions?
A device description is written in EDDL or Electronic Device Description Language, which is a structured text declaration language that is similar to an XML, HTML web page or SGML document. EDDL isn’t a program or programming language in the classic sense. It doesn’t need to be translated for each new operating system. It is interpreted at runtime by the EDD host instead. EDDL is standardized in IEC 61804-3 and IEC 61804-4. Profiles exist for the different fieldbuses to take into account the specific properties of the respective fieldbus.
EDDL can theoretically be used with any protocol. However, the language is most widely used in the world of process automation with HART, Foundation fieldbus, Profibus, and Profinet. EDDL can explain device parameters and their dependencies, visual representations for user interactions can be defined and communication paths with which the system can access device data can be described. Via different menu hierarchies, a display suitable for PC software and a display for small communications handsets can be implemented in the same EDD. EDDL also includes the ability to define interactive methods based on a subset of ANSI C and EDDL specific Built-ins that implement an interactive user guidance through complex processes such as calibrations or first commissioning of equipment.
Why update device descriptions?
It’s important to update device descriptions regularly. Whether you use a HART Communicator or one of the other software-enabled devices available to talk to your field devices, you have to have the correct device descriptions in the communications tool, or your tool will not recognize newer transmitters and control valves. Staying current with your device descriptions helps you avoid:
- Being shut out of new equipment
- Having your instrument or valve operate in a generic mode
- Surprising difficulties at startup and commissioning
How to update device descriptions. It’s not as hard as you think!
If you have a license from Emerson, they’ll update your device descriptions (DDs), but Emerson only supports the 475 HART Communicator at this time. ProComSol supplies software-based EDDL communications in PC, iOS, and Android operating systems. You can use this type of software instead of the 475. Beamex and Meriam provide Communicator emulators in their calibration devices. Watch this video to learn more about updating device descriptions.
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Walt Boyes has more than 40 years of experience in the automation industry, including Executive Committee experience in three companies, and board of directors service in both for-profit and not-for-profit companies. Walt is principal in Spitzer and Boyes LLC, a technology consulting firm assisting companies to better market their products in manufacturing and automation. He has contributed to many industry publications as both writer and editor. View Walt’s full bio.