Tutorial: Instrumentation / DCS integration languages, part 1, EDDL

Tools to help integrate instrumentation into your DCS are available. They help with configuration, communication, calibration and HMIs.


One of the tools that can help you get more from your instrumentation and other process control devices are integration languages, such as EDDL and FDT. While the two have many similar characteristics and capabilities, there are subtle differences. This month we consider EDDL . ( Read an earlier article on the competing technologies .)

EDDL (electronic device description language) was developed originally simply as DDL through a collaboration between Rosemount (now Emerson Process Management), Siemens, and Endress+Hauser as a utility that could communicate with HART enabled instrumentation via a hand-held device. The objective was to create a system that would allow control system builders a means to avoid having to write specialized software for their systems to communicate with a variety of device manufacturers. It is agnostic to communication protocol, and can operate with standard analog wiring, or with fieldbus networks such as Foundation Fieldbus or Profibus.

Originally, the DDL utility had three major functional parts:

* Language—Syntax structures to enable a device’s designer to describe the field device parameters.
* Methods—A small scripting language to allow the device’s design engineer to write something like an interactive calibration feature that can operate on a PC or hand-held communicator.
* Menus—A hierarchical description of the parameters and how you want them organized.

Once it became clear that users wanted to be able to extend DDL’s capabilities, the group added three major enhancements and rechristened it EDDL:

* Definition of parameter screen displays (how devices should be displayed);
* Ability to have charts and graphs; and
* Persistent data, meaning you can save things you create for later use.

An EDDL file for a given device is like a plain text document that you can open in any number of word processing applications; while the text will always be the same, the way you see it on screen and how you manipulate it depends on the characteristics of the application you’re running.

When a control system opens an EDDL file, the system uses it as appropriate for the application. Unlike HART, the file does not exist in the device, so it doesn’t feed information to the system. The EDDL file is contained in the control system in a library. If you have a number of the same devices (e.g. the same pressure transmitter used in multiple locations) you only need one EDDL file for the group.

Control system vendors often have a wide variety of device files already in the system, in the same way that a computer can have drivers for a variety of printers from various manufacturers. Even if you change or upgrade control system platforms, the EDDL file for a given device remains the same. Conversely, if the device is upgraded, you can easily add the file for the upgrade to your control system.

The host control system builder has to support the platform, which has caused something of a division between builders. While there are builders who work with both EDDL and FDT, most only support one or the other

So what are the functions that EDDL supports? How can it help you when installing a new device?

* All the parameters for setting up the device are included;
* Calibration routines for that device are included;
* All the HART diagnostics and secondary variables are outlined in detail;
* How data should be displayed on the HMI is defined; and
* How to graph the process variable is described.

None of this information is required to use a given device; however, like HART capabilities, EDDL provides tools that will allow you to get the most from a device, particularly in the context of a larger asset management program. Moreover, it supports consistency in HMI and data displays, which has many direct benefits.

Like HART, EDDL capabilities are there and can provide these important tools. All you have to do is use them.

—Peter Welander, process industries editor, PWelander@cfemedia.com ,
Control Engineering Process Instrumentation & Sensors Monthly
Register here and scroll down to select your choice of free eNewsletters.

No comments
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
The System Integrator Giants program lists the top 100 system integrators among companies listed in CFE Media's Global System Integrator Database.
The Engineering Leaders Under 40 program identifies and gives recognition to young engineers who...
This eGuide illustrates solutions, applications and benefits of machine vision systems.
Learn how to increase device reliability in harsh environments and decrease unplanned system downtime.
This eGuide contains a series of articles and videos that considers theoretical and practical; immediate needs and a look into the future.
Choosing controllers: PLCs, PACs, IPCs, DCS? What's best for your application?; Wireless trends; Design, integration; Manufacturing Day; Product Exclusive
Variable speed drives: Smooth, efficient, electrically quite motion control; Process control upgrades; Mobile intelligence; Product finalists: Vote now; Product Exclusives
Machine design tips: Pneumatic or electric; Software upgrades; Ethernet advantages; Additive manufacturing; Engineering Leaders; Product exclusives: PLC, HMI, IO
This article collection contains the 5 most referenced articles on improving the use of PID.
Learn how Industry 4.0 adds supply chain efficiency, optimizes pricing, improves quality, and more.

Find and connect with the most suitable service provider for your unique application. Start searching the Global System Integrator Database Now!

Cyber security cost-efficient for industrial control systems; Extracting full value from operational data; Managing cyber security risks
Drilling for Big Data: Managing the flow of information; Big data drilldown series: Challenge and opportunity; OT to IT: Creating a circle of improvement; Industry loses best workers, again
Pipeline vulnerabilities? Securing hydrocarbon transit; Predictive analytics hit the mainstream; Dirty pipelines decrease flow, production—pig your line; Ensuring pipeline physical and cyber security