April 2008

Different technologies, similar goals: Device integration

Significant end user confusion surrounds the FDT and EDDL communication technologies, said the ARC Advisory Group.

FDT is the Field Device Tool and EDDL is Electronic Device Description Language. There are ongoing collaboration initiatives to develop a unified solution for field device integration.

However, enhancements have blurred the differences making selection of FDT or EDDL increasingly confusing. ARC recently tackled the situation from an end user perspective to provide practical guidelines.

FDT and EDDL are fundamentally different technologies aimed at a similar goal of providing easy plug-and-play access to information in smart field devices.

FDT is a universal field-device communication interface to allow access of data for higher-level applications and can work in many more industries beyond process control.

EDDL and its enhanced brethren commonly designated by eEDDL is text-based language used to describe the communication attributes of a smart field device. FDT uses DTMs that usually platform on DDL, the previous generation of EDDL, and can be more expensive for manufacturers, but suppliers may or may not pass the cost to end users.

The basis for EDDL, DDL, has been in use for over a decade and is governed by the IEC 61804-3 standard, while FDT approvals are still pending.

Third-party testing organizations WIB and BIS tested and evaluated EDDL and FDT and recently presented their results. The results highlighted the similarities and the differences.

When analyzing just the features of the two technologies they look similar. Their differences are most evident when we look at them from the user's perspective. That is because the features are not equally important to the unique enterprises where they deploy.
In general, FDT has more power to provide functionality that is more complex, and EDDL provides an economical small footprint solution adept at providing field device calibration and configuration.

FDT provides a universal format for suppliers to develop software for field-device health analytics and other solutions in a standard way capable of working across vendor applications.

EDDL for HART, Foundation Fieldbus, and Profibus worked well with multiple vendor devices in supplier communication protocol specific applications.

ARC uses the third party test findings and its own experience to fashion qualitatively an application list to use as a first step in the technology selection process.

*1 check = needs improvement, 2 checks = competitive, 3 checks = excellent