iDTM unites FDT and EDDL
31 March 2008
The agony of choice! Up to now, those involved in device integration have had a tough time deciding whether to use EDDL (Electronic Device Description Language) or FDT (Field Device Tool). A lot has been written about the two technologies here and in other sources.
The underlying technology however should not be an obstacle to device integration. Endress+Hauser and software provider CodeWrights have implemented an idea of the NAMUR working group 2.6 ‘Field Bus’ where EDDL is smoothly integrated into an FDT-based frame application. The new software, called iDTM™, ‘interprets’ the DD or EDD of a field device so that the device can be used in E+H’s Plant Asset Management System. The CodeWrights solution is not unique and can be licensed for any FDT frame application.
With FDT Technology, field devices and communication components (remote I/Os, gateways, etc.) can be operated with just one software tool regardless of the component manufacturer or communication protocol. More and more users in both process and factory automation are realising the benefits of FDT and using the technology in their plants. In the meantime, suitable communication DTMs are available for almost every communication hardware version which enables the user to map any network and topology to an FDT application. And more importantly, almost every field device manufacturer can provide their customers with dedicated device DTMs.
Recent comparative tests of the EDDL and FDT integration technologies conducted by Shell Global Solutions on behalf of the Dutch user organisation WIB confirmed that EDDL and FDT are complementary technologies, each with its particular area of application. The results also clearly show that FDT is by far the superior technology in terms of efficiency, functionality, and graphic support.
With the interests of users in mind, in April 2007 at Hannover Fair the EDDL Co-operation Team (ECT) and the FDT Group announced their intention to develop a standardised solution for device integration that is compatible with both technologies. The solution, called FDI (Field Device Integration), is aimed at uniting the benefits of FDT and EDDL and guaranteeing the customer openness, freedom of choice, and investment protection.
However, it will take some time until FDI is ready for the market. With the smart iDTM solution, users can benefit from a combination of both technologies today with a more or less ‘light FDI’ version.
iDTM interprets HART DDs/EDDs (Profibus and Foundation Fieldbus will follow) thereby enabling the integration of HART devices without dedicated device DTMs in FieldCare, which is part of Endress+Hauser’s Plant Asset Management System. It also allows the operation of less complex devices that are only described with DD/EDD. In this context, the FDT-based infrastructure is used for open, vertical communication from the control room to the field device.
The software is based on the original standard HART interpreter SDC625 from the HART Communication Foundation (HCF) which is also used for HART DD/EDD certification. iDTM supports HART devices registered with the HCF (a complete list of all devices is provided on the HCF Web site) and can integrate the entire HCF DD library with the certified HART DDs/EDDs. Since the HCF has already tested and examined the function of the device descriptions used, a maximum level of DD/EDD reliability can be guaranteed.
iDTM not only uses the HCF standard interpreter but also ensures that the DDs/EDDs are processed in exactly the same way as in the HCF standard tool. The interpreter acts as an independent component and is separated from the FDT-specific function in iDTM by means of a defined interface.
New or modified DDs/EDDs can also be added to iDTM. In the process, every change is logged and can be undone. The DDs/EDDs of the device manufacturer are integrated into iDTM exactly as they are certified. No changes are made. As a result, the user receives the exact functionality as offered by the device manufacturer through the DD/EDD.
iDTM allows devices that don’t have DTMs to be used in FieldCare. The solution combines the familiar DTM user interface with the basic device functionality described in the DD/EDD. The user interface of the iDTM was developed in compliance with the DTM Style Guide and thus has the same look-and-feel as other dedicated device DTMs. iDTM offers the complete device functionality as implemented by the manufacturer in the registered DD/EDD, and no more than that.
iDTM processes the existing device descriptions during DTM runtime and combines the benefits of FDT and EDDL in a common environment. Because it is a runtime-based process, users have the advantage that they can continue to use the DTM already deployed in the asset management environment without changing it—even if the most recent devices, with a corresponding device description, are used. This is achieved by embedding the standard DD interpretation software into the well-proven DTM technology. Users therefore work with open standards and certified technologies.
Like every other DTM, iDTM uses the existing communication structures in a plant, thereby bringing the DD/EDD-based devices into the open, vertical communication world supported by FDT. As a result, users can manage these devices from a central location and document them fully.
Furthermore, by means of an interface concept, the function scope provided in the DD/EDD can thus be extended as required with software modules. Functions that cannot be depicted by the DD/EDD can be implemented. These software modules can offer both new additional graphical user interfaces and graphical user interface-free functions (e.g. for condition monitoring). As a result, software extensions are created that can either supplement just one individual device type, or a whole device library beyond their DD/EDD functions, depending on the user’s needs and requirements.
An individual entry appears in the FieldCare device catalogue for every device type supported by iDTM. In this way, the user can sort the device types by manufacturer, protocol, or category, and select them. The bus scan function recognises the devices and automatically assigns the right DTM to the project regardless of whether it is a dedicated DTM or the iDTM.
Currently, it is not known when the first products with FDI Technology will be available on the market. The iDTM concept creates a bridge between EDDL and FDT today, thereby providing a pragmatic and future-proof solution that releases customers from their current dilemma during device integration.
Endress+Hauser provides iDTM as of February 2008 as part of its FieldCare software, and older versions can be upgraded. CodeWrights will offer this solution to other system providers and users in the course of 2008.
Dr. Raimund Sommer and Sandra Gisy, Endress+Hauser Process Solutions AG;
Dr. Rolf Birkhofer and Stefanie Schattling, CodeWrights GmbH
Figure 1: Example of a dedicated device DTM in FieldCare
Figure 2: DD/EDD integration in FieldCare with iDTM
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