The Caro Report: Dick on EDDL, FDT/DTM

From an email earlier this month, Dick Caro writes: I have written several articles on FDT/DTM. Originally, I was quite negative about this technology, but after being "educated" by several field instrument suppliers I have finally resolved the important differences between FDT/DTM and EDDL. I thought that this information would be good to share with my fellow SP104 committee members.The most basic difference between them is that -- * FDT/DTM allows the instrument supplier to format the HMI screen display for that instrument * EDDL allows the HMI supplier (typically the DCS vendor) to format the screen display for all field instrumentsI have polled several end users with this generality, and they mostly agree that it is more important that they not train their process operators for each type of field instrument. They want the DCS supplier to control the look-and-feel of the HMI.However, in my conversations with some instrument suppliers, I find that there are some diagnostic and calibration displays that cannot be made available via EDDs (they tell me). They find that they can COMPLEMENT the EDD with their own tools by using FDT/DTM. I have no reason to doubt their conclusion. While DCS and independent HMI suppliers can offer a wide variety of graphic tools, I am sure that creative instrument suppliers knowing the deep technology of their sensing and actuation methods can create high added value displays that only they know about, particularly for diagnostics.There are many other technical and procedural differences that may be important in competitive situations, but my overall conclusion is that these are COMPLEMENTARY technologies.

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  • Dick Caro’s initial reply is now a bit dated. In the case of the original EDDL (aka DD in the HART and FF standard) from 1992 the DCS manufacturer had to format the screen page

     

    The Enhanced EDDL standard from 2006 now allows the instrument supplier to format the HMI screen page for that instrument

     

    There is video clip showing instrument manufacturer controlling "content-and-structure" of the instrument pages in a few different systems:

    http://www.youtube.com/watch?v=cnrpngC7tts

     

    I agree with Dick that it is important that end user not train their process operators for each type of field instrument. The DCS supplier should control the "look-and-feel" of the HMI - just like in traditional DD.

     

    Caro is right that instrument suppliers knowing the deep technology of their sensing and actuation methods can create high added value pages that only they know about, particularly for diagnostics. With enhanced EDDL graphics, menu system, and wizards they can now do it.

     

    That is, with enhanced EDDL users can have it both ways: the instrument page "content-and-structure" controlled by instrument manufacturer and "look-and-feel" controlled by system manufacturer. This is possible because EDDL graphics is rendered just like HTML pages in a web browser.

     

    System manufacturers now also do a better job implementing EDDL wizards (aka methods). The same YouTube channel also has a video on calibration wizards from the instrument manufacturer driving user's interaction with the system.

     

    There are many other technical and procedural differences that remain.

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