How to identify high-value projects

IT'S IRONIC; in their endless quest to reduce costs while increasing output and quality, many manufacturers have been ignoring one of the most potent technologies for achieving those ends. Not only that, it’s a technology in which most of them already have made substantial investments!

The technology? HART. For years, instrument and systems vendors have been incorporating HART communications capabilities into field devices, enabling those devices to send digital information, including diagnostic information and secondary variables, to host systems. (The HART Communications Foundation estimates that more than 15 million HART-capable devices are installed worldwide.) But with the exception of maintenance personnel tramping into the field with handheld communicators to configure instruments, most users have left HART’s benefits untapped.

Those days are coming to an end, however. Instrument vendors are providing open access to their devices through readily available device descriptions; control systems providers are including HART I/O hardware in their products as well as asset management software; and many vendors are marketing products that enable the owners of legacy, analog-only systems to access the power of HART.

So, with HART data more accessible and potentially useful, key questions users face are:

• What’s the best way for my company to access that data?
• How do we identify applications in which we can use HART to generate business value?

A Brief History
HART, an acronym for Highway Addressable Remote Transducer, was developed in the late 1980s and became publicly available in the early 1990s.

Unlike other recent field communications protocols, such as Foundation Fieldbus and Profibus, which are totally digital, HART is a “hybrid” analog/digital technology. An instrument’s primary variable is transmitted via the industry standard analog 4-20 mA signal, but up to four secondary variables and device diagnostic information can be digitally “piggybacked” on it. As a result of these digital communications capabilities, users have access to extensive data from their devices, including diagnostic information and -- in the case of some instruments -- multiple process variables (i.e., a pressure transmitter also might be capable of providing temperature data).

In 1993, the former HART Users Group formed the HART Communications Foundation (HCF), which assumed ownership of the protocol and responsibility for administering and maintaining it. As part of its mission, HCF tests systems and devices for HART compliance and provides educational services to vendors and users.

In HART’s early years, many instrument vendors quickly adopted the technology, but kept a proprietary hold on the device descriptions that enable a host--such as a control system, an asset management system or a configurator--to communicate with its devices. Sandro Esposito, a Masoneilan digital products specialist, recalls that nearly every instrument maker had its own software package for “talking” to its device, effectively rendering that device an “island of automation.”

Charlie Piper, fieldbus product manager for Invensys’ Foxboro business unit, agreed. “There are more than 500 different HART devices in the marketplace, and there’s lots of information you can get about their performance, such as when valve positioners are starting to wear out or stick,” he says. “But until recently no one had come up with a way for all the host vendors to have a user interface to do these neat things with everyone else's device.”

Today, however, most vendors make their Device Description (DD) files openly available. HCF maintains and distributes a library of hundreds of DDs that enable any HART host (e.g., control system, configurator, asset management system, safety system, etc.) to communicate with a vast array of field devices. That development is coupled with the development of comprehensive applications to monitor assets, such as Siemens’ Process Device Manager, Emerson Process Management’s AMS Device Manager, and Honeywell’s Asset Manager PKS. As a result, users now are able to access most – if not all – of their device information from a single screen, regardless of device manufacturer.

In recent months, HCF has developed new tools and technologies to make development of HART-complaint DDs easier. These include the new Device Description Integrated Development Environment (DD-IDE), which is designed to streamline development, testing and maintenance of DDs and facilitate the creation of product applications with DD capabilities.

“The DD-IDE supports the iterative DD development style with a fast and efficient integrated tool set. Each step in the edit-build-test cycle is supported in a DD-aware editing environment,” says Wally Pratt, HCF’s chief engineer.

Also near completion is the Enhanced Device Description Language (eDDLEDDL) specification. eDDLEDDL gives vendors the ability to add new capabilities to DDs while improving cross-platform compatibility and facilitating device set-up. (See details elsewhere in this supplement.)

HART-enabled instruments deliver greater value than ever before, says Dave Smith, manager of Yokogawa’s plant network technology center. “The processing power of the devices is increasing greatly,” says Smith. “Therefore, field instruments feature additional functionality, including diagnostic type functions, predictive functions and others.”

Jim Cobb, marketing manager of Emerson Process Management’s Rosemount Division, notes that users are increasingly aware of the capabilities of the digital field. “One of the reasons is that suppliers are better implementing features to use the capabilities of HART devices,” says Cobb. “Another reason, ironically, is that there’s been so much talk about fieldbus in recent years. People are realizing that HART is capable of delivering many of the same benefits as fieldbus.”