ISA TECH/97 Highlights From Anaheim, Calif., Day Two

By Control Engineering Staff October 8, 1997

Boeing Explores Development of ‘Smart’ Transducer Bus

Lee Eccles of Boeing Commercial Airplane Co. began his presentation in the ‘Use of Automation to Enhance Productivity in the Aerospace Industry’ by asking the question ‘why bother?’

In structural sensing and testing of airplane wings and fuselages at Boeing, a lot of effort goes into simply setting up the test. Structures for destructive testing of a wing or testing flight-control actuators require huge setup times. According to Mr. Eccles, some tests require as many as 6,000 strain gages and over 600 miles of wiring routed through an airplane’s structure. Analog sensors used previously required signal conditioners and amplifiers as well, complicating setup and troubleshooting. ‘Smart’ devices would incorporate the signal conditioning and amplification job in the devices themselves.

System requirements for a proposed bus system included various sample rates, a variety of data word lengths, simple wiring, and simple troubleshooting.

Cost was an important reason for searching for a way to incorporate ‘smart’ digital sensors in their testing. System testing labs at Boeing use over 9,000 channels with a cost of between $500-3500 per channel and four-to-nine wires per channel. Switching to a digital data acquisition system would require only two or three pairs of wires for up to 256 channels and bring per-channel costs down to around $500. Mr. Eccles estimated the adjusted setup costs for the analog system at around $17 million as opposed to estimates for a new bus-based data acquisition system as much as low as $5 million.

One added advantage of the proposed bus-based system would be increased accuracy of the tests. A downside of the new gages is the affect of environmental factors such as temperature on the calibration of devices. Costs for calibration of the devices would actually increase.

Mr. Eccles concluded by saying that Boeing plans to support the IEEE-1451.2 standard and is considering using an off-the-shelf fieldbus system for implementation.

IEEE 1451.2 Demonstrated at ISA

Developed by the National Institute of Standards and Technology (NIST) in conjunction with more than 25 companies, the IEEE-1451.2 promises to simplify the task of interfacing ‘smart’ transducers into networks in use in industry.

The network-independent, digital interface creates a common method for networks to read sensors, set actuators, and access historical information on the devices. According to Jim Moore, director of corporate technology at Moore Products, ‘This provides the opportunity for achieving ‘plug and play’ interoperability over a local area network or the Internet.’

According to Kang Lee, head of NIST’s sensor integration group and chairman of the IEEE TC-9 committee that developed the standard, separating transducers from the peculiarities of the network protocols should translate into larger markets for sensor and actuator manufacturers.

The standard includes a network capable application processor, 10-wire transducer-independent interface, a set of communication protocols, and a transducer electronic data sheet (TEDS). According to Mr. Lee, TEDS is the ‘core’ of the standard, providing a common format for capturing and communicating information about each device on a network. ‘The TEDS enables device-level intelligence and self-identification of devices. This simplifies installation, integration, and maintenance,’ said Mr. Lee.


New Photomicrosensor for Liquid Level Applications

The new EE-SPX613 photomicrosensor from Omron is built for sensing liquids in any transparent or semitransparent 6-13 mm diameter tubing with a wall thickness of 1 mm. Built for small spaces and small equipment, it features a talc-free cord, allowing use in clean-room environments. Features include a built-in amplifier and operation mode selector. Omron

Historical Database System Links Plant Systems

FoxHistory from Foxboro provides plant information management functionality for its I/A series systems and other automation platforms.

FoxHistory’s graphical user interface can be used in systems with as few as 200 points to those with as many of tens of thousands. Applications for accessing historical data include FoxExplorer for data trending and charting, Data for Windows for accessing data from desktop spreadsheet and database applications, for accessing statistical process control charts, and Remote Process Graphics for viewing and interacting with I/A series process displays using X Window technology.

FoxHistory runs on Solaris-based I/A series stations, Windows NT-based I/A series stations, Window NT 4.x network servers, and Solaris 2.x network servers. Foxboro

I/O and Intelligent Control Modules for Open Communication Networks

The Modicon Momentum System introduces twenty different types of I/O and intelligent control modules for connecting to a variety of open standard communication networks. Available modules include discrete inputs, outputs, and bi-directional form in dc and ac, analog inputs and outputs, combination analog/discrete inputs and outputs, and specialty modules for high-speed counting.

Sensors and actuators using two-to-four wires can be wired directly to the I/O modules, and the plug-in connectors and bus bar can be removed without disturbing field wiring. Screw terminals accommodate wires to 12 awg to facilitate the upgrade of mature control systems. Modicon