IEEE adds plug-and-play to smart transducer interface

10/06/2004

New TEDS Standard Will Expand Pool of Network-Compatible Transducers

A new standard from the Institute of Electrical and Electronics Engineers (IEEE, www.ieee.org) adds plug-and-play capability to analog transducers for use in networks designed for digital instruments and measurement systems.

The standard, IEEE 1451.4, "Standard for a Smart Transducer Interface for Sensors and Actuators—Mixed-Mode Communication Protocols and Transducer Electronic Data Sheet (TEDS) Formats," promises to accelerate the use of networked sensors by simplifying transducer installation, network creation, and system maintenance and upgrade.

The standard creates a universal system for the essential information digital networks need to identify, characterize, interface with and use signals from analog sensors.

The IEEE 1451 family offers common interfaces among sensors, actuators, instruments and networks that allow for interoperable and interchangeable transducers. IEEE 1451.1 addresses the overall network and how to link transducers in systems and networks. IEEE 1451.2 looks at how to place digital transducers on a network. IEEE 1451.3 is a multidrop standard that allows for placing many transducers on the same cable. The working group is now developing IEEE P1451.5, which is similar to 1415.3, but allows for wireless communications for transducers.

"The P1451.4 standard permits the huge number of installed analog transducers that now exist to be tied into digital systems," says Torben Licht, 1451.4 Working Group chair and product manager at Bruel & Kjaer. "The protocols it contains replace the diverse transducer solutions manufacturers had introduced with limited success.

It will have a major effect by dramatically expanding the pool of network-compatible transducers and the use of control networks. It also gives sensor and actuator manufacturers the interfaces they need to deliver products for multiple instruments and networks without having to redesign for compatibility."

David Potter, Working Group vice-chair and platform manager at National Instruments, says this is a practical standard that makes the TEDS concept compatible with analog measurement. "In essence," he adds, "the standard, by adding self-identification at the transducer analog interface, has the potential to make any measurement system, analog or digital, easier to set up, configure and maintain."

The standard takes advantage of EEPROM chips embedded in sensors to house and communicate details needed for plug-and-play capability. Manufacturers obtain identifiers for chips from the Internet (a site currently being created). A complete TEDS may contain sections for identification and properties for a type of sensor, such as accelerometer, microphone, strain gage, thermocouple, thermistor and many others. The TEDS may also contain a calibration template for the sensor.

For specialized sensor requirements, template description files can be written by companies or users and published on the web site. The standard also allows for virtual TEDS files that reside on the Internet for use when embedded memory is unavailable.

"Many companies are beginning to adopt the standard." says Potter, "EEPROMs are now available for placement in both existing and new sensors, and several companies have begun shipping IEEE 1451.4-compliant products."