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301 975 6602 Telephone
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Gaithersburg, MD 20899-8220

Introduction to IEEE P1451

Transducers, defined here as sensors or actuators, serve a wide variety of industry's needs, manufacturing, industrial control, automotive, aerospace, building, and biomedicine are but a few. Since the transducer market is very diverse, transducer manufacturers are seeking ways to build low-cost, networked, and wireless smart transducers. Many sensor control networks or fieldbus implementations are currently available, each with its own strengths and weaknesses for a specific application class. Interfacing the smart transducers to all of these control networks and supporting the wide variety of protocols require very significant efforts and are costly to transducer manufacturers. However, using digital communication schemes, networked or wireless transducers can eliminate a large number of lengthy parallel analog wiring and thus reduces the installation, maintenance, and upgrade costs of sensor-based systems. And the use of microprocessors to handle the digital communication has also opened the opportunity for adding intelligence to sensors and actuators. One problem for transducer manufacturers though, is the large number of wired and wireless networks on the market today. Currently, it is too costly for transducer manufacturers to make unique smart transducers for each network on the market. Therefore an universally accepted set of open standards, like the suite of IEEE 1451 smart transducer interface standards for sensors and actuators, are developed to address these issues.

Objective of IEEE 1451

The objective of this project is to develop a family of smart transducer interface standard IEEE 1451. This set of standards is to make it easier for transducer manufacturers to develop smart devices and to interface those devices to networks, systems, and instruments by incorporating existing and emerging sensor- and networking technologies.

Brief Description of the Family of IEEE 1451 Standards

The IEEE 1451, a family of Smart Transducer Interface Standards, describes a set of open, common, network-independent communication interfaces for connecting transducers (sensors or actuators)to microprocessors, instrumentation systems, and control/field networks.The key feature of these standards is the definition of Transducer Electronic Data Sheets (TEDS). The TEDS is a memory device attached to the transducer,which stores transducer identification, calibration, correction data,measurement range, and manufacture-related information, etc. The goal of 1451 is to allow the access of transducer data through a common set of interfaces whether the transducers are connected to systems or networks via a wired or wireless means. The family of IEEE 1451 standards are sponsored by the IEEE Instrumentation and Measurement Society's Sensor Technology Technical Committee chaired by Kang Lee.

IEEE P1451.0 * defines a set of common commands, common operations, and TEDS for the family of IEEE 1451 smart transducer standards. Through this command set, one can access any sensors or actuators in the 1451-based wired and wireless networks. The functionality is independent of the physical communications media between the transducers and the network node called Network Capable Application Processor (NCAP). This makes it much easier to add other proposed 1451.X physical layers to the family as technology advances in the future.

IEEE 1451.1 *** defined a common object model describing the behavior of smart transducers. It defines a measurement model that streamlines measuremnt processes. It also defined the communication models used for the standard, which included the client-server and publish-subscribe models. Application software running in the NCAP based on IEEE 1451 communicated with transducers through the different IEEE 1451.X physical layer standards as required for a particular application. Communications among NCAPs and to higher level systems are supported in a network neutral manner.

IEEE 1451.2 *** defined a transducers-to-NCAP interface and TEDS for a point-to-point configuration. Transducers are part of a Transducer Interface Module (TIM). The original standard describes a communication layer based on enhance SPI (Serial Peripheral Interface) with additional HW lines for flow control and timing. This standard is being revised to add support for the popular serial UART interface.

IEEE 1451.3 defined a transducer-to-NCAP interface and TEDS for multi-drop transducers using a distributed communications architecture. It allowed many transducers to be arrayed as nodes, on a multi-drop transducer network, sharing a common pair of wires.

IEEE 1451.4 *** defined a mixed-mode interface for analog transducers with analog and digital operating modes. A TEDS was added to a traditional two-wire, constant current excited sensor containing a FET amplifier. The TEDS model was also refined to allow a bare minimum of pertinent data to be stored in a physically small memory device, as required by tiny sensors. Templates are used to describe the data structure of TEDS. The current templates cover acclerometers, strain gages, current loop sensors, microphones, thermcouples, and more.

IEEE P1451.5 * defines a transducer-to-NCAP interface and TEDS for wireless transducers. Wireless communication protocol standards such as 802.11 (WiFi), 802.15.1 (Bluetooth), 802.15.4 (ZigBee) are being considered as some of the physical interfaces for IEEE P1451.5. One should be able to get the same sensor data from the wireless sensor implementing any of these three wireless protocols.

IEEE P1451.6 * defines a transducer-to-NCAP interface and TEDS using the high-speed CANopen network interface. Both intrinsically safe and non-intrinsically safe applications are being supported. It defines a mapping of the 1451 TEDS to the CANopen dictionary entries as well as communication messages, process data, configuration parameter, and diagnosis information. It adopts the CANopen device profile for measuring devices and closed-loop controllers.

* The proposed standard is being developed.
** The proposed standard has been balloted and is awaiting publication.
*** The standard is in publication and can be acquired at the web site.

TEDS=Transducer Electronic Data Sheet
NCAP=Network Capable Application Processor
STIM =Smart Transducer Interface Module

Where to Purchase the IEEE 1451 Standards

A copy of these standards in publication or released draft specificationscan be ordered on the IEEE website,or from IEEE by calling 1-800-678-4333 (in US and Canada) or 1-732-981-0600(outside US and Canada) or by fax 1-732-981-9667.

Contact: Kang Lee, NIST, 301-975-6604,