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Figure 1. (a) A smart transducer model; (b) This architecture adds TEDS and the system partition into NCAP (Network Capable Application Processor) and TIM (Transducer Interface Module) with TII (Transducer Independent Interface) Smart Transducer Interface in Embedded Systems for Networked Sensors Based on the Emerging IEEE 1451 Standard: H2 Detection Case Study Sergio Saponara, Esa Petri, Luca Fanucci, Pierangelo Terreni Dept. of Information Engineering, University of Pisa Via G. Caruso, 16 – I-56122 Pisa (Italy) E-mail: {sergio.saponara, esa.petri, l.fanucci, p.terreni}@iet.unipi.it Abstract—Sensors and actuators are used, often networked in a distributed control system, in a number of applications ranging from industrial automation to environmental condition monitoring/control, to intelligent transport systems or to homeland defense. The paper reviews the implementation for embedded systems of a sensor network interface, based on the emerging IEEE 1451 family of standards, targeting smart transducers, i.e. sensors or actuators integrating on-chip also the mixed-signal processing chain and a digital communication host port. As application case example, a networked system of hydrogen sensors to monitor the gas leak in hydrogen-based vehicles is presented. Keywords-Distributed Sensors/Actuators, Wireless Sensor Networks, Embedded Systems for Sensor Signal Conditioning, Hydrogen Leakage Measurements, Automotive Safety, Internet of Things I. INTRODUCTION A smart transducer is the integration of an analog or digital sensor or actuator element, a processing unit and a communication interface [1]. A smart transducer comprises a hardware or software device consisting of a small, compact unit containing a sensor or actuator element, a microcontroller, a communication controller and the associated software for signal conditioning, calibration, diagnostics and communication [2]. Based on this premise, a smart transducer model is shown in Fig. 1. It consists of four main parts: transducers (sensors and actuators), signal conditioning and data conversion, application processor, and network communication. The analog output of a sensor is conditioned and amplified, then converted to a digital format by an A/D converter. The digitized sensor signal can then be easily processed by a microprocessor using a digital application control algorithm. The measured or calculated parameters can be passed on to a host or monitoring system in a network by means of a network communication protocol. In a reverse manner, an actuation command sent from a host via the network can be used to control an actuator. To address the need for standardized interfaces and architectures for smart networked transducers, this paper illustrates in Section II the general architecture of a system of networked transducers and in Section III reviews the emerging IEEE1451 family of standards. In Section IV an application case study is proposed: a networked system of hydrogen/methane sensors to monitor the gas leak in multi-fuel vehicles. II. ARCHITECTURE OF NETWORKED SMART TRANSDUCERS In response to industry’s need for a set of standardized sensor interfaces, the IEEE Instrumentation and Measurement Society’s Technical Committee on Sensor Technology has sponsored the development of a suite of smart transducer interface standards for sensors and actuators, known as the IEEE 1451. To go beyond the previous definitions, an IEEE 1451 smart transducer is defined as a smart transducer that provides functions in addition to those necessary for generating a correct representation of a sensed or controlled quantity. This functionality typically simplifies the integration of the transducers into applications in a networked environment. This Authorized licensed use limited to: University of North Carolina at Charlotte. Downloaded on January 27, 2010 at 11:47 from IEEE Xplore. Restrictions apply.TABLE I. IEEE 1451.0 TEDS Mandatory Meta TEDS Transducer Channel TEDS User’s transducer name TEDS PHY TEDS Optional Calibration TEDS Frequency Response TEDS Transfer Function TEDS Text based TEDS (*) End user application specific TEDS Manufacturer defined TEDS (*) Optional Text based TEDS Meta-Identification TEDS Transducer Channel Identification TEDS Calibration Identification TEDS Location and Title TEDS Geographic Location TEDS TABLE II. GENERAL FORMAT OF TEDS Field Description Type # octets - TEDS lenght UInt32 4 1 to N Data Block Variable Variable - Checksum UInt16 2 means IEEE 1451 smart transducers have capabilities for self-identification, self-description, self-diagnosis, self-calibration, location-awareness, time-awareness, data processing, reasoning, data fusion, alert notification (report signal), standard-based communication protocols and data formats [3],[4]. IEEE 1451 smart transducers represent a step forward towards the Internet of Things paradigm. Fig. 1(a) shows the conventional smart transducer architecture, while Fig. 1(b) illustrates an IEEE 1451 smart transducer. In the latter, the addition of the Transducer Electronic Data Sheet (TEDS) can be noticed, along with the partitioning of the system into two main components: a Network Capable Application Processor (NCAP) and a Transducer Interface Module (TIM), connected through a Transducer Independent Interface (TII). The NCAP, a network node, performs application processing and network communication functions, while the TIM consists of a number of sensors and actuators with the relevant signal conditioning and data conversion circuits. Up to 255 devices can be combined in a single TIM, and this is very useful when working with large sensor arrays such as Micro-Electro-Mechanical-System (MEMS) devices or a large mix of sensors and actuators. The TII defines a communication medium and a protocol for transferring sensor information. This interface provides a set of operations, such as read, write, read and write messages, read and write responses, etc. The network interface defines a network communication protocol for NCAP transactions over the network. Besides the standardization of the communication interface, the other key feature of an IEEE 1451 smart transducer is the specification of the TEDS and its formats. The TEDS stores manufacture-related information for the transducers, such as manufacturer identification, measurement range, accuracy and calibration data (e.g. to recover offset or gain errors), similar to the information contained in


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UNCC ECGR 6185 - Study Notes

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