Understanding Smart Sensors - Nomads.usp

274 Understanding Smart Sensors• IEEE 1451.1 Network Capable Application Processor InformationModel (approved by IEEE as full-use standard);• IEEE 1451.2 Transducer to Microprocessor Communication Protocoland Transducer Electronic Data Sheet (TEDS) Formats (approved byIEEE as full-use standard);• IEEE P1451.3 Digital Communication and Transducer ElectronicData Sheet (TEDS) Formats for Distributed Multidrop Systems;• IEEE P1451.4 Mixed-Mode Communication Protocols and TransducerElectronic Data Sheet (TEDS) Formats.As noted, IEEE 1451.1 and 1451.2 have been balloted and accepted asfull-use standards.A number of new terms and acronyms were developed to deal with theelements of smart sensors in an interoperable network. The TEDS is amachine-readable specification of the characteristics of the transducer interface[2]. A smart transducer interface module (STIM) includes the TEDS and thesupporting electronics including the transducer on the transducer side of thehardware interface to the network-capable application processor (NCAP). TheNCAP is a device that supports a network interface, application functionality,and general access to the physical world via one or more transducers. Atransducer-independent interface (TII) is a 10-wire digital communicationinterface that allows an NCAP or host to obtain sensor readings or actuatoractions as well as request TEDS data [1].As shown in Figure 12.1 [1], the four standards tie together theelements linking smart sensors (the STIMS), bus-interface modules, andmixed-mode transducers to the network through the NCAP. The standardsrepresent an extensive effort to provide sufficient detail to achieve interoperabilitywhile allowing flexibility for manufacturers of components, subsystems,and systems.Table 12.1 compares the 1451 family members [3]. The major commonelement is the TEDS or the ability to support a TEDS. The hardware interface,the distance between elements, the signal converter, and the measurement leveldifferentiate the four family members. The approved IEEE 1451.1 and 1451.2standards are thorough documents that are hundreds of pages long. Theremaining sections in this chapter provide more detail on the various familymembers, but interested readers are directed toward the actual documents andthe references.