Understanding Smart Sensors - Nomads.usp

Standards for Smart Sensing 293object [13]. To fit into the digital network defined by other 1451 standards,the bidirectional digital communication of self-identification, test, and programmablesignal conditioning is being defined with consideration for simplicityand low cost. P1451.4 will offer compatibility with legacy systems andprovide a transition path to 1451 [13]. Both sensors and actuators are supportedby P1451.4, and yet the interface will be invisible from the network’sperspective.Figure 12.15 shows the TEDS and high-level P1451 object for an analogtransducer [13]. For many P1451.4 applications, it is not practical to includethe network interface (the NCAP) with the transducer, because of size limitationsor harsh operating environment considerations. However, the transducerTEDS must contain enough information to allow the higher level P1451 objectto fill in any gaps.Figure 12.16 is an example of an IEEE P1451.4 implementation. TheNCAP and TEDS characteristics are defined in 1451.1 and 1451.2 and refinedas necessary for a mixed-mode network in P1451.4. Minimizing the amount ofnonvolatile memory is one goal of the standard’s developers. The 1451.4TEDS includes the categories and parameters listed in Table 12.7 [13].12.7 Extending the System to the NetworkThe IEEE 1451.2 standard instigated industry design activity based on itsanticipated approval [14]. Its subsequent approval and the addition of IEEEHigh-levelP1451 objectInterfacelogicXDCRTransducer(TEDS)IEEE P1451.4mixed-modetransducerNetworkFigure 12.15 IEEE P1451.4 interface. (After: [13].)