Understanding Smart Sensors - Nomads.usp

282 Understanding Smart SensorsThe standard introduces the concept of a STIM, defines a TEDS, which is anintegral part of the STIM, and the TII, the physical interface between theSTIM and the NCAP [6]. Figure 12.9 shows the relationship between the elementsdefined in IEEE 1451.2 and the network [5]. Note that a single sensor oractuator or many channels of transducers may exist in a single STIM. This sectionexplains key aspects of the STIM, TEDS, TII, and the built-in tools forenabling smarter systems.12.4.1 STIMThe STIM in Figure 12.9 can contain from 1 to 255 transducers of varioustypes [5]. A STIM is controlled by an NCAP module through a dedicated digitalinterface. A STIM meets the requirements of 1451.2 if it:• Supports the required performance;• Contains a properly formatted TEDS;• Has a physical interface that implements the lines, protocol, and timingof the TII.IEEE 1451.2 defines four types of sensors, one actuator, and an eventdetector [5]. The four sensor types all read some variable, convert the data fromanalog to digital form, and make the data available. There are six types oftransducer:NetworkNetworkcapableapplicationprocessor(NCAP) orhostmicroprocessorClockData outData inSelectNSDETTriggerTrigger_ackInterrupt+5VCommonInterfacelogicTEDSSignalconditioningandconversionSmarttransducerinterfacemoduleTransducer#1°°°Transducer#255Figure 12.9 Hardware partitioning proposed by IEEE 1451.2. (After: [5].)