Understanding Smart Sensors - Nomads.usp

286 Understanding Smart SensorsMeta-TEDSOne per STIM:Contains the overalldescription of the TEDS datastructure, worst-case STIM,timing parameters, and channelgrouping informationCalibrationTEDSOne per STIM channel:Contains the lastcalibration date,calibraton interval, andall the calibrationparameters supportingthe multisegment modelChannel TEDSOne per STIM channel:Contains upper/lower rangelimits, physical units, warmuptime, presence of self-test,uncertainty, data model,calibration model, andtriggering parametersApplicationspecificTEDSExtensionTEDSMultiple per STIM:For applicationspecficuseMultiple per STIM:Used to implementfuture and industryextensions to 1451.2Figure 12.11 General layout of TEDS [8].as shown in Table 12.4 [9]. The lines are defined more thoroughly in the standard,and the power supply aspects are discussed further in Section 12.4.5. Thestandard does not define a standard connector but leaves that as a flexibilityitem to the discretion of the user.12.4.4 Calibration/Correction EngineIEEE 1451.2 describes a correct algorithm that allows users to convert ADCoutput into engineering units for sensors and engineering units into input to anADC for actuators [10]. Lookup tables, linear conversions, and multiple-inputpolynomial surface calibrations are among the possible uses of those data forsensors. The calibration TEDS contains the capability to perform:• First-order conversion with a single segment straight line;• Segmented first-order conversion for nonlinear sensors where higheraccuracy is required;• Level detector for simple two-state detection;• Level detector with hysteresis;• Higher order conversion with a single segment;• Multiple-input conversion for transducers that need to achieve thehighest possible accuracy.