Understanding Smart Sensors - Nomads.usp

318 Understanding Smart SensorsOriginal capwaferControlelectrodesOptical coatingFusion bonded layerGapBondingpadsCorrugatedsupportAntireflectivecoatingMovable siliconmassFigure 14.1 Fabry-Perot interferometer. (After: [8].)14.4.2 HVAC Sensor ChipImproved energy efficiency and energy management are major driving forcesfor new products. The energy consumption is directly achieved by usingimproved efficiency power devices and control techniques, such as PWM. Thecontrol techniques allow variable-frequency-drive motors to be implemented inbuilding automation. Buildings in the United States account for 35–40% ofthe nation’s energy consumption.All the MEMS devices for an HVAC system eventually may be integratedinto a single device, like the one shown in Figure 14.2 [10]. In addition to thesensors, signal conditioning to amplify the signal, calibrate offset and full-scaleoutput, and compensate for temperature effects could be included on thisdevice. Because it most likely will use CMOS technology for the semiconductorprocess, an onboard ADC also could be integrated. Other system capabilitiescould include fuzzy logic and neural network interpretation of the inputsignals. That is especially true if an array of chemical sensors is used to indicatea wide variety of chemical species and overcome many of the problems of availablechemical-sensing products. Currently, sensors are not that highly integratedand are specified on an as-required basis. That is because of theadditional cost they add to the initial system installation and their inability tofunction without requiring more maintenance than other parts of the system.