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1、附录ADesignofaHighPrecisionTemperatureMeasurementSystem1IntroductionSensorsareoneofthemostimportantelementsusedinmanyinstrumentationcircuits.Theyareusedinmanyindustrialapplicationsandtakeacertainformofinput(temperature,pressure,altitude,etc.)andconvertitintoreadingsthatcanbei
2、nterpreted.Manytypesofsensorsarenonlinearinnaturefromwhichalinearoutputisdesired.Therearemanydifferentsensorsfortemperaturemeasurementandthermocouplesarethemostcommonlyused.Theyarepreferredinindustrialapplicationsduetotheirlowcost,wideoperationrange,fastresponsetimeandaccur
3、atewhentheirpeculiaritiesareunderstood.Thermocoupleshavealsooutputsnonlinearlyrelatedtotemperature.Therefore,sensormodelingandlinearizationtechniquesarenecessary.Tosolvethelinearizationproblemofasensor,therearegenerallytwomethodsproposed.Thefirstonerequiresnonlinearanalogci
4、rcuitandthesecondusesnumericalmethodsthatarecomputedbymicroprocessororcomputer.Analogcircuitsarefrequentlyusedforimprovingthelinearityofthesensorcharacteristics,whichimpliesadditionalanaloghardwareandtypicalproblemsassociatedtoanalogcircuitssuchastemperaturedrift,gainandoff
5、seterror.Usingthesecondmethod,sensornonlinearitiescanbecompensatedbymeansofarithmeticoperations,ifanaccuratesensormodelisavailable(directcomputationofthepolynomials),oruseofamultidimensionallook-uptable.Directcomputationofthepolynomialmethodismoreaccuratebuttakesalongtimefo
6、rcomputation,whilethelook-uptablemethod,thoughfaster,isnotveryaccurate.Inrecentyears,applicationofANNshasemergedasapromisingareaofresearchinthefieldofinstrumentationandmeasurement.Itprovidesaneurocomputingapproachforsolvingcomplexproblemsespeciallyinnonlinearsystemmodelingw
7、hichthenetworkitselfisanonlinearsystem.Thisisextremelyusefulwhentheareaofinterestisabsolutelynonlinearincludingtheexperimentaldatathatisusedfortraining.OneofthemostpowerfulusesofANNsisinfunctionapproximation(curvefitting).InterpolationbasedonANNprovideslowerinterpolationerr
8、orswhencomparedwithconventionalnumericalinterpolation.Intheworkwepresenthere,highp
