自动化专业外文文献Word文档下载推荐.docx

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TherelationshipbetweenthemeasuredandthesensoroutputsignalisusuallyobtainedbycalibrationtestsandisreferredtoasthesensorsensitivityK1=output-signalincrement/measuredincrement.Inpractice,thesensorsensitivityisusuallyknown,and,bymeasuringtheoutputsignal,theinputquantityisdeterminedfrominput=output-signalincrement/K1.

3CharacteristicsofanIdealSensor

Thehighsensorshouldexhibitthefollowingcharacteristics.

（a）highfidelity-thesensoroutputwaveformshapebeafaithfulreproductionofthemeasured;

thereshouldbeminimumdistortion.

（b）Thereshouldbeminimuminterferencewiththequantitybeingmeasured;

thepresenceofthesensorshouldnotalterthemeasuredinanyway.

（c）Size.Thesensormustbecapableofbeingplacedexactlywhereitisneeded.

（d）Thereshouldbealinearrelationshipbetweenthemeasuredandthesensorsignal.

（e）Thesensorshouldhaveminimumsensitivitytoexternaleffects,pressuresensor,forexample,areoftensubjectedtoexternaleffectssuchvibrationandtemperature.

（f）Thenaturalfrequencyofthesensorshouldbewellseparatedfromthefrequencyandharmonicsofthemeasurand.

Sensorscanbedividedintothefollowingcategories：

1ElectricalSensor

Electricalsensorexhibitmanyoftheidealcharacteristics.Inadditiontheyofferhighsensitivityaswellaspromotingthepossibleofremoteindicationormesdurement.

Electricalsensorcanbedividedintotwodistinctgroups:

（a）variable-control-parametertypes,whichinclude:

（i）resistance

（ii）capacitance

（iii）inductance

（iv）mutual-inductancetypes

Thesesensorallrelyonexternalexcitationvoltagefortheiroperation.

（b）self-generatingtypes,whichinclude

（i）electromagnetic

（ii）thermoelectric

（iii）photoemissive

（iv）piezo-electrictypes

Theseallthemselvesproduceanoutputvoltageinresponsetothemeasurandinputandtheireffectsarereversible.Forexample,apiezo-electricsensornormallyproducesanoutputvoltageinresponsetothedeformationofacrystallinematerial;

however,ifanalternatingvoltageisappliedacrossthematerial,thesensorexhibitsthereversibleeffectbydeformingorvibratingatthefrequencyofthealternatingvoltage.

2ResistanceSensor

Resistancesensormaybedividedintotwogroups,asfollows:

（i）Thosewhichexperiencealargeresistancechange,measuredbyusingpotential-dividermethods.Potentiometersareinthisgroup.

（ii）Thosewhichexperienceasmallresistancechange,measuredbybridge-circuitmethods.Examplesofthisgroupincludestraingaugesandresistancethermometers.

3CapacitiveSensor

Thecapacitancecanthusmadetovarybychangingeithertherelativepermittivity,theeffectivearea,orthedistanceseparatingtheplates.Thecharacteristiccurvesindicatethatvariationsofareaandrelativepermittivitygivealinearrelationshiponlyoverasmallrangeofspacings.Thusthesensitivityishighforsmallvaluesofd. 

Unlikethepotentionmeter,thevariable-distancecapacitivesensorhasaninfiniteresolutionmakingitmostsuitableformeasuringsmallincrementsofdisplacementorquantitieswhichmaybechangedtoproduceadisplacement.

4InductiveSensor

Theinductancecanthusbemadetovarybychangingthereluctanceoftheinductivecircuit.

Measuringtechniquesusedwithcapacitiveandinductivesensor:

（a）A.C.excitedbridgesusingdifferentialcapacitorsinductors.

（b）A.C.potentiometercircuitsfordynamicmeasurements.

（c）D.C.circuitstogiveavoltageproportionaltovelocityforacapacitor.

（d）Frequency-modulationmethods,wherethechangeofCorLvariesthefrequencyofanoscillationcircuit.

Importantfeaturesofcapacitiveandinductivesensorareasfollows:

（i）resolutioninfinite

（ii）accuracy±

0.1%offullscaleisquoted

（iii）displacementranges25*10-6mto10-3m

（iv）risetimelessthan50uspossible

Typicalmeasurandsaredisplacement,pressure,vibration,sound,andliquidlevel.

5LinearVariable-differentialTtransformer

6Piezo-electricSensor

7ElectromagneticSensor

8ThermoelectricSensor

9PhotoelectricCells

10MechanicalSensorandSensingElements

Ininformationage,theinformationindustryincludesinformationgathering,transmission,processthreeparts,namelysensortechnology,communication,computertechnology.Becauseofultralargescaleintegratedcircuit’srapiddevelopmentafterhavingbeendevelopedModerncomputertechnologyandcommunication,notonlyrequestssensorprecisionreliability,speedofresponseandgaininformationcontentrequestmoreandmorehighbutalsorequestsitscosttobeinexpensive.Theobvioustraditionalsensoriseliminatedgraduallybecauseofthefunction,thecharacteristic,thevolume,thecostandsoon.Asworlddevelopmanycountriesarespeedinguptothesensornewtechnology’sresearchandthedevelopment,andallhasobtainedtheenormousbreakthrough.Nowthesensornewtechnologydevelopmentmainlyhasfollowingseveralaspects:

Usingthephysicalphenomenon,thechemicalreaction,thebiologicaleffectasthesensorprinciplethereforetheresearcheswhichdiscoveredthenewphenomenonandtheneweffectarethesensortechnologicalimprovingways.itisimportantstudiestodevelopednewsensor’sthefoundation.JapaneseSharpCorporationusesthesuperconductivitytechnologytodevelopsuccessfullythehightemperaturesuperconductivitymagneticsensorandgetthesensortechnologysignificantbreakthrough.Itssensitivityissohighandonlyinferiorinthesuperconductivityquantuminterferencecomponent.Itsmanufacturecraftisfarsimplerthanthesuperconductivityquantuminterferencecomponent.Mayuseinmagnetismimageformationtechnology.Soithasthewidespreadpromotedvalue.

Usingtheimmunebodyandtheantigenmeetsoneanothercompoundwhentheelectrodesurface.Itcancausetheelectrodepotentialchangeandusethisphenomenontobepossibletogeneratetheimmunitysensor.Theimmunitysensormakeswiththiskindofimmunebodymaytosomeorganisminwhetherhasthiskindofantoriginalworkinspection.Likemayinspectsomebodywiththehepatitisvirusimmunebodywhethercontractsthehepatitis,playstoisfast,theaccuraterole.TheUSUCsixthbranchhasdevelopedthiskindofsensor.

Thesensormaterialistheimportantfoundationforsensortechnology,becausethematerialsscienceisprogressiveandthepeoplemaymakeeachkindofnewsensorForexamplemakingthetemperaturesensorwiththehighpolymerthinfilm;

Theopticalfibercanmakethepressure,thecurrentcapacity,thetemperature,thedisplacementandsoonthemanykindsofsensors;

Makingthepressuretransmitterwiththeceramics.Thehighpolymercanbecometheproportionadsorptionandthereleasehydrogenalongwiththeenvironmentrelativehumiditysize.Thehighpolymerelectricityliesbetweentheconstanttobesmall,thehydrogencanenhancethepolymerthecoefficientofdialecticalloss.Makingthecapacitorthehighpolymerdielectricmedium,determinestheelectriccapacitycapecitythechange,thenobtainstherelativehumidity.Makingtheplasmausingthisprincipletogatherthelegitimatepolystyrenefilmtemperaturesensorbelow,ithasthecharacteristic.

Measuredthewetscopeiswide;

Thetemperaturerangeiswide,mayreach-400℃~+1,500℃;

Thespeedofresponseisquick,issmallerthan1S;

Thesizeissmall,mayuseinthesmallspacemeasuringwet;

Thetemperaturecoefficientissmall.

Theceramicelectriccapacitytypepressuretransmitterisonekinddoesnothavetheintermediaryfluidthedrytypepressuretransmitter.Usestheadvancedceramictechnology,theheavyfilmelectronictechnology,itstechnicalperformanceisstable,theyeardriftingquantityissmallerthan0.1%F.S,warmfloatsissmallerthan±

0.15%/10K,anti-overloadsstrongly,mayreachthemeasuringrangeseveralhundredtimes.Thesurveyscopemayfrom0to60mpa.GermanE+HCorporationandtheAmericanKahloCorporationproductisattheleadingposition.

Theopticalfiberapplicationissendthematerialsignificantbreakthrough,itsusesinmostearlytheopticalcommunicationtechniques.Intheopticalcommunicationusediscoveredworksasenvironmentalconditionchangeandsoonthetemperature,pres-sure,electricfield,magneticfield,causesthefiberoptictransmissionlightwaveintensity,thephase,thefrequency,changeandsoonthepolarizationcondition,thesurveylightwavequ