機械工程測試技術(shù)

朽木易折，金石可鏤。千里之行，始于足下。第頁/共頁MechanicalEngineeringTestingTechnologyMechanicalEngineeringTestingTechnologyisabasictechnologycourseandprofessionaltechnologycourse.Thiscoursemainlydealswithbasicknowledgerequiredbytestingwork,especiallydynamictestingwork.Mainlyincluding:analysisoftestingsignalsanddataprocessing,evaluatingmethodofstaticanddynamiccharacteristicsoftestingequipment,sensorincommonuse,intermediateexchangingcircuit,workingprincipleandcharacteristicofrecordinginstrument,measurementofsometypicalmechanicalparameters.Asensorisadevicethatmeasuresaphysicalquantityandconvertsitintoasignalwhichcanbereadbyanobserverorbyaninstrument.1,溫度傳感器主要有兩種熱電阻溫度傳感器（熱敏電阻）和熱電偶溫度傳感器熱敏電阻利用電阻隨溫度變化的特點制成的傳感器。主要使用半導體。半導體的電阻隨溫度升高而下降。特點：材料成本低，加工方便，但是使用時容易受環(huán)境溫度影響。應(yīng)用：空調(diào)的自動調(diào)溫系統(tǒng)，當傳感器檢測到房間的溫度低于設(shè)定溫度時，空調(diào)控制器就會發(fā)送信號啟動空調(diào)壓縮機，制冷；當傳感器檢測到房間的溫度達到設(shè)定的溫度時，就會想空調(diào)控制器發(fā)送一個信號，告訴控制器“環(huán)境已達到設(shè)定溫度”，這個時候，控制器就會發(fā)送信號停止壓縮機的運行。電飯煲的煮飯過程也是使用了這種溫度傳感器。Therearetwomajorthermalresistancetemperaturesensors.Thermistor:Athermistorisatypeof\o"Resistor"resistorwith\o"Electricalresistance"resistanceproportionaltoits\o"Temperature"temperature.Resistancevarieswithtemperature.ThematerialofthissensorMainlyuseofsemiconductors.Theresistanceofthesemiconductordecreaseswithincreasingtemperature.

Features:Lowcostofmaterials,processingconvenience,butwhenitused,itwillbesusceptibletoenvironmentaltemperature.

Applications:airconditioningthermostatsystem,whenthesensordetectstheroom’stemperaturedropsbelowthesettemperature,theairconditioningcontrollerwillsendasignaltostartairconditioningcompressorsandstartrefrigerating;whenthesensordetectstheroom’stemperaturereachesthesettemperature,thecontrollerwillsendasignaltostoptheoperationofthecompressor.

Ricecookercookingprocessisalsousingthistemperaturesensor.

Thermocouple:Itconvertstemperaturetoanoutputvoltagewhichcanbereadbya\o"Voltmeter"voltmeter（伏特計）.Athermocoupleconsistsoftwoconductorsofdifferentmaterials(usuallymetalalloys)thatproducea\o"Voltage"voltageinthevicinity（附近）ofthepointwherethetwoconductorsareincontact.Thermocoupleisawidelyusedtypeof\o"Listoftemperaturesensors"temperaturesensorformeasurementandcontrolandcanalsobeusedtoconvertatemperature\o"Gradient"gradientintoelectricity.Thethermoelectriceffectisthedirectconversionof\o"Temperature"temperaturedifferencestoelectric\o"Voltage"voltageandvice-versa.Athermoelectricdevicecreatesavoltagewhenthereisadifferenttemperatureoneachside.Conversely,whenavoltageisappliedtoit,itcreatesatemperaturedifference.Attheatomicscale,anappliedtemperature\o"Gradient"gradientcauseschargecarriersinthematerialtodiffusefromthehotsidetothecoldside.Thiseffectcanbeusedtogenerateelectricity,measuretemperatureorchangethetemperatureofobjects.Becausethedirectionofheatingandcoolingisdeterminedbythepolarityoftheappliedvoltage,thermoelectricdevicesareefficienttemperaturecontrollers.Theterm"thermoelectriceffect"encompassesthreeseparatelyidentifiedeffects:theSeebeckeffect,PeltiereffectandThomsoneffect.TheSeebeckeffectistheconversionof\o"Temperature"temperaturedifferencesdirectlyinto\o"Electricity"electricityThePeltiereffectisthepresenceofheatatanelectrifiedjunctionoftwodifferentmetals.Thomsoneffectdescribestheheatingorcoolingofacurrent-carryingconductorwithatemperaturegradient.Anycurrent-carryingconductor(exceptfora\o"Superconductor"superconductor)withatemperaturedifferencebetweentwopointseitherabsorbsoremitsheat,dependingonthematerial.2，壓力傳感器Pressuresensor:畫圖解釋Itisthedevicethatisabletodetectthepressurevalue,convertstheforcetotheelectricsignal,whichcanbereadbyavoltmeter.Piezoresistivepressuresensorisoneofcommonlyusedpressuresensor.Principle:利用某些物質(zhì)的壓電效應(yīng)。某些物體例如石英，在受到壓力的時候，內(nèi)部會形成電場。這個電場的大小反映了它所受到外力的大小。因此，我們可以使用這種材料做成壓電式傳感器，通過測量材料所產(chǎn)生的電場來間接測量力的大小。應(yīng)用：在許多大型商場的扶手電梯中，普通都會有壓力傳感器的。這種傳感器安裝在電梯的踏板下，當有客人站上電梯時候，電梯就會加速到正常速度向上；當沒有人乘坐電梯時，電梯以比較低的速度運行，從而節(jié)約了能量。這個就是壓力傳感器應(yīng)用的例子。

piezoelectric[pai,i:z?ui'lektrik]transducer壓電傳感器Principle:Usingthepiezoelectriceffectofcertainsubstances.Someobjectssuchasquartz[kw?:ts]石英,Whenitisunderpressure,itwillformaninternalelectricfield.Thestrengthofthefieldreflectsthestrengthoftheforce.Therefore,wecanmakeuseofthismaterialtomakeapiezoelectricsensor,bymeasuringthestrengthoftheelectricfieldtoindirectlymeasurethestrengthoftheforce.

Application:

Inmanylargeshoppingmalls,escalators自動扶梯,ingeneral,willhaveapressuresensor.Thesensorinstalledinthepedal踏板oftheelevator,whenacustomersetfootonthestopsofelevatorandthentheelevatorwillacceleratetonormalspeed;whennoonetaketheelevator,theelevatorisrunningarelativelylowspeed.Byusingthepressuresensorcanhelptheelevatorsavingenergy.Thisisanexampleofpressuresensorapplication.

3，紅外線傳感器。infraredtransducer利用紅外線的物理性質(zhì)來舉行測量的傳感器。任何物質(zhì)，只要它本身具有一定的溫度（高于絕對零度），都能輻射紅外線。紅外線傳感器測量時不與被測物體直接接觸，因而不存在摩擦，并且有靈巧度高，響應(yīng)快等優(yōu)點。應(yīng)用；許多自動門就是這個原理，當有人臨近的時候，傳感器檢測到物體發(fā)射的紅外線，于是就把這個信號送到控制電路，使自動門打開。3,theinfraredsensor.Infraredtransducer

thesensorusingthephysicalpropertiesoftheinfraredrays/ultraredraystomeasure.Anysubstance,aslongasititselfhasacertaintemperature(aboveabsolutezero),canemitinfraredradiation.Whentheinfraredsensorwork,itwillnotindirectcontactwiththemeasuredobject,andthereforethereisnofriction,andhashighsensitivity,fastresponse,andsoon.

Application;

Manyautomaticdooristhisprinciple,thetimewhensomeoneclosetothedoor,thesensordetectsinfraredraysemittedbyobjects,soitwillsendthesignaltothecontrolcircuit,theautomaticdoorsopen.

4，煙霧傳感器smoketransducer將空氣中的煙霧濃度變量轉(zhuǎn)換成有一定對應(yīng)關(guān)系的輸出信號的裝置。這種傳感器廣泛應(yīng)用在防火的設(shè)施中，現(xiàn)在的大部分建造類都會安裝這種煙霧傳感器。這是異常實用的。4,smokesensor/smoketransducerrelatetotheinnerionofthematerial.TheSmokeconcentrationintheairavariable,thisdevicecanconvertthisvariableintoaelectricsignalwhichcanbereadbythecircuit.

Thesensorsarewidelyusedinfirepreventionfacilities,nowmostofthebuildingswillinstallthesmokesensor.Thisisveryuseful.位移傳感器：displacementsensor正電荷Positivecharge負電荷Negativecharge電動勢electromotiveforce電壓voltage差動式DifferentialSensor

感應(yīng)

ElectromagneticinductionCapacitivepressuresensor:usesthechangeof\o"Capacitance"capacitanceduetochangeofthedistancebetweentheplatesofacapacitorbecauseofchangeinpressuretocalcula