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1、This course is relatively more practical, we have learned the general form of a test system .it consisted of 5 parts, namely, the object being tested, detection unit, the conversion circuit,controlunits,outputunitsWevemainlylearned how a four important parts of a control system. They are controller,

2、actuator,sensor(傳感器)andtransducer.(變送Themostimportantpartofthissystemisthedetectionunit and we learn some basic knowledge abouA sensor is a device that measures a physical ty and convertsitintoasignalwhichcanbereadbyanobserveror by an instrument.1,溫度傳感器 主要有兩種 熱電阻溫度傳感器(熱敏電阻和熱電熱敏電阻 利用電阻隨溫度變化的特點(diǎn)制成的傳感器。

3、主要使用半導(dǎo)體 。半導(dǎo)體的電阻隨溫度升高而下降。特點(diǎn): 材料成本低,加工方便,但是使用時(shí)容易受環(huán)境溫度影響。應(yīng)用:空調(diào)的自動(dòng)調(diào)溫系統(tǒng),當(dāng)傳感器檢測(cè)到房間的溫度低于設(shè)定溫度時(shí),空調(diào)控制器就會(huì)發(fā)送信號(hào)啟動(dòng)空調(diào)壓縮機(jī),制冷;當(dāng)傳感器檢測(cè)到房間的溫度達(dá)到設(shè)定的溫度時(shí),就會(huì)想空調(diào)控制器發(fā)送一個(gè)信號(hào),告訴控制器“環(huán)境已達(dá)到設(shè)定溫度”,這個(gè)時(shí)候,控制器就會(huì)發(fā)送信號(hào)停止壓縮機(jī)的運(yùn)行。電飯煲的煮飯過程也是使用了這種溫度傳感器。There are two major thermaltemperature sensor (thermistor) and thermocouple temperature sensor

4、varies with temperature.The materialof thissensor Mainlyuse ofsemiconductors.The ofthesemiconductordecreaseswith increasing temperature.Features:Lowcost ofmaterials, processingconvenience, butwhen it used , it will be susceptible to environmental temperature.Applications: air conditioning thermostat

5、 system, when the sensor detects the rooms temperature drops below the set temperature, the air conditioningcontrollerwillsendasignal tostartairconditioning compressors and start refrigerating; when the sensor detects the roomstemperaturereachesthesettemperature,thecontrollerwill send a signal to st

6、op the operation of the compressor.RicecookercookingprocessisalsousingthistemperatureAthermocouple 熱電偶 convertstemperaturetoanoutput voltagewhich can be read by a voltmeter 伏特計(jì).1,Temperature Pt resistor, thermistor(熱敏電阻)。:A thermistor is a type of resistor with proportional to its temperature.2,壓力傳P

7、ressure畫圖解isthedevicethatisabletodetectthepressure value,converts theforcetotheelectric signal,whichcan be by a voltmeter or an ammeter.Piezoresistivepressuresensor isOneofcommonlyused pressure sensor.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(shí)候,會(huì)形成電場(chǎng)。這個(gè)電場(chǎng)的大小反映了它所受到外力的大小。因此,可以使用這種材料做成壓電式傳感器,通過測(cè)量材料所產(chǎn)生的電場(chǎng)

8、來(lái)間接測(cè)量力的大小。應(yīng)用:在許多大型商場(chǎng)的扶手電梯中,一般都會(huì)有壓力傳感器的。這種傳感器安裝在電梯的踏板下,當(dāng)有客人站上電梯時(shí)候,電梯就會(huì)加速到正常速度向上;當(dāng)沒有人乘坐電梯時(shí),電梯以比較低的速度運(yùn)行,從而節(jié)省了能量。這個(gè)就是壓力傳感器應(yīng)用的例子。 piezoelectricpai,i:zuilektriktransducer電傳Principle:Usingthepiezoelectric effect of certain substances. Some objects such as quartzkw:ts石英When it is under pressure, it will for

9、m an internal electric field. Thestrengthofthefieldreflectsthestrengthoftheforce. Therefore,wecanmakeuseofthismaterialtomakeapiezoelectric sensor, by measuring the strength of the electric field to indirectly measure the strength of the force.In many large shop malls, escalators 自動(dòng)扶梯, in general, wi

10、ll have a pressure sensor. The sensor installed in the pedal板 of the elevator, when a customer set foot on the stops of elevatorandthentheelevatorwillacceleratetonormalspeed;when noonetaketheelevator,theelevatorisrunningarelativelylow speed. By using the pressure sensor can help the elevatorsavingen

11、ergy.Thisisanexampleofpressuresensor3,紅外線傳感器。infrared 利用紅外線的物理性質(zhì)來(lái)進(jìn)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(duì)零度)都能輻射紅外線。紅外線傳感器測(cè)量時(shí)不與被測(cè)物體直接接觸,因而不存在摩擦,并且有靈敏度高,響應(yīng)快等優(yōu)點(diǎn)。應(yīng)用;許多自動(dòng)門就是這個(gè)原理,當(dāng)有人接近的時(shí)候,傳感器檢測(cè)到物體發(fā)射的紅外線,于是就把這個(gè)信號(hào)送到控制電路,使自動(dòng)門打開。3, the infraredsensor.Infraredthesensorusing thephysicalpropertiesoftheinfraredrays/ultrare

12、d rays tomeasure. Anysubstance, aslongas ititselfhasa certain temperature (above absolute zero), can emit infrared radiation.Whentheinfraredsensorwork,itwill notindirectcontactwith the measured object, and therefore there is no friction, and has high sensitivity, fast response, and so on.Manyautomat

13、icdooristhisprinciple,thetimewhensomeone close to the door ,the sensor detects infrared rays emitted by objects, so it will send the signal to the control circuit, the automatic doors open.4smoke將空氣中的煙霧濃度變量轉(zhuǎn)換成有一定對(duì)應(yīng)關(guān)系的輸出信號(hào)的裝置。這種傳感器廣泛應(yīng)用在防火的設(shè)施中,現(xiàn)在的大部分建筑類都會(huì)安裝這種煙霧傳感器。這是非常實(shí)用的。4, smoke sensor /smoke transd

14、ucerrelatetotheinnerionofthe The Smoke concentration in the air a variable, this device can convert this variable into a electric signal which can be read by the circuit. The sensors are widely used in fire prevention facilities, now mostofthebuildingswillinstallthesmokesensor.Thisis位移傳感器:displaceme

15、n正電荷Positivecharge負(fù)電荷Negativecharge 電動(dòng)勢(shì)electromotive force 電壓 voltage差動(dòng)式 Differential Sensor感應(yīng) Electromagnetic Capacitive pressure sensor: uses the change of capacitance due to change ofthedistancebetweentheplatesofacapacitorbecauseofchangein pressure to calculate the pressure.(公式推導(dǎo))(4、Controller: i

16、s a device whionitors and affects the operational conditionsofacontrolsystemandacontrolleristhecoreinstrument of acontrol system.Specificallyacontroller canoutput acontrol signalbycomparingthemeasuringsignalfromatransducerandtheset Therearealsoinnumerableapplications forsensorsofwhiost people are ne

17、ver aware. Applications include cars, machines, aerospace, medicine, manufacturing and robotics.A sensor is a device which receives and responds to a signal. A sensors sensitivity indicates how much the sensors output changes when the measured ty changes. For instance, if the mercury in a thermometer moves1 cmwhenthetemperaturechangesby1C,thesensitivityis1 cm/C (it is basically the slope Dy/Dx assuming a linear characteristic). Sensors that measure very small changes must have very highsensitivities.Sensorsalsohaveanimpactonw

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