溫度測量儀表資料

1、Level 1 - TemperatureRMT Training - 05 /981Level 1溫度測量儀表基礎(chǔ)溫度測量儀表基礎(chǔ)Level 1 - TemperatureRMT Training - 05 /982Topics:Slide No: 為什么要測量溫度為什么要測量溫度? 3 - 5 溫度的定義溫度的定義 6 - 8 溫度測量技術(shù)溫度測量技術(shù) 14 - 40 傳感器的附件傳感器的附件 41 - 52 溫度變送器溫度變送器 53 - 64Level 1 - TemperatureRMT Training - 05 /983 因為溫度影響許多物質(zhì)的屬性因為溫度影響許多物質(zhì)的屬性: 同

2、時同時,溫度是影響以下工藝過程的關(guān)鍵因素溫度是影響以下工藝過程的關(guān)鍵因素:物理及化學(xué)反應(yīng)的速率物理及化學(xué)反應(yīng)的速率粘度粘度物質(zhì)的狀態(tài)物質(zhì)的狀態(tài)材料的強度材料的強度食品的質(zhì)量及品味食品的質(zhì)量及品味工業(yè)過程的安全工業(yè)過程的安全紙漿與造紙紙漿與造紙乳品工業(yè)的巴氏滅菌消毒乳品工業(yè)的巴氏滅菌消毒真空包裝真空包裝化學(xué)反應(yīng)化學(xué)反應(yīng)Level 1 - TemperatureRMT Training - 05 /984 安全安全 效率效率 例如空分工業(yè)例如空分工業(yè) 產(chǎn)品的質(zhì)量及產(chǎn)出率產(chǎn)品的質(zhì)量及產(chǎn)出率 溫度偏離優(yōu)化值會導(dǎo)致溫度偏離優(yōu)化值會導(dǎo)致; 產(chǎn)出率極低 產(chǎn)生廢物 精確的控溫將帶來高的出率精確的控溫將帶來高的

3、出率: 煉廠常壓分餾 催化裂化Level 1 - TemperatureRMT Training - 05 /985 貿(mào)易交接貿(mào)易交接買賣雙方的交易量買賣雙方的交易量確定氣體的標(biāo)態(tài)體積時確定氣體的標(biāo)態(tài)體積時,溫度測量極為重要溫度測量極為重要給定體積氣體中的物質(zhì)含量給定體積氣體中的物質(zhì)含量 將隨溫度升高而減少 將隨溫度降低而增加溫度測量誤差將導(dǎo)致溫度測量誤差將導(dǎo)致: 用戶的支出將有很大的誤差Level 1 - TemperatureRMT Training - 05 /986SteamColdWaterHotWaterLoad Disturbance TTTICI/P溫度控制回路通常的問題是溫度

4、控制回路通常的問題是: 液體對加熱輸入的反應(yīng)有很大的滯后液體對加熱輸入的反應(yīng)有很大的滯后 因此需要某些先進(jìn)控制策略因此需要某些先進(jìn)控制策略例如前饋控制例如前饋控制Level 1 - TemperatureRMT Training - 05 /987373 100 672 212 273 0 492 32 0 -273 0 -460 C = 5/9 (F - 32 ) F = 9/5 (C) + 32 K = 273 +C R = 460 + FBOILING POINT OF WATERICE POINTABSOLUTE ZEROkELVINCELSIUSRANKINEFAHRENHEITLe

5、vel 1 - TemperatureRMT Training - 05 /988C = 5/9 FF = 9/5 C K = CR = FExample: 2 points in a process differ in temperature by 100 C. These 2 points differ by 180 Fi.e. 180 = 9/5(100)Whereas, they also differ by 100K20C= 20 + 273= 293K20C= 9/5*(20) +32= 68FLevel 1 - TemperatureRMT Training - 05 /989使

6、用不同溫度膨脹系數(shù)的雙金屬片及連桿齒輪系統(tǒng)組成的使用不同溫度膨脹系數(shù)的雙金屬片及連桿齒輪系統(tǒng)組成的溫度指示儀表溫度指示儀表.Level 1 - TemperatureRMT Training - 05 /9810例如例如:蒸汽溫度計蒸汽溫度計基本原理是利用可揮發(fā)性液體受熱后產(chǎn)生汽化,汽化壓力經(jīng)毛細(xì)管傳導(dǎo)至指示機構(gòu).其壓力與溫度成正比!利用液體的汽化膨脹特性制成的溫度計利用液體的汽化膨脹特性制成的溫度計測溫探頭導(dǎo)壓毛細(xì)管壓力指示Level 1 - TemperatureRMT Training - 05 /9811Example:石英晶體溫度計石英晶體溫度計外形類似于RDT熱電阻的封裝,可以實現(xiàn)

7、高精度的直接數(shù)字測溫,但價格昂貴!利用晶體的諧振頻率與溫度之間的關(guān)系制成的溫度儀表利用晶體的諧振頻率與溫度之間的關(guān)系制成的溫度儀表.Level 1 - TemperatureRMT Training - 05 /9812例如例如: 光電式紅外線輻射溫度計光電式紅外線輻射溫度計/非接觸式測溫儀非接觸式測溫儀.原理基于任何物體均有溫度的熱輻射原理基于任何物體均有溫度的熱輻射,例如紅外線輻射例如紅外線輻射.Level 1 - TemperatureRMT Training - 05 /9813Example:半導(dǎo)體溫度敏感元件半導(dǎo)體溫度敏感元件RTD 金屬熱電阻金屬熱電阻基本原理基本原理:利用導(dǎo)體的

8、溫度與電阻的相關(guān)關(guān)系進(jìn)行溫度測量利用導(dǎo)體的溫度與電阻的相關(guān)關(guān)系進(jìn)行溫度測量. 分為負(fù)溫度系數(shù)分為負(fù)溫度系數(shù)NTC及正溫度系數(shù)及正溫度系數(shù)PTC兩種兩種半導(dǎo)體熱敏電阻半導(dǎo)體熱敏電阻ThermistorLevel 1 - TemperatureRMT Training - 05 /9814什么是什么是 RTD ?esistance emperature etector Platinum resistance changes with temperatureRosemounts Series 78, 88Rosemounts Series 68, 58Series 65兩種常見的制造工藝兩種常見的制

9、造工藝:線繞式或薄膜式線繞式或薄膜式Wire-wound sensing elementThin-film sensing element鉑電阻鉑電阻 (Platinum usually): 元件的溫度常數(shù)元件的溫度常數(shù)/PT100Typical Tc=9s50%FS!Level 1 - TemperatureRMT Training - 05 /9815 RTD的工作原理的工作原理?重復(fù)性精度好 IEC 751/PT100鉑電阻的特性曲線(Ro=100 Ohms)050100150200250300350-2000200400600800Resistance (Ohms)Temperatur

10、e (oC)oCOhms0100.0010103.9020107.7930111.67International Resistance vs. Temperature Chart:IEC 751IEC751IEC 751 Constants are :- A = 0.0039083, B = - 5.775 x 10 -7, If t=0, C=0, If t=0C, then b = 0)IEC 751 CurveTemperature (oC)Resistance (W W)Class B Tolerance The transmitter does not use the IEC 751

11、 standard curve. Instead, the Callendar-Van Dusen constants can be used in the equation below to create the true sensor curve. Or, the actual IEC 751 constants A,B, and C can be used in the IEC 751 equation if known. Sensor Matching - Mapping the Real RTD Curve4th Order Callendar-VanDusen EquationLe

12、vel 1 - TemperatureRMT Training - 05 /9827Hot junction兩種異型金屬形成的結(jié)點兩種異型金屬形成的結(jié)點.Cold junction+-MV只要引自該結(jié)點的導(dǎo)線的另一端的溫度與結(jié)點溫度有所不同只要引自該結(jié)點的導(dǎo)線的另一端的溫度與結(jié)點溫度有所不同,該溫該溫度差將會在這一點的導(dǎo)線間產(chǎn)生與溫度成正比的度差將會在這一點的導(dǎo)線間產(chǎn)生與溫度成正比的MV電勢電勢!溫度高的一端稱之為熱端溫度高的一端稱之為熱端,反之為冷端反之為冷端.DT該MV數(shù)可以由標(biāo)準(zhǔn)化的標(biāo)度表格查到!作為實用性測溫技術(shù)作為實用性測溫技術(shù),冷端的溫度必須知道冷端的溫度必須知道!什么是熱電偶什么

13、是熱電偶?Level 1 - TemperatureRMT Training - 05 /9828 +-MVHeatHot junctionCold junctionoC Millivolts00.000100.591201.192301.801Thermoelectric Voltagevs. Temperature Chart:TYPE E THERMOCOUPLED DT-20020406080-50005001000Voltage (mV)Temperature (oC)IEC584IEC 584-熱電偶的溫度熱電偶的溫度/MV轉(zhuǎn)換標(biāo)準(zhǔn)轉(zhuǎn)換標(biāo)準(zhǔn)參考溫度參考溫度Level 1 - Tem

14、peratureRMT Training - 05 /9829Grounded improved thermal conductivity quickest response times susceptible to electrical noiseUngrounded slightly slower response time not susceptible to electrical noiseSingle GroundedDual GroundedSingle UngroundedHot-Junction ConfigurationsLevel 1 - TemperatureRMT Tr

15、aining - 05 /9830Unisolated junctions at the same temperature both junctions will typically fail at the same timeIsolated junctions may/may not be at the same temperature increased reliability for each junction failure of one junction does not affect the otherHot-Junction ConfigurationsDual Unground

16、ed, Un-isolatedDual Ungrounded, IsolatedLevel 1 - TemperatureRMT Training - 05 /9831ICEBATHT1 = 10CWhy is Cold Junction Compensation needed?MeasureReferenceIronConstantan+_VoltMeterT2 = 100 + 10C5.812 mV 2 種方法種方法: 將冷端置于冰浴桶中將冷端置于冰浴桶中 NOT Practical ! C-100-0+0100 MILLIVOLTS 0-4.6320.0000.0005.268 2-4.

17、550-0.9951.0195.376 6-4.876-0.3010.3035.594 10-5.036-0.5010.5075.812 14-5.194-0.6990.7116.031熱電偶分度表熱電偶分度表Level 1 - TemperatureRMT Training - 05 /9832MeasureReferenceJunctionIronConstantan+_TransmitterT2 = 110C4.186 mV另一種方法另一種方法:冷端補償冷端補償.Electronic Circuitrypassing current through a 通常的做法通常的做法!Connec

18、tion HeadExtension WiresExample: Ambient Temp = 30C C-100-0+0100 MILLIVOLTS 0-4.6320.0000.0005.268 10-5.036-0.5010.5075.812 30-5.801-1.4811.5366.907 60-6.821-2.8923.1158.560 80-7.402-3.7854.1869.667+ +1.536 mV= 5.722 mV1100 CSpecial Thermocouple R, S or BLevel 1 - TemperatureRMT Training - 05 /9840

19、為什么要延長段為什么要延長段? 降低由過程傳導(dǎo)的溫度降低由過程傳導(dǎo)的溫度延伸探頭的插入深度延伸探頭的插入深度將探頭拆除時教方便將探頭拆除時教方便兩種類型兩種類型: 螺母及對絲/Coupling and nipple. 聯(lián)結(jié)器及對絲/Union and nipple.01020304050603456789815C Oven Temp.540C Oven Temp.250C Oven Temp.Extension Length, InchesHousing Temp.Rise Above Ambient CTransmitter Housing Temperature Rise vs.Exten

20、sion Length for a test InstallationLevel 1 - TemperatureRMT Training - 05 /9841FExample #1 4 inch extension01020304050603456789815C Oven Temp.Extension Length, InchesHousing Temp.Rise Above Ambient CExample of ApplicationTransmitter Housing Temperature Rise vs.Extension Length for a test Installatio

21、nLets say:Temp Limit of Transmitter is 70CAmb. Temp is 32C 62C Ceiling32C + 30CFExample #2 6 inch extension 52C Ceiling32C + 20CLevel 1 - TemperatureRMT Training - 05 /9842什么是熱套管什么是熱套管 ? 對傳感器進(jìn)行保護(hù) 方便超出傳感 很大的時間常數(shù) (一般為傳感器的5倍)不同的材質(zhì)不同的材質(zhì) ?考慮到腐蝕溫壓等級Level 1 - TemperatureRMT Training - 05 /9843ProcessPressu

22、reTimeResponseWake FrequencyPriceDragForceRating: 1= BestThermowell Design Styles - Comparison Table311 or 21211311231 or 212TaperedSteppedStraightLevel 1 - TemperatureRMT Training - 05 /9844 螺紋連接最常見的安裝容易拆卸 焊接式永久性安裝高流速高溫高壓用于無泄漏場合 法蘭安裝防腐要求高流速高溫Level 1 - TemperatureRMT Training - 05 /9845損壞原因損壞原因-1馮馮-

23、卡爾曼效應(yīng)及尾流振動卡爾曼效應(yīng)及尾流振動.熱套管的自然諧振頻率熱套管的自然諧振頻率.Level 1 - TemperatureRMT Training - 05 /9846流體的牽拽作用引起套管的折斷流體的牽拽作用引起套管的折斷!FLOWSTRESSLevel 1 - TemperatureRMT Training - 05 /9847 過高的靜壓引起套管的變形過高的靜壓引起套管的變形.Level 1 - TemperatureRMT Training - 05 /9848外形外形材質(zhì)材質(zhì)尺寸尺寸流速及流量流速及流量過程壓力溫度過程壓力溫度密度和粘度密度和粘度管道尺寸管道尺寸T 型套的計算型套

24、的計算: 1.尾流頻率尾流頻率 2.自然諧振頻率自然諧振頻率 3.牽拽力牽拽力 4. 靜壓力靜壓力Look on the back of your Sensor PDS!Level 1 - TemperatureRMT Training - 05 /9849Sensor 7 to 10 sec Sensor in Thermowell 60 to 120 secTransmitter.5 to .9 secProcessSeconds to HoursLevel 1 - TemperatureRMT Training - 05 /9850A 4-20 mA transmitter is spa

25、nned 50 to 150C. Express the span in the following units:1. to F2. to K3.What is the temperature reading if the above transmitter outputs 10 mA?C4.An old differential temperature indicator witha scale of 0 - 100F is reading 60F. What is that reading in C?C5.An Pt 100 RTD has the following C.V.D constantsR0 =100.00W, = 0.003842