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1、关于热电偶热电阻关于热电偶热电阻第一页，讲稿共三十七页哦热电偶（热电偶（ThermocoupleThermocouple）n工业过程中使用范围很广的一种测温元件。n特点：n其热电动势与温度在小范围其热电动势与温度在小范围内基本上呈单值、线性关系；内基本上呈单值、线性关系；n稳定性好；稳定性好；n测温范围宽，高温热电偶测测温范围宽，高温热电偶测温上限可达温上限可达2800；n精度较高。精度较高。第二页，讲稿共三十七页哦热电偶外形图热电偶外形图第三页，讲稿共三十七页哦铠装热电偶铠装热电偶具有能弯曲、耐高压、具有能弯曲、耐高压、热响应时间快和坚固热响应时间快和坚固耐用等许多优点耐用等许多优点。第四页
2、，讲稿共三十七页哦热电偶温度变送器热电偶温度变送器第五页，讲稿共三十七页哦常用热电偶型号n基本为定型生产，有标准化分度表。n常用型号：n铂铑铂铑3030-铂铑铂铑6 6热电偶（也称双铂铑热电偶，分热电偶（也称双铂铑热电偶，分度号度号B）；测温范围）；测温范围300-1600300-1600。n铂铑铂铑1010-铂电偶（分度号铂电偶（分度号S）；测温范围）；测温范围0-0-13001300。n镍铬镍铬-镍硅（镍铬镍硅（镍铬-镍铝，分度号镍铝，分度号K）热电偶；）热电偶；测温范围测温范围-50-1000-50-1000。第六页，讲稿共三十七页哦将两种不同材质的导体或半导线在其端点实现物理接触；当回
3、路两端温度不同时，回路中出现电势差。AB热电偶产生的直流热电势与温度有准确的单值对应关系，且幅值不超过几十毫伏。热电偶-基于热电效应实现温度检测.第七页，讲稿共三十七页哦冷端热端AB热电偶的总热电动势=接触电动势+温差电动势忽略温差电动势第八页，讲稿共三十七页哦热电偶冷端温度对被测温度的影响热电偶冷端温度对被测温度的影响 n只有当热电偶冷端温度只有当热电偶冷端温度T0保持不变时，热保持不变时，热电势才是被测温度电势才是被测温度T T的单值函数：的单值函数：nEAB(t，t0)=EAB(t)-EAB(t0)n冷端温度能恒定吗？冷端温度能恒定吗？n反例说明：反例说明：1.1.热端温度恒定，冷端变动
4、；热端温度恒定，冷端变动；2.2.同一个热电势，可以对应无穷多组冷热同一个热电势，可以对应无穷多组冷热端温度。端温度。第九页，讲稿共三十七页哦n只有将冷端温度保持为只有将冷端温度保持为0，或者进行一，或者进行一定的修正才能得到准确的测量结果。该过定的修正才能得到准确的测量结果。该过程程称为称为热电偶的冷端温度补偿。热电偶的冷端温度补偿。n关于热电偶的分度表。关于热电偶的分度表。热电偶的冷端温度补偿热电偶的冷端温度补偿第十页，讲稿共三十七页哦热电偶的分度表（热电偶的分度表（K型）型）第十一页，讲稿共三十七页哦热电偶的分度表（热电偶的分度表（K型）型）第十二页，讲稿共三十七页哦热电偶的分度表（热电
5、偶的分度表（K型）型）第十三页，讲稿共三十七页哦热电偶的分度表（热电偶的分度表（K型）型）第十四页，讲稿共三十七页哦热电偶的分度表（热电偶的分度表（K型）型）第十五页，讲稿共三十七页哦如何固定冷端温度？如何固定冷端温度？用普通导线连接用普通导线连接可以吗？为什么可以吗？为什么？第十六页，讲稿共三十七页哦热电偶的补偿导线注意：补偿导线并没注意：补偿导线并没有补偿作用，其实质有补偿作用，其实质是延伸热电偶。是延伸热电偶。此时显示仪表能显示此时显示仪表能显示准确的温度值吗？准确的温度值吗？第十七页，讲稿共三十七页哦热电偶冷端补偿方法热电偶冷端补偿方法n1.冰浴法第十八页，讲稿共三十七页哦n2.查表法
6、（计算法）查表法（计算法）n依据：热电偶的中间温度定律依据：热电偶的中间温度定律n EAB(t，0)=EAB(t，t0)+EAB(t0，0)热电偶冷端补偿方法热电偶冷端补偿方法第十九页，讲稿共三十七页哦热电偶冷端计算法补偿例题n用分度号为K的镍铬-镍硅热电偶测量温度，在没有采取冷端温度补偿的情况下，显示仪表指示值为500，而这时冷端温度为60。n试问：实际温度应为多少？试问：实际温度应为多少？n如果热端温度不变，设法使冷端温度保持在如果热端温度不变，设法使冷端温度保持在2020，此时显示仪表的指示值应为多少？，此时显示仪表的指示值应为多少？第二十页，讲稿共三十七页哦热电偶冷端计算法补偿例题n显
7、示仪表指示值为显示仪表指示值为500500时，查表可得此时显示时，查表可得此时显示仪表的实际输入电势为仪表的实际输入电势为20.64mV20.64mV，即，即 n冷端温度为冷端温度为6060产生的电势：产生的电势：n由由23.076mV23.076mV查查表可得：表可得：t=557t=557。即。即实际实际温度温度为为557557。第二十一页，讲稿共三十七页哦热电偶冷端计算法补偿例题n当热端为557，冷端为20时，由于E（20，0）=0.798mV,故有：n查表可得显示仪表指示值应为538.4。n大家想想：此种方法在实际中如何实现？大家想想：此种方法在实际中如何实现？第二十二页，讲稿共三十七页
8、哦n3.电桥补偿法热电偶冷端补偿方法明白为什么要这样明白为什么要这样补偿？如何补偿的补偿？如何补偿的？RCU采用了什么接法采用了什么接法？第二十三页，讲稿共三十七页哦第二十四页，讲稿共三十七页哦热电阻（热电阻（RTDRTD）n在中、低温区，热电偶输出的热电动势很小在中、低温区，热电偶输出的热电动势很小,并且冷端温度不易得到完全补偿；并且冷端温度不易得到完全补偿；n而在中、低温区，用热电阻比用热电偶做为而在中、低温区，用热电阻比用热电偶做为测温元件时的测量精确度更高；测温元件时的测量精确度更高；n热电阻特点：性能稳定、测量精度高，一般热电阻特点：性能稳定、测量精度高，一般可在可在-270900范
9、围内使用（范围内使用（推荐在推荐在150以下时选用以下时选用）。）。第二十五页，讲稿共三十七页哦热电阻外形热电阻外形第二十六页，讲稿共三十七页哦不同热电阻特点及分度号n铂在氧化介质或高温时，物理、化学性质稳定。分度铂在氧化介质或高温时，物理、化学性质稳定。分度号有号有Pt100Pt100、Pt10Pt10。测温范围。测温范围-200-850-200-850。n铜在铜在-50-150-50-150稳定性好，超过稳定性好，超过100100易被氧化。分度号易被氧化。分度号有有Cu50Cu50、Cu100Cu100。测温范围。测温范围-50-150-50-150。n镍在我国含量少，不常用。分度号有镍在
10、我国含量少，不常用。分度号有Ni100Ni100、Ni300Ni300和和Ni500Ni500。测温范围。测温范围-60-180-60-180。n三种热电阻中，铂（三种热电阻中，铂（特别是特别是Pt100Pt100）使用最广）使用最广）第二十七页，讲稿共三十七页哦0200400600800-2001234CuPtNit/价格便宜，线性程度好，但温度高易于氧化。精度高、稳定性好、性能可靠、耐氧化能力强、测温范围宽。但电阻温度系数比较小，电阻值与温度之间呈非线性关系，且价格较贵。不同热电阻的特性（线性度）不同热电阻的特性（线性度）第二十八页，讲稿共三十七页哦Pt100分度表分度表温度温度电电阻阻值
11、值（）（）（JJG 229-87）R0=100.000123456789-20018.49-19022.8022.3721.9421.5121.0820.6520.2219.7919.3618.93-18027.0826.6526.2325.8025.3724.9424.5224.0923.6623.23-17031.3230.9030.4730.0529.6329.2028.7828.3527.9327.50-16035.5335.1134.6934.2733.8533.4333.0132.5932.1631.74-15039.7139.3038.8838.4638.0437.6337.21
12、36.7936.3735.95-14043.8743.4543.0442.6342.2141.7941.3840.9640.5540.13-13048.0047.5947.1846.7646.3545.9445.5245.1144.7044.28-12052.1151.7051.2050.8850.4750.0649.6449.2348.8248.41-11056.1955.7855.3854.9754.5654.1553.7453.3352.9252.52-10060.2559.8559.4459.0458.6358.2257.8257.4157.0056.60-9064.3063.9063
13、.4963.0962.6862.2861.8761.4761.0660.66-8068.3367.9267.5267.1266.7266.3165.9165.5165.1164.70-7072.3371.9371.5371.1370.7370.3369.9369.5369.1368.73-6076.3375.9375.5375.1374.7374.3373.9373.5373.1372.73-5080.3179.9179.5179.1178.7278.3277.9277.5277.1376.73-4084.2783.8883.4883.0882.6982.2981.8981.5081.1080
14、.70-3088.2287.8387.4387.0486.6486.2585.8585.4685.0684.67-2092.1691.7791.3790.9890.5990.1989.8089.4089.0188.62第二十九页，讲稿共三十七页哦Pt100分度表分度表0100.00100.39100.78101.17101.56101.95102.34102.73103.12103.5110103.90104.29104.68105.07105.46105.85106.24106.63107.02107.4020107.79108.18108.57108.96109.35109.73110.1
15、2110.51110.90111.2830111.67112.06112.45112.83113.22113.61113.99114.38114.77115.1540115.54115.93116.31116.70117.08117.47117.85118.24118.62119.0150119.40119.78120.16120.55120.93121.32121.70122.09122.47122.8660123.24123.62124.01124.39124.77125.16125.54125.92126.31126.6970127.07127.45127.84128.22128.601
16、28.98129.37129.75130.13130.5180130.89131.27131.66132.04132.42132.80133.18133.56133.94134.3290134.70135.08135.46135.84136.22136.60136.98137.36137.74138.12100138.50138.88139.26139.64140.02140.39140.77141.15141.53141.91110142.29142.66143.04143.42143.80144.17144.55144.93145.31145.68120146.06146.44146.81
17、147.19147.57147.94148.32148.70149.07149.45130149.82150.20150.57150.95151.33151.70152.08152.45152.83153.20140153.58153.95154.32154.70155.07155.45155.82156.19156.57156.94150157.31157.69158.06158.43158.81159.18159.55159.93160.30160.67160161.04161.42161.79162.16162.53162.90163.27163.65164.02164.39170164
18、.76165.13165.50165.87166.14166.61166.98167.35167.72168.09180168.46168.83169.20169.57169.94170.31170.68171.05171.42171.79190172.16172.53172.90173.26173.63174.00174.37174.74175.10175.47第三十页，讲稿共三十七页哦Pt100分度表分度表680338.92339.23339.54339.85340.16340.48340.79341.10341.41341.72690342.03342.34342.65342.96343
19、.27343.58343.89344.20344.51344.82700345.13345.44345.75346.06346.37346.68346.99347.30347.60347.91710348.22348.53348.84349.15349.45349.76350.07350.38350.69350.99720351.30351.61351.91352.22352.53352.83353.14353.45353.75354.06730354.37354.67354.98355.28355.59355.90356.20356.51356.81357.12740357.42357.73
20、358.03358.34358.64358.95359.25359.55359.86360.16750360.47360.77361.07361.38361.68361.98362.29362.59362.89363.19760363.50368.80364.10364.40364.71365.01365.31365.61365.91366.22770366.52366.82367.12367.42367.72368.02368.32368.63368.93369.23780369.53369.83370.13370.43370.73371.03371.33371.63371.93372.22
21、790372.52372.82373.12373.42373.72374.02374.32374.61374.91375.21800375.51375.81376.10376.40376.70377.00377.20377.59377.89378.19810378.48378.78379.08379.37379.67379.97380.26380.56380.85381.15820381.45381.74382.04382.33382.63382.92383.22383.51383.81384.10830384.40384.69384.98385.28385.57385.87386.16386
22、.45386.75387.04840387.34387.63387.92388.21388.51388.80389.09389.39389.68389.97850390.26-第三十一页，讲稿共三十七页哦Cu50分度表分度表Cu50Cu50分度表分度表TT0 0-1-1-2-2-3-3-4-4-5-5-6-6-7-7-8-8-9-90 0505049.78649.78649.57149.57149.35649.35649.14249.14248.92748.92748.71348.71348.49848.49848.28448.28448.06948.069-10-1047.85447.854
23、47.63947.63947.42547.42547.2147.2146.99546.99546.7846.7846.56646.56646.35146.35146.13646.13645.92145.921-20-2045.70645.70645.49145.49145.27645.27645.06145.06144.84644.84644.63144.63144.41644.41644.244.243.98543.98543.7743.77-30-3043.55543.55543.34943.34943.12443.12442.90942.90942.69342.69342.47842.4
24、7842.26242.26242.04742.04741.83141.83141.61641.616-40-4041.441.441.18441.18440.96940.96940.75340.75340.53740.53740.32240.32240.10640.10639.8939.8939.67439.67439.45839.458-50-5039.24239.2420 0505050.21450.21450.42950.42950.64350.64350.85850.85851.07251.07251.28651.28651.50151.50151.71551.71551.92951.
25、929101052.14452.14452.35852.35852.57252.57252.78652.786535353.21553.21553.42953.42953.64353.64353.85753.85754.07154.071202054.28554.28554.554.554.71454.71454.92854.92855.14255.14255.35655.35655.5755.5755.78455.78455.99855.99856.21256.212303056.42656.42656.6456.6456.85456.85457.06857.06857.28257.2825
26、7.49657.49657.7157.7157.92457.92458.13758.13758.35158.351404058.56558.56558.77958.77958.99358.99359.20759.20759.42159.42159.63559.63559.84859.84860.06260.06260.27660.27660.4960.49505060.70460.70460.91860.91861.13261.13261.34561.34561.55961.55961.77361.77361.98761.98762.20162.20162.41562.41562.62862.
27、628606062.84262.84263.05663.05663.2763.2763.48463.48463.69863.69863.91163.91164.12564.12564.33964.33964.55364.55364.76764.767707064.98164.98165.19465.19465.40865.40865.62265.62265.83665.83666.0566.0566.26466.26466.47866.47866.69266.69266.90666.906808067.1267.1267.33367.33367.54767.54767.76167.76167.
28、97567.97568.18968.18968.40368.40368.61768.61768.83168.83169.04569.045909069.25969.25969.47369.47369.68769.68769.90169.90170.11570.11570.32970.32970.54470.54470.76270.76270.97270.97271.18671.18610010071.471.471.61471.61471.82871.82872.04272.04272.25772.25772.47172.47172.68572.68572.89972.89973.11473.
29、11473.32873.328第三十二页，讲稿共三十七页哦Cu50分度表分度表11073.54273.75173.97174.18574.474.61474.82875.04375.25875.47712075.68675.90176.11576.3376.54576.75976.97477.18977.40477.61813077.83378.04878.26378.47778.69278.90779.12279.33779.55279.76714079.98280.19780.41280.62780.84381.05881.27281.48881.70481.91915082.134第三十
30、三页，讲稿共三十七页哦半导体热敏电阻（Thermistor）n包括正温度系数PTC、负温度系数NTC和临界温度电阻CTR 三类。n连续测温中主要采用负温度系数NTC；而PTC和CTR一般用于制作位式作用温度开关。n热容量小，响应快；但互换性差，热电特性非线性大。测温范围-50-300。第三十四页，讲稿共三十七页哦热电偶、热电阻的选型 n根据工艺要求的测温范围和使用要求确定根据工艺要求的测温范围和使用要求确定相应分度号的热电偶、热电阻。相应分度号的热电偶、热电阻。n优先选择优先选择一体化热电偶或热电阻一体化热电偶或热电阻温度变送温度变送器，直接输出标准信号。器，直接输出标准信号。n采用采用DCSDCS或或PLCPLC系统时，若系统时，若AIAI模块有模块有RTDRTD或标或标准热电偶输入方式，从经济性出发可不必准热电偶输入方式，从经济性出发可不必选择一体化温度变送器。选择一体化温度变送器。第三十五页，讲稿共三十七页哦测温元件管道安装原则 n测量流动介质（管道内）温度时，应保证传感器与介质充分接触，与被测介质成逆流状态（至少呈正交式）安装。n感温点应处于管道中流速最大的地方。n尽可能增大传感器的插入深度，温度计应斜插或在管道弯头处插入。n当测温管道过细（直径小于80）时，安装测温元件需加装扩充管。第三十六页，讲稿共三十七页哦感谢大家观看第三十七页，讲稿共三十七页哦