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单击此处编辑母版标题样式,第三章 检测技术,过程设备控制技术,演示文档,路漫漫其悠远,少壮不努力，老大徒悲伤,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,工业常用的温度检测技术仪表,一、热电偶温度计：,1、原理：,热电效应,(,t E ),基本结构：两根不同的导体材料焊接而成。,工作端（热端）,t,t,A,B,自由端（冷端）,t,0,t,0,如果:,N,A,N,B,tt,0,则：,E,AB,(t,t,0,)=E,AB,(t) E,AB,(t,0,),E,AB,(t,t,0,),t,0,= 0, E,t,关系表 （分度表）,2 、常用热电偶：,铂铑,10, 铂：,S,分度号,镍铬镍硅：,K,镍铬铜镍：,E,注意：不同分度号分度表不同。,（t,0,= 0,） E,t,关系不同,主要特点比较：,S,K,E,检测范围（,）,-201300,（1600）,-50900（1200）,-40600（900）,精度,高,中,低,灵敏度,低,中,高,价格,高,适中,低,注意,：,1、不同分度号分度表不同。,分度表,：,t,0,= 0,；,E,t,关系表,2、热电势与温度之间是非线性关系。,E,AB,(t,0) = E,AB,(t,t,0,)+ E,AB,(t,0,0),3、热电偶前标电极为正极，后标电极为负极。,当,t t,0,时,；,E,AB,(t,t,0,)0,3、热电偶冷端温度的处理,：,为什么要进行冷端温度补偿？,答：因为分度表是在,t,0,=0,时的对应关系，且所用仪表都是在,t,0,=0,刻度，而实际情况,t,0,0,，,且经常波动，故需进行冷端温度补偿。,A、补偿导线：,t,t,0,/,A,B,t,0,A,/,B,/,作用：,将冷端从温度较高、波动较大移到温度较低、相对稳定的位置。,条件：,材料热电特性（0100,）,与相应热偶相同或相近。,材料价格比相应热偶低，来源丰富。,E,AB,(t,t,0,),常用补偿导线,：,铂铑,10, 铂（,S,）,铜铜镍,镍铬镍硅（,K,）,镍铬镍硅,铜康铜,镍铬铜镍（,E,）,镍铬铜镍,延伸型,替代型,使用注意：,正负不能接错,；,与所配热电偶同型号,；, 接点温度相同；,使用环境温度范围小于,100,。,补偿导线的方法也称是热偶冷端温度的部分（不完全）补偿法。,B、,冷端温度补偿：,E,AB,(t,t,0,),E,AB,(t,0),冰浴法：,计算法：,仪表零点调整法：,补偿电桥法：,E,AB,(t,t,0,)+ E,AB,(t,0,0)= E,AB,(t,0),E,AB,(t,t,0,/,)+ E,AB,(t,0,/, t,0,)= E,AB,(t, t,0,),4、热电偶温度计的组成：,t,t,0,A,B,t,0,A,B,显,示,表,1. 热电偶（感温元件）2. 显示仪表3. 连接导线（补偿导线及铜线）,t,t,0,A,B,t,0,A,B,冰浴法图,补偿电桥法,显,示,t,0,t,0,t,0,t,0,t,A,B,E,AB,（t， t,0,）,R,CU,R,3,R,2,R,1,a,b,E,E = E,AB,(t,t,0,)+ U,ab,= E,AB,(t,t,0,)+ E,AB,(t,0,0),= E,AB,(t,0),t,0,R,CU,不变,电 桥,E,G,R,1,R,2,R,3,R,4,平衡电桥,不平衡电桥,桥路平衡,平衡条件：,R,1,R,3,=R,2,R,4,（I,G,=0),桥路不平衡,R,1,R,3,R,2,R,4,a,b,U,ab,+,I,1,I,2,U,ab,= I,1,R,4,I,2,R,3,R,cu,t,0,R,CU,U,CU,分度表：,分度号：,S,冷端温度为0,温度,0,1,2,3,4,5,6,7,8,9,热 电 动 势,mV,0,0.000,0.005,0.011,0.016,0.022,0.027,0.033,0.038,0.044,0.050,10,0.055,0.061,0.067,0.072,0.078,0.084,0.090,0.095,0.101,0.107,20,0.113,0.119,0.125,0.131,0.137,0.143,0.140,0.154,0.161,0.167,30,0.173,0.179,0.185,0.191,0.197,0.203,0.210,0.216,0.222,0.228,分度号：,K,冷端温度为0,温度,0,1,2,3,4,5,6,7,8,9,热 电 动 势,mV,0,0.000,0.039,0.079,0.119,0.158,0.198,0.238,0.277,0.317,0.357,10,0.397,0.437,0.477,0.517,0.557,0.597,0.637,0.677,0.718,0.758,20,0.798,0.838,0.879,0.919,0.960,1.000,1.041,1.081,1.122,1.162,30,1.203,1.244,1.285,1.325,1.366,1.407,1.448,1.489,1.529,1.570,K分度表,计算法例：,例：,K,型热电偶测温，冷端温度为30，测得的热电势为,24.9,mV，,求热端温度。,解：,E,AB,（t，0） E,AB,（t，30） E,AB,（30，0）,24.91.20326.103,mV,查分度表得,t628.3,5、热电偶的结构：,、,普通型：,（装配型）,热电极、绝缘管、保护管、接线盒,装配型热电偶外型：,、,套管型（铠装热电偶）：,热电极、绝缘材料、金属套管合为一体,铠装式热电偶具有细长、容易弯曲、热响应时间快、耐振动、耐温、抗压和坚固耐用等优点。它可用作直接测量，也可以作为装配式热电偶的内芯元件，以取代传统的瓷珠串套式元件。尤其适宜安装在管道之间狭窄、弯曲和要求快速反应，微型化和特殊测温场合。,二、热电阻温度计：,1、原理：,金属导体或半导体电阻的阻值随温度变化而变化,金属导体：t Rt,半导体：t Rt,2 、常用热电阻：,A、,铂电阻：,B、,铜电阻：,分度号,Pt,10,（R,0,=10）,Pt,100,（R,0,=100）,Cu,50,（R,0,=50）,Cu,100,（R,0,=100）,检测范围,（,）,200650,50150,精度,高,低,3、热电阻的结构：,电阻体、绝缘管、保护管、接线盒,
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