3-热敏传感器

温敏传感器•利用某些材料或元件的物理特性与温度有关这一性质，将温度的变化转化为电量的变化温度传感器类型和特征接触式：热电偶、热敏电阻、铂热电阻非接触式：红外线测温∎纯金属RTD1.Pt,Cu,Ni,Fe等纯金属2.α=0.2%℃-1~0.7%℃-1热电阻铂电阻的电阻-温度关系•Rt=R0(1+At+Bt2)0℃t650℃•Rt=R0[1+At+Bt2+C(t-100)t3]-200℃t0℃•Pt100,Pt10，Pt1000•测量电路（平衡电桥）PT100电阻与温度关系数据•表2.5（P83）PT1000电阻与温度关系数据，见资料接线方式•二线式图2.26•三线式消除引线误差•四线式消除引线误差***任一两线之间阻值是0，是一端铂电阻应用电路1123456ABCD654321DCBATitleNumberRevisionSizeBDate:20-Oct-2011SheetofFile:H:\传感器技术A\实训指导10医电\PT1000.ddbDrawnBy:Vin1GND3+5V2U1MC1403C2104R671KR6610KR6910KR7010K567U19BOPA227732184U19AOPA2277RW4500+5+5-5R6875KC1105C3473TEPvaTEPvbTEPvcRW510KRtPT1000铂电阻应用实训•焊接电路•测量Vb和Vc•计算放大倍数PTiPT1PT2PT3PT4PT5PT6PT7PT8阻值（Ω）10501100115012001250130013501000TEPvc(V)0.4981.011.512.032.543.053.570TEPvb(mV)-61-123-185-248-310-371-4340温度值（℃）12.825.738.651.664.685.590.80123456ABCD654321DCBATitleNumberRevisionSizeBDate:11-Oct-2011SheetofFile:D:\课程\传感器技术A\实训指导10医电\PT1000.ddbDrawnBy:Rw1Rw2Rw3R110KR210KR3100R42K213A1213A21516A3R510KR610KR710KR1010KR810KR910KGNDGNDUoVCCRtPT100铂电阻应用电路2•图2.28P85UiR7R9*)U2U1(UoR6R5R4U2U1R4UiU1U2•电路中输入级由A1、A2两个同相输入运算放大器电路并联，再与A3差分输入串联的三运放差动放大电路构成，其中A1、A2是增加电路的输入阻抗。•电路优点：差模信号按差模增益放大，远高于共模成分（噪声）•决定增益的电阻（R5、R4、R7、R8）•当R5=R6、R7=R8、R9=R10时，两级的总增益为两个差模增益的乘积，即：•Av=-(（R4+2R5）/R4)(R9/R7)•=-(1+2R5/R4)*(R9/R7)铂电阻应用电路3****与应用电路2比较，零点和放大倍数均可调123456ABCD654321DCBATitleNumberRevisionSizeBDate:11-Oct-2011SheetofFile:D:\课程\传感器技术A\实训指导10医电\PT1000.ddbDrawnBy:RTθRw1Rw2Rw3R110kR210k5110k10k10k10010k32184U1ALM358567U1BLM35832184U2ALM358567U2BLM35810kUo+12热敏电阻•1.Mn,Ni,Cu,Fe,Zn氧化物或化合物按不同配比烧结而成。•2.α=-1%℃-1~-6%℃-1(NTC)负温度系数NTC型热敏电阻NegativeTemperatureCoefficient正温度系数PTC型热敏电阻PositiveTemperatureCoefficient临界温度CTR型热敏电阻CriticalTemperatureResistor热敏电阻(Thermistor)的类型图1热敏电阻的特性曲线NTC电阻-温度特性eTTBTRR)011(0热力学温度T=273+t材料系数B2000~6000K热敏电阻线性化)22(TiBTBRRiTiP)22(TiBTBGGiTiS恒压源供电恒流源供电温度上下限报警电路效果：低于温度下限亮LED1（绿灯），正常不亮灯，高于温度上限亮LED2（红灯）。热电偶传感器•热电偶测温基本原理图1热电偶工作原理图冷端热端EAB(t,t0)=eAB(t)–eAB(t0)=eAB(t)+eBA(t0)热电偶温度计组成1-热电偶;2-导线;3-测量仪表热电偶分度号热电极材料使用温度范围（℃）S铂铑合金（铑含量10%）纯铂0-1600R铂铑合金（铑含量13%）纯铂0-1600B铂铑合金(铑含量30%)铂铑合金(铑含量6%)500-1700K镍铬镍硅-200-+1200T纯铜铜镍-200-+350•J铁铜镍-200-+750•N镍铬硅镍硅-200-+1200•E镍铬铜镍-200-+800中间金属定则EAB(t,t0)=eAB(t)+eBC(t1)+eCB(t1)+eBA(t0)=eAB(t)+eBA(t0)=eAB(t)-eAB(t0)中间温度定则•EAB(t,t0)=eAB(t,t1)+eAB(t1,t0)补偿导线•导线太短,冷热接近,冷端不冷.导线太长,价格昂贵.解决的办法是采用一种专用的导线,将热电偶的冷端延伸出来,这种专用的导线就叫补偿导线冷端温度补偿•各种热电偶的温度-热电势关系曲线是在冷端温度保持为00C的情况下得到的,因此,我们在应用热电偶测温时,只有将冷端温度保持为00C,或者是进行一定的修正才能得出准确的测量结果.这样做,就成为热电偶的冷端温度补偿.铜-康铜热电偶分度表(自由端温度0℃)工作端温度0123456789de/dt(µV/℃)00.0000.0390.0780.1160.1550.1940.2340.2730.3120.35238.6100.3910.4310.4710.5100.5500.5900.6300.6710.7110.75139.5200.7920.8320.8730.9140.9540.9951.0361.0771.1181.15940.4301.2011.2421.2841.3251.3671.4081.4501.4921.5341.57641.3401.6181.6611.7031.7451.7881.8301.8731.9161.9582.00142.4502.0442.0872.1302.1742.2172.2602.3042.3472.3912.43543.0602.4782.5222.5662.6102.6542.6982.7432.7872.8312.87649.8702.9202.9653.0103.0543.0993.1443.1893.2343.2793.32544.5803.3703.4153.4913.5063.5523.5973.6433.6893.7353.78145.3903.8273.8733.9193.9654.0124.0584.1054.1514.1984.24446.01004.2914.3384.3854.4324.4794.5294.5734.6214.6684.71546.8*表中热电势单位mVT型K型热电偶放大电路•镍铬-镍硅P70图2.15123456ABCD654321DCBATitleNumberRevisionSizeBDate:4-Jul-2011SheetofFile:D:\课程\传感器技术A\实训指导10医电\PT1000.ddbDrawnBy:1516A3R31KR1510R2120KGNDGNDUoC14.7uRP13K12J1热电偶GND放大倍数计算？***参考同相运放Av计算查阅铜-康铜热电偶分度表求出加热端温度t。下表是做热电偶测温实验所得数据。（差动放大器增益为100倍）室温（℃）电压表读数(V)26℃0.120VA电压表