传感器的信号处理

1、第一节 信号处理概述 1、信号的引出 2、补偿电路 3、放大电路 第二节 传感器信号的引出 1、电荷放大器 2、射极跟随器 3、电桥放大器 第三节 信号补偿电路 1、非线性补偿 2、温度补偿 第四节 精密放大电路 1、测量放大器 2、集成测量放大器 3、隔离放大器 第 九 章传 感 器 的 信 号 处 理SENS R1信号的引出补偿电路放大电路第一节 信号处理概述Department of Electronic Science and Engineering, Nanjing University Principles and Applications of Novel SensorsSENS

2、 RPrinciples and Applications of Novel2引出传感器的信号，通常需要考虑传感器输出信号的类型、传感器的内阻等因素。一、信号的引出 传感器信号读出电路外界物理量电压（电流）电荷电阻电容电感电势电压电流新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 3传感器外界物理量电压（电流）电荷电阻电容电感电势电压电流信号读出电路对信号读出电路的要求抗干扰能力强将电荷信号转换为常

3、规后续电路可以处理的电压或电流信号将传感器的高内阻转换为低输出阻抗RsRLVsVLRs多大导致VL下降新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 4Rs多大导致VL下降最常见的射极跟随器电路是晶体管共集电极电路，有时为了进一步提高电路的输入阻抗，可以采用自举电路与共集电极电路并用或者采用达林顿电路与共集电极电路并用的形式。也有用运算放大器构成射极跟随器的。射极跟随器RsRLVsVLrinrout

4、新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 5举例电荷型传感器传感器的等效CsQ+-等效为电荷源Q = CsesCsei+-等效为电压源es = Q /Cs这些有源电荷器件都具有高内阻、小功率的特点新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineeri

5、ng, Nanjing University 6CcQCsCiCfGcGiGfVo+-电荷放大器利用电容反馈原理将输入电荷量转换为电压信号，使放大器的输出电压正比于传感器的电荷信号。是一种具有高增益的运算放大器，其主要特点是输出阻抗低，因此，可以将传感器的高输出阻抗转换为低输出阻抗，起到阻抗匹配的作用。 传感器信号引出电荷放大器新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 7二、补偿电路 在传感器

6、的应用中，总是希望传感器的特性不受环境温度的影响，为此，需要采用一定的办法，将环境温度对传感器的影响程度加以抑制，将其限定在一定的范围以内。我们总希望传感器的输出量与被测物理量是线性关系，从而保证在整个测量范围内灵敏度比较均匀，便于测量结果的处理。然而，实际的传感器往往是非线性的输出特性，它们输出的电信号与被测物理量之间的关系是非线性的。为此，必要的时候，需要对传感器的信号加以线性化。 线性补偿温度补偿新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engine

7、ering, Nanjing University 8三、放大电路 传感器输出的信号一般在幅值上不能满足后续器件的满值要求，因此，测量电路通常都有信号放大级。把传感器输出的微弱信号放大到足以推动指示器、记录仪或各种控制机构。信号放大的功能把传感器输出的微弱信号放大到与模数转换器件输入电压范围相吻合的量。具有很高的共模抑制比以及高增益、低噪声和高输入阻抗，满足这种要求的放大电路习惯上被称作测量放大器（或精密放大器、仪表放大器）。传感器信号放大的电路要求新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Elect

8、ronic Science and Engineering, Nanjing University 9电荷放大器射极跟随器电桥放大器第二节 传感器信号的引出Department of Electronic Science and Engineering, Nanjing University Principles and Applications of Novel SensorsSENS RPrinciples and Applications of Novel10理想的电荷放大器电荷放大器工作原理 一、电荷放大器 QCsCfVo+-反馈电容传感器固有电容Vo= - Q/Cf新型传感器原理及应

9、用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 11电荷放大器的原理电路 CcQCsCiCfGcGiGfVo+-反馈电容传感器固有电容输入电缆等效电容输入电缆漏电导放大器输入电容放大器输入电导反馈电导 新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanji

10、ng University 12作为电压源的等效电路CceiCsCiCfGcGiGfVo+-VFAdei=Q/Cs(es VF)jCs VF (Gc + Gi ) + j(Cc + Ci)(VF Vo)(Gf + jCf ) 新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 13(es VF)jCs = VF (Gc + Gi ) + j(Cc + Ci)+ (VF Vo)(Gf + jCf ) 在通

11、常情况下，Gc、Gi和Gf均很小 CfGfVo+-VFAdVo= - AdVFVF = - Vo /Ad新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 14电荷放大器误差特性 定义测量误差:=理想电荷放大器输出 - 实际电荷放大器输出理想电荷放大器输出忽略不计新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Ele

12、ctronic Science and Engineering, Nanjing University 15电荷放大器频率特性如果Ad足够大幅频特性 相频特性 新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 16VoMax= Q/Cf低频截止频率L(fL)令时间常数= Cf /Gf新型传感器原理及应用Principles and Applications of Novel SensorsDepart

13、ment of Electronic Science and Engineering, Nanjing University 17时间常数= Cf /Gf为了降低f L，必须增大反馈回路时间常数，需要大的C f及R f (= 1/ G f )。举 例2、G f =10-12（-1）、A d =104、C f =10000pF ，则f L为0.1610-4Hz 1、G f =10-10（-1）、A d =104、C f =100pF，则f L为0.16HzCceiCsCiCfGcGiGfVo+-VFAdei=Q/Cs新型传感器原理及应用Principles and Applications of

14、 Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 18CceiCsCiCfGcGiGfVo+-VFAdei=Q/Cs高频截止频率H(fH)若输入电缆很长，将变得很大若C c100pF/m，则100m电缆为104pF、1000m电缆为105pF同时，电缆的R c亦随之增大，约几十/100m相对而言，C i 、G i可以忽略新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Sc

15、ience and Engineering, Nanjing University 19电荷放大器噪声及漂移特性 噪声来源：1、较长的输入电缆 2、输入级元器件的电噪声零漂因素：1、输入级差动晶体管的失调电压 2、输入级差动晶体管的失调电流如果输入级用场效应管，则输入偏置电流很小，放大器的失调电压成为引起的主要原因。 新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 20噪声Vn产生的输出噪声电压V1

16、： Vn j(Cc+Cs)+Gi+Gc = (V1-Vn)(jCf+Gf) 结论：Cs和Cc越小、Cf越大，V1越小。若输入电缆长（Cc大），反馈电容Cf小，则噪声电压Vn的增益大，在输出端引起的噪声电压V1也就大。 CcQCsCiCfGcGiGfV1+-等效输入噪声电压等效输入失调电压UnUoffset新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 21零漂Voffset产生的输出漂移电压V2 ：

17、 Voffset j(Cc+Cs)+Gi+Gc = (V2-Vn)(jCf+Gf) 结论：减小Gi、Gc，同时增大Gf，可以减小电荷放大器的 零漂。不过，减小Rf 会导致下限截止频率提高。零漂变化比较缓慢，可视= 0 因此，减小零点漂移与降低下限截止频率是互相矛盾的，必须根据具体使用情况选择适当的Rf值。 新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 22C1VoVcC2T1R1R2RsReRLV

18、s二、射极跟随器 射极跟随器具有高输入阻抗、低输出阻抗的特点，从而能够更好地拾取传感器输出信号，射极跟随器可以作为前置电路，对传感器进行阻抗匹配。 传感器内阻耦合电容偏置电阻稳定晶体管工作点共集电极射极跟随电路 新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 23电路的交流等效电路电流放大系数晶体管输入电阻r1= RBE +（1+）Re / RL跟随器输入阻抗Rin = R1 / R2 / r1跟随

19、器输入阻抗：Rinr1VoT1R1R2RsReRLVsRBE新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 24电路的交流等效电路跟随器输出阻抗： Ra与RBE串联，再与Re并联VoT1R1R2RsReRLVsRBERaRout电流放大系数输出阻抗 Ra = R1 / R2 / Rs 新型传感器原理及应用Principles and Applications of Novel SensorsDepa

20、rtment of Electronic Science and Engineering, Nanjing University 25自举式射极跟随电路 电路的输入阻抗VcVoT1R1R2RsReRLVsC1C2C3R3RBE自举电阻新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 26达林顿电路 SU30MKKVoT1R1R2RsRe2RLVsC1C2Re1T2Vc新型传感器原理及应用Princip

21、les and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 27新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University -+UoutUin+-集成放大器构成的射级跟随器28三、电桥放大器 IL电桥输出电压： 条件：负载电阻 RL 负载电流 IL 0 RiRf

22、-+UoutRbUin+-ER1R4R3R2RLUo新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 29电桥输出电压： 条件：负载电阻 RL 负载电流 IL 0 ILRiRf-+UoutRbUin+-ER1R4R3R2RLUo成立吗？新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Scien

23、ce and Engineering, Nanjing University 30RinIinRL (Rin) 的条件不满足，所以，此式不成立所以，不能由此得出电路的输出RiRf-+UoutRbUin+-ER1R4R3R2RLUoIL新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 31半桥式电桥放大器设外界物理量使传感器电阻Rs由R变化到R(1+) 若=R / R R 1 RRsRRRf+-RfVR

24、Vo新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 36参考源浮地式电桥放大器RRsRRRf+-RpVRVoR1VnVp新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 37VnRRsRRRf+-VRVoR

25、pVp同相输入式电桥放大器当1时：RS = R（1+）新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 38非线性补偿温度补偿第三节 信号补偿电路Department of Electronic Science and Engineering, Nanjing University Principles and Applications of Novel SensorsSENS RPrinciples

26、 and Applications of Novel39传感器放大器线性化器一、非线性补偿 开环补偿法 V1 = f(x) V2 =a + KV1 Vo= b + Sx V2 =a + K f(x) xV1V2Vo新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 40传感器放大器线性化器-xV1VFVVo闭环补偿法 Vo = SxV1 = f(x)Vo = KVV = V1 VFV = f(x) VF

27、新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 41VC = KCx 分段补偿法 xiVS = f (x) VC = KCxi VS = f (xi) 传感器非线性化器xf (x)K(x)VSVC显然，这是一个难以实现的运算新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science an

28、d Engineering, Nanjing University 42VxV1V2V3Vnx1x2x3xn折线方程为VSi = Vi + Ki (x xi)VS = f (x) 用折线近似曲线新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 43V1V2V3VnVxx1x2x3xnVSi = Vi + Ki (x xi)VC = KCx VS = f (x) biVci = (Vi bi)+ KC

29、(x xi) Vi bi消除Vi Vci = VSi Ki (x xi) bi + KC (x xi)= (VSi bi )+ (KC Ki )(x xi) 新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 44Vci = VSi bi + (KC Ki )(x xi) 令K = KC KiVSi = Vi + Ki (x xi)+新型传感器原理及应用Principles and Applicatio

30、ns of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 45差动补偿法 设传感器两路基本输出为：y1 (x) = a0 + a1x + a2x2 + +anx2ny2 (-x) = a0 + a1(-x) + a2(-x)2 + +a2n(-x)2n互为差动两路信号相减y (x) = y1 (x) - y2 (-x) = 2(a1x + a3x3 + a5x5 +a2n-1x2n-1）非线性误差非线性误差新型传感器原理及应用Principles and Application

31、s of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 46举 例CC1C2新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 47二、温度补偿 零点温度补偿减法运算设有传感器输出：随温度变化的零点漂移传感器补偿环节-xTV(T)=fb(T)y(x)=b0+fb(T)+K1x+ K2x2

32、+-+y(x)=b0+K1x+ K2x2+新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 48举 例可用AD590代替 传感器补偿环节-xTV(T)=fb(T)y(x)=b0+fb(T)+K1x+ K2x2+-+y(x)=b0+K1x+ K2x2+新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electroni

33、c Science and Engineering, Nanjing University 49零点温度补偿乘法运算设有传感器输出：随温度变化的灵敏度漂移乘法器TVT = 1 / fb(T)传感器补偿环节x新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 50举 例霍尔电势VH = KHIBKH = KH0 1+(T T0 )霍尔元件总的灵敏度K（= KHI）如果I = I0 / 1+(T T0 )，

34、 则K为常数信号放大一定的倍率K(T)，则VH = K(T) KHIB为常数K(T) = K0 / 1+(T T0 )新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University 51测量放大器集成测量放大器隔离放大器第三节 精密放大电路Department of Electronic Science and Engineering, Nanjing University Principles and Appli

35、cations of Novel SensorsSENS RPrinciples and Applications of Novel52第四节 精密放大电路 一、测量放大器 工作原理新型传感器原理及应用Principles and Applications of Novel SensorsDepartment of Electronic Science and Engineering, Nanjing University RGVoV1V2R1R2R3R4R6R5+-+-+-53RGR1R2R3R4R6R5+-+-+-I1I2IGV2 = V5 V4V3V5V6V1V2VoV1 = V4+新型传感器原理及应用Principles an