第五章电压测量

1、第第5 5章章 电压测量电压测量5.1 概述5.2 电压标准5.3 交流电压的测量5.4 直流电压的数字化测量及A/D转换原理5.5 电流、电压、阻抗变换技术及数字多用表5.6 数字电压表测量的不确定度及 自动校准、自动量程技术5.7 电压测量的干扰及抑制技术211( )NkVukN23204639.94(20)0.929(20)0.0092(20)0.00006(20) 10( )tEEttttV+-V1V2V3V4R1R2R3R4R5R6(R1=R2=R3=R4)1234V +V +V +VV=4561oRVVR312412340VVVVVVVVRRRR12344VVVVVV561oRVV

2、R2JefVK VhnJfVnK高高频频电电压压V0V1RFDCDCRFR RGR RR RR RT TR RT TC CC CVRF2201222222RFTTTVVVRRR22014RFVVV1RCt tu(t)Vp0UmTU01( )TUu t dtT01( )TUu t dtT20.637ppUVV2VTR20( )Tu tdtR201( )TVu t dtT10.7072ppVVVppVKV峰值有效值21.41/2pppVKVFVKV有效值平均值(1/2)1.112/2 2pFpVKV（）TTDVpCRLu(t)CDRLu(t)VpabVPu(t)tcminmax(),sdLRr C

3、TR CTI0u(t)D1D2D3D4CCu(t)D1D2I001( )( )22Todmdmu tu tIdtTrrrroI( )u t201( )TVu t dtT2( )ut0TAu(t)Vrms冷冷端端T T0 0热热端端T T2IVR Ru u( (t t) )冷冷端端T T0 0加加热热丝丝热热端端T T热热偶偶M Mu uA A连连接接导导线线I IR Ru u( (t t) )冷冷端端T T0 0加加热热丝丝热热端端T T测测量量热热偶偶电电流流表表平平衡衡热热偶偶+ +- -V Vo oE Ex xE Ef fV Vi i热热端端T T连连接接导导线线差差分分放放大大器器22

4、12(.)kVkVV峰峰值值检检波波表表头头( (读读数数= =) )Vpu(t)V22pVV2ppVV任意pV任意2pppVVKK任意任意任意任意2,pppppppppVVK VKVkkKKKKK任意任意任意任意任意任意任意21 .4 121 .4 1ppKKp（ 任 意 波 ） 峰 值 V（ 任 意 波 ） 有 效 值 V221222ppppKKKKV平平均均值值检检波波表表头头( (读读数数= =) )u(t)V0 .91 .1 122FVVVKV0.9VV任意V任意0.9FFVKVK任意任意任意任意V,FFFFVVKVKVKkK任意任意任意任意任意0.91.11FFFFKKkKK任意任

5、意任意0.90.9FK（任意波）均值V（任意波）有效值V0.910.91.1110.90.9FFFFFKKKKK1 1.4100%29%1.4 FVKV方波VVVVFK方波1 0.9100%11%0.9411( )(sinsin3sin5.)35pu tVtttVP0T=1uStu(t)224111.352ppVVV1pPVKV方波22224111110.9735792ppVV100%3%VV 峰峰值值检检波波器器步步进进分分压压器器直直流流放放大大器器uA步步进进分分压压器器斩斩波波稳稳零零式式放放大大器器uA(a)峰峰值值检检波波器器( (探探头头内内) )(b)步步进进分分压压器器宽宽带

6、带交交流流放放大大器器均均值值检检波波器器uA1210lgPdBP2111VPR2222VPR1220lgVdBV10lgwmxP dBP mW20.7751600mW 20lg0.775xVVV VP dBxxmP mWP dB xxVV VV dB输输入入衰衰减减器器宽宽带带交交流流放放大大器器均均值值检检波波器器uAd dB B“输输入入电电平平”选选择择标标准准电电平平震震荡荡器器“输输入入阻阻抗抗”选选择择“电电平平校校准准”dB103.162120lg1010dB 2 0 lg7 00 .7 7 5xVd B 0 .7 7 52 0 lg7 0|ooVVxVd BV0 10lgWm

7、ViZP dBP dBZ输输入入电电路路中中频频放放大大器器均均值值检检波波器器dB混混频频器器2 2fZ2(固固定定)f2(固固定定)带带通通滤滤波波器器窄窄带带滤滤波波器器混混频频器器1 1f1(可可调调)fZ1(固固定定)fx(第第一一本本振振)(第第二二本本振振)010lgiZZ输输入入电电路路A A/ /D D转转换换器器数数字字显显示示器器逻逻辑辑控控制制电电路路时时钟钟发发生生器器模模拟拟部部分分数数字字部部分分Vx1420.1mV100%0.05%200mV1100%0.05%2000( %)xmVVV ( %)mxxVVVV %xV%mV%mV( %)xVVn 字V%mV%(

8、0.01%0.005%)mxVV 111112481625V+2.5V+1.25V+0.625V+=10VrrrrrrnVVVVVV52.51.250.6259.375rVVVVVV10.6252逐逐次次逼逼近近移移位位寄寄存存器器( (S SA AR R) )D/A转转换换器器Vx+-比比较较器器C CL LK KSTARTA/D转转换换结结果果2-12-nMSBLSBVrN N2xrnNVV241101)108.1252xVVV（斜斜波波电电压压发发生生器器QQSETCLRSR&000时时钟钟计计数数器器主主门门VrVx+-+-门门控控信信号号输输入入比比较较器器接接地地比比较较器

9、器a计计数数输输入入0VxVx、V Vr r门门控控信信号号计计数数输输入入NV Vr rt1bT0T0 xVkTkT NrVkRCrVkRC0 xVkTkT N0rxVVT NRC0rVTR CxVN010000100 Hz100fkms00512351.23ms100kHzNTNTf10V/100ms 51.23ms=5.123VxVkT主主门门计计数数器器逻逻辑辑控控制制电电路路数数字字输输出出时时钟钟S1S2CRVx-VrVr积积分分器器比比较较器器-+-+S S1 1 S S2 2Vot0t1复复零零t2t3VoVomT1T2N1N2t积积分分波波形形计计数数器器输输入入a.b.清清

10、零零T0f0T011T02111tomxxtTVV dtVRCRC 10TxxVV dt1TRC32210()tomromrtTVV dtVVRCRC21xrTVVT221xrNVVeNN121xxrNNVVVe1rVeN21111()tsmomxsmxtTTVVvdtVvRCRCRC 主主门门高高位位计计数数器器A A逻逻辑辑控控制制电电路路数数字字输输出出时时钟钟S1S2CRVx-Vr积积分分器器比比较较器器-+-+S S1 1S S2 2Vot0t1复复零零t2t31VoVomT1T2N1N2t积积分分波波形形计计数数器器输输入入a.b.清清零零低低位位计计数数器器B B主主门门清清零零

11、-+ABR1R2R3t32T3N3VtVr/10nVtN N2 2N3f0T0T0T0231110nxrTTTVVRCRC11 022033 0,TN TTN T TN T2311()10rxnVVNNeNN1rVeN23110nNNNIx9009090.90.1(200mV)200A A(200mV)2mA A(200mV)20mA A(200mV)200mA A(200mV)2A A恒恒流流源源( (可可调调) )A A/ /D DR Rx xIr-+A Am mp p恒恒流流源源( (可可调调) )A A/ /D D-+A Am mp pIrVrR1Rx精精密密电电阻阻VoVr取取样样电

12、电阻阻1xorRVVR 1oxrVRRV A AC C/ /D DC CI I/ /V VZ Z/ /V VD DV VM MC CP PU UD DC CA AC CI IZ Z12,xlxlRRRR34,linlinRRRRR Rx xIrIrVxDMMRl1Rl2R Rx xIrIrVxDMMRl1Rl2Rl3Rl4( %)xmVVV( %)xVVn 字%xV%mV1234()xxNk k k k VkV1234kk k k k1234kk k k k31241234%kkkkkkkkkk12341121231234ooooVVVVVkk kk k kk k k k%mVVVxN0理理想

13、想特特性性转转换换误误差差影影响响下下的的特特性性满满度度误误差差影影响响下下的的特特性性（平平行行于于理理想想特特性性）读读数数误误差差和和满满度度误误差差共共同同影影响响下下的的实实际际转转换换特特性性V HLI0DVMRsVxRiiixxxHLxsissRxxxsiiRVVVVVRRRRVVVRRR 000()xHLxsxxsIxxxxVVVI RVVI RVVVV( %)/xmVV0.015100%100%0.3%5.00 xxxVV 0.025100%100%0.17%15.00 xxxVV 001iRIsixIRRV 936611 102 103 101000 102 935611

14、 102 101.2 101000 100.2 UosIB-+RC积积分分器器ViVoUosVot实实际际积积分分器器输输出出理理想想积积分分器器输输出出12LSBUos+-AViVo=A(Vi+Uos)Uos+-AViVo=AVi+Uos+-+-K1K2K3+-C0A1+AosU1oososAVUUA11oiososiosiosAAVA VUUAVUAVUAA0osNkU000A/D转转换换器器VxVr0VNxNrN0衰衰减减/ /放放大大器器转转换换系系数数k k总总漂漂移移U Uo os sS1S2S3()rrosNk VU()xxosNk VU00()()xxososxrrososrN

15、Nk VUkUVNNk VUkUV00 xxrrNNVVNN( %)xmVVV %mxxVVVV VxVm0%mxVV %0199.9mV180mV1.999V1.8V19.99V18V199.9V180V1200V干干扰扰信信号号un被被测测电电压压VxHLDVM被被测测电电压压VxHLDVM干干扰扰信信号号ucmHLDVMHLDVMunun外外部部感感应应信信号号Vx存存在在干干扰扰的的信信号号源源+Eucmsin()nnnuUt1101()TomxnxnTVVudtVuRCRC101111111111sin()cos()cos22sinsin222sinsin()Tnmnnnnnnnnn

16、nnnnnuUtdtTUTTUTTTU TTTTTTT 由nu1sinnTT1(0,1,2,)nTkTk1sinnTT1(0,1,2,)nTnnTnunu1max1sinnnnnU TTuTTmax()20lgnnUNMR dBu11()20lgsinnnTTNMR dBTT5 50 06 60 01 10 00 02 20 00 05 50 00 00 02 20 04 40 0N NM MR R( (d dB B) )f fn n= =1 1/ /T Tn n( (H Hz z) )T T1 1= =1 10 0m ms sT T1 1= =1 10 00 0m ms s2 20 0d dB B/ /1 10 0倍倍频频程程1(0,1,2,)nTkTk1(0,1,2,)nTnnT0Vxr1r2rcmUcmRsHLGZiI1I2DVM( (机机壳壳) )B112 21212212212()()(,)(,)cnHLHLscmcmscmsicmcmiscmcmcmcmUUUUI rRI rUUrRrrRrZrrUrZr r R rrrUrr r 12,r r,scmR riZcmU()20lgcmcnUCMR dBUcnUcmU112 22 2()cnHLHLsUUUUI rRI rI r 12siRrZr12IIVxr1r2rcmUcmRsHLGZiI1I2DVM( (机机