第五章電壓測量

1、第第5 5章章 電壓測量電壓測量5.1 概述5.2 電壓標準5.3 交流電壓的測量5.4 直流電壓的數(shù)字化測量及A/D轉(zhuǎn)換原理5.5 電流、電壓、阻抗變換技術(shù)及數(shù)字多用表5.6 數(shù)字電壓表測量的不確定度及 自動校準、自動量程技術(shù)5.7 電壓測量的干擾及抑制技術(shù)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高高頻頻電電壓壓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熱熱端端T T2IVR Ru u( (t t) )冷冷端端T T0 0加加熱熱絲絲熱熱端端T T熱熱偶偶M Mu uA A連連接接導(dǎo)導(dǎo)線線I IR Ru u( (t t) )冷冷端端T T0 0加加熱熱絲絲熱熱端端T T測測量量熱熱偶偶電電流流表表平平衡衡熱熱偶偶+ +- -V Vo oE Ex xE Ef fV Vi i熱熱端端T T連連接接導(dǎo)導(dǎo)線線差差分分放放大大器器22

4、12(.)kVkVV峰峰值值檢檢波波表表頭頭( (讀讀數(shù)數(shù)= =) )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平平均均值值檢檢波波表表頭頭( (讀讀數(shù)數(shù)= =) )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 峰峰值值檢檢波波器器步步進進分分壓壓器器直直流流放放大大器器uA步步進進分分壓壓器器斬斬波波穩(wěn)穩(wěn)零零式式放放大大器器uA(a)峰峰值值檢檢波波器器( (探探頭頭內(nèi)內(nèi)) )(b)步步進進分分壓壓器器寬寬帶

6、帶交交流流放放大大器器均均值值檢檢波波器器uA1210lgPdBP2111VPR2222VPR1220lgVdBV10lgwmxP dBP mW20.7751600mW 20lg0.775xVVV VP dBxxmP mWP dB xxVV VV dB輸輸入入衰衰減減器器寬寬帶帶交交流流放放大大器器均均值值檢檢波波器器uAd dB B“輸輸入入電電平平”選選擇擇標標準準電電平平震震蕩蕩器器“輸輸入入阻阻抗抗”選選擇擇“電電平平校校準準”dB103.162120lg1010dB 2 0 lg7 00 .7 7 5xVd B 0 .7 7 52 0 lg7 0|ooVVxVd BV0 10lgWm

7、ViZP dBP dBZ輸輸入入電電路路中中頻頻放放大大器器均均值值檢檢波波器器dB混混頻頻器器2 2fZ2(固固定定)f2(固固定定)帶帶通通濾濾波波器器窄窄帶帶濾濾波波器器混混頻頻器器1 1f1(可可調(diào)調(diào))fZ1(固固定定)fx(第第一一本本振振)(第第二二本本振振)010lgiZZ輸輸入入電電路路A A/ /D D轉(zhuǎn)轉(zhuǎn)換換器器數(shù)數(shù)字字顯顯示示器器邏邏輯輯控控制制電電路路時時鐘鐘發(fā)發(fā)生生器器模模擬擬部部分分數(shù)數(shù)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轉(zhuǎn)轉(zhuǎn)換換器器Vx+-比比較較器器C CL LK KSTARTA/D轉(zhuǎn)轉(zhuǎn)換換結(jié)結(jié)果果2-12-nMSBLSBVrN N2xrnNVV241101)108.1252xVVV（斜斜波波電電壓壓發(fā)發(fā)生生器器QQSETCLRSR&000時時鐘鐘計計數(shù)數(shù)器器主主門門VrVx+-+-門門控控信信號號輸輸入入比比較較器器接接地地比比較較器器a計計

9、數(shù)數(shù)輸輸入入0VxVx、V Vr r門門控控信信號號計計數(shù)數(shù)輸輸入入NV Vr rt1bT0T0 xVkTkT NrVkRCrVkRC0 xVkTkT N0rxVVT NRC0rVTR CxVN010000100 Hz100fkms00512351.23ms100kHzNTNTf10V/100ms 51.23ms=5.123VxVkT主主門門計計數(shù)數(shù)器器邏邏輯輯控控制制電電路路數(shù)數(shù)字字輸輸出出時時鐘鐘S1S2CRVx-VrVr積積分分器器比比較較器器-+-+S S1 1 S S2 2Vot0t1復(fù)復(fù)零零t2t3VoVomT1T2N1N2t積積分分波波形形計計數(shù)數(shù)器器輸輸入入a.b.清清零零T0

10、f0T011T02111tomxxtTVV dtVRCRC 10TxxVV dt1TRC32210()tomromrtTVV dtVVRCRC21xrTVVT221xrNVVeNN121xxrNNVVVe1rVeN21111()tsmomxsmxtTTVVvdtVvRCRCRC 主主門門高高位位計計數(shù)數(shù)器器A A邏邏輯輯控控制制電電路路數(shù)數(shù)字字輸輸出出時時鐘鐘S1S2CRVx-Vr積積分分器器比比較較器器-+-+S S1 1S S2 2Vot0t1復(fù)復(fù)零零t2t31VoVomT1T2N1N2t積積分分波波形形計計數(shù)數(shù)器器輸輸入入a.b.清清零零低低位位計計數(shù)數(shù)器器B B主主門門清清零零-+AB

11、R1R2R3t32T3N3VtVr/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( (可可調(diào)調(diào)) )A A/ /D DR Rx xIr-+A Am mp p恒恒流流源源( (可可調(diào)調(diào)) )A A/ /D D-+A Am mp pIrVrR1Rx精精密密電電阻阻VoVr取取樣樣電電阻阻1

12、xorRVVR 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理理想想特特性

13、性轉(zhuǎn)轉(zhuǎn)換換誤誤差差影影響響下下的的特特性性滿滿度度誤誤差差影影響響下下的的特特性性（平平行行于于理理想想特特性性）讀讀數(shù)數(shù)誤誤差差和和滿滿度度誤誤差差共共同同影影響響下下的的實實際際轉(zhuǎn)轉(zhuǎn)換換特特性性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 102

14、 101.2 101000 100.2 UosIB-+RC積積分分器器ViVoUosVot實實際際積積分分器器輸輸出出理理想想積積分分器器輸輸出出12LSBUos+-AViVo=A(Vi+Uos)Uos+-AViVo=AVi+Uos+-+-K1K2K3+-C0A1+AosU1oososAVUUA11oiososiosiosAAVA VUUAVUAVUAA0osNkU000A/D轉(zhuǎn)轉(zhuǎn)換換器器VxVr0VNxNrN0衰衰減減/ /放放大大器器轉(zhuǎn)轉(zhuǎn)換換系系數(shù)數(shù)k k總總漂漂移移U Uo os sS1S2S3()rrosNk VU()xxosNk VU00()()xxososxrrososrNNk V

15、UkUVNNk VUkUV00 xxrrNNVVNN( %)xmVVV %mxxVVVV VxVm0%mxVV %0199.9mV180mV1.999V1.8V19.99V18V199.9V180V1200V干干擾擾信信號號un被被測測電電壓壓VxHLDVM被被測測電電壓壓VxHLDVM干干擾擾信信號號ucmHLDVMHLDVMunun外外部部感感應(yīng)應(yīng)信信號號Vx存存在在干干擾擾的的信信號號源源+Eucmsin()nnnuUt1101()TomxnxnTVVudtVuRCRC101111111111sin()cos()cos22sinsin222sinsin()Tnmnnnnnnnnnnnnn

16、nuUtdtTUTTUTTTU 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/

17、 /1 10 0倍倍頻頻程程1(0,1,2,)nTkTk1(0,1,2,)nTnnT0Vxr1r2rcmUcmRsHLGZiI1I2DVM( (機機殼殼) )B112 21212212212()()(,)(,)cnHLHLscmcmscmsicmcmiscmcmcmcmUUUUI rRI rUUrRrrRrZrrUrZr r R rrrUrr r 12,r r,scmR riZcmU()20lgcmcnUCMR dBUcnUcmU112 22 2()cnHLHLsUUUUI rRI rI r 12siRrZr12IIVxr1r2rcmUcmRsHLGZiI1I2DVM( (機機殼殼) )BZ2輸輸入入