简易模拟集成万用表

20132014

学年

第2

学期《

模拟电子技术课程计报告题专

目业

简模集万表电工及自化班

级12电工及自化1）班word档可自由复制编辑

课题名指导教（职称）

任务书简易模集成万用表江春红执行时

2013~2014学年

第

学期

第14

周学生姓张羽晨徐晶晶何永康

学号120914107112091410601209141018

承担任设计直电压表并进仿真设计直电流表并进仿真设计交电压表并进仿真丁

伟

1209141008

设计交电流表并进仿真孙学峰邓忠建

12091410421209141007

设计欧表并进行仿整理测数据、整理完成课设计报告设计目

1、通过对集成万表的的计了解由成运组成的电压、电等电路，学在实际路中应用；2、一步熟集成运放的性应用1、流电压量范围0~25V）±5%；2、流电流量范围0~20mA）±5%3交流电测量范围及率范围有效值0~10V）±5%，50Hz~1000Hz设计要4、流电流量范围及频范围：效值（0~20mA）±5%；5、姆表测（Ω；6、用模拟成电路，器自选。word档可自由复制编辑

绪论万用电表简称万用表或三用表在国家标准中称作复用表万用电表实际上是一种可以进行多种项目测量的便携式仪器主要用于测量电压电流、电阻另外可粗略判断电容器、晶体三极管及二极管、集成电路等元器件的性能好坏。在测量中万用电表的接入因不影响被测电路原来的工作状态这就要求电压表应具有无穷大的输入电阻电流表的内阻应为零但实际上万用电表表头的可动线圈总有一定的电阻，例如100uA的表，其内阻约为1K，用它进行测量时将会影响被测量，会引起误差此外交流电表中整流二极管的压降和非线性特性也会产生误差如果在万用电表中使用运算放大器就能大大降低这些误差提高测量精度在欧姆表中采用运算放大器，不仅能得到线性刻度，还能实现自动调零。运算放大器电路性能的优劣直接影响到万用表的性能。本文从运算放大器电路的结构、原理出发，在阐述运算放大器电路结构、原理的基础上用运算放大器设计电路实现万用表的电路设计。通过仿真与实际电路性能指标的测试、分析、比较,总结出各种电路方案的特点,为电路设计初学者提供一定的参考借鉴。word档可自由复制编辑

目录任务书·························································································································绪论····························································································································3第一章题目要求与方案论证··························································································51.1简模拟集成万用表···························································································1.1.1目要求···································································································1.1.2方论证·································································································1.2课设计目的·····································································································第二章电子线路设计····································································································62.1万表工作原理·································································································62.1.1直流电压原理··························································································2.1.2直流电流原理··························································································2.1.3交流电压原理··························································································2.1.4交流电流原理··························································································2.1.5电阻原理································································································92.2运制万用表的电路设·················································································102.2.1图：·····································································································102.2.2流电压的电路图：···················································································122.2.3流电流的电路图：···················································································122.2.4流电压的电路图：···················································································132.2.5流电流的电路图：···················································································132.2.6姆表电路图：·························································································14第三章结果与分析······································································································153.1用用测量各种电流、电压和电·····································································153.1.1直电流的测量······················································································153.1.2交电流的测量·······················································································153.1.3流电压的测量·························································································163.1.4交电压的测量·······················································································173.2测结及分析·································································································173.2.1流电压的测量结果及分析：·······································································173.2.2流电流的测量结果及分析：·······································································173.2.3流电压的测量结果及分析：·······································································183.2.4流电流的测量结果及分析：·······································································183.2.5姆表测量结果及分析：·············································································18总结···························································································································19参考文献·····················································································································19附录···························································································································19word档可自由复制编辑

第一章

题目要求与案论证1.1易模拟成万用表1.1.1题目要求1、直流电压测量范围0~25V）±5%；2、直流电流测量范围）±5%；3、交流电压测量范围及频率范围：有效值（）±5%，50Hz~1000Hz4、交流电流测量范围及频率范围：有效值（）±5%；5、欧姆表测程0~1KΩ5%；6、采用模拟集成电路，器件自选。1.1.2方案论证在测量中电表的接入应不影响被测电路的原工作状态这就要求电压表应具有无穷大的输入电阻流表的内阻应为零实际上用表表头的可动线圈总有一定的电阻。例如100μA的表头，其内阻约为1KΩ，用它进行测量时将影响被测量量，引起误差。此外交流电表中的整流二极管和非线性特性也会产生误差如果在万用表中使用运算放器，就能大大降低这些误差高测量精度在欧姆表中采用运算放大器不仅能得到线性刻度，还能实现自动调零。1.2程设计的1、通过对集成万用表的的设计、了解由集成运放组成的测电压、电流等电路，学会在实际电路中应用；2、进一步熟悉集成运放的线性应用。word档可自由复制编辑

第二章

电子线路设2.1用表工原理万用表的基本原理是利用一只灵敏的磁电式直流电流（微安表做表头当微小电流通过表头，就会有电流指示表头不能通过大电流，所以，必须在表头上并联与串联一些电阻进行分流或降压，从而测出电路中的电流、电压和电阻。下面分别介绍。2.1.1测直流电压原理图2-1为同相端输入高进度直流电压表电原理图为了减小表头参数对测量精度的影响，将表头至于运算放大器的反馈回路中，这时，流经表头的电流与表头的参数无关，只要改变R1一个电阻，就可以进行量程的切换。图表头电流I与被测电压Ui的关系为：I=Ui/R1应当指出图1适用于测量电路与运算放大器共地的有关电路此外当被测电压较高时，在运放的输入端应设置衰减器。word档可自由复制编辑

2.1.2测直流电流原理图2-2是浮地直流电流表的电原理图电流测量中地电流的测量是普遍存在的。例如若被测电流无接地点属于这种情况为此应把运算放大器的电源也对地浮动。按此种方式构成的电流表就可像常规电流表那样，串联在任何电流通路中测量电流。图表头电流I与被测电流I1间关系为：I=(1+R1/R3)I

1可见改变电阻比可调节流过电流表的电流以提高灵敏度该图被测电流回路无接地点，即所谓浮地电流时，则把运算放大器的电源也对地浮起来。word档可自由复制编辑

2.1.3测交流电压原理由运算放大器二极管整流桥和直流毫安表组成的交流电压表如图2-3所示被测交流电压Ui加到运算放大器的同相端，故有很高的输入阻抗，又因为负反馈能减小反馈回路中的非线性影响故把二极管桥路和表头至于运算放大器的反馈回路中减小二极管本身非线性的影响。图表头电流I与被测电压ui的关系为：I=Ui/R1word档可自由复制编辑

RR2.1.4测交流电流原理图4图2-4为浮地交流电流表头读数由被测交流电流的全波整流平均值决定，即RI)I22.1.5测电阻原理图2-5在此电路中，运算放大器改用单电源供电，北侧电阻跨在运算放大器的反馈回路中，同相端加基准电压U。REFword档可自由复制编辑

可见，电流I于被测电阻成正比，而且表头具有线性刻度，改变值，可改变欧姆表的量程。这种欧姆表能自动调零Rx=0是电路改成电压跟随器U＝U,故表头电OREF流为零，从而实现了自动调零。二极管D起保护作用，如果没有D，当Rx超量程时，特别是当→∞，运算放大器的输出电压将接近电源电压使表头过载有了D就可使输出钳位，防止表头过载。调整R2，可实现满量程调节。2.2运放制万用表的电设计2.2.1总图：如图，为设计的总电路图。word档可自由复制编辑

电路说明黑框以外部位是万用表的内部结构黑框以内是四种可能的待测元件四种功能的切换是以开关、S3、的控制完成的，其中在图示初始状态下，开关S1赋予控制键A，其余三个的控制键是B，这就能有四种组合方式，从而达到四种电表的测量功能。A1010

B0110

电表类型直流电流交流电压直流电压交流电流其中1示对应键在初始态下按下，0表示初态。黑框中以类似的方式快速切换，便于仿真的进行。word档可自由复制编辑

2.2.2直流电压的电路图：说明：5v为测直流电压2.2.3直流电流的电路图：说明：为待测直流电流word档可自由复制编辑

2.2.4交流电压的电路图：说明：5V为测流电压有效值2.2.5交流电流的电路图：说明：为待测交流电流峰值word档可自由复制编辑

2.2.6欧姆表电路图：说明：R6为测电阻，可制程word档可自由复制编辑

第三章3.1用万用测量各种电、电压电阻对所设计的各个电表进行仿真。3.1.1直流电流的测量

结果与分析3.1.2交流电流的测量word档可自由复制编辑

3.1.3直流电压的测量word档可自由复制编辑

3.1.4交流电压的测量3.2测量结及分析3.2.1直流电压的测量结果及分析：测量电压

绝对误差

相对误差输入电压

10.003V15.003V20.004V

0.040%0.030%0.020%0.020%3.2.2直流电流的测量结果及分析：测量电流

绝对误差

相对误差5mA

0.0600%输入电流

10mA15mA

0.0200%0.0067%word档可自由复制编辑

3.2.3交流电压的测量结果及分析：输入电压

tcos100cos100cos100

测量电压1.0400V4.0100V9.0200V

绝对误差0.0400V0.0100V0.0200V

相对误差4.00%2.50%2.20%3.2.4交流电流的测量结果及分析：

测量电流5.002mA

绝对误差0.002mA

相对误差0.040%输入电流

0.003mA

0.030%

0.003mA

0.020%3.2.5欧姆表测量结果及分析：输入电阻

ΩΩΩ

测量电阻303.5Ω601.8Ω902.2Ω

绝对误差3.5Ω1.8Ω2.2Ω

相对误差0.44%0.31%0.22%word档可自由复制编辑

总结万用表主要用于测量电压电流电阻另外可粗略判断电容器晶体三极管及二极管、集成电路等元器件的性能好坏文从运算放大器电路的结构、原理出发，在阐述运算放大器电路结构、原理的基础用运算放大器设计电路实现万用表的电路设计。通过仿真与实际电路性能指标的测试、分析、比较,结出各种电路方案的特点,为电路设计初学者提供一定的参考借鉴课题中万用电表的电性能测试要用标准电压电流表校正欧姆表用标准电阻校正。考虑实验要求不高，建议用数字式万用电表作为标准表。通过这次课程设计让我们懂得了理论与实际操作之间的差距我们体会到了模电理论知识的实用发现了自身知识的不足，积累了课程设计的经验。小组合作共同完成任务更让我们学会了合理分工与协调合作会到合作的重要性认识到每一个课题务都需要小组成员的共同努力与付出课程设计从各方面让我们组全体成员都学到了很多，十分感谢学校给我们学习的机会。由于我们第一次进行此类课程设计在完成课题时难免有很多纰漏所以在课程设计过程中江老师的多次认真辅导和热心帮助让我们有很大进步使我们受益匪浅最后我们全组成员对江老师的辛勤辅导表示由衷的感谢。参考文献[1]清华大学电子学教研组编童诗白华成英主编.《模拟电子技术基础第版北京；高等教育出版社，[2]王艳春主编子技术实验与Multisim真》合肥；合肥工业大学出版社，[3]衣承斌，刘京南编《模拟集成电子技术基础》南京；东南大学出版社，附录一、实验设备和主要元器件1、运算放器HA177412、毫伏表表头满偏电