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山东理工大学毕业设计（论文）题目：小电阻精确测量系统设计学院：电气与电子工程学院专业：电子信息工程学生姓名：丰坤指导教师：宋德杰毕业设计（论文）时间：二〇一〇年三月一日～六月二十日共十六周摘要I摘要在电路测试过程中常常会碰到由于忽略某些小电阻的影响引起实验数据与理论值之间存在较大误差的情况，从而影响测试效果。例如电感器、变压器中往往存在铜电阻，地铁铁轨的电阻，扬声器连接线的电阻，过电流保护电路中的检测电阻等。所以测量这些小电阻是电子测量中的一个常见课题。由于小电阻数值较小，一般的指针万用表无法测量出来；通常实验室里会用电桥进行测量，但电桥操作手续较烦，又不能直接读出被测电阻阻值。鉴于此，我们采用了MSP430F149单片机作为控制核心，利用单片机的优势设计了该测量系统。该测量系统可直接从LED数码管上读出所测得的电阻值，测量范围从几mΩ到1Ω之间，同时可以把测试的数据进行储存，然后经串行口送入上位机，通过上位机的强大功能，可以对所测得的数据进行分析、处理。该测试仪的测量精度高达±0.05%，并采用四端测量法，电阻值不受引线长短及接触电阻的影响。不仅测量简便，读数直观，且测量精度、分辨率也高于一般电桥。可用于实验室、研究所，尤其适用于工作现场。关键词:四端测量法，小电阻，恒流源，MSP430系列单片机AbstractIIAbstractInthecircuitthetestingprocessoftenencounteredlittleresistanceastheimpactofneglectcausedbysomeexperimentaldatawithlargeerrorbetweenthetheoreticalvalue,andtherebyaffectthetestingresults.Forexample,inductors,transformers,thereisoftencopperresistance,theresistanceoftheMTRtracks,thespeakercable'sresistance,over-currentprotectioncircuitinthedetectionofresistanceandsoon.Therefore,measuringthesmallresistanceisacommonelectronicmeasurementtopic.Asthelowresistancevaluesmallerpointermultimetertomeasurethegeneralout;usuallywillpowerthelaboratorytomeasurethebridge,butbridgeovertroubleoperatingprocedures,cannotdirectlyreadthemeasuredresistances.Inviewofthis,weuseaMSP430F149microcontrollerasthecontrol,usingoftheadvantagesofsinglechipdesignofthemeasurementsystem.ThemeasuringsystemcancontroldirectlyfromtheLEDdigitalreadoutthemeasuredresistancevalue,measuringrangefromafewmΩbetween1Ω,whilethetestdatacanbestored,andthenintothePCviaserialport,throughthePC'spower,canbemeasuredbytheanalysisofthedata,processing.Thetester'smeasurementaccuracyupto±0.05%,andtheuseoffour-terminalmeasurement,theresistancefromleadlengthandcontactresistance.Measurednotonlysimple,intuitivereadings,andmeasurementaccuracy,resolutionisalsohigherthanthebridge.Itcanbeusedinlaboratories,researchinstitutes,especiallysuitablefortheworksite.Keywords:Four-terminalmeasurement，Littleresistance;MSP430MCU，Constantcurrentsource目录III目录摘要..............................................................................................................................IAbstract......................................................................................................................II目录..........................................................................................................................III引言..............................................................................................................................11.1前述....................................................................................................................11.2小电阻测量技术的发展.....................................................................................1第一章方案的分析与论证..........................................................................................3第二章硬件电路的设计..............................................................................................52.1总体设计............................................................................................................52.2单元电路的设计.................................................................................................52.2.1电压源...........................................................................................................52.2.2恒流源............................................................................................................72.2.3信号放大........................................................................................................82.2.4单片机.........................................................................................................102.2.5LED显示.....................................................................................................142.2.6串口通信.....................................................................................................162.2.7键盘..............................................................................................................172.2.8存储模块......................................................................................................172.2.9单片机复位..................................................................................................18第三章系统软件设计................................................................................................203.1软件开发平台简介...........................................................................................203.2程序流程图.......................................................................................................203.2.1系统主程序.................................................................................................203.2.2A/D转换模块..............................................................................................223.2.3串口通信模块..............................................................................................223.2.4键盘模块......................................................................................................233.2.5.显示模块..................................................................