基于单片机的数字毫欧表毕业设计基于单片机的智能温度测试控制仪的毕业设计.doc

基于单片机的数字毫欧表设计 摘 要 当今社会数字万用表的应用已经非常普及，它在测量电阻时采用的 “比例法” 确美中不足的是，还是觉得AT89S52单片机的数字毫欧表设计是采用伏安法测量电阻。采用TLC5615数模转换芯片和LM358运算放大器及三极管TIP41构成的压控恒流源提供恒定的电流。测量电阻时可选择的电流分别为1mA，10mA，100mA。测量电阻的量程分别为40.00Ω、4000mΩ、400.0mΩ。测量的电压信号通过LM358运算放器放大100倍后经过TLC1549模数芯片传入单片机进行计算处理并在数码管上输出电阻值。 测量直流类毫欧至数十欧的小电阻，主要用于电动机、扬声器、继电器等线圈的直流电阻，由于他们的直流电阻数值不大，普通万用表实际很难测量到准确数值，以单片机为处理核心设计出的数字毫欧表就能够很好的解决这种测量难题，具有很高的研发实用价值。 关键词：单片机；毫欧表；压控恒流源；运算放大器The Design of Digital Milliohmmeter Based on MCU Abstract In nowdays ,the digital multimeters which wildly used in every fields. The method of “Ratio Algxithm” ,adapted while measuring resistances have improved the measuring accuary. But,the ordinary digital multimeters’ ability of measuring thumbnail resistances can not up to scrach while measuring thumbnail resistances. The digital milliohmeters can do better .so,its appearance,is reasonable. The digital milliohmeters based on MCU AT89S52 adapt voltage-ammeter method to measure resistances . With ADC TLC5615 and operational amplifier LM358 and transistor TIP41 forms voltage-constant-current source to supply current .While measuring resistance ,it can adapt 1mA,10mA,100mA current.The range of resistance-measuring can be 40Ω,400mΩ, 4000mΩ.The voltage signal can be magnificated 100 times by LM358, then converted by TLC549 ,then sended to MCU ,prossed and displayed the value of resistances. The digital milliohmeters can measure DCdozens ohms resistance .It mainly used in measuring resistances of electromotors , loudspeakers ,and relays’ loops .Their loops’ resistances is too diny to be measured by ordinary digital multimeters.The task demand to design a digital milliohmeters by MCU to solve the problem.It’s worthly to be studied. Keywords: MCU; milliohmeters ;voltage-costant-current source;operational amplifier目 录 引言 1 第1章 绪论 2 1.1 研究背景与意义 2 1.2研究现状 2 1.3 研究内容 4 第2章 方案设计 5 2.1 方案选择 5 2.2.总体方案设计 7 第3章 硬件设计 9 3.1AT89S52单片机简介 9 3.2 数控恒流源设计 12 3.3 电压放大模块设计 14 3.4 AD转换与单片机处理 14 3.5 DA转换 1