毕业论文___基于恒流源的数字式小电阻测试仪.doc

摘 要 近年来，直流微、小电阻测试仪得到了比较快的发展。微电阻测量大多采用hj直流微欧计，一般采用恒流源作为测试电流，一般情况下电流值为l00A～200A的大电流，通过大电流变压器和高频开关电源这种方法来实现大电流的恒流效果，使用这种大电流恒流的测试仪进行电阻测试时，测试工作电流较大，测试工作时间相对较长，因此被测电阻的温升会受到影响，从而使其的电阻阻值的测量精度降低了，此外，这一类型的电阻测试仪体积较大、重量较大，不便于携带，对工作现场的使用也受限制，其生产制造成本也比较高。因此，基于恒流源的数字式小电阻测试仪的设计急需亟待解决。本设计给出了一种以AT89S51为控制核心的高精度小阻值电阻测试仪的设计，系统测试小阻值1Ω到10Ω的电阻阻值。采用恒流源输出恒定电流的方法，采用C51语言对单片机进行了编程，并对整个测量系统进行了软件仿真。 关键词：阻值；电阻测量 ；AD620 ；恒流源 ；ADC0809 Abstract In the last few years, the little, micro DC resistance tester has been developed very fast.Most of the DCmicro resistance measurement of micro ohmmeter, generally using a constant current source as thetest current, current for high current100A ~ 200A, the high frequency switching power supply and current transformer to achieve constant current effect of high current, resistance test instrumentusing the high current constant current, large working current test the test, work for a long time, so it will affect the measured resistance temperature rise, so that the measurement accuracy of the resistance is reduced, in addition, this type of resistance tester of large volume, heavy weight,inconvenient carrying, use on the job site is restricted, the production cost is too high.Therefore, the design of digital resistance tester small constant current source to be solved based on. This paper presents a design of AT89S51 high precision low resistance tester control core,testing system of small resistance 1 ohm to 10 ohm resistor. By using the method of constant current source output constant current, C51 language is used to program the microcontroller, and the whole measurement system simulation software. Keywords: resistance; resistance measurement; AD620; constant-current source; ADC0809 目录 摘要 I Abstract II 第1章 绪论 1 1.1课题研究的背景、意义 1 1.2 系统设计的基本思路 2 1.3 系统的主要性能指标 2 第2章 系统方案论证 3 2.1 小电阻的测量方法 3 2.1.1 脉冲大电流测量法 3 2.1.2 直流恒流源测量法 3 2.2 小阻值电阻测量中的关键技术 4 2.2.1 恒流源的选取 4 2.2.2 放大器的选择 4 2.2.3 A/D转换器的选择 4 第3章 系统硬件电路设计 5 3.1 硬件电路设计总体方案 5 3.2 整机硬件系统方框图 5 3.3