基于AT89C51的金属材料电阻率测量仪

以AT89C51微处理器为核心组成智能型微电阻测量仪．该仪器依据四探针法原理，采用高稳定度的恒流源电路，低漂移、低噪声的直流放大器电路和自动量程转换电路构成测量回路．恒流源采用深度负反馈技术，其稳定度、电压调整率和温度漂移分别小于0．1％，0．1％和0．05％／℃．采用了分时测量、共同一测量回路的自校准方法，高稳定恒电流分时通过待测试样和内置标准电阻，电压测量回路的输入阻抗高达20MΩ以上，消除了试样接触电阻的影响．通过对高精度标准电阻器组BZ-3的检测表明，全量程中的最大非线性误差为0．12％，对各种标号的漆包线的测量误差小于0．5％，对金属试样在腐蚀液体中的腐蚀情况能进行动态监测，对大试样粉末冶金样品的微小电阻也能进行精确的测量

An instrument based on AT89C51 for measuring resistivity of metal materials

An instrument controlled by microprocessor AT89C51 for measuring the resistivity of metal materials was in-troduced. It is based on the principle of Four-point probe method and has a high stable constant current power source,highly sensitive, low noise, low drift DC gain amplifier, a highly resolution A/D converter and an automatic range selec-tor controlled by microprocessor AT89C51. The constant current power source is constructed in degenerative feedbacktechnique. Its stability, voltage relative regulation and temperature drift are less than 0. 1% ,0.1% and 0.05% respec-tively. In measurement process, the constant current follows Rs and Rχ at a time sharing process and a method of onlineself-diagnosis was used. A serial of precise standard resisters BZ-3 was used to adjust the instrument. The results showedthat the maximum error is less than 0.12%. The error is less than 0.05% in measuring the resistivity of several kinds ofenameled wire. For large piece of metal samples with low resistance, the instrument can have accurate results