基于MAX038的简易小电容测试仪设计

摘要

A MAX038⁃based simple tester for small capacitances was designed in this paper. Its principle is that the external capacitor of MAX038 is taken as the tested capacitor to provide corresponding frequency signal output. TM4C123GH6PM is selected to measure frequency with equal precision and calculate the value of the tested capacitance. In order to improve the accuracy,the curves are piecewise fitted by the least square method,and they are piecewise contrasted with high⁃accuracy LCR table in the test process to realize auto correction and display measurement results. The tester can detect 10 pF~1 μF capacitors. The test results show that the tester has the characteristics of stable operation and rapid measurement,and its accuracy can reach grade 1.%设计了一种基于MAX038函数信号发生器的小电容测试仪，其原理是将函数发生器的外接电容看作被测电容而产生相应的频率信号输出，选用TM4C123GH6PM 微控制器实现等精度测量频率值，然后计算出被测电容值。为了提高准确度，采用最小二乘法分段拟合曲线，同时与准确度较高的LCR表进行分段比对测试，实现自动修正并显示测量结果。该测试仪测量范围为10 pF~1μF的小电容。测试结果表明，该测试仪具有运行稳定，测量快速的特点，准确度可达1级。