摘要
该文设计了一款简易的微小电容测量仪。该测量仪以MSP4305529单片机作为控制核心,系统通过1路频率可变的方波信号对2路RC移相回路激励,并对激励后信号整形异或从而得到占空比正比于RC移相回路电容差值的PWM波信号,通过ICL7135实现对PWM积分后直流电压的测量,从而计算出待测电容的大小。该方法相较于传统电容测量仪具有电路简单、测量便利、小巧便携、测量精度较高,成本低廉等特点。实际测试表明,该系统对小电容测量范围从1 p F^10 n F,测量精度可达2%,具有较强的实际应用意义。
This paper introduces a simple measuring instrument of micro-capacitance. The measuring instrument adopts MSP4305529 MCU as the control core. By means of a square wave signal with alterable frequency to excite two RC phase-shift circuits,then we operate the excited signal with the ＂reshaping＂ and ＂exclusive-or＂ method,as a result,a PWM wave signal can be obtained,whose duty cycle was directly proportional to capacitive difference in RC phase-shift circuit. Through ICL7135 to achieve the integral of the PWM,we measure DC voltage and then get the capacitance value. Compared with the traditional measuring instrument in micro-capacitance,the method has the following advantages：simple circuit,convenient measurement,portability,high measuring accuracy,low cost and etcetera. Through the actual test,this measuring instrument can be concluded that the instrument can measure capacitance ranging from IpF to 10nF. The test data reflects that the measurement accuracy of the capacitance can be up to2%.
出处
《自动化与仪表》
2015年第1期19-23,共5页
Automation & Instrumentation
基金
成都理工大学中青年骨干教师培养计划资助项目(JXGG201408)
国家自然科学基金资助项目(41474159)
四川省大学生创新创业训练计划项目(201410616034)
