摘  要:微小电容的检测在国内外也都被积极的进行着研究。一般来说，它的基本的原理是通过激励信号连续对被测电容进行充放电，形成与被测电容成比例的电压、电流、频率或者脉冲宽度的信号，通过得到的值然后进行换算，从而测量出被测电容的容值。微小电容的基本检测原理有：电容—频率测量法，电容—电压法，电容— 数字A/D转换法等。电容数字转换器AD7746精确度很高，适合微小形变的测量。本文设计的电路是由电容测量模块即AD7746、单片机AT89C52、测量显示模块74LS138和显示管组，以及电源模块ADP3303 四个模块组成。我们利用AD7746实现电容信号的输入采集和电容到数字信号之间的转换功能，并将转换的结果送入单片机进行处理。单片机用于完成与AD7746的通信，实现与AD7746间的数据传输，运算AD7746的转换数据，驱动显示数码管的扫描工作，最后数据通过数码管显示出来

关键词：AD7746； 微小电容； 测量电路

Abstract:  The detection of small capacitance at home and abroad is active research. In general, its basic principle is that the excitation signal on the measured capacitance charge and discharge, the formation of the measured capacitance is proportional to voltage, current, frequency or pulse width signal, and then translated by the value obtained to measure capacity, the measured capacitance value. Small capacitance detection principle: the capacitance - frequency measurement, capacitance - voltage method, capacitance - digital, the A / D conversion method. Capacitance-to-digital converter AD7746 accuracy is high, suitable for the measurement of small deformation. In this paper, the design of the circuit is by the capacitance measurement module, while the AD7746, the microcontroller AT89C52, measurement display module 74LS138 and display tube group, and the power supply module, the ADP3303 four module composition. We use the acquisition and capacitance of the AD7746 capacitance signal input to digital signal conversion between function and convert the results into the microcontroller for processing. The microcontroller used to complete the AD7746 between the data transmission with the AD7746 communications, computing the AD7746's conversion data driven display digital scanning tube, the final data by digital tube display.

Key words: AD7746; Small capacitance; Measurement circuit