低功耗介电测量系统的改进与实验

发布时间：2018-06-22 19:25

本文选题：介电测量 + 低功耗　；参考：《合肥工业大学》2017年硕士论文

【摘要】：介电测量被广泛应用于检测产品特性的工业过程控制中,如含水率、密度、厚度、毒素含量等无损检测。课题组已研制了应用于食品安全检测领域的低功耗介电系统,但是,该系统测量频率范围窄、易受工频干扰、且不能计算介电常数。本文改进了现有介电测量系统的软硬件,设计了基于电容数字转换技术的系统,分别对两套系统进行了测量实验。重新设计了原有介电测量系统的前向通道电路,提高传感器输出信号的幅度;通过采用DC/DC与LDO相结合的方式优化电源电路,并严格区分数字与模拟电源;采用金属屏蔽罩、地平面设计等方法提高系统抗工频干扰及噪声的能力。采用分段设置采样频率来提高频谱分析算法的精度;通过最小二乘法建立传感器极间电容与被测材料介电常数的模型。分别做了传感器空测、板材损伤检测及板材介电常数测量实验,结果表明:改进后的系统在整个扫频区间内具有较高的稳定性;系统能够有效检测出损伤板材;系统能够实现对介电常数的稳定检测,且测量值随频率的增大而减小,并逐渐趋于稳定。研制了基于电容数字转换芯片AD7745的介电测量系统。系统以MSP430为核心,包括电容数字转换(CDC)模块、电容输入扩展模块、人机交互模块及电源管理模块。系统软件上,包括主监控程序、初始化模块、中断模块、数据采集模块、人机交互模块、算法模块等。实现了电容到数字信号的转换、读取、介电常数计算、显示等功能。结果表明:在32KHz下,系统重复性误差为0.0503pF;系统能够准确分辨出受损板材;系统能够快速、稳定的实现介电常数检测。
[Abstract]:Dielectric measurement is widely used in industrial process control for testing product characteristics, such as moisture content, density, thickness, toxin content and other nondestructive testing. A low power dielectric system has been developed for food safety detection. However, the system can not calculate the dielectric constant because of its narrow measuring frequency range, easy to be interfered by power frequency and unable to calculate the dielectric constant. This paper improves the hardware and software of the existing dielectric measurement system, designs the system based on the capacitance digital conversion technology, and carries out the measurement experiments on two sets of systems. The forward channel circuit of the original dielectric measurement system is redesigned to improve the amplitude of the output signal of the sensor. The power circuit is optimized by the combination of DC / DC and LDO, and the digital and analog power supply is strictly distinguished. Ground plane design and other methods to improve the system's ability to resist power frequency interference and noise. The sampling frequency is set up to improve the precision of spectrum analysis algorithm, and the model of sensor capacitance and dielectric constant is established by least square method. The results show that the improved system has high stability in the whole sweep frequency range, and the system can detect the damaged plate effectively. The system can detect the dielectric constant stably, and the measured value decreases with the increase of frequency, and tends to be stable gradually. A dielectric measurement system based on AD7745 is developed. MSP430 is the core of the system, including capacitive digital conversion (CDC) module, capacitive input expansion module, man-machine interaction module and power management module. System software, including the main monitoring program, initialization module, interrupt module, data acquisition module, human-computer interaction module, algorithm module and so on. Realize the conversion of capacitance to digital signal, reading, dielectric constant calculation, display and other functions. The results show that the repeatability error of the system is 0.0503pF at 32kHz, the system can accurately distinguish the damaged plate, and the system can detect the dielectric constant quickly and stably.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM934.33

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