本文選題：介電測量 + 低功耗�。� 參考：《合肥工業(yè)大學(xué)》2017年碩士論文

【摘要】：介電測量被廣泛應(yīng)用于檢測產(chǎn)品特性的工業(yè)過程控制中,如含水率、密度、厚度、毒素含量等無損檢測。課題組已研制了應(yīng)用于食品安全檢測領(lǐng)域的低功耗介電系統(tǒng),但是,該系統(tǒng)測量頻率范圍窄、易受工頻干擾、且不能計算介電常數(shù)。本文改進了現(xiàn)有介電測量系統(tǒng)的軟硬件,設(shè)計了基于電容數(shù)字轉(zhuǎn)換技術(shù)的系統(tǒng),分別對兩套系統(tǒng)進行了測量實驗。重新設(shè)計了原有介電測量系統(tǒng)的前向通道電路,提高傳感器輸出信號的幅度;通過采用DC/DC與LDO相結(jié)合的方式優(yōu)化電源電路,并嚴格區(qū)分數(shù)字與模擬電源;采用金屬屏蔽罩、地平面設(shè)計等方法提高系統(tǒng)抗工頻干擾及噪聲的能力。采用分段設(shè)置采樣頻率來提高頻譜分析算法的精度;通過最小二乘法建立傳感器極間電容與被測材料介電常數(shù)的模型。分別做了傳感器空測、板材損傷檢測及板材介電常數(shù)測量實驗,結(jié)果表明:改進后的系統(tǒng)在整個掃頻區(qū)間內(nèi)具有較高的穩(wěn)定性;系統(tǒng)能夠有效檢測出損傷板材;系統(tǒng)能夠?qū)崿F(xiàn)對介電常數(shù)的穩(wěn)定檢測,且測量值隨頻率的增大而減小,并逐漸趨于穩(wěn)定。研制了基于電容數(shù)字轉(zhuǎn)換芯片AD7745的介電測量系統(tǒng)。系統(tǒng)以MSP430為核心,包括電容數(shù)字轉(zhuǎn)換(CDC)模塊、電容輸入擴展模塊、人機交互模塊及電源管理模塊。系統(tǒng)軟件上,包括主監(jiān)控程序、初始化模塊、中斷模塊、數(shù)據(jù)采集模塊、人機交互模塊、算法模塊等。實現(xiàn)了電容到數(shù)字信號的轉(zhuǎn)換、讀取、介電常數(shù)計算、顯示等功能。結(jié)果表明:在32KHz下,系統(tǒng)重復(fù)性誤差為0.0503pF;系統(tǒng)能夠準確分辨出受損板材;系統(tǒng)能夠快速、穩(wěn)定的實現(xiàn)介電常數(shù)檢測。
[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.
【學(xué)位授予單位】：合肥工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM934.33

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