極微小電容的檢測技術(shù)研究
發(fā)布時間：2018-07-16 09:17
【摘要】：電容測微技術(shù)具有低功耗、高精度、動態(tài)性能好、穩(wěn)定性高和非接觸測量等特點，，廣泛應用于位移、液位、壓力等參數(shù)的測量。隨著超精密制造及現(xiàn)代工業(yè)生產(chǎn)的發(fā)展對檢測精度要求越來越高，在微位移測量領域檢測精度已達到納米量級，納米級位移變化對應的電容變化在fF量級，寄生電容干擾在pF量級，在如此大背景噪聲下實現(xiàn)弱信號檢測是提高電容測微精度亟需解決的基礎性問題。 針對以上問題，本論文首先對四種電容測量方法原理及優(yōu)缺點進行調(diào)研，最終選擇了交流激勵式作為本課題采用的電容測量方法。交流激勵式電容測量系統(tǒng)主要包括前級電路、信號發(fā)生單元和信號解調(diào)單元，對各單元傳統(tǒng)實現(xiàn)方式進行分析和優(yōu)化，在此基礎上完成系統(tǒng)設計。本論文完成的主要工作如下： 1、電容位移傳感器電容測量電路指標分析及系統(tǒng)輸入確定 對衡量電容測量系統(tǒng)性能的噪聲、分辨率、帶寬等指標從定義、原理及測量方法等方面進行闡述與分析。電容變化范圍是設計電容測量系統(tǒng)的輸入，采用電磁仿真軟件CST建立了電容傳感器模型，通過仿真確定了系統(tǒng)輸入范圍。 2、極微小電容測量系統(tǒng)設計 前級電路用以實現(xiàn)C-V(電容-電壓)轉(zhuǎn)換，其性能對系統(tǒng)分辨率起著決定性的作用。在前人研究基礎上本文提出了一種新的電容橋電路，該電容橋包括測量臂和參考臂，測量臂測得的電容傳感器電壓通過1:1放大器引到參考臂，將參考臂輸出電壓乘以合適的倍數(shù)反饋到激勵源，這樣可以提高系統(tǒng)抗干擾能力并且增大前級電路輸出電壓變化范圍。前人采用的橋式電路由兩個激勵源，一個參考電容和電容傳感器組成，通過調(diào)節(jié)激勵源電壓使橋電路達到平衡此時電容傳感器電容與參考電容比值等于兩個激勵源電壓之比，通過比例關系可以得到電容傳感器電容值。與橋式電路相比，電容橋電路具有結(jié)構(gòu)簡單、動態(tài)性好、抗干擾能力強和測量精度高等特點。 信號發(fā)生單元采用ADI公司高精度性能優(yōu)良的DDS芯片實現(xiàn)。信號解調(diào)單元包括檢波電路和低通濾波器，檢波電路采用開關全波檢波，低通濾波器采用FDNR濾波器。 在上述方案基礎上完成極微小電容檢測系統(tǒng)設計，并且搭建實驗平臺，對所設計系統(tǒng)進行相關實驗測試，測試結(jié)果表明：該系統(tǒng)在150~650um量程范圍內(nèi)可以實現(xiàn)30nm分辨率，示值穩(wěn)定性0.1mV/30min。
[Abstract]:Capacitive micrometer has the advantages of low power consumption, high precision, good dynamic performance, high stability and non-contact measurement. It is widely used in the measurement of displacement, liquid level, pressure and other parameters. With the development of ultra-precision manufacturing and modern industrial production, the precision of measurement has reached the nanometer order, and the capacitance corresponding to the change of nanometer displacement is in the order of FF. The parasitic capacitance interference is in the order of PF and the weak signal detection under such a large background noise is a basic problem that needs to be solved to improve the accuracy of capacitance measurement. Aiming at the above problems, this paper firstly investigates the principle, advantages and disadvantages of four capacitance measurement methods, and finally chooses AC excitation as the capacitance measurement method adopted in this subject. The AC excitation capacitance measurement system mainly includes the front-stage circuit, the signal generating unit and the signal demodulation unit. The traditional realization of each unit is analyzed and optimized, and the system design is completed on the basis of the analysis and optimization. The main work of this paper is as follows: 1. The analysis of capacitive displacement sensor capacitance measurement circuit index and the determination of system input to measure the capacitance measurement system performance of noise, resolution, bandwidth and other indicators from the definition, The principle and measurement method are expounded and analyzed. The range of capacitance variation is the input of designing capacitance measurement system. The capacitance sensor model is established by using the electromagnetic simulation software CST. The input range of the system is determined by simulation. 2. A very small capacitance measuring system is designed to realize C-V (capacitance-voltage) conversion. Its performance plays a decisive role in the resolution of the system. On the basis of previous studies, a new capacitance bridge circuit is proposed in this paper. The capacitance bridge consists of a measuring arm and a reference arm. The voltage of the capacitance sensor measured by the measuring arm is led to the reference arm by the 1:1 amplifier. The output voltage of the reference arm is multiplied by the appropriate multiple to the excitation source, which can improve the anti-interference ability of the system and increase the range of the output voltage of the former circuit. The bridge circuit is composed of two excitation sources, a reference capacitance and a capacitive sensor. By adjusting the voltage of the excitation source, the bridge circuit is balanced when the ratio of capacitance to reference capacitance of the capacitive sensor is equal to the ratio of the voltage of the two excitation sources. The capacitance value of capacitive sensor can be obtained by proportional relationship. Compared with the bridge circuit, the capacitor bridge circuit has the advantages of simple structure, good dynamic, strong anti-interference ability and high measurement precision. The signal generating unit is implemented by ADI DDS chip with high precision and excellent performance. The signal demodulation unit consists of demodulation circuit and low-pass filter. The detection circuit uses full wave detector on switch and FDNR filter is used for low-pass filter. On the basis of the above scheme, the design of the very small capacitance detection system is completed, and the experimental platform is built. The test results show that the system can realize the 30nm resolution in the range of 150~650um range. The stability is 0.1 MV / 30 min.
【學位授予單位】：中國科學院研究生院(長春光學精密機械與物理研究所)
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TM934.23;TP212
[Abstract]:Capacitive micrometer has the advantages of low power consumption, high precision, good dynamic performance, high stability and non-contact measurement. It is widely used in the measurement of displacement, liquid level, pressure and other parameters. With the development of ultra-precision manufacturing and modern industrial production, the precision of measurement has reached the nanometer order, and the capacitance corresponding to the change of nanometer displacement is in the order of FF. The parasitic capacitance interference is in the order of PF and the weak signal detection under such a large background noise is a basic problem that needs to be solved to improve the accuracy of capacitance measurement. Aiming at the above problems, this paper firstly investigates the principle, advantages and disadvantages of four capacitance measurement methods, and finally chooses AC excitation as the capacitance measurement method adopted in this subject. The AC excitation capacitance measurement system mainly includes the front-stage circuit, the signal generating unit and the signal demodulation unit. The traditional realization of each unit is analyzed and optimized, and the system design is completed on the basis of the analysis and optimization. The main work of this paper is as follows: 1. The analysis of capacitive displacement sensor capacitance measurement circuit index and the determination of system input to measure the capacitance measurement system performance of noise, resolution, bandwidth and other indicators from the definition, The principle and measurement method are expounded and analyzed. The range of capacitance variation is the input of designing capacitance measurement system. The capacitance sensor model is established by using the electromagnetic simulation software CST. The input range of the system is determined by simulation. 2. A very small capacitance measuring system is designed to realize C-V (capacitance-voltage) conversion. Its performance plays a decisive role in the resolution of the system. On the basis of previous studies, a new capacitance bridge circuit is proposed in this paper. The capacitance bridge consists of a measuring arm and a reference arm. The voltage of the capacitance sensor measured by the measuring arm is led to the reference arm by the 1:1 amplifier. The output voltage of the reference arm is multiplied by the appropriate multiple to the excitation source, which can improve the anti-interference ability of the system and increase the range of the output voltage of the former circuit. The bridge circuit is composed of two excitation sources, a reference capacitance and a capacitive sensor. By adjusting the voltage of the excitation source, the bridge circuit is balanced when the ratio of capacitance to reference capacitance of the capacitive sensor is equal to the ratio of the voltage of the two excitation sources. The capacitance value of capacitive sensor can be obtained by proportional relationship. Compared with the bridge circuit, the capacitor bridge circuit has the advantages of simple structure, good dynamic, strong anti-interference ability and high measurement precision. The signal generating unit is implemented by ADI DDS chip with high precision and excellent performance. The signal demodulation unit consists of demodulation circuit and low-pass filter. The detection circuit uses full wave detector on switch and FDNR filter is used for low-pass filter. On the basis of the above scheme, the design of the very small capacitance detection system is completed, and the experimental platform is built. The test results show that the system can realize the 30nm resolution in the range of 150~650um range. The stability is 0.1 MV / 30 min.
【學位授予單位】：中國科學院研究生院(長春光學精密機械與物理研究所)
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TM934.23;TP212
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