本文選題：痕量氣體檢測　切入點(diǎn)：QEPAS　出處：《重慶大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：痕量氣體檢測技術(shù)已經(jīng)在空氣污染監(jiān)測、工業(yè)生產(chǎn)、醫(yī)學(xué)診斷等領(lǐng)域發(fā)揮著重要的角色，，其中石英增強(qiáng)光聲光譜技術(shù)（Quartz Enhanced Photoacoustic Spectroscopy,QEPAS）是一種完全無背景的氣體檢測技術(shù)，因其具有體積小、靈敏度高、響應(yīng)速度快以及適合實(shí)時在線測量等優(yōu)點(diǎn)而被廣泛地應(yīng)用。針對一些特殊情況，例如高溫、高濕度、強(qiáng)電磁場干擾環(huán)境中以及易燃、易爆和有毒有害氣體的檢測，目前的檢測技術(shù)還是存在一些局限性。本文利用光纖法珀振動傳感技術(shù)獲取與氣體濃度相關(guān)的石英音叉振動信號替代了傳統(tǒng)方法中獲取音叉壓電信號，同時采用法珀傳感器工作點(diǎn)穩(wěn)定技術(shù)，進(jìn)一步提高QEPAS系統(tǒng)的解調(diào)精度和穩(wěn)定性。 論文從石英增強(qiáng)光聲光譜系統(tǒng)的原理出發(fā)，詳細(xì)地推導(dǎo)了氣體光聲理論和音叉的振動幅值與氣體的濃度關(guān)系。理論分析了波長調(diào)制和諧波檢測技術(shù)的必要性。采用光纖法珀傳感器拾取音叉的振動信號，從多光束干涉公式詳細(xì)地分析了法珀傳感器輸出信號與音叉振動幅值的關(guān)系，并通過仿真和實(shí)驗(yàn)分析了工作點(diǎn)漂移對解調(diào)結(jié)果的嚴(yán)重影響，結(jié)合波長補(bǔ)償技術(shù)使得工作點(diǎn)穩(wěn)定在正交相位點(diǎn)上，以獲得更好的解調(diào)結(jié)果。 石英增強(qiáng)光聲光譜光纖法珀解調(diào)系統(tǒng)設(shè)計(jì)主要包括光源光纖激光器的設(shè)計(jì)和工作點(diǎn)反饋控制設(shè)計(jì)。論文中詳細(xì)分析了摻鉺光纖放大原理，設(shè)計(jì)了基于可調(diào)諧FP濾波器的光纖激光器，得到其功率可達(dá)10mW、調(diào)諧范圍為1525nm~1565nm以及線寬約為0.00051nm�；贚abVIEW軟硬件平臺，設(shè)計(jì)了反饋式光纖法珀傳感控制模塊。由采集卡獲得傳感器的輸出信號并由軟件對其進(jìn)行濾波和取直流處理，采用得到的直流電壓與靜態(tài)工作點(diǎn)電壓之差作為誤差反饋信號，利用數(shù)字PID技術(shù)將工作點(diǎn)鎖定在正交相位點(diǎn)上，提高光纖法珀傳感器的穩(wěn)定性，從而提高了光聲信號探測的準(zhǔn)確性。 為了驗(yàn)證基于法珀傳感的石英增強(qiáng)光聲光譜系統(tǒng)的可行性，實(shí)驗(yàn)中選擇水蒸汽作為測試氣體樣本，在開放環(huán)境中對水汽進(jìn)行測試實(shí)驗(yàn)。由實(shí)驗(yàn)結(jié)果計(jì)算得到其歸一化等效噪聲吸收系數(shù)為1.81×10-7cm-1W/Hz1/2。與傳統(tǒng)的QEPAS氣體探測系統(tǒng)相比較，該方法的探測靈敏度提高了4倍。該系統(tǒng)具有成本低和探測效率高、抗電磁干擾及防燃防爆能力和適合長距離在線檢測等優(yōu)點(diǎn)。
[Abstract]:Trace gas detection technology has played an important role in air pollution monitoring, industrial production, medical diagnosis and other fields. Quartz enhanced photoacoustic spectroscopy (Quartz Enhanced Photoacoustic SpectroscopyQEPAS) is a completely groundless gas detection technology. It is widely used because of its small size, high sensitivity, high response speed and suitable for real time on-line measurement. It can be used in some special cases, such as high temperature, high humidity, strong electromagnetic field interference and flammability. Detection of explosive and toxic gases, At present, there are still some limitations in the detection technology. In this paper, we use the fiber Fabry-Perot vibration sensing technology to obtain the quartz tuning fork vibration signal which is related to the gas concentration instead of the traditional method to obtain the tuning fork piezoelectric signal. At the same time, the demodulation accuracy and stability of QEPAS system are further improved by using the technology of working point stabilization of Fabry-Perot sensor. Based on the principle of quartz enhanced photoacoustic spectroscopy system, The relationship between the vibration amplitude of the tuning fork and the concentration of the gas is derived in detail. The necessity of wavelength modulation and harmonic detection is analyzed theoretically. The vibration signal of the tuning fork is picked up by the fiber optic Fabry-Perot sensor. The relationship between the output signal of the Fabry-Perot sensor and the amplitude of the tuning fork vibration is analyzed in detail from the multi-beam interference formula, and the serious influence of the working point drift on the demodulation result is analyzed by simulation and experiment. Combined with wavelength compensation technology, the working point is stabilized on the orthogonal phase point to obtain better demodulation results. The design of quartz enhanced photoacoustic spectrum fiber Fabry-Perot demodulation system mainly includes the design of light source fiber laser and the design of operating point feedback control. A fiber laser based on tunable FP filter is designed. Its power is up to 10mW, tuning range is 1525nm / 1565nm and linewidth is about 0.00051nm.Based on LabVIEW software and hardware platform, The feedback fiber Fabry-Perot sensor control module is designed. The output signal of the sensor is obtained by the acquisition card and filtered and processed by the software. The difference between the obtained DC voltage and the static working point voltage is used as the error feedback signal. In order to improve the stability of optical fiber Fabry-Perot sensor and improve the accuracy of photoacoustic signal detection, digital PID technology is used to lock the working point on the orthogonal phase point. In order to verify the feasibility of quartz enhanced photoacoustic spectroscopy system based on Fabry-Perot sensor, water vapor was selected as the test gas sample in the experiment. The normalized equivalent noise absorption coefficient is 1.81 脳 10 ~ (-7) cm ~ (-1) W / H ~ (-1 / 1 / 2), which is compared with the conventional QEPAS gas detection system. The system has the advantages of low cost, high detection efficiency, anti-electromagnetic interference and flame-proof capability and suitable for long distance on-line detection.
【學(xué)位授予單位】：重慶大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：O657.3;TP212

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