本文選題：紅外吸收光譜 + TDLAS　； 參考：《吉林大學(xué)》2017年碩士論文

【摘要】：本論文選題來源于國家科技支撐計(jì)劃課題:煤礦用紅外CO檢測儀(傳感器)研發(fā),課題編號:2013BAK06B04。煤礦環(huán)境下,需要時刻監(jiān)測CH_4、CO等氣體的濃度,以保障煤礦生產(chǎn)的安全。在眾多的氣體檢測方法中,可調(diào)諧激光二極管吸收光譜(Tunable Diode Laser Absorption Spectroscopy,TDLAS)技術(shù)檢測精度高、響應(yīng)速度快、無需接觸測量,被廣泛應(yīng)用。TDLAS技術(shù)中,用低頻鋸齒波信號與高頻正弦波信號掃描/調(diào)制激光器,在檢測儀后端,需要利用鎖相放大器從氣體吸收信號中提取諧波信號以表征氣體濃度。商用鎖相放大器價格昂貴、體積大、不便用于集成儀器中;本文研制了專用于TDLAS氣體檢測系統(tǒng)的數(shù)字正交鎖相放大器,價格低、體積小、硬件電路簡單、便于集成。首先,深入介紹了紅外吸收光譜技術(shù)與TDLAS技術(shù)中的相關(guān)理論,包括朗伯比爾定律、直接吸收光譜(Direct Absorption Spectroscopy,DAS)技術(shù)原理、波長調(diào)制光譜(Wavelength Modulated Spectroscopy,WMS)技術(shù)原理、諧波檢測原理、鎖相放大器原理等,并利用MATLAB對理論部分進(jìn)行了仿真,驗(yàn)證了所提算法的正確性。其次,設(shè)計(jì)了數(shù)字鎖相放大器的硬件電路,包括光電轉(zhuǎn)換電路、減法電路、AD采樣電路、鍵盤矩陣電路、LCD驅(qū)動電路、SCI(Serial Communication Interface,串行通信接口)通信電路及DSP(Digital Signal Processor,數(shù)字信號處理器)最小系統(tǒng)等。再次,對數(shù)字鎖相放大器的程序流程圖進(jìn)行了詳細(xì)介紹,并對其中的兩個中斷、低通濾波、諧波波形顯示等模塊給出了具體的設(shè)計(jì)方案。利用Simulink建立了鎖相放大器的功能模型并進(jìn)行了用例測試。最后,開展了相關(guān)實(shí)驗(yàn),測試了鎖相放大器的性能。對單頻正弦波信號提取諧波的實(shí)驗(yàn)表明,一次諧波的幅值與輸入正弦波信號的峰峰值成線性關(guān)系。對模擬差分吸收信號提取諧波的實(shí)驗(yàn)表明,諧波信號的峰峰值與模擬氣體濃度成線性關(guān)系。開展了CH_4氣體實(shí)驗(yàn),從差分吸收信號中提取了諧波信號,對氣體濃度進(jìn)行了標(biāo)定,測試了檢測系統(tǒng)的穩(wěn)定性并計(jì)算了Allan方差。CH_4濃度為0 ppm時,所測濃度的波動范圍為-61.2457 ppm~+84.4715 ppm;Allan偏差-積分時間曲線表明,積分時間為0.1 s時,1σ檢測下限約為16.89212 ppm,當(dāng)積分時間增加到3.8 s時,1σ檢測下限降低為3.05046 ppm。本論文的創(chuàng)新點(diǎn):1.自主設(shè)計(jì)并研制了專用于TDLAS氣體檢測系統(tǒng)的數(shù)字正交鎖相放大器,其硬件電路簡單,算法中只需存儲少量參考信號幅值與數(shù)字濾波器系數(shù)。2.該鎖相放大器可以作為數(shù)據(jù)處理和諧波提取模塊,從而用于任何基于TDLAS技術(shù)的氣體檢測儀中,檢測多種氣體的濃度,具有普遍適用性。
[Abstract]:This thesis is from the national science and technology support plan project: coal mine infrared CO detector (sensor) research and development, subject number: 2013BAK06B04. In the coal mine environment, it is necessary to monitor the concentration of CH4CO at all times in order to ensure the safety of coal production. Among many gas detection methods, tunable laser diode Diode Laser Absorption spectroscopy (TDLAS) technique is widely used in many fields, such as high precision, fast response, no need for contact measurement, and is widely used in .TDLAS technology. Using low frequency sawtooth signal and high frequency sine wave signal to scan / modulate laser, it is necessary to extract harmonic signal from gas absorption signal by phase-locked amplifier at the back of detector to characterize gas concentration. Commercial phase-locked amplifiers are expensive, large in volume and inconvenient to be used in integrated instruments. In this paper, a digital quadrature phase-locked amplifier for TDLAS gas detection system is developed, which has the advantages of low price, small volume, simple hardware circuit and easy integration. Firstly, the related theories of infrared absorption spectroscopy and TDLAS technology are introduced, including Lamberbilt's law, direct Absorption spectroscopydas, wavelength modulation Modulated spectroscopy, harmonic detection, etc. The theory of phase-locked amplifier is simulated by MATLAB, and the correctness of the proposed algorithm is verified. Secondly, the hardware circuit of digital phase-locked amplifier is designed, including photoelectric conversion circuit, subtraction circuit and AD sampling circuit. Keyboard matrix circuit, LCD driver circuit, SCI Serial Communication Interface (Serial Communication Interface) communication circuit and DSP(Digital Signal process processor) minimum system, etc. Thirdly, the program flow chart of digital phase-locked amplifier is introduced in detail, and the design scheme of two interrupt, low-pass filter and harmonic wave display module are given. The function model of phase locked amplifier is established by Simulink and the use case test is carried out. Finally, relevant experiments are carried out to test the performance of the phase locked amplifier. The experiment of extracting harmonics from single frequency sinusoidal signal shows that the amplitude of the first harmonic is linearly related to the peak value of the input sinusoidal signal. The experiment of extracting harmonics from simulated differential absorption signal shows that the peak value of harmonic signal is linearly related to the concentration of simulated gas. The CH_4 gas experiment was carried out, the harmonic signal was extracted from the differential absorption signal, the gas concentration was calibrated, the stability of the detection system was tested, and the Allan variance. CH4 concentration was calculated when the concentration was 0 ppm. The range of variation of the measured concentration is -61.2457 ppm ~ 84.4715 ppm ~ (-1) Allan deviation-integral time curve shows that when the integral time is 0.1 s, the detection limit of 1 蟽 is about 16.89212 ppm, and when the integral time is increased to 3.8 s, the detection limit of 1 蟽 is reduced to 3.05046 ppm. The innovation of this thesis is 1: 1. A digital quadrature phase-locked amplifier for TDLAS gas detection system is designed and developed. Its hardware circuit is simple and only a few reference signal amplitudes and digital filter coefficients should be stored in the algorithm. The phase-locked amplifier can be used as a module of data processing and harmonic extraction, so it can be used in any gas detector based on TDLAS technology to detect the concentration of multiple gases.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN722

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