共查询到17条相似文献，搜索用时 62 毫秒
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研究了音叉式石英晶振的个体尺寸、安放角度、探测部位以及外部污染对整个石英增强光声光谱系统(QEPAS)的探测灵敏度影响。测试了国内外十种不同音,结果表明顶端为楔形构造的音叉式石英晶振比规则的长方体构造的音叉拥有更高的品质因数(Q值)。在相同的测试条件下探测水的吸收线(7 306 cm-1)时获得更高的灵敏度,探测信号的强度相差高达50%。在研究音叉安放角度对探测信号影响的实验中,发现音叉的旋转角度与俯仰角度对探测信号的强度几乎没有影响,但是当光束以角度φ斜入射时,更多的噪声被带入到测量中。在正入射的情况下音叉的最佳响应位置在距离音叉底部约3.1 mm。定性研究了外部杂物污染对音叉频率的影响,发现随着污染物的附着,石英音叉的频率会呈现降低的趋势,提供了一种改变音叉式石英晶振的共振频率的方法,为石英音叉用于较低调制频率的探测提供了一种理论可能,这对于石英增强光声光谱技术用于V-T弛豫率较慢的痕量气体检测有重要的意义。 相似文献
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设计并演示了一种全光型石英增强光声光谱技术, 该技术在传统的石英增强光声光谱系统中增加了另一束探测光束, 把与气体浓度成正比的石英晶振振臂的振动幅值转化为探测光束的强度变化, 实现了探测气体处无电子元件的全光学系统. 如此的设计使该系统具有较强的抗电磁干扰能力和非常小的传感头体积, 能够用于探测空间受限或探测环境恶劣的情况下, 并实现远距离探测. 在这种配置下, 探测大气压下的水汽, 获得的噪声等效吸收系数为1.13×10-6 cm-1W/√Hz. 进一步讨论了优化系统和提升其探测灵敏度的途径.
关键词：
石英增强光声光谱
音叉式石英晶振
气体传感 相似文献
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实验中设计了一种基于微型非共振腔的石英增强光声光谱痕量气体传感器, 用来检测非纯氦气中的痕量氨气浓度. 该传感器采用的微型非共振腔只在空间上限制声波扩散以达到增强信号目的, 而不是像传统微型共振腔一样依靠共振效应. 如此的设计使探测小分子无机气体的光谱测声器尺寸远远小于共振腔的配置而有利于准直. 不同气压下的信号和噪声也被研究, 用来优化传感器性能. 在这种配置下和27.7 kPa的最优气压下, 获得的最佳氨气探测灵敏度为463 ppb (1σ , 1 s积分时间), 相应的归一化噪声等效吸收系数为4.3×10-9cm-1W/√Hz.
关键词：
气体传感器
石英增强光声光谱
音叉式石英晶振
类氢气体纯度分析 相似文献
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光纤倏逝波型石英增强光声光谱技术 总被引：1，自引：0，他引：1
采用块状光学准直聚焦透镜组的传统石英增强光声光谱(QEPAS)技术存在体积难以缩减,结构稳定性不佳,无法适应空间狭小、振动复杂的特殊环境等缺点.基于此,将光纤倏逝波技术与QEPAS技术相结合,提出了一种新型微纳结构光纤QEPAS痕量气体检测技术.实验中,为了提高QEPAS系统信号幅值,优化了石英音叉与激光束的空间位置、激光波长调制深度,同时对比了两种不同共振频率的石英音叉,最终采用共振频率较低的30.720 kHz石英音叉作为声波探测元件,获得的检测极限为6.25×10~(-4)(体积分数),归一化噪声等效吸收系数为4.18×10~(-7)cm~(-1).W·Hz~(-1/2). 相似文献
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珐珀解调的石英增强光声光谱气体探测系统 总被引：1，自引：0，他引：1
提出一种珐珀解调,适用于开放环境的全光式石英增强光声光谱气体探测系统。基于石英增强光声光谱系统,采用法珀干涉解调代替传统的电解调方式,通过拾取石英音叉的叉指侧面与光纤端面之间形成的法珀腔的腔长变化解调得到被测气体的光声光谱信号。构建了实验系统,在开放环境中完成了对空气中水蒸气的探测实验,得到其归一化噪声等效吸收系数为2.80×10-7 cm-1.W.Hz-1/2。结果表明,该探测系统的探测灵敏度是传统石英增强光声光谱探测系统的2.6倍。该系统具有极强的抗电磁干扰能力、能够用于易燃易爆气体检测、适用于高温、高湿度等恶劣环境并实现远距离多点、组网探测。 相似文献
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光声光谱气体检测技术是利用光声效应实现痕量气体检测的一项重要技术,具有高灵敏度、高选择性、零背景信号、可实时在线监测等优点,在环境监测、采矿冶金、能源电力、医疗卫生等领域发挥着至关重要的作用。考虑到气体检测应用环境的复杂性,实际的检测环境往往是多种组分气体同时存在且需要监测每种组分气体的含量,此时对多组分气体进行同时检测的技术就显得尤为重要。首先介绍了光声光谱气体检测技术的基本原理和特点,主要从光源和光声池的角度阐述了以光学复用方法为核心的光声光谱技术在多组分气体检测中的应用,并分析了石英增强光声光谱技术的特点及其在多组分气体检测中的应用,最后对光声光谱多组分气体检测技术的发展趋势进行了总结与展望。 相似文献
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以标准商用石英音叉（QTF）为测声模块的石英增强光声光谱（QEPAS）技术是近年来发展迅速的一种痕量气体检测技术。标准商用QTF拥有的小体积,高Q值,高共振频率的特性使QEPAS技术具有结构紧凑且对环境噪声免疫的特性。但传统商用QTF狭窄的振臂间距以及较高的共振频率,使其无法在光源光束质量较差或被测气体弛豫率较低的情况下被很好的应用于QEPAS系统。为克服上述难题,非标准商用QTF（f0≠32.7 kHz）被设计制作并越来越多的被装配于QEPAS系统中。因此,QTF共振频率对QEPAS系统信噪比的影响需要被详细研究。以水汽为目标气体,采用二次谐波调制解调技术研究了QTF共振频率对基于QEPAS技术传感器性能的影响。实验结果表明,QTF共振频率的变化对QEPAS系统的输出信号及噪声均有显著影响且QTF共振频率与QEPAS系统信噪比之间存在反比关系。上述结论对QEPAS系统中非标准QTF的设计及使用均具有重要的指导价值,对该类传感器的研发及应用意义重大。 相似文献
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CHEN Zheng;SUN Bo;DONG Lei;WU Hongpeng 《光子学报》2023,52(3):268-277
Quartz-enhanced photoacoustic spectroscopy technology has the characteristics of zero-background, excitation wavelength independence, compact structure and cost-effectiveness. Compared with conventional photoacoustic spectroscopy, the innovation of the quartz-enhanced photoacoustic spectroscopy is that a quartz tuning fork is employed as an acoustic transducer instead of the wideband microphone. However, the narrow gap size and the high resonant frequency of the commercially available quartz tuning fork prongs limit the abroad application of quartz-enhanced photoacoustic spectroscopy in many fields. To overcome the disadvantage mentioned above, a custom quartz tuning fork which can reduce the resonance frequency while keeping high quality factor was designed. The finite element software COMSOL Multiphysics was used to estimate the stress field distribution along the quartz tuning fork prongs when the quartz tuning fork was designed. The calculation method of resonant frequency is analyzed by combining thr Euler-Bernoulli equation. For a traditional tuning fork quartz, to reduce the resonant frequency of the tuning fork, the length of the prongs should be increased while the width of the prongs should be reduced. At the same time, to obtain a higher quality factor, the width of the prongs must be increased, which results a higher resonant frequency of a tuning fork. Hence, the high quality factor and the low resonance frequency cannot be taken into account at the same time for the traditional shape of tuning fork quartz. From the results of theoretical analysis, the hammer-shaped prongs can optimize the strain field between the prongs and their support effectively. Hence, a quartz tuning fork with hammer-shaped prongs was designed. The homemade quartz tuning fork has the larger gap size ~800 μm between two prongs, which is nearly three times larger than the prongs' gap size of the standard quartz tuning fork. In the meantime, the quality factor and the resonant frequency of the homemade quartz tuning fork were optimized by 14% and 62% respectively, and the compact quartz-enhanced photoacoustic spectroscopy sensor for C2H2 detection was demonstrated by using hammer-shaped quartz tuning fork to verify the performance characteristics of the novel custom quartz tuning fork. A near-infrared distributed feedback diode laser with a center wavelength of 6 523.88 cm-1 and an output power of ∼12 mW was served as the C2H2 quartz-enhanced photoacoustic spectroscopy sensor excitation source. A so-called acoustic micro-resonator was employed in addition to the hammer-shaped quartz tuning fork for increasing the C2H2 quartz-enhanced photoacoustic spectroscopy signal amplitude via the acoustic resonance effect. The acoustic micro-resonator was assembled in an “on-beam” quartz-enhanced photoacoustic spectroscopy configuration, in which the acoustic micro-resonator was formed by two metallic thin tubes and was coupled to the homemade quartz tuning fork via the excited sound wave in gas contained inside the acoustic micro-resonator tubes. Both the length and assembly position of the acoustic micro-resonator were optimized in terms of signal amplitude and signal-to-noise ratio. And the two parameters mentioned above were selected to be 9 mm and 1.5 mm by experiment respectively. The second-harmonic detection technique was employed to reduce the sensor background noise and simplify the data process. The wavelength modulation depth was optimized at room temperature and atmospheric pressure. The hammer-shaped quartz tuning fork based C2H2 sensor achieved a minimum detection limit of 282×10-9 for a 300 ms averaging time and 12 dB/oct filter slope, which corresponds to a normalized noise equivalent absorption coefficient of 3.84×10-9 ![]()
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对音叉作受迫振动的规律及音叉振动周期与双臂质量的关系进行了研究,自制了新型的音叉受迫振动与共振实验仪,该仪器不仅可以手工调节做实验,而且可以实现计算机实时测量. 相似文献
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WANG Qiang;WANG Hao;XIAO Cong;LI Jinsong 《光子学报》2023,52(3):220-228
Laser spectroscopy is a powerful analytical technique based on the interaction process of light and matter （including absorption, reflection, scattering, refraction, interference, etc.）, which can provide various useful information （such as composition, concentration, velocity, flux, etc.） by analyzing the detected spectral signal and combing the related physical principles. With the continuous innovation of modern laser light sources and photodetector devices, the laser spectroscopy technique has also been developed rapidly. In terms of the three core components of the laser spectroscopy system （i.e., laser light source, absorption cell, and photodetector） and signal enhancement and noise suppression methods, various advanced laser spectroscopy techniques or detection methods have been developed. Quartz-enhanced photoacoustic spectroscopy and photothermal spectroscopy is a new and rapidly developing laser spectroscopy technique, which utilizes miniaturized quartz tuning forks as detectors with the advantages of small size, high quality factor, and low cost. Quartz-enhanced photoacoustic spectroscopy is a spectroscopic technique that measuring the aco of light and gas in a radiation-free relaxation process, which utilizes the resonance effect and piezoelectric effect of the quartz tuning fork as an acoustic detector. However, the quartz-enhanced photothermal spectroscopy technique is based on the thermoelastic effect using quartz tuning fork as a light detector. To date, quartz-based enhanced photoacoustic and photothermal spectroscopy have been successfully applied to detect many small molecules with narrow absorption spectra and several large molecules with broad, unresolved spectral absorption features. These two techniques have been widely used for developing real-time and compact trace gas sensors with high sensitivity and selectivity.In this paper, a dual-spectroscopy detection technique based on quartz tuning forks is proposed to further improve the sensitivity of the quartz tuning fork based spectroscopic detection technique. To demonstrate this proposed gas detection technique, atmospheric water vapor （H2O） was used for the analytic target and a dual-spectroscopy gas detection system based on two quartz tuning fork detectors （i.e. （QCTF1 and QCTF2） is developed by combing a near-infrared （NIR） diode laser emitting near 1 392 nm, the laser beam is directly coupled into an optical fiber collimator and allowing pass between the two vibrating arms of the QCTF1 detector, which is used to detect the photoacoustic signal generated from the absorption process of atmospheric water vapor. The laser beam between the two arms of the QCTF1 is then focused on the surface of the side arm of the QCTF2 detector through a CaF2 lens, which is used to detect the photothermal signal generated in the same environmental conditions. Moreover, the wavelength tuning characteristics of the laser were measured before the experiments, and the dependence of the emission wavelength on the driving voltage of the DFB laser at a temperature of 34 ℃ was obtained to ensure that the laser emission wavelength could effectively cover the absorption line of H2O near the optical wavelength of 1 391.67 nm. Since other gas molecules in ambient air, such as CH4, CO, O2 and CO2 have not obvious absorption features near 1 391.67 nm, therefore, the spectral interference from other molecules can be effectively avoided. The resonance profile curve and the signal amplitude of the quartz tuning fork detectors are precisely measured as a function of the excitation position, and the optimal modulation frequency and excitation position are also experimentally determined, which is of great significance to improve the detection sensitivity of the proposed dual-spectroscopy detection technique. To further improving the sensitivity, the wavelength modulation technique is combined with the phase-dependent characteristics, and the effective signal enhancement of the wavelength modulated photoacoustic and photothermal spectral signals are realized by using the difference detection principle, which effectively utilizes the laser power compared with the single spectraldetection method used in the traditional detection scheme. The experimental results show that the overall Signal-to-Noise ratio （SNR） of the proposed dual-spectroscopy detection technique is 1.97 and 1.24 times higher than those of photoacoustic and photothermal spectral signal, respectively, which effectively improves the system detection sensitivity. Finally, the relationship between the photoelectric conversion efficiency of the quartz tuning fork and the incident laser power in the dual-spectroscopy detection technique is investigated. The experimental results show that the quartz tuning fork detector has a good linear response to the incident laser power with a regression coefficient R 2=0.996, which indicates the sensitivity can further improved by using laser sources with more high output power. 相似文献
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基于石英增强光声光谱技术,以中心波长为2.0μm的窄线宽分布反馈式半导体激光器(DFB)为激励光源,采用波长调制及二次谐波解调技术通过改变激光器工作电流实现波长扫描完成了痕量CO2气体检测系统,并通过优化实验参数确定了常压下激光最佳调制深度,实现了高灵敏CO2浓度的检测。通过改变待测气体中的水汽浓度,研究了水汽对CO2气体探测结果的影响,结果显示在水汽浓度低于0.2%范围内,CO2气体光声信号随H2O浓度的上升而明显增强,当浓度高于此值后,H2O浓度的增加对CO2光声信号的增强作用几乎维持不变。数据显示,常温常压下H2O分子通过提高分子弛豫率最多可将二氧化碳R16吸收线的光声信号幅值提高约2.1倍。优化后的装置可以很好的实现大气中CO2浓度的检测。该装置获得的最小探测灵敏度为19ppm(1σ,300ms积分时间),相应的归一化噪声等效吸收系数为4.71×10-9 cm-1·W·Hz-1/2。 相似文献
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对石英音叉增强型光声光谱(QEPAS)系统中常用的石英音叉进行了有限元模态计算,获得石英音叉前6阶振型与模态频率,认知了第4阶对称摆动振型为有效振动,利用单因素法分析了石英音叉的音臂长度l1、音臂宽度w1、音臂厚度t、音臂切角θ、音臂圆孔直径d及音臂圆孔高度h对低阶有效共振频率(Fre)的影响,敏感度依次为:l1> w1>d>θ>t>h,考虑实际设计情形,筛选出了l1,w1,d与h四个石英音叉设计变量,采用Box-Behnken实验设计方案与RSM(response surface methodology)方法,以Fre为函数目标,建立l1,w1,d与h的二次回归响应面模型,得到了参数之间的交互作用,利用Design-Expert软件对响应面模型进行设计参数反求,结果表明,在15 000 Hz≤Fre≤25 000 Hz计算区域内误差较小,基本满足QEPAS系统的计算需求,所提出的研究与设计方法具有一定通用性,可为QEPAS系统中石英音叉结构参数设计提供参考。 相似文献