Developing CH4 detection limit at λ= 1.654 μm by suppressing optical interference fringes in wavelength modulation spectroscopy

2018 ◽  
Vol 255 ◽  
pp. 2614-2620 ◽  
Author(s):  
Wenke Liang ◽  
Yunfeng Bi ◽  
Qiang Zhou ◽  
Xiaozhou Dong ◽  
Tieliang Lv
Keyword(s):  
Detection Limit ◽  
Wavelength Modulation Spectroscopy ◽  
Wavelength Modulation ◽  
Optical Interference ◽  
Modulation Spectroscopy ◽  
Interference Fringes

Pressure-Dependent Detection of Carbon Monoxide Employing Wavelength Modulation Spectroscopy Using a Herriott-Type Cell

2017 ◽  
Vol 71 (5) ◽  
pp. 809-816 ◽  
Author(s):  
Chuanliang Li ◽  
Yingfa Wu ◽  
Xuanbing Qiu ◽  
Jilin Wei ◽  
Lunhua Deng
Keyword(s):  
Carbon Monoxide ◽  
Detection Limit ◽  
Second Harmonic ◽  
Wavelength Modulation Spectroscopy ◽  
Wavelength Modulation ◽  
Modulation Spectroscopy ◽  
Dependent Relationship ◽  
Low Concentrations ◽  
Allan Variation ◽  
Lock In

Wavelength modulation spectroscopy (WMS) combined with a multipass absorption cell has been used to measure a weak absorption line of carbon monoxide (CO) at 1.578 µm. A 0.95m Herriott-type cell provides an effective absorption path length of 55.1 m. The WMS signals from the first and second harmonic output of a lock-in amplifier (WMS-1 f and 2 f, respectively) agree with the Beer–Lambert law, especially at low concentrations. After boxcar averaging, the minimum detection limit achieved is 4.3 ppm for a measurement time of 0.125 s. The corresponding normalized detection limit is 84 ppm m Hz–1/2. If the integrated time is increased to 88 s, the minimum detectable limit of CO can reach to 0.29 ppm based on an Allan variation analysis. The pressure-dependent relationship is validated after accounting for the pressure factor in data processing. Finally, a linear correlation between the WMS-2 f amplitudes and gas concentrations is obtained at concentration ratios less than 15.5%, and the accuracy is better than 92% at total pressure less than 62.7 Torr.

Mid-infrared ChG-on-MgF2 waveguide gas sensor based on wavelength modulation spectroscopy

2021 ◽  
Author(s):  
Mingquan Pi ◽  
Chuantao Zheng ◽  
Huan Zhao ◽  
Zihang Peng ◽  
Jiaming Lang ◽  
...  
Keyword(s):  
Gas Sensor ◽  
Wavelength Modulation Spectroscopy ◽  
Wavelength Modulation ◽  
Mid Infrared ◽  
Modulation Spectroscopy
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