An on-line measurement method of gas absorptivity based on fast Fourier transform
A technology of Fourier transform and measurement method, which is applied in the online measurement of gas absorptivity, and in the field of absorptivity measurement based on tunable diode laser absorption spectrum direct absorption method technology, which can solve the problem that wavelength modulation method cannot accurately measure absorptivity and direct absorption In order to achieve the effect of automatic software processing, strong anti-interference ability and high repeatability of data processing
Active Publication Date: 2020-10-13
TSINGHUA UNIV
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[0005] The purpose of the present invention is to solve the problem that the baseline fitting uncertainty of the direct absorption method is large and the wavelength modulation method cannot accurately measure the absorptivity in TDLAS technology, and to provide an online absorptivity measurement method based on fast Fourier transform analysis
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[0069] 1) Embodiment Taking CO molecule as an example, measure its (2←0)R(11) spectral line absorptivity, and select its central wavelength v from the spectral database 0 =4300.699cm -1 ; A sinusoidal signal with a frequency f=1000Hz is generated by a signal generator and input to the laser controller 2 to modulate the output current of the laser controller 2, thereby modulating the wavelength v of the output laser of the tunable semiconductor laser 3 0 nearby;
[0070] 2) The laser light generated by the tunable semiconductor laser 3 is divided into two paths through the optical fiber beam splitter 4, one path passes through the gas chamber 5 to be measured after being collimated, and the transmitted light intensity is received by the first photodetector 6; Enter the interferometer 7, detect the outgoing light intensity of the interferometer 7 by the second photodetector 8, the first and the second detector convert the optical signal into an electrical signal and pass it int...
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The invention discloses a gas absorptivity online measurement method based on fast Fourier transform, and belongs to the technical field of tunable diode laser absorption spectroscopy (TDLAS). According to the method, a sine wave is adopted to modulate the output wavelength of a tunable semiconductor laser, a characteristic frequency spectrum containing absorption information is extracted throughfast Fourier transform on the transmission light intensity, the transmission light intensity is reconstructed, and other frequency noise signal interferences such as particulate matter and light intensity fluctuation can be effectively eliminated; a relationship between the laser light intensity and the wavelength is established based on an intermediate variable eta, and the transmission light intensity obtained by reconstruction is fitted with eta as an independent variable to realize synchronous online measurement of the incident light intensity and the gas absorptivity. The method is simpleand convenient to operate and wide in application range; the problems that a direct absorption method is large in base line fitting uncertainty and a wavelength modulation method cannot accurately measure the absorptivity are solved, and the gas absorptivity measurement precision is effectively improved.
Description
technical field [0001] The invention relates to an online measurement method of gas absorption rate, in particular to an absorption rate measurement method based on tunable diode laser absorption spectrum direct absorption method technology, and belongs to the technical field of laser spectrum and gas measurement. Background technique [0002] Tunable diode laser absorption spectroscopy (TDLAS) is a laser measurement technology that uses a narrow-band laser to scan molecular absorptivity, and then infer gas temperature, concentration and other parameters. Due to its non-contact, high measurement sensitivity, and anti-interference It has gradually developed into one of the main means of gas parameter diagnosis. [0003] Gas absorption rate is a key core parameter of TDLAS technology, and its high-precision online measurement has received extensive attention and research. At present, gas absorptivity is usually measured by the direct absorption method (DAS) based on triangula...
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IPC IPC(8): G01N21/39
CPCG01N21/39G01N2201/0612
Inventor 彭志敏杜艳君丁艳军
Owner TSINGHUA UNIV