Gas absorptivity online measurement method based on fast Fourier transform

A technology of Fourier transform and measurement method, which is applied in the field of absorptivity measurement based on tunable diode laser absorption spectrum direct absorption method technology, and the field of gas absorptivity online measurement, which can solve the problem that wavelength modulation method cannot accurately measure absorptivity and direct absorption. It can solve the problems such as large uncertainty of baseline fitting, and achieve the effect of automatic software processing, strong anti-interference ability, and high data processing repeatability.

Active Publication Date: 2019-04-30
TSINGHUA UNIV
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Problems solved by technology

[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 modula

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  • Gas absorptivity online measurement method based on fast Fourier transform
  • Gas absorptivity online measurement method based on fast Fourier transform
  • Gas absorptivity online measurement method based on fast Fourier transform

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Embodiment

[0069] 1) Example Take CO molecule as an example, measure its (2←0)R(11) spectral line absorbance, and select its center wavelength v from the spectral database 0 =4300.699cm -1 ; A sine 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, and then modulate the wavelength v of the laser output from the tunable semiconductor laser 3 0 nearby;

[0070] 2) Divide the laser light generated by the tunable semiconductor laser 3 into two paths through the fiber beam splitter 4, one path passes through the gas cell 5 to be tested after being collimated, and receives the transmitted light intensity through the first photodetector 6; the other path laser light Into the interferometer 7, the second photodetector 8 detects the intensity of the emitted light from the interferometer 7. The first and second detectors convert the light signals into electrical signals and are collected by t...

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Abstract

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 gas absorption rate measurement method, in particular to an absorption rate measurement method based on a tunable diode laser absorption spectrum direct absorption method technology, and belongs to the technical field of laser spectroscopy 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 the molecular absorption rate, and then infer gas temperature, concentration and other parameters. Due to its non-contact, high measurement sensitivity, and anti-interference The advantages such as strong ability have gradually developed into one of the main methods of gas parameter diagnosis. [0003] Gas absorption rate is the key core parameter of TDLAS technology, and its high-precision online measurement has received extensive attention and research. At present, the gas absorption rate is usually measured by the...

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Application Information

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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
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