Composite multi-harmonic-based online gas concentration measurement method

A technology of gas concentration and measurement method, which is applied in the direction of color/spectral characteristic measurement, etc., can solve the problems of inaccurate determination of wavelength modulation method and concentration measurement error, and achieve the elimination of the influence of laser intensity fluctuations, high signal-to-noise ratio and sensitivity, The effect of expanding the scope of application

Inactive Publication Date: 2014-06-18
TSINGHUA UNIV
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Problems solved by technology

[0007] In order to solve the problem that the wavelength modulation method cannot accurately determine the linear function and cause concentration measurement errors, the present invention provides an online gas concentration measurement method based on multiple harmonics, which can directly determine the gas concentration and simplify the measurement process.

Method used

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  • Composite multi-harmonic-based online gas concentration measurement method
  • Composite multi-harmonic-based online gas concentration measurement method
  • Composite multi-harmonic-based online gas concentration measurement method

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Embodiment

[0045] 1) Example to measure CO 2 As an example, the thermometer 5 and the scale measure the temperature T=293K and the optical path L=120cm of the gas medium 6 respectively, and the total pressure P=19.75±0.10kPa of the gas to be measured. According to the type of the gas to be measured, determine its mole Mass M=44, CO was selected from the spectral database 2 The center frequency v of the absorption spectrum 0 , line strength S(T), self-widening coefficient χ self and the air widening factor χ air Table 1 below:

[0046] Table 1CO 2 Molecule 6982.0678cm -1 Spectral constants of spectral lines

[0047]

[0048] 2) Take the tunable semiconductor laser 3 as the light source, and use the laser controller 2 to control the output frequency of the tunable semiconductor laser 3 to be stable at the center frequency v 0 place;

[0049] 3) Input the high-frequency amplitude-modulated sinusoidal signal generated by the signal generator 1 to the laser controller 2 to modulate...

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Abstract

The invention discloses a composite multi-harmonic-based online gas concentration measurement method and belongs to the technical field of tunable diode laser absorption spectroscopy (TDLAS). The method comprises the following steps: determining the line width of an absorption line by virtue of a ratio of second harmonics to quadruple harmonics, and calculating to obtain a linear function; and calculating the gas concentration according to a deduced ratio of second harmonics to first harmonics under strong absorption conditions. According to the method, the gas concentration is measured under the strong absorption conditions by the second and first harmonic signal mark-free method of absorption signals, the influence of laser intensity fluctuation, photoelectric amplification factors and other factors is eliminated, the signal to noise ratio and measurement accuracy are improved, the problem that a concentration measurement error is caused in a wavelength modulation method because the linear function of the absorption line is uncertain is effectively solved, the gas concentration measurement accuracy is improved, and the application range of the TDLAS technology is widened.

Description

technical field [0001] The invention relates to an on-line measurement method of gas pressure and concentration, in particular to an on-line measurement method of gas concentration based on tunable laser diode absorption spectrum technology. Background technique [0002] Real-time online detection of environmental pollution gases, flammable and explosive gases, and combustion atmosphere is a key technology in environmental protection, industrial safety production, energy saving and emission reduction. Tunable diode laser absorption spectroscopy (TDLAS) uses a narrow-band laser to scan the absorption line of the gas, and obtains the concentration of the gas to be measured by analyzing the intensity of the laser absorbed by the gas. Compared with the traditional sampling gas detection technology, TDLAS technology has the advantages of non-contact online measurement, strong selectivity, high sensitivity, and fast response. It can measure the average level of gas concentration i...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N21/39
Inventor 彭志敏丁艳军蓝丽娟
Owner TSINGHUA UNIV
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