Method and device for detecting target gas concentration

Abstract

The invention discloses a method and device for detecting the concentration of a target gas. The method is used when the laser absorption intensity of the target gas in the gas to be measured is equivalent to the background. The method includes: selecting the target gas and the reference Gas; select an absorption peak of the target gas as the target absorption peak, and select an absorption peak of the reference gas as the reference absorption peak; obtain the fundamental wave intensity at the current value corresponding to the reference absorption peak; use the target absorption peak and the reference The difference of the current value corresponding to the absorption peak is obtained to obtain the second harmonic intensity due to absorption at the current value corresponding to the target absorption peak in the gas to be measured; according to the second harmonic intensity at the current value corresponding to the target absorption peak The concentration of the target gas in the gas to be measured is obtained by referring to the intensity of the fundamental wave at the current value corresponding to the absorption peak. By applying the invention, the gas concentration can be accurately calculated without increasing volume and cost, and the influence of the background is eliminated.

Description

technical field [0001] The invention relates to the technical field of gas detection, in particular to a method and a device for detecting the concentration of a target gas when the target gas is a weakly absorbing gas. Background technique [0002] When using Tunable Diode Laser Absorption Spectroscopy (TDLAS, TunableDiodeLaserAbsorption Spectroscopy) method for gas concentration detection, wavelength modulation technology (WMS) is generally used to scan the center frequency in the wavelength by scanning the DC bias point of the AC signal, so as to obtain the The change curve of the second harmonic of the signal. Since the PI curve of the laser is not an absolute straight line in the linear region, coupled with the nonlinearity introduced by nonlinear factors in the system such as amplifiers and analog-to-digital conversion (AD), even when the concentration of the gas to be measured is zero, the obtained quadratic The harmonic value will not be completely 0, but there is a...

AI Technical Summary

Problems solved by technology

[0006] 1. Due to the addition of a reference optical path, the volume and cost are increased;

[0007] 2. Since the reference light path and the detection light path are in different environments, the influence of light intensity loss caused by scattering and other reasons cannot be eliminated, so the influence caused by the background cannot be eliminated accurately

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