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Gas detection method and gas detection device

A gas detection, photoacoustic gas technology, applied in measurement devices, analysis of fluids using sonic/ultrasonic/infrasonic waves, generation of ultrasonic/sonic/infrasonic waves, etc., can solve problems such as disk noise

Inactive Publication Date: 2008-04-02
LEISTER PROCESS TECH
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Modulation with a modulation wheel allows higher frequencies, but the vibration of the wheel produces noise at exactly the modulation frequency
[0006] The second disadvantage of low frequencies is that for resonance absorption the length of the absorption area needs to be more than 1 meter

Method used

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  • Gas detection method and gas detection device
  • Gas detection method and gas detection device

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Embodiment Construction

[0024] Figures 1 and 2 are the well-known principles of the different photoacoustic sensors discussed above.

[0025] Fig. 3 and Fig. 4 are graphs showing the relationship between the gas absorption intensity GAS and the laser intensity L1 and the wavelength WL. These two figures show the change in gas absorption. As shown in Figure 3, a laser intensity peak locked to a certain wavelength only detects gas absorption at that certain wavelength. Due to the difference in the absorption intensity of the broadband spectrum, moving 0.1 nm to one side of the laser wavelength will cause the absorption intensity to differ by about 30-50%. Therefore, results can vary over a wide range. By sweeping the laser peak along the wavelengths given in Figure 4, the absorption signature of the target gas is flattened to an average value.

[0026] Although the invention is described below using a laser diode as the laser source, the invention is not limited to this arrangement and other suitabl...

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Abstract

A gas detection method by using a photo acoustic near infrared gas sensor with a laser source and such a gas sensor comprising at least one amplitude modulated laser source, a gas chamber for receiving the gas to be detected, a microphone attached to the gas chamber, a photo detector for receiving the laser light after having passed through the gas filled gas chamber, processing means comprising a modulation frequency generator for providing a modulation signal for the at least one laser source and a control means for determining the gas concentration. The laser source changes it output wavelength across each cycle of the amplitude modulation between a minimum wavelength and a maximum wavelength. The result of this measurement scheme is that during each modulation cycle, the laser source scans its complete available wavelength range so that the absorption features of the target gas are levelled out to a mean value. This mean value is relatively insensitive to small variations of the laser's center wavelength; which are introduced by temperature variations.

Description

technical field [0001] The present invention relates to a gas detection method using a photoacoustic near-infrared gas sensor with a laser source, such a gas sensor comprising at least one amplitude-modulated laser source, a gas chamber for receiving the gas to be detected, a microphone connected to the gas chamber, for receiving Photodetectors of the laser light of the gas-filled gas chamber, processing means including a frequency-modulated generator for supplying at least one laser source with a modulation signal, and control means for determining the gas concentration. Background technique [0002] The principle of photoacoustic gas detection is well known (Fig. 1): an infrared filter 2 placed in front of a broadband emitter 1' (usually a light bulb) is used to select light whose wavelength corresponds to the absorption line of the target gas. Light of a selected wavelength propagates through a gas region 4 (typically in a tube 5), which may contain a target gas. If the ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N29/02G01N29/34
CPCG01N21/1702
Inventor B·威林M·科利A·塞弗
Owner LEISTER PROCESS TECH
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