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Detecting method and device for methane concentration

A technology of methane concentration and detection method, which can be used in measurement devices, color/spectral property measurement, material analysis by optical means, etc., and can solve problems such as economic and people's safety loss

Inactive Publication Date: 2006-01-04
JILIN UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, since the content of methane in the air exceeds 5.3%, it will explode in case of fire, so it is also an explosive gas. The coal mine gas explosion will bring great losses to the national economy and people's safety.

Method used

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  • Detecting method and device for methane concentration
  • Detecting method and device for methane concentration
  • Detecting method and device for methane concentration

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0032] Embodiment 1 illustrates the difference principle

[0033]When the cavity length of F-P just makes the transmitted light of LED coincide with the absorption line of methane, the light intensity received by the detector is the lowest at this time, and contains the information of methane concentration; adjust the cavity length of F-P to make the transmitted light of LED coincide with the absorption line of methane The absorption lines of methane are staggered, and the detector receives the maximum light intensity at this time; the concentration of methane can be calculated according to the theoretically derived formula through the two measured light intensities.

Embodiment 2

[0034] Embodiment 2 specifies detection device

[0035] The detecting device of methane concentration of the present invention is by image 3 shown. image 3 Among them, 1 is a light source, and the emission spectrum is in the range of 1400nm to 1800nm; 7 is a photodiode, which can be an InGaAs photodiode, as a component that receives an optical signal and converts the optical signal into a corresponding electrical signal; 8 is a lock-in amplifier, Together with the photodiode 7, it constitutes a detection system; 11 is a collimating lens, which converts the light emitted by the light source 1 into parallel light, so as to pass through the gas to be detected; 12, is the gas to be detected; 13 is a converging lens, which increases the methane information. The collection area of ​​optical signal; 14 is Fabry-Perot etalon; 15 is focusing lens; 16 is signal generator, preferably uses multifunctional function signal generator, and the sawtooth wave signal that produces is Fabry-Pe...

Embodiment 3

[0036] Embodiment 3 The specific process and example of detecting methane

[0037] The specific process of using the device of the present invention is as follows: firstly adjust the F-P etalon so that the cavity length is 0.507mm; the sawtooth wave signal generated by the signal generator is added to the piezoelectric ceramic tube to adjust the F-P cavity length. When the length of the cavity makes the F-P transmission peak coincide with the absorption peak position of methane, the photodiode 7 detects the minimum value I of the light intensity min ; When changing the long distance of the cavity to stagger the absorption peak of the transmission peak and methane, the photodiode 7 detects the maximum value I of the light intensity max , and then brought into the theoretically derived formula, the concentration of methane can be obtained. In order to improve the signal-to-noise ratio of the system, a lock-in amplifier can be used for detection, and its RS232 output port can be...

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Abstract

The present invention belongs to the field of gas detecting technology. The methane concentration detecting method includes using light source in certain spectrum range and resonance cavity with two high reflectivity inner surfaces; detecting the light from the light source and through the detected gas and the resonance cavity; regulating the length of the resonance cavity to detect the maximum light strength and the minimum light strength; and calculating the methane concentration with the formula. The detecting device includes LED light source, collimating lens, converging lens, Fabry-Perot etalon, detection system, computer, and signal generator. The present invention has low cost, convenient optical path collimation and high sensitivity.

Description

technical field [0001] The invention belongs to the field of gas detection. In particular, it relates to a method and device for methane detection using infrared light emitting diode (LED) as light source, Fabry-Perot etalon (hereinafter referred to as F-P) etalon frequency selection, and differential principle. Background technique [0002] Methane is a combustible gas and another important natural fuel after coal and petroleum. But because methane exceeds 5.3% in the air, it will explode in case of fire, so it is another kind of explosive gas. The coal mine gas explosion brings great losses to the national economy and people's safety. At the same time, the increase of methane content in the atmosphere will also produce a greenhouse effect, which is also an important issue of environmental protection. [0003] The prior art similar to the present invention is an article titled "Research on Differential Absorption Optical Fiber Methane Gas Sensor", which was published in "...

Claims

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Application Information

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IPC IPC(8): G01N21/35G01N21/3504
Inventor 高锦岳姜云康智慧曲艺孙晓峰
Owner JILIN UNIV
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