Device and method for measuring mean concentration of gas in open space

Abstract

The invention discloses a device and a method for measuring the mean concentration of gas in open space. The device comprises a semiconductor laser, a semiconductor laser controller, an optical fiber coupler, an erbium-doped optical fiber amplifier, a photoelectric detector, an optical transceiving antenna, a single-mode optical fiber and a data processing unit. According to the method, a cavity ring-down technology is used to measure the cavity ring-down time of a laser at a wavelength of an absorption spectrum peak of to-be-measured gas and a laser at a wavelength out of the absorption spectrum range respectively, the absorption coefficient of the gas is obtained through calculation, and then the absolute concentration of the gas is solved through calculation according to the relation of the gas absorption coefficient, the absorption section and the concentration; meanwhile, a detection distance calculated through measurement of the time interval of ring-down pulse; the mean concentration of the gas is obtained through calculation on the basis of the known integrated concentration of the gas in the open space and detection distance. The method has the characteristics of high measurement sensitivity and high anti-interference capacity.

Description

technical field [0001] The invention relates to a device for measuring the average concentration of gas in an open space, in particular to a device and a method for measuring the average gas concentration based on cavity ring-down technology and pulse ranging technology. The device can be used in gas telemetry, acetylene leakage detection and other fields. Background technique [0002] With the development of petrochemical industry, if flammable, explosive, toxic and other dangerous gases leak during production and transportation, it will cause poisoning, fire and even explosion accidents, seriously endangering people's lives and property safety. Therefore, the measurement technology of the average gas concentration has a wide range of application requirements in the detection of dangerous and toxic gases, as well as in the process detection and control of various industrial manufacturing. Optical detection methods, such as tunable diode absorption spectroscopy and cavity r...

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Problems solved by technology

Put the precision ring down cavity outdoors and connect it through optical fiber, and the ammonia concentration at a fixed point in the open space can be measured, and it has reached the order of 11ppbv (see the reference "Remote open-pathcavity-ringdownspectroscopicsensingoftracegasesinair,basedondistributedpassivesensorslinkedbykm-longopticalfibers", OPTICSEXPRESS ,Vol.22,No.11.13171-13189,2014) but the obtained gas concentration is the average concentration of the space at a fixed point, and the average concentration of the gas in the entire open space cannot be obtained

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