Calibration-free gas concentration measuring device and method

A gas concentration measurement and measurement device technology, applied in the field of measurement, can solve problems such as high measurement accuracy and fast response, and achieve the effects of high-precision gas concentration measurement, improving measurement speed, and reducing maintenance.

Active Publication Date: 2020-05-08
TSINGHUA UNIV
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Problems solved by technology

In these cases, it is difficult for a single method to respond quickly in such a wide concentration measurement range, and it is difficult to mai

Method used

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  • Calibration-free gas concentration measuring device and method
  • Calibration-free gas concentration measuring device and method
  • Calibration-free gas concentration measuring device and method

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Embodiment

[0045] 1) Take CO and N 2 Taking mixed gas as an example, the absorption spectrum line is selected from the HITRAN spectral database, and its center frequency ν 0 6374.406cm -1 , the spectral line intensity S is 2.13×10 -23 cm -1 / (molec·cm -2 ); the temperature T of the mixed gas is about 25°C, the pressure P is about 100.6kPa, and the effective optical path L of the long optical path gas absorption cell is 120m. Configured CO and N 2 The gas mixture concentration X ranges from 4ppm to 1.09%;

[0046] 2) Measure the gas absorption rate and gas concentration by direct absorption spectroscopy: such as figure 1 As shown, the tunable semiconductor laser 3 is used as the light source, and the current and temperature of the tunable semiconductor laser are set by the laser controller 2, so that the laser wavelength is fixed at the central wavelength v 0 place. The external modulation of the laser controller 2 is turned on by the computer 1 so that it can load the triangular ...

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Abstract

The invention relates to a calibration-free gas concentration measuring device and method. The device comprises a direct absorption spectrum device and a ring-down spectrum device, and gas chambers ofthe two devices are communicated with each other and share one laser. Emergent light of the laser is divided into two beams, one beam enters the direct absorption spectrum device, the other beam enters the ring-down spectrum measuring device; and time-sharing measurement of the two spectrum technologies is achieved through program control. According to the method, the gas concentration is obtained by directly fitting the transmission light intensity, and calibration-free measurement of the direct absorption spectrum is realized. And cavity ring-down time is calculated by utilizing the gas absorption rate measured by the direct absorption spectrum and the ring-down time of gas absorption contained in the ring-down spectrum measurement, so that the calibration-free measurement of the ring-down spectrum is realized. Measurement results are intelligently selected according to the measurement accuracy and ranges of the two spectrums, the measurement accuracy is about 10-20 ppm when the concentration is high and is smaller than 1 ppm when the concentration is low; calibration is not needed in the measurement process; and the device and method have the advantages of being high in measurement speed, easy to operate and the like.

Description

technical field [0001] The invention relates to a gas concentration measurement method based on direct absorption spectrum technology and cavity ring-down technology, belonging to the field of measurement technology. Background technique [0002] Tunable laser diode absorption spectroscopy (TDLAS for short) has the advantages of non-contact, fast response and wavelength selectivity. Direct absorption spectroscopy (DAS for short) in TDLAS has a clear physical concept and is easy to operate. It is often used to measure parameters such as gas concentration and temperature, and has been widely used in high-concentration and strong-absorption environments. For trace gas monitoring and weak absorption, more complex techniques such as cavity ring-down spectroscopy (CRDS) are often used. [0003] When the gas absorption cell length is 1m, the minimum detectable absorbance α of DAS min about 10 -4 ~10 -5 , the corresponding absorption coefficient κ is about 10 -6 ~10 -7 cm -1 ...

Claims

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Application Information

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IPC IPC(8): G01N21/39
CPCG01N21/39G01N2021/391G01N2021/399
Inventor 彭志敏王振丁艳军
Owner TSINGHUA UNIV
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