Development Of A High Precision Multi-component Gas Sensor Based On Hollow Waveguide

Small gas sensor based on hollow waveguide is a new type of sensor that developed in recent years,it has attracted special attention,its research is still not sufficient in many aspects and there exist many problems,for example,gas flow will lead to pressure drop in pipeline,which will affect the broadening of spectral line,and it also includes the interference of optical fringes and noise.In this paper,based on the status mentioned above,we analyze the gas sensor based on the hollow waveguide in deep,and develop a high-precision multi-component gas sensor based on the hollow waveguide.The main work of this paper includes:Firstly,we proposed the performance enhancement method of gas sensor based on hollow waveguide.We study the pressure drops carried by gas flow in hollow waveguide,and propose a method to enhance the sensitivity of hollow waveguide gas sensor.We mainly adopted an optimized negative pressure 1)narrow the spectral line and deduce the spectral line interference;2)increase the sensitivity of WMS-2f signal.The simulation and experiment results show that the influence of flow error of high precision gas mass flowmeter on full width at half maximum and integral absorbance of spectral line is controlled within 0.061% and 0.062%,respectively.Through optimized air flow speed,the sensitivity of WMS-2f signal is improved 18.3%,which enhance the performance of gas sensor based on hollow waveguide without any additional software or hardware expenditure.Secondly,the method of interference removal combined with empirical mode decomposition and multi-component spectral fitting is developed.In order to solve the main factors that affect the precision of gas measurement,including adjacent line,optical fringes and noise interference,this paper firstly adopts the method of optimizing the modulation amplitude to promote the ratio of signal-to noise,and uses empirical mode decomposition to further remove the optical fringes,at last,the multi-component spectral fitting technique is used to reduce the adjacent interference,and the gas concentration is retrieved by multi-spectral fitting technique.The results showed that the correlation coefficient between signals after interference suppression and simulation signal up to 99%,the interference signals are effectively removed and the original signals are well retained.Thirdly,a multi-component gas sensor based on hollow waveguide is designed.The proposed method of interference removal is applied,it not only realizes the rapid measurement of methyl sulfide,but also solves the interference of near absorption spectrum,and realizes the simultaneous and high-precision measurement of dimethyl sulfide,methane and water.The experimental results show that the measurement uncertainty of dimethyl sulfide,methane and water was as low as 80 ppb,20 ppb and 0.01%,respectively.The measurement sensitivity of dimethyl sulfide was increased by 20 ppb,and the detection limit was reduced to 9.6 ppb.Which show that the sensor can realize high-precision simultaneous detection of multi-component gas.The performance enhancement method of gas sensor based on hollow waveguide is presented in this paper,i.e.through optimized negative pressure working mode,it reduces the interference of spectral line effectively,and improves the sensitivity of gas measurement up to 18.3%.Meanwhile,by optimizing the modulation amplitude and combining the empirical mode decomposition technology,we have effectively eliminated the optical fringes and noise signals whose correlation coefficient with the original signal is as low as 0.02.The concentrations of dimethyl sulfide,methane and water are retrieved by multi-component spectral fitting technique in the later stage,and designed the high-precision multi-component gas sensor based on hollow waveguide,which is of great of significance for the actual factory pollution.