Study On The Zero-order Fringe Automatic Positioning And Performance Of Optical Interference Methane Detector

Traditional optical interference methane detector has shortcomings such as subjective influence on measurement results and large measurement errors introduced by humans.To overcome shortcomings,in this paper,the characteristic of the white light interference fringe pattern is analyzed,photoelectric conversion device CCD is used to replace the original eyepiece ruler structure for improving the measuring device,and peak extraction and Gaussian fitting is used to automatically locate zero-order fringe.Calibrating the detector with water column pressure gauge is to obtain a linear relationship for measuring methane concentration,test platform built and four methane concentration standard gases chosen.Performance of measurement accuracy and measurement stability of the detector are tested,the factors influence of temperature and non-methane gas on the measurement results of the detector are studied.Zero-order fringes in the interference fringes formed by different methane concentrations are accurately located.The fringe displacements are calculated according to the position of the zero-order fringe at different concentrations,The relationship between displacement and concentration is linearly fitted,which can be used to calculate the concentration value through the displacement caused by the unknown methane concentration.The performance test results show that,compared with the MT 28-2005 technical standard,the measurement error of the improved detector is better than the standard requirement.The temperature drift experiment of the detector is carried out by using a high and low temperature test box.According to the temperature drift of the zero-point,linear compensation and quadratic term compensation are used.The results show that the effect of quadratic term compensation is better.Theoretical measurement values of the common coal mine non-methane gas such as carbon dioxide are calculated.That theoretical calculation values are basically close to the experimental measurement values is proved by standard gas concentration experiment.Therefore,theoretical calculation formula can be used to judge the influence of the presence of non-methane gas on the measurement accuracy of the optical interference methane detector.