Design of the Mixed Gas Quantitative Analysis Based on Grating Spectral

A method of mixed gas quantitative analysis with near infrared spectroscopy （NIR）is described. A single plane diffraction grating is used in the monochromatic spectrum system. A quantitative analysis system is designed and constructed according to the parameters of the monochromator. The narrowband beam testing and spectral scanning experiments with methane and ethane are carried out. A 10nm narrowband beam is successfully obtained by the monochromatic system when the entrance slit width is 2mm. And a step-scanning resolution of the outgoing beam’s centre wavelength with 0.1nm can be realized within the spectra of 1.0-1.8μm. The results show that methane and ethane have a maxim characteristic absorption spectrum respectively with the centre wavelength of 1653nm and 1690nm existing between the spectra of 1.6-1.8μm, which is consistent with the HITRAN database. Presented approach has a successful application in online mixed gas monitoring with the characteristics of simple structure and low cost.