The theoretical and experimental exploration of a novel water-vapor concentration measutrment scheme based on scanning spectrometry

According to the near infrared absorption spectrum, a novel water-vapor concentration detection scheme based on scanning spectrometry is proposed. The experiment device adopts narrowband illuminant distributed feedback laser diode (DFB - LD) as the source and uses the method of taking the average value of multiple stacking signals to improve the signal-to-noise ratio. The accuracy and resolution which are verified by the micro-water generator reach 20ppm and 10 ppm respectively. In addition, the variation of the absorption coefficient of the water-vapor spectral center wavelength with different pressures is analyzed, and based on that, we get the conclusion that the line-shape function can be fitted by Lorenz line-shape and Gaussian line-shape when the pressure is more than 0.4atm and less than 0.005atm respectively. Besides, the method of using the integral area of absorption spectrum to measure gas concentration is elaborated for the first time. Especially when the pressure is higher than atmospheric pressure, this method which could improve the resolution and accuracy is a feasible one to calculate gas concentration in engineering.