Detection of water vapor concentration based on differential value of two adjacent absorption peaks

A novel method based on differential value of two adjacent absorption peaks is presented to detect concentration of water vapor. This new method is available to solve insufficiency during measurement of water vapor concentration based on scanning spectra using single absorption line, especially difficulty of selection of reference point causing by random noise and broadening with relatively high pressure. For the two absorption lines, the intensity of the transition should be different and distinguished easily and the following absorption lines are selected: 1367.862 and 1368.597 nm. Differential value of the two absorption peaks appears a linear relation to water vapor concentration. Based on the principle of this novel method, we design a detection system. The measuring result indicates the accuracy and resolution of this system can reach to 20 and 10 ppm, respectively