The application of exponential filter on optical measurement of atmospheric compositions

In optical measurement of atmospheric compositions based on differential absorption technology, traditional noise suppression method based on running average needs to store the old values to be used evenly, thus costing large memory and introducing significant delay to the response speed. To overcome the drawbacks of the running average method, exponential filter is used in this paper. The principle of exponential filter is firstly analyzed. Then the response speed and the filtering effect are compared with the running average. The experiment results show that with exponential factor of 0.95, the response speed is close to that of running average with running window of 40, but the filtering effect better than the latter. While maintaining the response speed of running average with running window of 40, the standard deviation of the measured concentration can be decreased from 18 ppb to around 15 ppb with exponential filter. Generally speaking, the exponential filter can improve the response speed dramatically while maintaining good filtering effect.