Abstract: As for the DOAS technology-based flue gas analyzer, wavelength drift may take place due to the impact of ambient temperature and vibration on its core part, i.e., the spectrometer. An online method to quickly calibrate the wavelength of the spectrometer is designed in this paper. By taking advantage of the characteristic absorption peaks of SO₂ standard gas in the wave bands of 202~214 nm and 280~310 nm, the three-order fitting is conducted based on the mapping relation of wave crest, trough and pixel, such that a rapid online calibration can be performed on the output wavelength of the spectrometer. The research results show that the drift can be reduced by 97.7% in the wave bands of 202~214 nm and 280~310 nm, with the indication error less than 2%, which turns out to be a significant improvement for the stability and measuring accuracy of the gas analyzer.

Key words: DOAS, flue gas concentration measurement, wavelength drift, characteristic absorption peak, wavelength pixels, mapping relation