Online calibration of the wavelength of spectrometer based on SO2 absorption spectrum
Ultraviolet differential absorption spectroscopy technology has been widely used in the monitoring of industrial flue gas emissions.The spectrometer,a core component of the UV flue gas analyzer,is susceptible to wavelength drift caused by temperature changes,which in turn affects the accuracy of pollutants monitoring results.In this paper,a soft wavelength calibration method for spectrometers is proposed.A standard SO2 absorption spectrum peak wavelength database is established through experiments.When the wavelength drift exceeds 0.02nm,the corresponding function between the spectrometer pixel and wavelength will be re-fitted using the pixel of the SO2 absorption peak in conjunction with the database.This method enables real-time calibration of the spectrometer wavelength.Experiments are conducted to validate the proposed calibration method.Results showed that with a 10℃environmental temperature range,this method can reduce the measurement error of 993mg/m3 NO standard gas from 115.2mg/m3 to 21.4mg/m3,with an absolute error reduction of 93.8mg/m3.The best wavelength calibration effect is achieved when the measured SO2 concentration is 1430mg/m3.For low-concentration measurement sites,the signal-to-noise ratio of the spectral signal can be amplified by increasing the number of spectral averages,thereby improving the effectiveness of the online wavelength calibration method.
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