Simultaneous measurement of CO and CO2 at elevated temperatures by diode laser wavelength modulated spectroscopy

Abstract One single semiconductor distributed-feedback (DFB) laser is used to demonstrate the possibility of simultaneous measurements of CO and CO 2 at elevated temperatures. Wavelength modulation spectroscopy with second-harmonic detection is used to improve the detection sensitivity and accuracy. The concentrations of CO and CO 2 are determined from the WMS-1-normalized absorption-based WMS-2 f signal peak heights of a proper line pair of CO and CO 2 near 6357.814 cm −1 and 6357.312 cm −1 , which are selected using some line-selection criterions for the target temperature range of 300–1000 K. The CO and CO 2 concentrations measurements are within 2.86% and 2.69% of the expected values over the tested temperature range 300–1000 K. The minimum detectable concentrations of CO and CO 2 at 1000 K are 250 ppm m and 280 ppm m respectively.