QEPAS sensor for simultaneously sensitive detection of NH3 and H2S based on frequency-division multiplexing

Xiang Chen; Hao Liu; Mai Hu; Zhenyu Xu; Hao Deng; Xueli Fan; Ruifeng Kan

doi:10.1117/12.2625056

27 March 2022 QEPAS sensor for simultaneously sensitive detection of NH₃ and H₂S based on frequency-division multiplexing

Xiang Chen, Hao Liu, Mai Hu, Zhenyu Xu, Hao Deng, Xueli Fan, Ruifeng Kan

Author Affiliations +

Proceedings Volume 12169, Eighth Symposium on Novel Photoelectronic Detection Technology and Applications; 121697Q (2022) https://doi.org/10.1117/12.2625056
Event: Eighth Symposium on Novel Photoelectronic Detection Technology and Applications, 2021, Kunming, China

Abstract

A sensitive sensor was built using frequency-division multiplexing quartz-enhanced photoacoustic spectroscopy (QEPAS) to simultaneously measure dissolved NH₃ and H₂S. Two distributed feedback (DFB) diode lasers with central wavelength located at 1512.2 nm and 1577.2 nm were employed as the light sources for the excitation of the photoacoustic signals which are detected by the quartz tuning fork (QTF). Two homemade analog lock-in amplifiers were utilized to retrieve the second harmonic (2f) components derived from the photoacoustic signals of NH₃ and H₂S, respectively. The results show that the interference between second harmonic signals of the two species can be effectively suppressed by using the varied modulation frequencies near the resonant frequency of the QTF according to the frequency-domain and time-domain analysis. An excellent linear response was observed within a wide range of concentration and the linear response coefficients were larger than 0.999. Allan deviation method was used to analyze the minimum detection limits of NH₃ and H₂S with 0.5 ppm and 4.6 ppm, corresponding to the normalized noise equivalent absorption coefficients (NNEA) of 1.2×10^-8 cm^-1W√Hz and 7.8×10^-9 cm^-1w√Hz, respectively. The detection system can satisfy the demand for precise measurements of NH₃ and H₂S.

Citation Download Citation

Xiang Chen, Hao Liu, Mai Hu, Zhenyu Xu, Hao Deng, Xueli Fan, and Ruifeng Kan "QEPAS sensor for simultaneously sensitive detection of NH₃ and H₂S based on frequency-division multiplexing", Proc. SPIE 12169, Eighth Symposium on Novel Photoelectronic Detection Technology and Applications, 121697Q (27 March 2022); https://doi.org/10.1117/12.2625056

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