Guolin LI, Qingzhi JIANG, Kun MA, Yue JIAO, Wenhai JI. Experimental Study on Methane Detection Based on Cascaded Integrator Comb of Digital Orthogonal Phase-locked in Amplifier[J]. Acta Photonica Sinica, 2021, 50(2): 122
- Acta Photonica Sinica
- Vol. 50, Issue 2, 122 (2021)
Fig. 1. The absorption spectrum of CH4, CO2, and H2O in the vicinity of 1 653 nm
Fig. 2. Experimental system installation diagram
Fig. 3. The relationship diagram of laser emission wavelength, current tuning and temperature tuning
Fig. 4. Quadrature lock-in amplifier working principle diagram
Fig. 5. Digital quadrature lock-in amplifier input and output signal simulation diagram
Fig. 6. The structure diagram design of narrow-band low-pass filter
Fig. 7. Simulation diagram of laser drive signal and analog gas absorption signal
Fig. 8. Simulation diagram of TDLAS-WMS system based on digital quadrature lock-in amplifier
Fig. 9. Second harmonic signal simulation diagram and fitting result diagram
Fig. 10. Output diagram of the second harmonic signal of CIC filter and LPF filter
Fig. 11. The relationship between the concentration inversion value and the set value of the TDLAS system based on CIC and LPF
Fig. 12. Experimental detection results of methane gas with concentration of 1~100 ppm
Fig. 13. Concentration inversion effect diagram of NIPALS-ELM and CLS algorithm models
Fig. 14. Stability test result graph and Allan analysis of variance graph
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Table 1. Comparison of concentration retrieving error between NIPALS-ELM and CLS algorithm models
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