研究目的
To develop a sensitive CO2 gas sensor to monitor CO2 concentrations using photoacoustic spectroscopy with a fixed wavelength quantum cascade laser.
研究成果
The FW-QCL based CO2-PAS sensor demonstrated high sensitivity, excellent signal stability, and a linear response to CO2 concentration. It achieved a 1σ MDL of 2.84 ppm at 1 s integration time, improving to 1 ppm at ~100 s. The sensor's robustness was confirmed by measuring CO2 concentrations from various emission sources, indicating its potential for industrial, environmental, and fire detection applications.
研究不足
The sensor's performance may be affected by system drifts over long integration times (>100 s). The study focuses on CO2 detection and may not be directly applicable to other gases without modification.
1：Experimental Design and Method Selection:
A PAS-based CO2 sensor system was designed using a FW-QCL emitting at 4.42 μm. The system included a resonant PA cell, a mechanical chopper for laser intensity modulation, and a correlation demodulation technique for noise reduction.
2：42 μm. The system included a resonant PA cell, a mechanical chopper for laser intensity modulation, and a correlation demodulation technique for noise reduction.
Sample Selection and Data Sources:
2. Sample Selection and Data Sources: A 30,000 ppm CO2–N2 gas mixture was diluted with pure N2 using mass flow controllers to vary CO2 concentrations.
3：List of Experimental Equipment and Materials:
FW-QCL (Model No. 41045-UF, Daylight Solutions), resonant PA cell with a condenser microphone, mechanical chopper, lock-in amplifier, and mass flow controllers.
4：Experimental Procedures and Operational Workflow:
The FW-QCL was operated in CW mode, and its intensity was modulated at the PA cell's resonant frequency. The PAS signal was detected and processed using a lock-in amplifier.
5：Data Analysis Methods:
The PAS signal was analyzed for stability, linear response to CO2 concentration, and long-term stability using Allan deviation analysis.
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