Frequency-Domain Detection for Frequency-Division Multiplexing QEPAS

To achieve multi-gas measurements of quartz-enhanced photoacoustic spectroscopy (QEPAS) sensors under a frequency-division multiplexing mode with a narrow modulation frequency interval, we report a frequency-domain detection method. A CH absorption line at 1653.72 nm and a CO absorption line at 2004...

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Bibliographic Details
Published in:Sensors (Basel, Switzerland) Switzerland), 2022-05, Vol.22 (11), p.4030
Main Authors: Chen, Xiang, Liu, Hao, Hu, Mai, Yao, Lu, Xu, Zhenyu, Deng, Hao, Kan, Ruifeng
Format: Article
Language:English
Subjects:
Absorption
Acoustics
Atmospheric pressure
Bandwidths
Carbon dioxide
Communication
Experiments
Frequency analyzers
Frequency division multiplexing
Frequency domain analysis
frequency-domain signal
Gas mixtures
Gases
Lasers
Low pressure
Methane
photoacoustic spectroscopy
quartz tuning fork
Resonant frequencies
Sensors
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Summary:To achieve multi-gas measurements of quartz-enhanced photoacoustic spectroscopy (QEPAS) sensors under a frequency-division multiplexing mode with a narrow modulation frequency interval, we report a frequency-domain detection method. A CH absorption line at 1653.72 nm and a CO absorption line at 2004.02 nm were investigated in this experiment. A modulation frequency interval of as narrow as 0.6 Hz for CH and CO detection was achieved. Frequency-domain 2 signals were obtained with a resolution of 0.125 Hz using a real-time frequency analyzer. With the multiple linear regressions of the frequency-domain 2 signals of various gas mixtures, small deviations within 2.5% and good linear relationships for gas detection were observed under the frequency-division multiplexing mode. Detection limits of 0.6 ppm for CH and 2.9 ppm for CO were simultaneously obtained. With the 0.6-Hz interval, the amplitudes of QEPAS signals will increase substantially since the modulation frequencies are closer to the resonant frequency of a QTF. Furthermore, the frequency-domain detection method with a narrow interval can realize precise gas measurements of more species with more lasers operating under the frequency-division multiplexing mode. Additionally, this method, with a narrow interval of modulation frequencies, can also realize frequency-division multiplexing detection for QEPAS sensors under low pressure despite the ultra-narrow bandwidth of the QTF.
ISSN:1424-8220
1424-8220
DOI:10.3390/s22114030