Compact VCSEL-based CO2 and H2O sensor with inherent wavelength calibration for safety and air-quality applications

Hangauer, Andreas; Chen, Jia; Seemann, K.; Karge, P.; Strzoda, R.; Amann, M.-C.

doi:10.1364/cleo.2010.jthb3

Cited by 1 publication

(1 citation statement)

References 8 publications

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“…In J. Chen and A. Hangauer's research, the broad scanning range was employed for the wavelength calibration while the narrow scanning was for gas concentration measurements using the linear least square curve fitting (LLSCF) algorithm [28], [29]. They concluded that the second harmonic detection had higher precision than the first harmonic detection [11].…”

Section: Comparedmentioning

confidence: 99%

VCSEL-Based Atmospheric Trace Gas Sensor Using First Harmonic Detection

et al. 2019

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This paper presents a measurement system based on 1 the first harmonic in tunable diode laser absorption spectroscopy 2 using a vertical-cavity surface-emitting laser to measure the 3 atmospheric CO 2 and H 2 O concentrations. The developed system 4 separates the residual amplitude modulation signal from the 5 harmonics and then eliminates it. A digital signal processing 6 is developed to autonomously infer the wavelength and light 7 intensities of the laser. The gas concentrations are determined 8 without extra calibration. The long-term measurements are taken 9 to validate the precision and accuracy of the system. Based 10 on the Allan variance analysis, the broad wavelength scanning 11 enhances the measurement precision, and the first-harmonic 12 detection can achieve about two times as high precision as the 13 traditional second-harmonic detection. The field measurements 14 implemented in early spring of 2018 in Munich were compared 15 with the commercial nondispersive infrared (NDIR) sensor. 16 The outcomes have revealed that our system has high accuracy 17 for the gas concentration measurements and high consistency 18 with the NDIR sensor. The diurnal variations of CO 2 concen-19 tration have demonstrated that CO 2 concentration in urban 20 areas is affected by the biosphere and meteorological conditions 21 and the daily anthropogenic activities. Furthermore, the air 22 trajectory analysis based on the HYSPLIT model has found that 23 the CO 2 emission sources primarily come from the southeast 24 of Munich. The developed system described in this paper has a 25 great potential for in situ trace gas concentration measurements, 26 the analysis on the polluted gas distributions, and the verification 27 of the pollutant transport model in urban areas. 28 Index Terms-Trace gas concentration, tunable diode laser 29 absorption spectroscopy (TDLAS), wavelength modulation spec-30 troscopy (WMS), first harmonic, vertical-cavity surface-emitting 31 laser (VCSEL). 32 I. INTRODUCTION 33 G REENHOUSE gases (GHG) have a significant negative 34 impact on the climate change. Research has indicated 35 that carbon dioxide (CO 2), one of the dominant GHG, has 36

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Section: Comparedmentioning

confidence: 99%