QEPAS with electrical co-excitation for photoacoustic measurements in fluctuating background gases

Mordmueller, Mario; Schade, Wolfgang; Willer, Ulrike

doi:10.1007/s00340-017-6799-3

Cited by 26 publications

(17 citation statements)

References 13 publications

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“…Thus, these techniques are independent detectors for all wavelength regions. Since its development in 2002 by Kosterev et al [6], QEPAS has been advanced to one of the most sensitive photoacoustic techniques [7][8][9]. The superior real absorbance of methane is verified by estimating the detection limits.…”

Section: Introductionmentioning

confidence: 99%

Comparison of the spectral excitation behavior of methane according to InP, GaSb, IC, and QC lasers as excitation source by sensor applications

et al. 2019

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The MIR wavelength regime promises better gas detection possibilities than the NIR or the visible region because of the higher absorbencies simulated by HITRAN. In the MIR region are many important absorption lines of significant gases, which are relevant in healthcare, production supervision, and safety and environmental monitoring. One of those gases is methane. CH4 shows significant variations in absorbance with a maximum at 3.3 μm, which results in low detection limits in the range of low ppm. Interband-cascade-and quantumcascade-based lasers emit at higher wavelengths, where the absorbencies of methane are higher. The comparison is done by analyzing the performance of two spectroscopy applications: tunable diode laser absorption spectroscopy and quartz-enhanced photoacoustic spectroscopy.

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Section: Introductionmentioning

confidence: 99%

Comparison of the spectral excitation behavior of methane according to InP, GaSb, IC, and QC lasers as excitation source by sensor applications

et al. 2019

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“…In this paper however, we report on the ability of a continuous phase modulation instead of a fixed setting which yields a steady measurement and additionally separates the photo-acoustically induced amplitude from the offset generated by the oscillator circuit. In [9,10] we already described the ability to incorporate a quartz micro-tuning fork with removed container in an oscillator circuit and to simultaneously focus a laser beam between the tuning fork's prongs to generate acoustic waves upon absorption of the molecule. Since the laser modulation signal is derived from the oscillation circuit that automatically adjusts to the current resonance frequency of the tuning fork, the laser is always modulated with the correct frequency.…”

Section: Methodsmentioning

confidence: 99%

Phase Optimized Photoacoustic Sensing of Gas Mixtures

Mordmueller

Edelmann²,

Knestel³

et al. 2020

Applied Sciences

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In this paper, we report on the progress of the auto-triggered quartz-enhanced photoacoustic spectroscopy (QEPAS) technique which operates without external frequency generators and ensures permanent locking to the current resonance frequency of the tuning fork. This is obtained by incorporating the tuning fork in an oscillator circuit that autonomously oscillates at the present resonance frequency that shifts with changing environmental conditions, e.g., density and viscosity of the surrounding gas, temperature, and pressure. Both, the oscillation amplitude as well as the frequency can be read from the oscillator circuit. The photoacoustic signal appears as an offset of the electrically induced signal amplitude. Since the sum amplitude depends on the phase relation between the electrical and photoacoustic driving forces, the phase is permanently modulated, enabling the extraction of the photoacoustic component by use of a second lock-in amplifier stage which is being referenced with the phase modulation frequency. The functionality of this method is demonstrated for methane detection in a carbon dioxide atmosphere in a concentration range from 0 to 100% and ammonia in synthetic air employing a pulsed mid infrared QCL around 1280 cm−1. The gas mixtures are motivated by the demands in biogas-analysis.

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“…La technique associée a elle aussi évolué : ainsi des principes comme la co-excitation acoustique/électrique [13] ou le battement fréquentiel [14] ont permis de réduire le temps de mesure à la dizaine de millisecondes, avec des détectivités de 40 ppm de méthane [14] par exemple.…”

Section: Les Poutres En Siliciumunclassified

Comprendre. Détection de gaz par spectroscopie photoacoustique : principe et mise en œuvre

Duquesnoy¹,

Melkonian²,

Lévy³

et al. 2018

Photoniques

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QEPAS with electrical co-excitation for photoacoustic measurements in fluctuating background gases

Cited by 26 publications

References 13 publications

Comparison of the spectral excitation behavior of methane according to InP, GaSb, IC, and QC lasers as excitation source by sensor applications

Comparison of the spectral excitation behavior of methane according to InP, GaSb, IC, and QC lasers as excitation source by sensor applications

Phase Optimized Photoacoustic Sensing of Gas Mixtures

Comprendre. Détection de gaz par spectroscopie photoacoustique : principe et mise en œuvre

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