Abstract
We present a four beam ratiometric setup for an integrating sphere based gas cell, which can correct for changes in pathlength due to sphere wall contamination. This allows for the gas absorption coefficient to be determined continuously without needing to recalibrate the setup. We demonstrate the technique experimentally, measuring methane gas at 1651nm. For example, contamination covering 1.2% of the sphere wall resulted in an uncompensated error in gas absorption coefficient of ≈41%. With the ratiometric scheme, this error was reduced to ≈2%. Potential limitations of the technique, due to subsequent deviations from mathematical assumptions are discussed, including severe sphere window contamination.
Highlights
Stringent safety regulations and the need for environmental monitoring are driving a demand for robust and reliable sensing solutions in harsh and hazardous work environments
The optical technique applied in this research is based on tunable diode laser spectroscopy, where the laser diode wavelength is scanned across a gas absorption line to give a high resolution determination of the gas concentration
Quantitative absorption measurements are governed by the Beer-Lambert law, which describes the measurement of the gas absorption coefficient at a known concentration as [3]
Summary
Stringent safety regulations and the need for environmental monitoring are driving a demand for robust and reliable sensing solutions in harsh and hazardous work environments. Conventional multipass cells can suffer from formation of etalons both within the cell and from the use of windows, with the consequence that the user may not fully achieve the desired improvement in signal to noise ratio resulting from the increased pathlength [6] Minimising these effects, as well as avoiding beam overlap whilst achieving a long pathlength, usually requires time consuming alignment. Our technique aims to provide a real-time pathlength adjustment in the event of sphere wall contamination using a low-frequency ratiometric configuration In this way, gas absorption measurements can continue to be made accurately, as long as increased contamination doesn’t reduce the detection sensitivity to below an acceptable detection limit
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
