Ethanol has a characteristic narrow band absorption peak (2989.6 cm-1) that overlaps heavily with the airborne water vapour spectrum, severely affecting detection accuracy when the ambient humidity varies significantly. To this end it is particularly critical to investigate a method to eliminate background effects and improve the accuracy of ethanol telemetry. Firstly, the second harmonic signal of ethanol concentration under 5000~20000ppm*m water vapour environment was simulated by multi-functional fitting method, and the multivariate linear relationship between the second harmonic amplitude and water vapour concentration and ethanol concentration is obtained. Two sets of signals were obtained in one triangular wave period using double modulated amplitude and linear regression was used to solve the coefficients of the two equations, which in turn inverted the ethanol concentration in other water vapour environments. Simulation results show that the maximum error is less than 2.23ppm*m. The method also eliminates the need for complex reference light paths or expensive wide-range tunable mid-infrared lasers, reduces measurement errors due to variations in ambient humidity, and provides a basis for further development of simple, miniaturised ethanol telemetry systems.
H2O is an important molecule in the atmosphere, which is closely related to climate change and industrial applications (such as combustion process). The detection of trace water vapor concentration is of great significance in earth ecology and industrial production. Tunable diode laser absorption spectroscopy (TDLAS) inverses the gas concentration by measuring the gas absorption spectrum. The wavelength of the common characteristic absorption peak of H2O molecule is 7181.16 cm-1. The spectral absorption peaks of different wavelengths are analyzed in the paper. It is proved that when 7306.75 cm-1 characteristic absorption peak is used to replace 7181.16 cm-1 characteristic absorption peak for concentration inversion, the influence can be reduced and the measurement accuracy can be improved by combining the target peak with the interference peak.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.