Article

Applications of Kalman filtering to real-time trace gas concentration measurements.

Rice Quantum Institute, Rice University, Houston, TX 77251-1892, USA.
Applied Physics B (Impact Factor: 1.78). 02/2002; 74(1):85-93. DOI: 10.1007/s003400100751
Source: PubMed

ABSTRACT A Kalman filtering technique is applied to the simultaneous detection of NH3 and CO2 with a diode-laser-based sensor operating at 1.53 micrometers. This technique is developed for improving the sensitivity and precision of trace gas concentration levels based on direct overtone laser absorption spectroscopy in the presence of various sensor noise sources. Filter performance is demonstrated to be adaptive to real-time noise and data statistics. Additionally, filter operation is successfully performed with dynamic ranges differing by three orders of magnitude. Details of Kalman filter theory applied to the acquired spectroscopic data are discussed. The effectiveness of this technique is evaluated by performing NH3 and CO2 concentration measurements and utilizing it to monitor varying ammonia and carbon dioxide levels in a bioreactor for water reprocessing, located at the NASA-Johnson Space Center. Results indicate a sensitivity enhancement of six times, in terms of improved minimum detectable absorption by the gas sensor.

0 Bookmarks
 · 
119 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: We report on an airborne demonstration of atmospheric oxygen optical depth measurements with an IPDA lidar using a fiber-based laser system and a photon counting detector. Accurate knowledge of atmospheric temperature and pressure is required for NASA's Active Sensing of CO<sub>2</sub> Emissions over Nights, Days, and Seasons (ASCENDS) space mission, and climate modeling studies. The lidar uses a doubled erbium-doped fiber amplifier and single photon-counting detector to measure oxygen absorption at 765 nm. Our results show good agreement between the experimentally derived differential optical depth measurements with the theoretical predictions for aircraft altitudes from 3 to 13 km.
    Applied Optics 09/2013; 52(25):6369-6382. · 1.69 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We propose a method for the measurements of the 17O/16O isotope amount ratio in water, based upon the use of a pair of offset-frequency locked extended-cavity diode lasers at 1.39 μm. This method enables one to acquire absorption spectra with an extremely high fidelity, exploiting the highly accurate, absolute, and repeatable frequency axis. One of the two lasers, namely the so-called slave laser, is continuously scanned across a pair of H216O and H217O lines at 7183.5 cm−1 and it interacts with a water vapor sample inside a multiple reflections cell, thus producing absorption spectra with a signal-to-noise ratio of the order of 4000 for a detection bandwidth of 1 kHz. The determination of the isotope amount ratio is performed through a careful analysis of the acquired spectra, by using semiclassical line profiles. In this respect, the influence of the choice of the line shape model is investigated. The experimental reproducibility of the spectrometer has been carefully assessed by means of an Allan variance analysis. Finally, the application of the Kalman filtering technique has shown that a precision of 0.6‰ can be achieved, from repeated spectral acquisitions over a time span of 6000 s.
    Physical Review A 11/2012; 86(5). · 3.04 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A compact isotope ratio laser spectrometry (IRLS) instrument was developed for simultaneous measurements of the D/H, 18O/16O and 17O/16O isotope ratios in water by laser absorption spectroscopy at 2.73 μm. Special attention is paid to the spectral data processing and implementation of a Kalman adaptive filtering to improve the measurement precision. Reduction of up to 3-fold in standard deviation in isotope ratio determination was obtained by the use of a Fourier filtering to remove undulation structure from spectrum baseline. Application of Kalman filtering enables isotope ratio measurement at 1 s time intervals with a precision (<1‰) better than that obtained by conventional 30 s averaging, while maintaining a fast system response. The implementation of the filter is described in detail and its effects on the accuracy and the precision of the isotope ratio measurements are investigated.
    Sensors (Basel, Switzerland). 01/2014; 14(5):9027-45.

Full-text (2 Sources)

View
28 Downloads
Available from
May 31, 2014