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

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.

Highly sensitive detection of methane by near-infrared laser absorption spectroscopy using a compact dense-pattern multipass cell

“…The detection sensitivity can be still improved by further averaging the data, locking the laser wavelength to the targeted absorption line center and increasing time constant of lock-in amplifier, or use filter technique like Kalman Filter [28,29]. Such DP-MPC based on silver (or gold) coated spherical mirrors is operational in a wide spectral response range which allows one to couple the DP-MPC to quantum cascade laser in the mid-IR.…”

Photoperiodic regulation of the sucrose transporter StSUT4 affects the expression of circadian-regulated genes and ethylene production

“…A detailed description of the system has been given elsewhere (Cristescu et al, 2008). Briefly, the detector consists of a CO 2 laser emitting radiation in the 10-μm infrared wavelength region and a photoacoustic cell, in which ethylene is detected.…”

Fast, broadband, rugged spectrometer for near-infrared measurements of organic solutions and multicomponent mixtures

“…7 and 8). Using the current instrument, the speed of the RadiaLight® motor can be increased by a factor of 20 for a time-to-measurement resolution of 375 ms. Further noise-reduction techniques like Kalman filtering 24 and auto-balance feedback circuitry 25 can be used to completely eliminate the need for averaging the signal. This would bring the achievable time-to-measurement resolution down to less than 10 ms.…”