Improving the ¹³CO₂ content measurement accuracy in exhaled air using the Kalman technique for filtering the experimental signal obtained by the tunable diode laser absorption spectroscopy method with the frequency modulation of the diode laser pump current

Abstract

This paper reports on the application of the Kalman method for processing the signal obtained by the tunable diode laser absorption spectroscopy method in an experimental circuit, which includes the frequency modulation of a diode laser pump current in combination with the synchronous detection technique. It has established that the implementing of this approach makes it possible to improve the measurement accuracy of the 13 CO 2 content, as well as the measurement accuracy of the 13 CO 2 and 12 CO 2 concentrations ratio in exhaled air to a level not exceeding 0.1%.

Experimental observation of the vibration-rotation radiation curves of 12C16O2 and 13C16O2 absorption constants ranging from 4860 to 4880 sm−1 by the tunable diode laser absorption spectroscopy method

“…Earlier, this method was used to measure the content of 13 C 16 O 2 (636) in a mixture with 12 C 16 O 2 (626) in exhaled air. Performed studies have shown that one of the most promising ranges for measurements is the region near a wavelength of 2 µm (frequency range: 4860-4880 sm −1 ), which contains a number of absorption curves of these molecules, to a minimum extent overlapping, and the experimental arrangement does not require complex and expensive equipment [18][19][20]. To accurately measure the content of 13 C 16 O 2 and 12 C 16 O 2 in the analyzed mixture, knowledge of the absorption constantvalues and their pressure dependence, since the measurements can be carried out at different pressures, are necessary.…”

Experimental measurement of collision broadening of vibrational-rotational spectral lines 12C16O2 and 13C16O2 in the 4860–4880 cm−1 region by diode laser absorption spectroscopy

“…One of the most promising, among the various methods for 13 C 16 O 2 detection, is the tunable diode laser absorption spectroscopy (TDLAS) method using singlefrequency tunable diodes lasers (TDL) as radiation sources [12][13][14][15][16][17][18][19][20]. Spectroscopic constants such as positions of the vibrational-rotational absorption lines centres, their intensities, the dependence of absorption constants and cross-sections on pressure, collision broadening constants, etc, are measured with great accuracy using this method.…”