Kalman’s method to improve accuracy of online ¹³С¹⁶O₂ measurement in the exhaled human breath using tunable diode laser absorption spectroscopy

Abstract

This study reports on the use of Kalman’s method for filtering an experimental signal to improve the accuracy of a 13С16О2 measurement in the exhaled human breath using tunable diode laser absorption spectroscopy with a semiconductor diode laser tunable near to a wavelength of 2 µm. It is shown that Kalman’s filtration allows a 5-fold increase in the detection accuracy of 13СО2.

Implementation of the adaptive Wiener filtering algorithm in the problem of measuring the 13CO2 content in expiratory air using the tunable diode laser absorption spectroscopy technique

“…One of the effective approaches for solving the problem of the highly accurate on-line measurement of 13 CO 2 content, in a mixture with 12 CO 2 in a human expiration for a non-invasive diagnosis of gastrointestinal cancer, is implementing the tunable diode laser absorption spectroscopy (TDLAS) technique using a tunable diode laser (TDL) as a source. This emits nearly a wavelength of 2 µm, where 13 CO 2 and 12 CO 2 have a number of weakly overlapping absorption lines, as noted earlier in a number of publications (see [1][2][3][4][5][6][7][8][9][10], for example).…”

“…In this paper, as before in [3,4], the Wiener filter has been used for processing an experimental signal obtained in [5]. It investigated the spectral range 4876.5-4879 cm −1 , in which the 13 CO 2 molecule had an absorption line P(12) and the 12 CO 2 molecule-in the absorption lines R (32) and R (34).…”

“…We have previously reported on the application of the EMD algorithm [3] and the Kalman filter [4] for filtering an experimentally recorded signal to improve the 13 CO 2 content measuring accuracy in human expiration, using a TDLAS technique based on the TDL at a wavelength of approximately 2 µm. This has established in these works that the application of these adaptive filtering techniques to the original signal allows one to obtain the measuring accuracy of 0.4% for 13 CO 2 content in a mixture with 12 CO 2 in expiratory air [3] and 0.15% [4], that is two or more than five times better, respectively; compared with the results obtained while processing the original signal using a non-adaptive fast fourier transform filter (FFT) [5].…”

The research on high‐performance CO2 gas measurement using the Kalman‐wavelet algorithm

“…According to the aforementioned theoretical derivation, interference fringe is a kind of low‐frequency noise and oscillates periodically in the time domain. The wavelet transform algorithm was used to decompose and reconstruct the detected signal in both the frequency domain and time domain to remove interference fringe 16–18 …”

“…The wavelet transform algorithm was used to decompose and reconstruct the detected signal in both the frequency domain and time domain to remove interference fringe. [16][17][18] 4 | EXPERIMENTAL…”