Medical Gas Diagnosis Via Diode Laser Absorption Spectroscopy PDF Download
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Author:
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ISBN:
Category :
Languages : en
Pages : 19
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Book Description
Development of a monitor to measure O2 and CO2 content in the expired air is the objective of this program. We use diode laser based combined wavelength and frequency modulation spectroscopy for detection of the O2 and CO2 in the expired air. A prototype for measuring O2 content was fabricated in November 1994. The prototype provides the necessary signal-to-noise ratio. The acquisition time constant was too long for accurate breath-by-breath oxygen content analysis. The long term system and laser stability have to be improved as well. In the current stage, a second prototype targeted on these issues is being fabricated.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 19
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Book Description
Development of a monitor to measure O2 and CO2 content in the expired air is the objective of this program. We use diode laser based combined wavelength and frequency modulation spectroscopy for detection of the O2 and CO2 in the expired air. A prototype for measuring O2 content was fabricated in November 1994. The prototype provides the necessary signal-to-noise ratio. The acquisition time constant was too long for accurate breath-by-breath oxygen content analysis. The long term system and laser stability have to be improved as well. In the current stage, a second prototype targeted on these issues is being fabricated.
Author: Lorenzo Cocola
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Patricia Kuntz Falcone
Publisher:
ISBN:
Category : Absorption spectra
Languages : en
Pages : 209
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Book Description
Author: Yufei Ma
Publisher: MDPI
ISBN: 3039283987
Category : Technology & Engineering
Languages : en
Pages : 278
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Book Description
Trace gas sensing technologies are widely used in many applications, such as environmental monitoring, life science, medical diagnostics, and planetary exploration. On the one hand, laser sources have developed greatly due to the rapid development of laser media and laser techniques in recent years. Some novel lasers such as solid-state, diode, and quantum cascade lasers have experienced significant progress. At present, laser wavelengths can cover the range from ultraviolet to terahertz, which could promote the development of laser gas sensing technologies significantly. On the other hand, some new gas sensing methods have appeared, such as photothermal spectroscopy and photoacoustic spectroscopy. Laser spectroscopy-based gas sensing techniques have the advantages of high sensitivity, non-invasiveness, and allowing in situ, real-time observation. Due to the rapid and recent developments in laser source as well as the great merits of laser spectroscopy-based gas sensing techniques, this book aims to provide an updated overview of the state-of-the-art laser gas sensing technologies.
Author: Kevin Duffin
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Tunable diode laser spectroscopy (TDLS) has become the preferred option for industrial gas monitoring. TDLS with direct detection provides absolute measurement of a rotational / vibrational gas absorption line transmission function, facilitating the extraction of gas concentration (from line strength measurement). TDLS with wavelength modulation spectroscopy (WMS) enables AC detection of absorption line derivatives at frequencies where laser and 1/f noise is reduced. Coupled with lock-in detection, this provides a sensitivity improvement of up to 2 orders of magnitude. At fixed temperature and pressure, calibration to signals measured on a known gas composition has been used successfully to determine system scaling factors. However, demand has grown for gas monitoring in environments where the gas pressure is constantly varying and unknown. This introduces significant errors in the analysis as the primary system scaling factor is a function of linewidth, which is varying with the unknown pressure. Errors also arise from the inaccuracies in determining a number of instrument scaling factors, including the AM and FM characterisation of the laser. Pressure measurements may be made and the errors in concentration corrected, if the gas absorption linewidth can be accurately measured from the recovered signals and the instrument scaling factors can be accurately determined. However, the lack of accurate in-situ wavelength referencing schemes for use in the field, make linewidth measurement extremely difficult. Add to this the fact that conventional TDLS / WMS measurements are prone to systematic interference and the errors accumulated from inaccurate instrument scaling (noted above) and linewidth measurement, could determine a large final error on the derived concentration and / or pressure. This work reports the proposal, development and validation of both an in-fibre wavelength referencing scheme and a new technique for measuring the absolute absorption line transmission function using TDLS with WMS. Measuring the absolute absorption line transmission profile, as a function of the laser's wavelength scan across the absorption line, facilitates the extraction of the gas concentration and pressure via comparisons to theory (based on HITRAN data). Through novel signal processing techniques, the approach is free from systematic distortion and is absolute without the need for calibration. This new approach provides many of the benefits of TDLS / WMS, whilst offering the simplicity and accuracy of TDLS with direct detection. The promising results show that we have significantly advanced TDLS technology towards realising a stand-alone instrument for determining accurate gas composition measurements in harsh industrial environments.
Author: Zhuan Liu
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author:
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ISBN:
Category :
Languages : en
Pages : 8
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Detection and identification of gas species using tunable laser diode laser absorption spectroscopy has been performed using vertical cavity surface emitting lasers (VCSEL). Two detection methods are compared: direct absorbance and wavelength modulation spectroscopy (WMS). In the first, the output of a DC-based laser is directly monitored to detect for any quench at the targeted specie wavelength. In the latter, the emission wavelength of the laser is modulated by applying a sinusoidal component on the drive current of frequency?, and measuring the harmonics component (2?) of the photo-detected current. This method shows a better sensitivity measured as signal to noise ratio, and is less susceptible to interference effects such as scattering or fouling. Gas detection was initially performed at room temperature and atmospheric conditions using VCSELs of emission wavelength 763 nm for oxygen and 1392 nm for water, scanning over a range of approximately 10 nm, sufficient to cover 5-10 gas specific absorption lines that enable identification and quantization of gas composition. The amplitude and frequency modulation parameters were optimized for each detected gas species, by performing two dimensional sweeps for both tuning current and either amplitude or frequency, respectively. We found that the highest detected signal is observed for a wavelength modulation amplitude equal to the width of the gas absorbance lines, in good agreement with theoretical calculations, and for modulation frequencies below the time response of the lasers (
Author: Christoph Dyroff
Publisher:
ISBN: 9783866443280
Category : Technology (General)
Languages : en
Pages : 0
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Book Description
This book discusses the mechanical and opto-electronic design of laser spectrometers for measuring two very important atmospheric gases, namely water vapor and its isotopic ratios, and formaldehyde. For measuring water vapor, shot-noise limited sensitivity has been achieved by a careful choice of system components and data processing. For measuring formaldehyde, a selective sample modulation exploiting the Stark effect has been used to greatly improve the sensitivity.
Author:
Publisher:
ISBN:
Category : Medicine
Languages : en
Pages : 2002
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Book Description
Vols. for 1963- include as pt. 2 of the Jan. issue: Medical subject headings.
Author: Xiaojuan Cui
Publisher:
ISBN:
Category : Technology
Languages : en
Pages :
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Book Description
Due to the fact of global warming, air quality deterioration and health concern over the past few decades, great demands and tremendous efforts for new technology to detect hazard gases such as CH4, CO2, CO, H2S, and HONO have been performed. Tunable diode laser absorption spectroscopy (TDLAS) is a kind of technology with advantages of high sensitivity, high selectivity, and fast responsivity. It has been widely used in the applications of greenhouse gas measurements, industrial process control, combustion gas measurements, medicine, and so on. In this chapter, we will briefly summarize the most recent progress on TDLAS technology and present several kinds of gas sensors developed mainly by our group for various field applications. These could expand from energy, environment, and public safety to medical science.
