The method for determining the absolute spectral sensitivity of fiber-optic spectrophotometers by brightness based on the use of a standard tungsten incandescent lamp is described. The reasons for the observed nonlinearity of the light characteristics of the AvaSpec 2048 spectrometer in the short-wave region of the spectrum are discussed. An example of the practical use of a fiber-optic spectrophotometer for recording spectra in the laser treatment of metals is given.
In the paper, the modified correlation method is presented as well as results of CO concentration measurements in
laboratory conditions using this method. Measurements were obtained for high CO concentrations (exceeding 50%) and
short optical path (1 and 2m long). The measurements can be treated as a reference for measurements for far low
concentrations and longer optical paths. Some simulation results also has been presented showing influence of
temperature and pressure on measurement accuracy.
Semiconductor lasers, which can be surely characterize by many of their advantages, have been used for measurements of concentration of gases for many years. Doing measurements in industrial conditions, because of its several difficulties, needs using special technology of measurements. In this article using modified, correlated absorption spectroscopy, in order to measure CO concentration, has been shown.
In this work is explored the effectiveness of application of various absorption laser spectroscopy methods for definition of gas components concentration in boilers' smoke gases. O2 and CO absorption spectrums are parsed, optimum absorption lines in near IR spectrum range (about 0.76 microns for O2 and 1.56 microns for CO) are selected and graphics of selected lines intensities and half-widths dependences on the temperature of controllable medium and pressure in it are given. Processes of monitoring of CO and O2 content in boilers smoke gases are simulated at usage of basic laser spectroscopy methods (integral, differential, modulation, correlation, modified correlation) and measurement inaccuracies are analyzed. It is ascertained, that for a decrease of methodical errors of concentration measuring it is necessary to take into account operated medium temperature and pressure. It is shown, that the least inaccuracies of CO and O2 concentration continuous monitoring at the presence of dissipative losses variations are ensured with the modified correlation method though its threshold sensitivity is less, than integral and correlation ones.
The work will present results of laboratory investigation of optoelectronic detector of carbon monoxide that uses an external cavity semiconductor laser turned within 1,5 and 1,6 μm. Measurement set-up incorporates cells 1 m and 2 m long containing the measured gas at variable concentration. Such set-up reflects the product of partial pressure and path length that can be found inside the power boiler.
Methods of determination of coordinates of the center of a narrow radiation beam by means of the CCD array are considered. For the continuous representation of images and noises the analytical expressions describing signal and noise functions at the output of optimal spatial filter are obtained, as well as the dispersion of optimal estimation of a position of Gaussian radiation beam. It is shown that using the CCD array the minimum error of estimation of the Gaussian beam position is observed when the beam effective diameter is approximately equal to 0.8 of lateral length of a light-sensitive cell of the array.
Operation of combustion process in power boilers in such a way that pollution standards are met and corrosion is limited requires continuous measurement of concentration of selected gases in the near wall layer of power boilers. The absorption spectroscopy is one of methods that allow such measurement. Specificity of the medium in which the measurement is to be made (among other things: high temperature, difficulties in installation of sources and detectors) requires utilization of optical fiber technology. Absorption spectra overlapping in the medium infrared range is an additional hindrance which makes application of special measurement algorithms necessary. A concept of structure of optoelectronic analyzer of CO concentration in the near wall layer of power boilers has been presented. The analyzer is based on modified correlation absorption spectroscopy within the range between 1557 nm and 1600 nm. Simulation results have been presented as well.
The operation principle of now used smokemeters is based on the measurement of attenuation of optical radiation transmitted through a vehicle emission and additional measurement of quantity of a compensation optical flux. The instability of instrumental constants of emitting-receiving and recording units of a measuring system due to the changes in measurement conditions (temperature, optical surfaces pollution, background illumination, etc.) results in the necessity of correction (tuning) of zero value by calibration measurements. Often (in quickly changed conditions) the calibration is difficult or even impossible. The additional measurements of a compensation flux reduce only influence of instability in emitted light pulse power (energy) on the measurement accuracy and cannot reduce an influence of other factors. Proposed method of exhaust opacity determination and devices for its realization are intended for operative determination of mass concentration of soot in the emission of vehicles. We propose the system in which sending and recording of sounding radiation is carried out by two light emitters and two photoreceivers on two crossing directions in a scattering medium (emission). In addition the same two photoreceivers register optical fluxes scattered by the medium (in the area of crossing of sounding directions). Mass concentration of the soot in an emission is determined on the base of registered sounding light fluxes, scattered by the emission fluxes and past through the emission fluxes.
Laser-location spectral methods of measurement of concentration of aerosol and gas emissions in an atmosphere, despite of their conclusive advantages - remoteness and efficiency - are not widespread because of multiparametrical dependence of registered signals and difficulties on their interpretation relative to determined characteristics. For solving of these problems in the report the opportunities of using the principles of synthesis of measuring laser systems are considered on the basis of the concept of elimination of a priori data, developed by the authors. This concept consists in the greatest possible exception of methodical errors caused by use of the a priori information, variation of uncontrollable physical processes in an environment and changes of instrumental constants of measuring tools. An efficiency of the proposed methods is evaluated.
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