RU2299424C1 - Optical-electronic spectral gas analyzer - Google Patents

Abstract

FIELD: gas analysis, possible use for determining qualitative and quantitative composition of gas mixtures, formed as a result of life activity of organisms or excreted during operation of various devices, internal combustion engines, and also for controlling quality of perfume products.

SUBSTANCE: device contains supply block, connected to output of which are lighting element, fast photo-shutter of input beam, fast photo-shutter of output beam, block of detectors, multi-channel amplifier, and connected to input is control block, through a digital-analog converter; optical trough, connected sequentially to which are fast photo-shutter of output beam, element for spectral dissolution of signal being analyzed, optical system, photo-receiver, multi-channel amplifier, analog-digital converter, control block, while lighting element, fast photo-shutter of input beam and optical trough are positioned on the same optical axis; and optical trough, fast photo-shutter of output beam, element for spectral dissolution of signal being analyzed, optical system, block of detectors are positioned on another optical axis. Optical system contains spectral windows ranging from 1 to ... n for transferring signal being analyzed to photo-detector, made in form of block of detectors, containing from 1 to ... n detectors, making it possible to separately record and transform optical signal being emitted in each predetermined range of spectrum.

EFFECT: expanded functional capabilities, increased resolution.

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Description

Optoelectronic spectral gas analyzer refers to the technique of gas analysis and can be used to determine the qualitative and quantitative composition of gas mixtures formed as a result of the life of organisms or released during the operation of various devices, internal combustion engines, as well as for quality control of perfumes.

A technical solution is known according to patent RU 2091764, IPC 6 G01N 21/61 of 08.16.94, published 09.27.97, Bulletin No. 27, “Fiber Optic Analyzer” (1). The invention relates to techniques for analytical and measuring instrumentation for the detection and determination of gas concentrations and can be used in coal, chemical, oil refining, gas and other industries. The device comprises sequentially mounted and optically coupled emitters, an input optical fiber, a multi-pass cell consisting of three spherical mirrors, an output optical fiber, an information recording and processing unit. A spectral integral demultiplexer is installed between the output optical fiber and the recording unit, and on the continuation of the collective mirror sphere in the immediate vicinity of its edge, the ends of the input and output optical fibers are installed on one side, both lens mirrors are mounted with the possibility of joint rotation relative to the center of curvature of the mirror collective in the common meridional plane of all mirrors.

The technical solution is also known according to patent RU 2083959, IPC 6 G01J 3/42 dated 03/21/95, published July 10, 1997, bulletin No. 19, "METHOD FOR MEASURING GAS CONCENTRATION BY THE CORRELATION FOURIER SPECTROSCOPY METHOD" (2).

The invention relates to methods for measuring gas concentrations in gaseous media by absorption spectroscopy, in particular to methods for measuring gaseous impurities in the atmosphere and controlling environmental pollution. The method of correlation Fourier spectroscopy involves measuring the intensities of a certain set of components of the Fourier spectrum of the received radiation, and the values of the Fourier variables of the measured Fourier components correlate with the positions of the maxima and minima in the Fourier spectrum of the absorption spectrum of the measured gas, and the received radiation is analyzed only in the wave number range where the measured gas has absorption lines.

With this method, for noticeable absorption of radiation, it is necessary that the concentration of the desired substance be sufficiently high (at least 0.001%), which determines the relatively low sensitivity of the devices.

The closest is the technical solution for the patent copyright certificate SU 1672814, IPC 6 G01N 21/31, 06.10.89, published 05/20/96, Bulletin No. 14, “GAS ANALYZER” (3).

The invention relates to techniques for gas analysis and can be used to determine the quantitative and qualitative composition of gas mixtures formed as a result of the activity of organisms or released during the operation of various devices, such as internal combustion engines.

This technical solution is aimed at expanding the functionality of the gas analyzer, by determining the qualitative composition of the gas mixture, and increasing the accuracy and sensitivity. In a gas analyzer containing a radiating diode whose pn junctions are identical in the same crystal, the focusing optical system with at least one element made in the form of a concave reflector with a photodetector in focus and an electronic circuit for extracting useful a signal connected to a photodetector, a diffraction grating is deposited on the surface of at least one of the reflectors, and / or the gas analyzer comprises a diffraction grating, in the meridional plane of which in the directions The main diffraction maxima are a diode and a photodetector. The diode is made in the form of a linear matrix with the number of elements N, determined by the condition with at least one element made in the form of a concave reflector with a photodetector in focus, and an electronic circuit for extracting a useful signal connected to the photodetector to the surface of at least one of reflectors, a diffraction grating is deposited, and / or the gas analyzer comprises a diffraction grating, in the meridional plane of which a diode and a photodetector are located on the directions of the main diffraction maxima. The diode is made in the form of a linear matrix with the number of elements N, determined by the condition

and the light-emitting region of each element has a transverse dimension h, which for non-overlapping absorption bands of gases satisfies the condition

and in other cases it is determined from the condition

- дисперсия решетки или системы;Where

- the dispersion of the lattice or system;

Δλ ′ is the resolution of the lattice or system;

Δλ is the smallest of the half-widths of the characteristic absorption bands of the proposed gases;

Δλ "is the half-width of the electroluminescence spectrum of the emitting diode;

H is the distance between the centers of the elements of the matrix.

But this device does not allow real-time determination of the presence of the desired substance, if it is present in the gas, if its concentration is so low that it does not cause noticeable absorption of electromagnetic radiation at a given wavelength, i.e. lies below the sensitivity threshold of the device.

The objective of the proposed technical solution is to create an optical-electronic spectral gas analyzer with advanced functionality and high resolution.

The problem is solved due to the fact that the optoelectronic spectral gas analyzer containing a lighting element connected to the output of the power supply, an optical cuvette, an element for forming the spectral decomposition of the analyzed signal, a photodetector and a control unit configured to process and output information, while it included a fast input beam shutter, a fast output beam shutter, and an optical system containing spectral windows for transmitting the analyzed signal to the receiver, made in the form of a block of detectors, a multi-channel amplifier, analog-to-digital and digital-to-analog converters, while photo-gates, a block of detectors and a multi-channel amplifier are connected to the output of the power supply, to the input of which a control unit is connected via a digital-to-analog converter, and a fast output beam photo-shutter, element for forming the spectral decomposition of the analyzed signal, optical system, detector block, multi-channel amplifier , an analog-to-digital converter and a control unit, a lighting element, a fast input beam shutter and an optical cuvette are located on the same optical axis, and an optical cuvette, a fast output beam shutter, an element for the spectral decomposition of the analyzed signal, the optical system and the detector block are located on another optical axis.

The proposed block diagram of an optoelectronic spectral gas analyzer, in which an element for forming the spectral decomposition of the analyzed signal is sequentially connected; a fast photo-gate of the output beam; an optical system containing spectral windows from 1 to ... n for transmitting the analyzed signal to a photodetector made in the form of a block detectors of the output optical signal, containing from 1 to ... n detectors, allowing individually register and convert the emitted optical signal into each m, a predetermined spectral range, a multi-channel amplifier of electrical signals coming from a photodetector, an analog-to-digital converter (ADC), a control unit, such as a computer, whose software includes a database of spectral characteristics of the analyzed substances and a pattern recognition program, as well as The gas analyzer control program allows you to create and analyze emission spectra, rather than absorption, as in existing analogs and prototypes.

Since the spectral lines of each substance have a certain width, it is impossible to simulate the wavelength and line width at the same time, unambiguous identification of substances is carried out with a very high degree of probability.

The ability to analyze the emission spectra recorded by the proposed device, rather than the absorption spectra, make it possible to detect the desired substances even in the case of negligible concentrations, when their number is measured in thousands of molecules, since modern PMTs can detect literally individual photons.

Using a computer with special software in the device allows analyzing the composition of the gas mixture in several seconds for several substances and the analysis can be carried out in real time.

The presence of an element for the formation of the spectral decomposition of the analyzed signal allows you to decompose the light pulse into the spectrum simultaneously with the focusing of the signal, which can significantly increase the resolution of the device.

The gas analyzer of the described type has not too large dimensions and mass, and can be performed both in stationary and in portable form.

The drawing shows a block diagram of an optoelectronic spectral gas analyzer, where the power supply 1, the lighting element 2, the fast photo-shutter of the input beam 3, the optical cuvette 4, the device for purging the optical cuvette with cleaning gas 5, the device for letting the analyzed gas mixture into the optical cuvette 6, fast an output beam 7 shutter, an element for forming the spectral decomposition of the analyzed signal 8, an optical system 9, a block of detectors 10, a multi-channel amplifier 11, an analog-to-digital converter (ADC) 12, a unit equation (BU) 13, digital-to-analog converter (DAC) 14.

Optoelectronic spectral gas analyzer is made as follows. The output of the power supply unit 1 is connected to: a lighting element 2, a fast photo-gate of the input beam 3, a device for purging the optical cell with a cleaning gas 5, a device for letting the analyzed gas mixture into the optical cell 6, an element for forming the spectral decomposition of the analyzed signal 8, detector block 10, a multi-channel amplifier 11, and the control unit 13 is connected to the input through a digital-to-analog converter (DAC) 14. Lighting element 2, a fast photo-shutter of the input beam 3, cuvette 4 are located on one optical axis, in along which the incoming beam passes, and the cuvette 4, a fast photo-shutter of the output beam 7, an element for forming the spectral decomposition of the analyzed signal 8, the optical system 9, the block of detectors 10 are located on another optical axis along which the output beam propagates.

A fast photo-shutter of the output beam 7, an element for forming the spectral decomposition of the analyzed signal 8, an optical system 9 for transmitting the analyzed signal to the block of detectors 10 of the output optical signal (from 1 to ... n), allowing individually registering the emitted optical a signal in each predetermined spectral range, a multi-channel amplifier 11 of electrical signals from block 10, an analog-to-digital converter (ADC) 12, a control unit 13, for example our PC, with the software which includes a database of spectral characteristics of the analytes and the pattern recognition software and management software gas analyzer, a digital to analog converter (DAC) 14.

Optoelectronic spectral gas analyzer operates as follows.

The operation of this device is based on the use of the duality principle (Yu.L. Ratis, 1984) for the numerical Fourier transform (see [4] - [6]). According to the duality principle, in the numerical or hardware integration of functions having sharp peaks (for example, spectral lines or bands in the radiation or absorption spectrum), it is necessary to consider the problem of recognizing an image (signal) both for the function itself and for its Fourier image. Since the delta peak in coordinate space turns into a substrate function in Fourier - conjugate space and vice versa, the simultaneous numerical or hardware analysis of both the function itself and its Fourier image allows minimizing the probability of a substance identification error by determining the qualitative composition of the gas mixtures according to radiation spectra, as well as increasing its accuracy and sensitivity. The control unit 13 through the DAC 14 generates a control signal to the power supply 1 to turn on the purge device of the optical cell 4 cleaning gas. After the optical cuvette 4 has been set for purging, the control unit 11 gives out sequentially through the DAC 14 control signals to the power unit 1, for switching on the analyzer gas inlet device 6 into the optical cuvette 4, for short-term inclusion of a powerful illuminator 2 and a fast input shutter 3 lighting system. As a result of pulsed illumination, some of the atoms and molecules that make up the analyzed gas mixture go into an excited state. Upon deexcitation, these atoms and molecules emit electromagnetic radiation in the infrared, visible and, in some cases, in the ultraviolet range. Simultaneously with closing the fast input shutter 3, the control unit 13 through the DAC 14, using the power supply 1, opens the fast output shutter 7. The element for forming the spectral decomposition of the analyzed signal 8 decomposes the light pulse formed in the optical cuvette 4 into a spectrum. After that, through the optical system 9, light pulses in each spectral window enter the block of detectors 10. After the optoelectric conversion using the block of detectors 10, the electric signals from each channel (spectral range) are sent to the multi-channel amplifier 11, from which the signal through the ADC 12 enters to the control unit 13 for digital information processing. The control unit 13 processes the input signal using an algorithm using the principle of duality, and provides information on the chemical composition of the gas mixture from each spectral window. The system of spectral windows is built taking into account the fact that many molecular compounds have fairly long-lived levels in the optical and infrared ranges. For each spectral range ω _i ≤ω≤ω _i + Δω _{i, the} output signal is recorded by the detector, where ω is the cyclic frequency of electromagnetic radiation emitted by atoms and molecules of the substance located in the optical cuvette 4, ω _i is the lowest cyclic frequency for the ith channel (spectral range), Δω _i is the width of the spectral window.

As a detector, a CCD array 9 is used.

Let n be the number of spectral windows that coincides with the number of detectors.

At the output of the block of detectors 10, we obtain a system of response functions (by the number of detectors n):

where n is the number of spectral windows;

F _i is the signal from the i-th detector (1≤i≤n);

t is time.

By the form of the functions F _i {(t, ω _i ≤ω≤ω _i + Δω _i ), the substances contained in the cell can be identified.

The system of spectral windows ω _i ≤ω≤ω _i + Δω _{i is} tuned to a specific substance. The average lifetime τ _{i of the} “gross level” is measured:

In this case, the device detects the presence of the desired substance and estimates its concentration with sufficient accuracy for practical purposes.

BIBLIOGRAPHY

1. RU 2091764, IPC 6 G01N 21/61 of 08.16.94, publ. 09/27/97, bull. No. 27, "Fiber Optic Analyzer."

2. RU 2083959, IPC 6 G01J 3/42 dated 03/21/95, publ. 07/10/97, bull. No. 19, "METHOD FOR MEASURING GAS CONCENTRATION BY THE CORRELATION FOURIER-SPECTROSCOPY METHOD" (2).

3. SU 1672814, IPC 6 G01N 21/31 dated 10/06/89, publ. 05/20/96, bull. No. 14, “GAS ANALYZER”.

4. Yu.L. Ratis, M.L. Kalyaev. Collective phenomena in heat-resistant coatings during thermal shock, Dep. VINITI, No. 6594-84 dated 10/08/1984

5. Yu.L. Ratis, VV Stolyar, A generalized Kalecki model for describing the economy of large cities. Market economy. Status, problems, prospects. Department of Economics, Russian Academy of Sciences, MIR, Samara, 1998, 6 pp.

6. Yu.L. Ratis, G. I. Leonovich, A. Yu. Melnikov, Light flux difrraction of fiber - optical and optical electronic transducers of mechanical displacement. Proceedings of SPIE, volume 3348, Computer and Holographic Optics and Image Processing, 1997, p.336-343.

Claims (1)

An optical-electronic spectral gas analyzer containing a power supply unit, a lighting element connected to a power supply unit, an optical cuvette, an element for generating a spectral decomposition of the analyzed signal, a photodetector and a control unit configured to process and output information, characterized in that fast input beam photo-shutter, fast output beam photo-shutter, optical system containing spectral windows for transmitting the analyzed signal to a photodetector made in de detector block, a multi-channel amplifier, analog-to-digital and digital-to-analog converters, while photo-gates, a detector block and a multi-channel amplifier are connected to the output of the power supply, to the input of which a control unit is connected via a digital-to-analog converter, and a fast photo-gate of the output beam is connected in series to the optical cuvette, element for forming the spectral decomposition of the analyzed signal, optical system, detector block, multi-channel amplifier, analog-to-digital conversion ovatel and a control unit, a lighting element, input beam fast shutter and optical cell arranged on the same optical axis and the optical cell, the output beam fast shutter element to form the spectral decomposition of the analyzed signal, the optical system and the sensor unit are arranged on different optical axes.