CN106769906B - Spectrometer data drift compensation method - Google Patents
Spectrometer data drift compensation method Download PDFInfo
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- CN106769906B CN106769906B CN201611156557.XA CN201611156557A CN106769906B CN 106769906 B CN106769906 B CN 106769906B CN 201611156557 A CN201611156557 A CN 201611156557A CN 106769906 B CN106769906 B CN 106769906B
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/27—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands using photo-electric detection ; circuits for computing concentration
- G01N21/274—Calibration, base line adjustment, drift correction
Abstract
The invention provides a compensation method based on spectrometer data drift, which comprises the following steps: acquiring a background spectrum and an absorption spectrum of a spectrometer; selecting an absorption spectrum in a corresponding waveband range according to the gas to be detected, and performing longitudinal correction compensation on the absorption spectrum by adopting data normalization processing; measuring and calculating the differential optical thickness under the test gas by adopting a Doas technology; comparing the absorption cross section with the waveform of the differential optical thickness to calculate the transverse offset between the absorption cross section and the differential optical thickness; translating the differential optical thickness by a lateral offset with reference to the absorption cross section until the absorption cross section is aligned with a waveform of the differential optical thickness; and calculating the concentration of the gas to be measured according to a least square method. The invention respectively carries out longitudinal compensation and transverse compensation on the absorption spectrum data of the gas to be measured, the concentration of the gas to be measured is more accurate, a large amount of test data do not need to be carried out aiming at each spectrometer, the workload of compensation and correction is reduced, and the efficiency is improved; the method has strong universality and high portability, and can be popularized and used in a large area.
Description
Technical Field
The invention belongs to the technical field of spectrum compensation, and particularly relates to a compensation method based on spectrometer data drift.
Background
The spectrometer is a device for detecting the wavelength position and intensity corresponding to a spectral line by a photoelectric detector, and is a core component of a spectral absorption technical instrument such as an ultraviolet differential absorption spectrum technology. With the continuous improvement of the national emission standards of flue gas, the existing infrared analysis instrument and the conventional ultraviolet differential absorption spectrum technology are difficult to meet the requirements of low detection limit, high sensitivity, high resolution and the like of flue gas analysis, and the requirements on the stability of a spectrometer, which is a core component of an ultraviolet differential absorption spectrum analyzer, are higher under the condition of long-time continuous operation. The data compensation method of the existing spectrometer comprises two methods, namely, firstly, the spectrometer is placed in a stable working environment, a controllable temperature box is additionally arranged outside the spectrometer, so that the spectrometer is in a stable temperature environment, and the analyzer can be calibrated and calibrated at regular intervals; the second method, relative position offset compensation, selects a relatively stable wavelength as a reference coordinate, and compensates the offset of other wavelength points by using the offset and offset coefficient.
However, the first compensation method places the spectrometer in the temperature-controllable box for a long time, the temperature environment exceeds the available temperature range of the spectrometer, the service life of the spectrometer is affected, and the firmware cost is easy to change along with the time; the second compensation mode needs to do a large amount of test data in advance, and the spectrometers themselves have differences, so that the transportability is very poor, the compensation workload is increased, the working efficiency is reduced, and the compensation method cannot be popularized on various platforms.
Disclosure of Invention
In view of the above drawbacks of the prior art, an object of the present invention is to provide a method for compensating data drift of a spectrometer, which is used to solve the problems of poor portability and low compensation efficiency of the spectrometer during compensation in the prior art.
To achieve the above and other related objects, the present invention provides a method for compensating data drift based on a spectrometer, comprising:
step 1, obtaining a background spectrum and an absorption spectrum of a spectrometer, wherein the background spectrum is spectrum data when standard gas is introduced, and the absorption spectrum is spectrum data when test gas is introduced;
step 2, selecting an absorption spectrum in a corresponding wave band range according to the gas to be detected, and performing longitudinal correction compensation on the absorption spectrum by adopting data normalization processing;
step 3, measuring and calculating the differential optical thickness under the test gas by adopting a Doas technology;
step 4, comparing the waveforms of the absorption cross section and the differential optical thickness to calculate the transverse offset between the absorption cross section and the differential optical thickness;
step 5, translating the differential optical thickness according to the transverse offset by taking the absorption section as a reference until the absorption section is aligned with the waveform of the differential optical thickness;
and 6, calculating the concentration of the gas to be measured of the compensated spectral data according to a least square method.
As described above, the spectrometer data drift-based compensation method of the present invention has the following beneficial effects:
the invention respectively carries out longitudinal compensation and transverse compensation on the absorption spectrum data of the gas to be measured, so that the concentration of the gas to be measured through the compensated data is more accurate, meanwhile, the method does not need to carry out a large amount of test data aiming at each spectrometer, the workload of compensation and correction is reduced, and the compensation efficiency is improved; in addition, the method has strong universality and high transportability, can be popularized to various platforms in a large area, and can be used for various concentrations.
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FIG. 1 is a flow chart of a spectrometer data drift-based compensation method according to the present invention;
fig. 2 is a graph showing spectral data based on the absorption cross section and differential optical thickness of a spectrometer according to the present invention.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict.
It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.
Referring to fig. 1, the present invention provides a method for compensating data drift based on a spectrometer, comprising:
step 1, obtaining a background spectrum and an absorption spectrum of a spectrometer, wherein the background spectrum is spectrum data when standard gas is introduced, and the absorption spectrum is spectrum data when test gas is introduced;
specifically, the light source of the spectrometer may be a xenon lamp light source or a deuterium lamp light source, the standard gas may be nitrogen, and the gas to be measured may be sulfur dioxide or/and nitric oxide in the polluted gas.
Step 2, selecting an absorption spectrum in a corresponding wave band range according to the gas to be detected, and performing longitudinal correction compensation on the absorption spectrum by adopting data normalization processing;
specifically, according to the property of the gas to be measured, a certain non-absorption reference selected point or the average value of the reference selected points of several continuous non-absorption points is selected in the absorption spectrum, and the absorption spectrum is subjected to longitudinal correction compensation by data normalization processing.
In this embodiment, the absorption band corresponding to the sulfur dioxide is 285-310 nm, the absorption band of the nitric oxide is 200-230 nm, and the average value of the spectrum data of the spectrometer according to the non-absorption reference selection points in the absorption band is calculated according to the absorption band corresponding to the selected gas.
Step 3, measuring and calculating the differential optical thickness under the test gas by adopting a Doas technology;
among them, differential absorption spectroscopy (Doas) is a photochemical concentration measurement method which is developed rapidly and is representative in the present year, and can realize accurate, rapid and on-line measurement. The gas species is identified by the specific differential absorption structure of the measured gas in the ultraviolet to visible light wave band, and the gas concentration is inverted according to the absorption spectrum intensity.
Specifically, for the gas to be measured, a light data group to be measured of the gas to be measured is selected from absorption spectra in corresponding absorption wave bands, a reference light data group corresponding to the absorption wave bands is selected from background spectra, and the absorption optical thickness of the gas to be measured is calculated according to the light data group to be measured and the reference light data group by adopting the Lambert law.
In the present embodiment, the Lambert's law is used to calculate the absorption optical thickness from the ratio between the reference light data set and the light data set to be measured.
Step 4, comparing the waveforms of the absorption cross section and the differential optical thickness to calculate the transverse offset between the absorption cross section and the differential optical thickness;
specifically, in the absorption spectrum, the absorption cross section corresponding to the gas to be measured is a fixed fluctuation value, the absorption cross section is used as a reference to compare waveforms of the differential optical thickness to be measured, several peak points near the maximum amplitude are selected, and the lateral offset between the two is calculated by adopting a peak-valley correspondence principle.
In this example, referring to fig. 2, a graph of spectral data based on the absorption cross section and the differential optical thickness of the spectrometer provided by the present invention is shown, where a curve with a relatively severe amplitude is the absorption cross section of the gas to be measured, and a curve with a relatively small amplitude is the differential optical thickness of the gas to be measured. Firstly, a curve of an absorption section is taken as a reference curve, wavelength position points corresponding to wave crests when the amplitude of the wave is maximum are searched, and a plurality of wave crest points or wave trough points are respectively selected on the left side and the right side of the wave crest points or the wave trough points; secondly, on the differential optical thickness corresponding curve, in contrast to the reference curve of the absorption section, selecting the wavelength position point corresponding to the peak point of the maximum amplitude and the corresponding peak point or valley point, and comparing the two curves to obtain the phase difference between the two curves, namely the transverse offset, wherein the number of the peaks and the valleys of the oscillogram of the differential optical thickness corresponding curve is far greater than the number of the peaks and the valleys on the absorption section corresponding curve.
Step 5, translating the differential optical thickness according to the transverse offset by taking the absorption section as a reference until the absorption section is aligned with the waveform of the differential optical thickness;
specifically, the wavelength positions corresponding to the maximum amplitude peaks of the absorption cross section and the differential optical thickness are searched, several peak points are selected on two sides of the wavelength position corresponding to the peak point of the maximum amplitude respectively, and the waveform of the differential optical thickness is translated in a peak-to-peak mode until the waveform of the absorption cross section coincides with the waveform of the absorption cross section.
In the present embodiment, the waveform of the differential optical thickness is shifted in the both-side directions with the maximum peak as the starting point according to the amount of the lateral shift in accordance with the principle that the peak is aligned with the peak until it coincides with the absorption cross-section waveform.
And 6, calculating the concentration of the gas to be measured of the compensated spectral data according to a least square method.
Specifically, assuming that the concentration of the gas to be measured is C, the compensated concentration of the gas to be measured is calculated by using a least square method according to the compensated absorption cross section of Y1 and the compensated absorption optical thickness of X1 according to the absorption cross section of the gas to be measured being Y and the absorption optical thickness of X.
In this embodiment, the absorption cross section Y and the absorption optical thickness X may be column matrices, the compensated absorption cross section Y1 and the absorption optical thickness X1 may be transposed matrices of corresponding column matrices, and the compensated concentration of the gas to be measured is calculated by using the least square method.
In summary, the invention respectively performs longitudinal compensation and transverse compensation on the absorption spectrum data of the gas to be measured, so that the concentration of the gas to be measured through the compensated data is more accurate, and meanwhile, the method does not need to perform a large amount of test data for each spectrometer, thereby reducing the workload of compensation and correction and improving the compensation efficiency; in addition, the method has strong universality and high transportability, can be popularized to various platforms in a large area, and can be used for various concentrations. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (4)
1. A method for spectrometer data drift-based compensation, comprising:
step 1, obtaining a background spectrum and an absorption spectrum of a spectrometer, wherein the background spectrum is spectrum data when standard gas is introduced, and the absorption spectrum is spectrum data when test gas is introduced;
step 2, selecting an absorption spectrum in a corresponding waveband range according to the gas to be detected, selecting a plurality of continuous and non-absorption reference selection points in the absorption spectrum, and performing longitudinal correction compensation on the absorption spectrum by adopting data normalization processing;
step 3, measuring and calculating the differential optical thickness under the test gas by adopting a Doas technology;
step 4, comparing the waveforms of the absorption cross section and the differential optical thickness to calculate the transverse offset between the absorption cross section and the differential optical thickness;
step 5, translating the differential optical thickness according to the transverse offset by taking the absorption section as a reference until the absorption section is aligned with the waveform of the differential optical thickness; searching the wavelength position corresponding to the maximum amplitude peak of the absorption cross section and the differential optical thickness, selecting a plurality of peak points on two sides of the wavelength position corresponding to the maximum amplitude peak point, and translating the waveform of the differential optical thickness in a peak-to-peak mode until the waveform of the differential optical thickness is superposed with the waveform of the absorption cross section;
and 6, calculating the concentration of the gas to be measured of the compensated spectral data according to a least square method.
2. The spectrometer data drift-based compensation method according to claim 1, wherein the step 3 specifically comprises:
and aiming at the gas to be measured, extracting a light data group to be measured of the gas to be measured from the absorption spectrum in a corresponding absorption wave band, selecting a reference light data group corresponding to the absorption wave band from the background spectrum, and calculating the absorption optical thickness of the gas to be measured by adopting a Lambert law according to the light data group to be measured and the reference light data group.
3. The spectrometer data drift-based compensation method according to claim 1, wherein the step 4 specifically comprises:
in an absorption spectrum, the absorption cross section corresponding to the gas to be measured is a fixed fluctuation value, the waveform of the differential optical thickness to be measured is compared by taking the absorption cross section as a reference, a plurality of peak points close to the maximum amplitude are selected, and the transverse offset between the two is calculated by adopting a peak-valley corresponding principle.
4. The spectrometer data drift-based compensation method according to claim 1, wherein the step 6 specifically comprises:
and assuming that the concentration of the gas to be detected is C, calculating the compensated concentration of the gas to be detected C1 by adopting a least square method according to the compensated absorption cross section Y1 and the compensated absorption optical thickness X1 according to the absorption cross section Y and the absorption optical thickness X of the gas to be detected.
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| CN107764796B (en) * | 2017-09-19 | 2019-07-26 | 华中科技大学 | A method of raw coal moisture, volatile matter are detected with baseline drift amount |
| CN109520941B (en) * | 2018-11-20 | 2021-02-09 | 天津大学 | Response function correction method of on-line spectral measuring instrument |
| CN111693491B (en) * | 2020-07-30 | 2023-01-06 | 重庆理工大学 | Method for measuring refractive index of transparent fluid based on Fabry-Perot interference |
| CN114384539B (en) * | 2021-12-21 | 2023-06-30 | 中国科学院光电技术研究所 | Absorption spectrum line phase shift speed measurement method based on background light synchronous difference |
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