CN114199820A - Gas concentration detection method and device - Google Patents
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Abstract
The embodiment of the invention provides a method and a device for detecting gas concentration, wherein the method comprises the following steps: obtaining an optical signal of an absorption spectrum through a laser and gas with known concentration, converting the optical signal into an electrical signal, removing a low-frequency sawtooth wave in the electrical signal, performing line amplification processing on a high-frequency component in the electrical signal again, and sampling the high-frequency signal in the electrical signal from a zero phase, wherein the sampling length is a sawtooth wave period; carrying out detection operation on the sampled signal according to the speed of sine wave frequency doubling to obtain a homodromous component; low-pass filtering the homodromous component to obtain a second harmonic; determining a peak value and a valley value from the second harmonic based on the relation between the maximum value in the second harmonic and a preset threshold value, calculating the intensity of an absorption peak according to the peak value and the valley value, and determining a calibration coefficient according to different gas concentrations and corresponding absorption peak intensities. And detecting the concentration of the gas based on the calibration coefficient. Thereby, the accuracy and speed of gas concentration detection are improved.
Description
Technical Field
The invention relates to the field of detection of gas isotope abundance, in particular to a method and a device for detecting gas concentration.
Background
In the process of detecting the gas concentration, a Tunable Diode Laser Absorption Spectroscopy (TDLAS) technology is generally adopted, and the method has the characteristics of no need of pretreatment, strong selectivity, high response speed, high accuracy, high precision and the like, and is widely applied to the detection fields of environment, medical treatment and the like in recent years. TDLAS is largely classified into direct absorption, frequency modulation, and wavelength modulation techniques from the viewpoint of a signal detection method.
The direct absorption spectrum technology has low accuracy, large calculated amount and easy generation of fitting errors, and the frequency modulation technology adopts a suitable condition that a modulation frequency which is simultaneously larger than the absorption line width is adopted, but the higher modulation frequency puts higher requirements on instrument equipment, thereby increasing the complexity of the system; the Wavelength Modulation Spectroscopy (WMS) technique has the characteristic that a harmonic signal proportional to the target gas concentration appears during the measurement process, rather than measuring a small change on a large signal, the accuracy also needs to be improved, and thus how to improve the accuracy of gas concentration detection becomes an urgent problem to be solved.
Disclosure of Invention
The embodiment of the invention aims to provide a method and a device for detecting gas concentration, which solve the problem of low accuracy of gas concentration detection in the prior art and improve the accuracy of gas concentration detection and the operation speed. The specific technical scheme is as follows:
a method of detecting a gas concentration, comprising:
when the gas to be detected is received, the absorption peak of the gas to be detected is calculated.
And determining the concentration of the gas to be detected based on a preset calibration coefficient and the absorption peak intensity of the gas to be detected. The preset calibration coefficient is the corresponding relation between the gas concentration and the absorption peak intensity.
The calibration coefficient is determined according to different gas concentrations and corresponding absorption peak intensities, and the determination process of the gas concentrations and the corresponding absorption peaks comprises the following steps:
the wavelength output by the laser is modulated through low-frequency sawtooth waves and high-frequency sine waves, an optical signal with an absorption spectrum is obtained based on a signal output by the modulated laser and gas with known concentration, and the optical signal is converted into an electric signal through a detector.
And carrying out high-pass filtering on the electric signal to remove low-frequency sawtooth waves in the electric signal.
And amplifying the high-frequency signal in the electric signal, and sampling the high-frequency signal in the electric signal from a zero phase.
And carrying out detection operation on the sampled signals according to the speed of sine wave frequency doubling to obtain homodromous components.
And carrying out low-pass filtering on the homodromous component to obtain a second harmonic.
Determining a peak value and a valley value from the second harmonic based on the relation between the maximum value of the absorption peak in a preset interval in the second harmonic and a corresponding preset threshold value, and calculating the intensity of the absorption peak according to the peak value and the valley value.
Optionally, the zero phases of the sine wave and the sawtooth wave are coincident.
Optionally, the determining a peak value and a valley value from the second harmonic based on a relationship between a maximum value in the second harmonic and a preset threshold, and calculating an absorption peak intensity according to the peak value and the valley value includes:
and detecting the maximum value of the absorption peak in each preset interval in the second harmonic, wherein each preset interval comprises a complete peak and a complete valley.
And regarding any interval, if the maximum value of the absorption peak in the interval is greater than the corresponding preset threshold value, taking the maximum value in the interval as a first peak value, and taking the minimum values on the left side and the right side of the first peak value in the interval as a first valley value and a second valley value respectively.
And taking the average value of the first peak value minus the first valley value and the second valley value as the absorption peak intensity.
Optionally, the determining a peak value and a valley value from the second harmonic based on a relationship between a maximum value in the second harmonic and a preset threshold, and calculating an absorption peak intensity according to the peak value and the valley value includes:
and detecting the maximum value of the absorption peak in each preset interval in the second harmonic, wherein each preset interval comprises a complete peak and a complete valley.
And for any one interval, if the maximum value of the absorption peak in the interval is not greater than the corresponding preset threshold value, taking the second harmonic at the first preset position in the interval as a second peak value, taking the second harmonic at the second preset position as a left valley value, and taking the second harmonic at the third preset position as a right valley value.
And taking the average value of the second peak minus the left valley and the right valley as the absorption peak intensity of the interval.
Optionally, the low-pass filtering the equidirectional component to obtain a second harmonic includes:
and carrying out low-pass filtering on the homodromous component through a Butterworth low-pass filter to obtain a second harmonic.
Optionally, the detecting operation is performed on the acquired signal according to the speed of sine wave frequency doubling to obtain a homodromous component, including:
and carrying out detection operation on the acquired signal according to the speed of sine wave frequency doubling, and dividing the signal of one period of the sine wave into a first period and a second period. The second period is subsequent to the first period.
The data in the first period and the second period are equally divided into two groups respectively, and the data of the group with the data position behind is inverted.
A gas concentration detection apparatus comprising:
a first calculation unit for calculating an absorption peak of the gas to be detected when the gas to be detected is received.
And the determining unit is used for determining the concentration of the gas to be detected based on a preset calibration coefficient and the absorption peak intensity of the gas to be detected. The preset calibration coefficient is the corresponding relation between the gas concentration and the absorption peak intensity.
The calibration coefficient is determined according to different gas concentrations and corresponding absorption peak intensities, and the determination process of the gas concentrations and the corresponding absorption peaks is determined by a calibration unit, which comprises:
and the detection unit is used for modulating the wavelength output by the laser through low-frequency sawtooth waves and high-frequency sine waves, obtaining an optical signal with an absorption spectrum based on the modulated signal output by the laser and the gas with known concentration, and converting the optical signal into an electric signal through the detector.
And the first low-pass filtering unit is used for carrying out high-pass filtering on the electric signal and removing the low-frequency sawtooth wave in the electric signal.
And the amplifying unit is used for amplifying the high-frequency signal in the electric signal, sampling the high-frequency signal in the electric signal from a zero phase, and the sampling length is one sawtooth period.
And the detection unit is used for carrying out detection operation on the sampled signals according to the speed of sine wave frequency doubling to obtain homodromous components.
And the second low-pass filtering unit is used for carrying out low-pass filtering on the homodromous component to obtain a second harmonic.
And the second calculation unit is used for determining a peak value and a valley value from the second harmonic wave based on the relation between the maximum value of the absorption peak in a preset interval in the second harmonic wave and a corresponding preset threshold value, and calculating the intensity of the absorption peak according to the peak value and the valley value.
Optionally, the zero phases of the sine wave and the sawtooth wave are coincident.
Optionally, the first computing unit includes:
and the first detection subunit is used for detecting the maximum value of the absorption peak in each preset interval in the second harmonic. Each predetermined interval includes a complete peak and valley.
And the first determining subunit is used for regarding any one interval, if the maximum value of the absorption peak in the interval is greater than the corresponding preset threshold value, taking the maximum value in the interval as a first peak value, and taking the minimum values on the left side and the right side of the first peak value in the interval as a first valley value and a second valley value respectively.
A second determining subunit, configured to subtract a mean value of the first valley and the second valley from the first peak value as an absorption peak intensity.
Optionally, the first computing unit includes:
and the second detection subunit is used for detecting the maximum value of the absorption peak in each preset interval in the second harmonic. Each predetermined interval includes a complete peak and valley.
And the third determining subunit is configured to, for any one interval, if the maximum value of the absorption peak in the interval is not greater than the corresponding preset threshold, take the second harmonic at the first preset position in the interval as a second peak value, take the second harmonic at the second preset position as a third valley value, and take the second harmonic at the third preset position as a fourth valley value.
And a fourth determining subunit, configured to use a mean value of the third valley and the fourth valley subtracted from the second peak value as the absorption peak intensity of the interval.
Optionally, the second low-pass filtering unit is configured to:
and carrying out low-pass filtering on the homodromous component through a Butterworth low-pass filter to obtain a second harmonic.
Optionally, the wave detection unit is configured to:
and carrying out detection operation on the acquired signal according to the speed of sine wave frequency doubling, and dividing the signal of one period of the sine wave into a first period and a second period. The second period is subsequent to the first period.
The data in the first period and the second period are equally divided into two groups respectively, and the data of the group with the data position behind is inverted.
According to the gas concentration detection method and device provided by the embodiment of the invention, the signal to noise ratio is improved by filtering the low-frequency sawtooth wave, the effective number of the signal is improved by amplifying the sine wave, the amplitude of the second harmonic wave is improved by acquiring the signal from the zero phase, the accuracy of the second harmonic wave is reduced, the peak value and the peak valley are respectively determined according to the relationship between the maximum value in the second harmonic wave and the preset threshold value, and the accuracy of the absorption peak can be further improved. Meanwhile, the sine wave is detected and operated through the speed of frequency doubling, and the operation speed is improved through a Butterworth low-pass filter. Therefore, the method of the embodiment improves the accuracy of gas concentration detection and the speed of calculation.
Of course, it is not necessary for any product or method of practicing the invention to achieve all of the above-described advantages at the same time.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a flow chart of a method for detecting a gas concentration according to an embodiment of the present invention;
FIG. 2 is a flow chart of a process for determining a gas concentration and a corresponding absorption peak provided by an embodiment of the present invention;
FIG. 3 is a schematic diagram of an electrical signal with a low frequency sawtooth waveform filtered according to an alternative embodiment of the present invention;
FIG. 4 is a schematic representation of the results of filtering through a Butterworth low pass filter according to another alternative embodiment of the present invention;
FIG. 5 is a schematic diagram of a second harmonic provided by another alternative embodiment of the present invention;
fig. 6 is a block diagram of a gas concentration detection apparatus according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention provides a method for detecting gas concentration, as shown in fig. 1, comprising the following steps:
and S101, calculating the absorption peak of the gas to be detected when the gas to be detected is received.
Optionally, in an optional embodiment of the present invention, the calculating the absorption peak of the gas to be detected may be to use the gas in a preset concentration interval, and calculate the absorption peak of the gas to be detected in the preset concentration interval through a determination process of the gas concentration and the corresponding absorption peak shown in fig. 2.
S102, determining the concentration of the gas to be detected based on a preset calibration coefficient and the absorption peak intensity of the gas to be detected. The preset calibration coefficient is the corresponding relation between the gas concentration and the absorption peak intensity.
Optionally, in an optional embodiment of the present invention, the obtaining manner of the calibration coefficient may be: for the absorption peak intensity of the gas concentration corresponding to the low to high value obtained in step S101, the absorption peak intensity is taken as the abscissa and the gas concentration is taken as the ordinate, and the two are subjected to linear fitting to obtain the calibration coefficient. Wherein, the gas of different compositions corresponds to different calibration coefficients.
Optionally, in another optional embodiment of the present invention, the absorption peak intensity may be the absorption peak intensity of the homomorphic substances of the gases with different compositions calculated in step S101 shown in fig. 1, which is not described herein again.
The calibration coefficients are determined according to the different gas concentrations and the corresponding absorption peak intensities, and the determination process of the gas concentrations and the corresponding absorption peaks, as shown in fig. 2, includes:
s201, modulating the wavelength output by the laser through low-frequency sawtooth waves and high-frequency sine waves, obtaining an optical signal with an absorption spectrum based on the modulated signal output by the laser and gas with known concentration, and converting the optical signal into an electric signal through a detector.
Optionally, in an alternative embodiment of the present invention, the modulated laser may output laser light with a specific wavelength. The specific modulation process may be: the low-frequency sawtooth wave and the high-frequency sine wave are input into the laser, the low-frequency sawtooth wave is used as a scanning signal, and the high-frequency sine wave and the low-frequency sawtooth wave are superposed, so that the laser can output laser with a specific wavelength. According to the invention, the laser is modulated, so that the laser can output laser with a specific wavelength, and the accuracy of subsequently acquired data is improved. The frequency of the low-frequency sawtooth wave and the high-frequency sine wave affects the wavelength output by the laser, and preferably, the wavelength output by the laser can be modulated by using a low-frequency sawtooth wave of 10Hz and a high-frequency sine wave of 5 kHz.
S202, high-pass filtering is carried out on the electric signals, and low-frequency sawtooth waves in the electric signals are removed.
Optionally, in an alternative embodiment of the present invention, the electrical signal includes a low-frequency sawtooth wave and a high-frequency sine wave. According to the invention, the high-pass filtering is carried out on the electric signal, so that the low-frequency sawtooth wave in the electric signal is filtered, the signal-to-noise ratio of the electric signal is improved, and the accuracy of subsequent data processing is further improved. For example, the spectral electrical signal output by the detector is high-pass filtered, and a low-frequency sawtooth wave of 10Hz is filtered out, so that a high-frequency sine wave signal of 5kHz is obtained. Since the high frequency sine wave signal is small in amplitude, the signal is amplified by a signal amplifier. As shown in FIG. 3, it can be seen that the low frequency sawtooth wave in FIG. 3 has been filtered out, improving the signal-to-noise ratio in the electrical signal, thereby improving the accuracy of subsequent data processing. The above-mentioned manner of performing high-pass filtering may be implemented by a high-pass filter.
And S203, amplifying the high-frequency signal in the electric signal, and sampling the high-frequency signal in the electric signal from a zero phase, wherein the sampling length is one sawtooth period.
Optionally, in an optional embodiment of the present invention, the amplifying of the high-frequency signal in the electrical signal may improve the effective number of the high-frequency sine wave, and improve the signal-to-noise ratio of the electrical signal, so as to improve the precision of the subsequent processing result of the high-frequency sine wave.
Alternatively, in another alternative embodiment of the present invention, in order to reduce the error of the subsequently obtained second harmonic, the prior art employs sampling the high frequency sine wave starting from a fixed phase. However, since the second harmonic amplitude is small at some fixed phase, the accuracy of the absorption peak intensity is affected. Therefore, in this alternative embodiment, the acquisition from the zero phase may be fixed, so as to reduce the error between the periods, thereby ensuring the overlap between the periods of the second harmonic, and simultaneously ensuring the high amplitude of the obtained second harmonic. The zero phases of the high-frequency sine wave and the sawtooth wave are superposed, and the acquisition is started from the zero phases of the high-frequency sine wave and the sawtooth wave.
For the convenience of understanding the step S203 shown in fig. 2, please refer to fig. 3 to understand another alternative embodiment of the present invention:
and synchronously acquiring an absorption spectrum signal with a high-frequency sine wave from a zero phase, and acquiring a signal of a sawtooth wave period, wherein the synchronous acquisition from the zero phase is to start the acquisition from the zero phase starting points of the sawtooth wave and the high-frequency sine wave. The high-frequency sine wave is in the form of
The high frequency sine wave is uniformly sampled at a sampling frequency of 5kHZ x 32, and 500 sine wave cycles are acquired with 32 data points per sine wave. The signal of one sawtooth wave period is collected for 16000 data points, and the periodic signal covers12C16O2、16O12C18O and13C16O2absorption spectrum information.
As shown in fig. 3, 12 periodic signals are acquired, each period starts from a zero phase point, and it can be seen that 12 groups of data have high coincidence, thereby providing a precondition for improving the stability and accuracy of subsequent data analysis.
And S204, carrying out detection operation on the sampled signal according to the speed of sine wave frequency doubling to obtain a homodromous component.
Optionally, in an optional embodiment of the present invention, the implementation of step S204 shown in fig. 2 may be to perform detection operation on the acquired signal according to a speed of sine wave frequency doubling, and if each sine wave period of the acquired signal is 32 data points, the speed of frequency doubling may be to divide the original 32 data into one sine wave period and divide the 16 data into a small period in sequence again. The sampling length may be a length of a sawtooth period.
Alternatively, in another alternative embodiment of the present invention, the small period obtained by frequency doubling may be processed differently when the detection operation is performed. Optionally, the implementation of step S204 may be:
the sampled signal is detected at the speed of sine wave frequency doubling, and a signal of one cycle of the sine wave is divided into a first cycle and a second cycle. Wherein the second period is subsequent to the first period.
The data in the first period and the second period are equally divided into two groups respectively, and the data in the group with the data position behind is inverted.
For example: assuming that each sine wave period of the acquired signal is 32 data points, the speed of frequency doubling is to divide the original 32 data into a sine wave period and divide the original 32 data into 16 data into a small period in turn, the first 8 data of each small period are unchanged, the last 8 data are multiplied by-1, and the result after operation is the above homodromous component. Wherein the multiplication by-1 is the operation of inverting.
And S205, low-pass filtering the homodromous component to obtain a second harmonic.
Optionally, in an alternative embodiment of the present invention, the low-pass filtering the homodromous component to obtain the second harmonic may be implemented by a butterworth low-pass filter.
For example, the employed frequency of the butterworth low pass filter is set to 160kHz, the pass band and stop band frequencies range from 0 to 500Hz, and the pass band and stop band attenuations range from 0.1 to 20. As shown in fig. 4, two sets of filter coefficients of the butterworth low-pass filter are calculated, and the two sets of filter coefficients are subjected to addition, subtraction and multiplication with the homodromous component, so that the obtained second harmonic sequence of the homodromous component is maximum, and the second harmonic of the orthogonal component is minimum. In fig. 4, the solid line represents the second harmonic of the same direction component, and the broken line represents the second harmonic of the orthogonal component. Through the arrangement, the calculation amount of the orthogonal component part is reduced, so that the analysis speed is improved compared with the prior art.
S206, determining a peak value and a valley value from the second harmonic based on the relation between the maximum value of the absorption peak in the preset interval in the second harmonic and the corresponding preset threshold value, and calculating the intensity of the absorption peak according to the peak value and the valley value.
Optionally, in an optional embodiment of the present invention, the determining the peak and the valley may be implemented by:
and detecting the maximum value of the absorption peak of each preset interval in the second harmonic, wherein each preset interval comprises a complete peak and a complete valley, and each preset interval is preset with an interval range.
And regarding any one interval, if the maximum value of the absorption peak in the interval is greater than the corresponding preset threshold value, taking the maximum value in the interval as a first peak value, and taking the minimum values on the left side and the right side of the first peak value as a first valley value and a second valley value respectively. Wherein, the method for obtaining the maximum value may be a maximum value method
And subtracting a first valley average value from the first peak value to obtain the absorption peak intensity of the interval, wherein the first valley average value is the average value of the first valley and the second valley.
For example, as shown in FIG. 5, 12C is set in advance16O2、16O12C18O and13C16O2is in the range of 2000 to 6000, 8000 to 12000 and 12500 to 16000, respectively, the maximum value of the absorption peak in the region is obtained by the maximum value method in each interval, and the maximum value is compared with a preset threshold value 2000. When the maximum value is larger than a preset threshold value, the concentration of the gas corresponding to the maximum value is high.
Optionally, in another optional embodiment of the present invention, the implementation of determining the peak value and the estimation may further be:
and detecting the maximum value of the absorption peak in each preset interval in the second harmonic, wherein each preset interval comprises a complete peak and a complete valley.
And aiming at any one interval, if the maximum value of the absorption peak in the interval is not greater than the corresponding preset threshold value, taking the second harmonic at the first preset position in the interval as a second peak value, taking the second harmonic at the second preset position as a left valley value, and taking the second harmonic at the third preset position as a right valley value.
And subtracting a second valley average value from the second peak value to obtain the absorption peak intensity of the interval, wherein the second valley average value is the average value of the left valley and the right valley.
For example, as shown in FIG. 5, set up12C16O2The second harmonic at the second preset position on the left side of the first preset position is used as a left valley value, and the second harmonic at the third preset position on the right side of the first preset position is used as a right valley value.
Alternatively, in another alternative embodiment of the present invention, the peak value V is used as a function ofpeakFirst valley/left valley
And second/right trough
Calculating the absorption peak intensity a:
alternatively, in another alternative embodiment of the present invention,
according to the invention, the signal to noise ratio is improved by filtering the low-frequency sawtooth wave, the effective digit of the signal is improved by amplifying the sine wave, the amplitude of the second harmonic wave is improved by acquiring the signal from the zero phase, the accuracy of the second harmonic wave is reduced, the peak value and the peak valley are respectively determined according to the relationship between the maximum value in the second harmonic wave and the preset threshold value, and the accuracy of the absorption peak can be further improved. Meanwhile, the sine wave is detected and operated through the speed of frequency doubling, and the operation speed is improved through a Butterworth low-pass filter. Therefore, the method of the embodiment improves the accuracy of gas concentration detection and the speed of calculation.
Optionally, the zero phases of the sine wave and the sawtooth wave are coincident.
Optionally, determining a peak value and a valley value from the second harmonic based on a relationship between a maximum value in the second harmonic and a preset threshold, and calculating an absorption peak intensity according to the peak value and the valley value, including:
and detecting the maximum value of the absorption peak in each preset interval in the second harmonic, wherein each preset interval comprises a complete peak and a complete valley.
And regarding any interval, if the maximum value of the absorption peak in the interval is greater than the corresponding preset threshold value, taking the maximum value in the interval as a first peak value, and taking the minimum values on the left side and the right side of the first peak value in the interval as a first valley value and a second valley value respectively.
The average of the first peak minus the first and second valleys is taken as the absorption peak intensity.
Optionally, determining a peak value and a valley value from the second harmonic based on a relationship between a maximum value in the second harmonic and a preset threshold, and calculating an absorption peak intensity according to the peak value and the valley value, including:
and detecting the maximum value of the absorption peak in each preset interval in the second harmonic, wherein each preset interval comprises a complete peak and a complete valley.
And for any one interval, if the maximum value of the absorption peak in the interval is not greater than the corresponding preset threshold value, taking the second harmonic at the first preset position in the interval as a second peak value, taking the second harmonic at the second preset position as a left valley value, and taking the second harmonic at the third preset position as a right valley value.
The average of the second peak minus the left and right valleys is taken as the absorption peak intensity in this interval.
Optionally, low-pass filtering the homodromous component to obtain a second harmonic, including:
and carrying out low-pass filtering on the homodromous component through a Butterworth low-pass filter to obtain a second harmonic.
Optionally, the detecting operation is performed on the collected signal according to the speed of sine wave frequency doubling to obtain the homodromous component, including:
and carrying out detection operation on the acquired signal according to the speed of sine wave frequency doubling, and dividing the signal of one period of the sine wave into a first period and a second period. The second period is subsequent to the first period.
The data in the first period and the second period are equally divided into two groups respectively, and the data of the group with the data position behind is inverted.
According to the invention, the signal to noise ratio is improved by filtering the low-frequency sawtooth wave, the effective digit of the signal is improved by amplifying the sine wave, the amplitude of the second harmonic wave is improved by acquiring the signal from the zero phase, the accuracy of the second harmonic wave is reduced, the peak value and the peak valley are respectively determined according to the relationship between the maximum value in the second harmonic wave and the preset threshold value, and the accuracy of the absorption peak can be further improved. Meanwhile, the sine wave is detected and operated through the speed of frequency doubling, and the operation speed is improved through a Butterworth low-pass filter. Therefore, the method of the embodiment improves the accuracy of gas concentration detection and the speed of calculation.
Corresponding to the embodiment of the method for detecting the gas concentration, the present invention further provides a device for detecting the gas concentration, as shown in fig. 6, including:
the first calculation unit 601 is configured to calculate an absorption peak of the gas to be detected when the gas to be detected is received.
A determining unit 602, configured to determine a concentration of the gas to be detected based on a preset calibration coefficient and an absorption peak intensity of the gas to be detected. The preset calibration coefficient is the corresponding relation between the gas concentration and the absorption peak intensity.
The calibration coefficients are determined from different gas concentrations and corresponding absorption peak intensities, the determination of the gas concentrations and corresponding absorption peaks is determined by a calibration unit 603, the calibration unit 603 comprises:
and the detection unit 604 is used for modulating the wavelength output by the laser through a low-frequency sawtooth wave and a high-frequency sine wave, obtaining an optical signal with an absorption spectrum based on the modulated signal output by the laser and the gas with a known concentration, and converting the optical signal into an electric signal through the detector.
The first low-pass filtering unit 605 is configured to perform high-pass filtering on the electrical signal to remove a low-frequency sawtooth wave in the electrical signal.
The amplifying unit 606 is configured to amplify the high-frequency signal in the electrical signal, and sample the high-frequency signal in the electrical signal from a zero phase, where the sampling length is one sawtooth period.
The detection unit 607 is configured to perform detection operation on the sampled signal at the speed of sine wave frequency doubling to obtain a homodromous component.
And a second low-pass filtering unit 608, configured to perform low-pass filtering on the equidirectional component to obtain a second harmonic.
And a second calculating unit 609, configured to determine a peak value and a valley value from the second harmonic based on a relationship between a maximum value of an absorption peak in a preset interval in the second harmonic and a corresponding preset threshold value, and calculate an absorption peak intensity according to the peak value and the valley value.
Optionally, the zero phases of the sine wave and the sawtooth wave are coincident.
Optionally, the first calculating unit 601 includes:
and the first detection subunit is used for detecting the maximum value of the absorption peak in each preset interval in the second harmonic. Each predetermined interval includes a complete peak and valley.
And the first determining subunit is used for regarding any one interval, if the maximum value of the absorption peak in the interval is greater than the corresponding preset threshold value, taking the maximum value in the interval as a first peak value, and taking the minimum values on the left side and the right side of the first peak value in the interval as a first valley value and a second valley value respectively.
And a second determining subunit, configured to use a mean value of the first peak value minus the first valley value and the second valley value as the absorption peak intensity.
Optionally, the first calculating unit 601 includes:
and the second detection subunit is used for detecting the maximum value of the absorption peak in each preset interval in the second harmonic. Each predetermined interval includes a complete peak and valley.
And the third determining subunit is configured to, for any one interval, if the maximum value of the absorption peak in the interval is not greater than the corresponding preset threshold, take the second harmonic at the first preset position in the interval as a second peak value, take the second harmonic at the second preset position as a third valley value, and take the second harmonic at the third preset position as a fourth valley value.
And a fourth determining subunit, configured to use a mean value of the third valley and the fourth valley subtracted from the second peak value as the absorption peak intensity of the interval.
Optionally, the second low-pass filtering unit 608 is configured to:
and carrying out low-pass filtering on the homodromous component through a Butterworth low-pass filter to obtain a second harmonic.
Optionally, the detection unit 607 is configured to:
and carrying out detection operation on the acquired signal according to the speed of sine wave frequency doubling, and dividing the signal of one period of the sine wave into a first period and a second period. The second period is subsequent to the first period.
The data in the first period and the second period are equally divided into two groups respectively, and the data of the group with the data position behind is inverted.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. It should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in the process, method, article, or apparatus that comprises the element.
All the embodiments in the present specification are described in a related manner, and the same and similar parts among the embodiments may be referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the system embodiment, since it is substantially similar to the method embodiment, the description is simple, and for the relevant points, reference may be made to the partial description of the method embodiment.
The above are merely examples of the present application and are not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.
Claims (10)
1. A method for detecting a gas concentration, comprising:
calculating the absorption peak of the gas to be detected when the gas to be detected is received;
determining the concentration of the gas to be detected based on a preset calibration coefficient and the absorption peak intensity of the gas to be detected; the preset calibration coefficient is the corresponding relation between the gas concentration and the absorption peak intensity;
the calibration coefficient is determined according to different gas concentrations and corresponding absorption peak intensities, and the determination process of the gas concentrations and the corresponding absorption peaks comprises the following steps:
modulating the wavelength output by the laser through low-frequency sawtooth waves and high-frequency sine waves, obtaining an optical signal with an absorption spectrum based on a modulated signal output by the laser and gas with a known concentration, and converting the optical signal into an electric signal through a detector;
carrying out high-pass filtering on the electric signal to remove low-frequency sawtooth waves in the electric signal;
amplifying the high-frequency signals in the electric signals, and sampling the high-frequency signals in the electric signals from a zero phase, wherein the sampling length is a sawtooth period;
carrying out detection operation on the sampled signal according to the speed of sine wave frequency doubling to obtain a homodromous component;
low-pass filtering the homodromous component to obtain a second harmonic;
determining a peak value and a valley value from the second harmonic based on the relation between the maximum value of the absorption peak in a preset interval in the second harmonic and a corresponding preset threshold value, and calculating the intensity of the absorption peak according to the peak value and the valley value.
2. The method of claim 1,
the zero phases of the sine wave and the sawtooth wave are coincident.
3. The method of claim 1, wherein determining peak and valley values from the second harmonic based on a relationship between a maximum value in the second harmonic and a preset threshold value, and calculating an absorption peak intensity from the peak and valley values comprises:
detecting the maximum value of the absorption peak of each preset interval in the second harmonic; each preset interval comprises a complete peak and a complete valley;
for any one interval, if the maximum value of the absorption peak in the interval is greater than the corresponding preset threshold value, taking the maximum value in the interval as a first peak value, and taking the minimum values on the left side and the right side of the first peak value in the interval as a first valley value and a second valley value respectively;
and taking the average value of the first peak value minus the first valley value and the second valley value as the absorption peak intensity.
4. The method of claim 1, wherein determining peak and valley values from the second harmonic based on a relationship between a maximum value in the second harmonic and a preset threshold value, and calculating an absorption peak intensity from the peak and valley values comprises:
detecting the maximum value of the absorption peak of each preset interval in the second harmonic; each preset interval comprises a complete peak and a complete valley;
for any one interval, if the maximum value of the absorption peak in the interval is not greater than the corresponding preset threshold value, taking the second harmonic at the first preset position in the interval as a second peak value, taking the second harmonic at the second preset position as a left valley value, and taking the second harmonic at the third preset position as a right valley value;
and taking the average value of the second peak minus the left valley and the right valley as the absorption peak intensity of the interval.
5. The method of claim 1, wherein low pass filtering the co-directional component to obtain a second harmonic comprises:
and carrying out low-pass filtering on the homodromous component through a Butterworth low-pass filter to obtain a second harmonic.
6. The method of claim 1, wherein the detecting the collected signal according to the speed of sine wave frequency doubling to obtain the homodromous component comprises:
carrying out detection operation on the acquired signal according to the speed of sine wave frequency doubling, and dividing a signal of one period of the sine wave into a first period and a second period; the second period is subsequent to the first period;
the data in the first period and the second period are equally divided into two groups respectively, and the data of the group with the data position behind is inverted.
7. A gas concentration detection apparatus, comprising:
the first calculation unit is used for calculating the absorption peak of the gas to be detected when the gas to be detected is received;
the determining unit is used for determining the concentration of the gas to be detected based on a preset calibration coefficient and the absorption peak intensity of the gas to be detected; the preset calibration coefficient is the corresponding relation between the gas concentration and the absorption peak intensity;
the calibration coefficient is determined according to different gas concentrations and corresponding absorption peak intensities, and the determination process of the gas concentrations and the corresponding absorption peaks is determined by a calibration unit, which comprises:
the detection unit is used for modulating the wavelength output by the laser through low-frequency sawtooth waves and high-frequency sine waves, obtaining an optical signal with an absorption spectrum based on the modulated signal output by the laser and gas with known concentration, and converting the optical signal into an electric signal through the detector;
the first low-pass filtering unit is used for carrying out high-pass filtering on the electric signal and removing low-frequency sawtooth waves in the electric signal;
the amplifying unit is used for amplifying the high-frequency signal in the electric signal, sampling the high-frequency signal in the electric signal from a zero phase, and the sampling length is one sawtooth period;
the detection unit is used for carrying out detection operation on the sampled signal according to the speed of sine wave frequency doubling to obtain a homodromous component;
the second low-pass filtering unit is used for carrying out low-pass filtering on the homodromous component to obtain a second harmonic;
and the second calculation unit is used for determining a peak value and a valley value from the second harmonic wave based on the relation between the maximum value of the absorption peak in a preset interval in the second harmonic wave and a corresponding preset threshold value, and calculating the intensity of the absorption peak according to the peak value and the valley value.
8. The apparatus of claim 7, wherein the zero phases of the sine wave and the sawtooth wave are coincident.
9. The apparatus of claim 7, wherein the first computing unit comprises:
the first detection subunit is used for detecting the maximum value of the absorption peak of each preset interval in the second harmonic; each preset interval comprises a complete peak and a complete valley;
the first determining subunit is configured to, for any one interval, if a maximum value of an absorption peak in the interval is greater than a corresponding preset threshold value, take the maximum value in the interval as a first peak value, and take minimum values on the left and right sides of the first peak value in the interval as a first valley value and a second valley value, respectively;
a second determining subunit, configured to subtract a mean value of the first valley and the second valley from the first peak value as an absorption peak intensity.
10. The apparatus of claim 7, wherein the first computing unit comprises:
the second detection subunit is used for detecting the maximum value of the absorption peak of each preset interval in the second harmonic; each preset interval comprises a complete peak and a complete valley;
a third determining subunit, configured to, for any one interval, if a maximum value of an absorption peak in the interval is not greater than a corresponding preset threshold, take a second harmonic at a first preset position in the interval as a second peak value, take a second harmonic at a second preset position as a third valley value, and take a second harmonic at the third preset position as a fourth valley value;
and a fourth determining subunit, configured to use a mean value of the third valley and the fourth valley subtracted from the second peak value as the absorption peak intensity of the interval.
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