Gas concentration detection method and device based on orthogonal phase locking

Abstract

The embodiment of the invention discloses a gas concentration detection method and device based on orthogonal phase locking, and the method comprises the steps: obtaining original data, and respectively generating a first reference signal and a second reference signal which are orthogonal to each other based on the original data; performing multiplication operation on the original data and the first reference signal to obtain I-channel original data, and performing multiplication operation on the original data and the second reference signal to obtain Q-channel original data; performing low-pass filtering on the I-channel original data and the Q-channel original data to obtain I-channel filtering data and Q-channel filtering data; calculating an I channel average value and a Q channel average value of the non-gas absorption interval; obtaining I channel correction data and Q channel correction data according to the I channel average value and the Q channel average value; and performing modulo operation on the I channel correction data and the Q channel correction data to obtain second harmonic absorption characteristics corresponding to the to-be-detected gas. By applying the scheme provided by the embodiment of the invention, the accuracy of gas concentration detection can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of gas concentration detection. Specifically, it relates to a gas concentration detection method and device based on quadrature phase-locked. Background Art

[0002] Currently known gas concentration detection methods mainly include the direct absorption method based on TDLAS (Tunable Diode Laser Absorption Spectroscopy) and the second harmonic method combining TDLAS and phase-locked technology. Phase-locked technology is divided into analog phase-locked and digital phase-locked. Among them, a large number of analog devices are required in analog phase-locked technology, and the performance of these analog devices will be affected by various environmental parameters, resulting in a significant reduction in the accuracy of measurement results; compared with analog phase-locked method, the digital phase-locked method has the characteristics of simple structure and strong flexibility.

[0003] The basic principle of quadrature digital phase-locking is that the modulated original signal is respectively multiplied by reference signals with a phase difference of 90°, the operation results are digitally low-pass filtered, the filtered results (i.e., the I channel and the Q channel) are directly squared and summed, and then square root (i.e., modulus) operation is performed. The specific calculation formula is: Further, the harmonic eigenvalue at a specific position is extracted according to the modulus result, that is, the gas concentration is reflected. As Figure 1 shown in the test results under the normal concentration of a certain gas, where the abscissa represents the wavelength and the ordinate represents the light intensity or amplitude; interval 0 is the non-gas absorption interval, and interval 1 is the gas absorption interval; the solid black line is the second harmonic waveform, the dotted line is the I channel data, and the dash-dotted line is the Q channel data. It can be seen that an obvious absorption peak will appear in interval 1 at the normal gas concentration.

[0004] However, when using the above method for gas concentration detection, when the gas concentration is low, after directly calculating the filtered I channel data and Q channel data according to the above formula, the absorption peak characteristics will be not obvious, deformed, etc. As Figure 2 shown, in this case, the eigenvalue at a specific position will not be able to truly reflect the gas concentration, that is, the concentration detection accuracy is low. Therefore, how to improve the accuracy of gas concentration detection when the gas concentration is low has become an urgent technical problem to be solved. Summary of the Invention

[0005] The present application provides a gas concentration detection method and device based on quadrature phase-locked to improve the accuracy of gas concentration detection. The specific technical solutions are as follows.

[0006] In a first aspect, an embodiment of the present application provides a gas concentration detection method based on quadrature phase-locked, the method includes:

[0007] Obtain the original data, and respectively generate a first reference signal and a second reference signal that are orthogonal to each other based on the original data; the original data is the data obtained after the modulated laser passes through the gas to be measured, is received and amplified, and undergoes analog-to-digital conversion.

[0008] Perform a multiplication operation on the original data and the first reference signal to obtain the original data of the I channel, and perform a multiplication operation on the original data and the second reference signal to obtain the original data of the Q channel.

[0009] Perform low-pass filtering on the original data of the I channel and the original data of the Q channel based on a preset low-pass digital filter to obtain the filtered data of the I channel and the filtered data of the Q channel.

[0010] Obtain a preset gas-free absorption interval and a gas absorption interval, and respectively calculate the average value of the I channel of the filtered data of the I channel in the gas-free absorption interval and the average value of the Q channel of the filtered data of the Q channel in the gas-free absorption interval.

[0011] Correct the filtered data of the I channel according to the average value of the I channel to obtain the corrected data of the I channel, and correct the filtered data of the Q channel according to the average value of the Q channel to obtain the corrected data of the Q channel.

[0012] Perform a modulo operation on the corrected data of the I channel and the corrected data of the Q channel to obtain the second harmonic absorption characteristics corresponding to the gas to be measured.

[0013] Optionally, the step of correcting the filtered data of the I channel according to the average value of the I channel to obtain the corrected data of the I channel, and correcting the filtered data of the Q channel according to the average value of the Q channel to obtain the corrected data of the Q channel includes:

[0014] When the average value of the I channel is greater than zero, use the difference between the filtered data of the I channel and the average value of the I channel as the corrected data of the I channel; when the average value of the I channel is less than zero, use the sum of the filtered data of the I channel and the average value of the I channel as the corrected data of the I channel; when the average value of the I channel is equal to zero, use the filtered data of the I channel as the corrected data of the I channel.

[0015] When the average value of the Q channel is greater than zero, use the difference between the filtered data of the Q channel and the average value of the Q channel as the corrected data of the Q channel; when the average value of the Q channel is less than zero, use the sum of the filtered data of the Q channel and the average value of the Q channel as the corrected data of the Q channel; when the average value of the Q channel is equal to zero, use the filtered data of the Q channel as the corrected data of the Q channel.

[0016] Optionally, the step of respectively generating a first reference signal and a second reference signal that are orthogonal to each other based on the original data includes:

[0017] The first reference signal Ref1 and the second reference signal Ref2 are respectively generated according to the following formulas:

[0018] Ref1 = A·sin[2π·(2ω 0 )·t]

[0019] Ref2 = A·cos[2π·(2ω 0 )·t];

[0020] where A is the amplitude, ω 0 is the frequency of the original data, and t is the time series.

[0021] Optionally, the cut-off frequency of the low-pass digital filter is less than the frequency ω of the original signal 0 .

[0022] Optionally, the method further includes:

[0023] Calculating characteristic parameters corresponding to the gas to be measured according to the second harmonic absorption characteristics corresponding to the gas to be measured;

[0024] Calculating the gas concentration of the gas to be measured according to the characteristic parameters.

[0025] In a second aspect, an embodiment of the present application provides a gas concentration detection device based on orthogonal phase-locking. The device includes:

[0026] A data acquisition module, configured to acquire original data, and respectively generate a first reference signal and a second reference signal that are orthogonal to each other based on the original data; the original data is the data obtained after the modulated laser passes through the gas to be measured, is received and amplified, and undergoes analog-to-digital conversion;

[0027] A data processing module, configured to perform a multiplication operation on the original data and the first reference signal to obtain I-channel original data, and perform a multiplication operation on the original data and the second reference signal to obtain Q-channel original data;

[0028] A data filtering module, configured to perform low-pass filtering on the I-channel original data and the Q-channel original data based on a preset low-pass digital filter to obtain I-channel filtered data and Q-channel filtered data;

[0029] An average value calculation module, configured to obtain a preset gas-free absorption interval and a gas absorption interval, and respectively calculate the I-channel average value of the I-channel filtered data in the gas-free absorption interval and the Q-channel average value of the Q-channel filtered data in the gas-free absorption interval;

[0030] A data correction module, configured to correct the filtered I-channel data according to the I-channel average value to obtain corrected I-channel data, and correct the filtered Q-channel data according to the Q-channel average value to obtain corrected Q-channel data;

[0031] A modulo operation module, configured to perform a modulo operation on the corrected I-channel data and the corrected Q-channel data to obtain the second harmonic absorption characteristic corresponding to the gas to be measured.

[0032] Optionally, the data correction module is specifically configured to:

[0033] When the I-channel average value is greater than zero, use the difference between the filtered I-channel data and the I-channel average value as the corrected I-channel data; when the I-channel average value is less than zero, use the sum of the filtered I-channel data and the I-channel average value as the corrected I-channel data; when the I-channel average value is equal to zero, use the filtered I-channel data as the corrected I-channel data;

[0034] When the Q-channel average value is greater than zero, use the difference between the filtered Q-channel data and the Q-channel average value as the corrected Q-channel data; when the Q-channel average value is less than zero, use the sum of the filtered Q-channel data and the Q-channel average value as the corrected Q-channel data; when the Q-channel average value is equal to zero, use the filtered Q-channel data as the corrected Q-channel data.

[0035] Optionally, the data acquisition module is specifically configured to:

[0036] Generate a first reference signal Ref1 and a second reference signal Ref2 respectively according to the following formulas:

[0037] Ref1 = A·sin[2π·(2ω 0 )·t]

[0038] Ref2 = A·cos[2π·(2ω 0 )·t];

[0039] Wherein, A is the amplitude, ω 0 is the frequency of the original data, and t is the time series.

[0040] Optionally, the cut-off frequency of the low-pass digital filter is less than the frequency ω 0 of the original signal.

[0041] Optionally, the device further includes:

[0042] A parameter calculation module, configured to calculate characteristic parameters corresponding to the gas to be measured according to the second harmonic absorption characteristics corresponding to the gas to be measured;

[0043] A concentration calculation module, configured to calculate the gas concentration of the gas to be measured according to the characteristic parameters.

[0044] In a third aspect, an embodiment of the present application provides a computer device, including: a memory and a processor, the memory and the processor are coupled;

[0045] The memory is used to store one or more computer instructions;

[0046] The processor is configured to execute the one or more computer instructions to implement the gas concentration detection method based on orthogonal phase-locking as described in the first aspect.

[0047] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, on which one or more computer instructions are stored, and the instructions are executed by a processor to implement the gas concentration detection method based on orthogonal phase-locking as described in the first aspect above.

[0048] In a fifth aspect, the present application provides a computer program product, the computer program product includes a computer program, and when the computer program is executed by a processor, it implements the gas concentration detection method based on orthogonal phase-locking as described in the first aspect.

[0049] In the embodiment of the present application, after filtering the I-channel data and the Q-channel data based on a low-pass filter, the average values of the I-channel data and the Q-channel data in the gas absorption-free interval can be calculated. That is to say, the noise magnitudes corresponding to the filtered data can be calculated respectively. Further, after correcting the I-channel data and the Q-channel data respectively according to the corresponding average values and then performing a modulo operation, the influence of noise on the data can be effectively reduced, so that the gas concentration can be truly reflected, and the gas concentration can be effectively detected even when the gas concentration is low, improving the accuracy of gas concentration detection. Description of the Drawings

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0051] Figure 1 Shows a schematic diagram of the test results when a certain gas has a normal concentration using a known method;

[0052] Figure 2Schematic diagram of test results when the concentration of a certain gas is low using a known method;

[0053] Figure 3 Schematic flow diagram showing a gas concentration detection method based on quadrature phase-locking provided by an embodiment of the present application;

[0054] Figure 4 For Figure 2 Schematic diagram of test results of the example shown using the method provided by an embodiment of the present application;

[0055] Figure 5 Schematic structural diagram of a gas concentration detection device based on quadrature phase-locking provided by an embodiment of the present application;

[0056] Figure 6 Schematic structural diagram of a computer device provided by an embodiment of the present application. Detailed implementation manners

[0057] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present application.

[0058] It should be noted that the terms "including" and "having" in the embodiments of the present application and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally further include unlisted steps or units, or may optionally further include other steps or units inherent to these processes, methods, products, or devices.

[0059] According to Fourier transform theory, any periodic signal can be decomposed into a sum of a series of sine (or cosine) signals whose frequencies are integer multiples of the original signal frequency. The second harmonic waveform is the set of amplitudes at each point of the signal component whose frequency is twice the original signal frequency after Fourier transform. Ideally, the second harmonic value in the gas-free absorption interval (or when the gas concentration is 0) should be 0, but in actual applications, affected by circuit noise and the sampling rate and resolution of the AD (Analog to Digital) converter, there is a certain DC noise in the filtered signal, resulting in the amplitude in the gas-free absorption interval not being 0.

[0060] To solve the problems of unobvious gas absorption characteristics and deformation under low concentration conditions, the embodiments of the present application disclose a gas concentration detection method and device based on orthogonal phase-locking, which can improve the accuracy of gas concentration detection. The embodiments of the present application will be described in detail below.

[0061] Figure 3 The flowchart of a gas concentration detection method based on orthogonal phase-locking provided by the embodiments of the present application is shown, as Figure 1 shown, the method includes the following steps:

[0062] S310: Obtain the original data, and based on the original data, generate a first reference signal and a second reference signal that are orthogonal to each other; the original data is the data obtained after the modulated laser passes through the gas to be measured, is received and amplified, and then undergoes analog-to-digital conversion.

[0063] The method provided by the embodiments of the present application can be implemented by the following architecture: a laser, a laser temperature control circuit, a direct digital synthesizer (DDS), a multi-pass absorption cell, a photodetector, an operational amplifier, an AD acquisition chip, an MCU (Microcontroller Unit) control chip, and a digital phase-locked calculation module.

[0064] Among them, the laser temperature control circuit can set the operating temperature of the laser to keep the operating temperature constant at T±0.0001°C. A sawtooth wave scanning signal is loaded between the LD+ and LD- pins of the laser to make the laser wavelength scanning width 2-3 times the full absorption line width of the gas and cover the complete gas absorption line; the sawtooth signal can be controlled by the MCU.

[0065] The digital frequency synthesizer DDS generates a first sine signal with a frequency of ω 0 and an amplitude of V1. The first sine signal is superimposed on the sawtooth wave scanning signal to modulate the wavelength emitted by the laser. The expression of the first sine signal can be: V1·sin[2π·ω 0 ·t], where ω 0 , V1 can both be controlled by the MCU, ω 0 is the frequency, V1 is the amplitude, and t is the time series.

[0066] The modulated laser passes through the multi-pass absorption cell containing the gas to be measured (the gas to be detected), is received by a high-speed photoelectric conversion detector, and the received signal is amplified by an operational amplifier. The high-sampling rate and high-resolution AD acquisition chip is responsible for analog-to-digital conversion of the converted (received and amplified) signal, and temporarily stores the converted original data in the buffer of the MCU control chip; the original data can be represented by Raw_data.

[0067] The MCU control chip is responsible not only for the coordinated control of the entire system, but also for the demodulation operation of the original data and the output of the results. Specifically, the MCU generates two reference signals with the same length as the original data, a frequency of 2ω 0 , an amplitude of A and orthogonal to each other (with a phase difference of 90°), and their expressions are:

[0068] Ref1 = A·sin[2π·(2ω 0 )·t]

[0069] Ref2 = A·cos[2π·(2ω 0 )·t];

[0070] where A is the amplitude, ω 0 is the frequency of the original data, and t is the time series.

[0071] S320: Multiply the original data by the first reference signal to obtain the original data of the I channel, and multiply the original data by the second reference signal to obtain the original data of the Q channel.

[0072] Specifically, the MCU can read the original data in the buffer and multiply it by the reference signals respectively to obtain the original data I' and Q' of the I channel and the Q channel:

[0073] I' = Raw_data·Ref1;

[0074] Q' = Raw_data·Ref2;

[0075] S330: Perform low-pass filtering on the original data of the I channel and the original data of the Q channel based on a preset low-pass digital filter to obtain the filtered data of the I channel and the filtered data of the Q channel.

[0076] Use the low-pass digital filter to perform low-pass filtering on I' and Q'. At this time, the obtained values are the amplitudes I and Q of the second harmonic of each data point. Specifically, a Butterworth digital filter can be selected, and the cut-off frequency is set to f 0 , and f 0 < ω 0 .

[0077] S340: Obtain the preset gas-free absorption interval and gas absorption interval, and calculate the average value of the I channel of the filtered data of the I channel in the gas-free absorption interval and the average value of the Q channel of the filtered data of the Q channel in the gas-free absorption interval respectively.

[0078] As described above, the laser wavelength scanning width is 2 - 3 times the gas complete absorption line. Therefore, the gas-free absorption interval 0 and the gas absorption interval 1 can be selected respectively.

[0079] In the embodiments of the present application, the average value of the I-channel filtered data in the gas absorption-free interval and the average value of the Q-channel filtered data in the gas absorption-free interval can be calculated respectively. That is to say, for the I-channel filtered data, the average value of the amplitudes of each point in the gas absorption-free interval can be calculated as the average value of the I-channel; for the Q-channel filtered data, the average value of the amplitudes of each point in the gas absorption-free interval can be calculated as the average value of the Q-channel.

[0080] S350: Correct the I-channel filtered data according to the average value of the I-channel to obtain the corrected I-channel data, and correct the Q-channel filtered data according to the average value of the Q-channel to obtain the corrected Q-channel data.

[0081] It can be understood that the gas absorption-free interval is the interval where the gas concentration is 0. Ideally, the corresponding second harmonic value should be 0. However, in practical applications, due to circuit noise and the AD sampling rate and resolution, there is a certain DC noise in the filtered signal, resulting in the amplitude of the gas absorption-free interval not being 0. That is to say, the average value of the I-channel or the average value of the Q-channel can reflect the corresponding noise level.

[0082] In the embodiments of the present application, the I-channel filtered data can be corrected according to the average value of the I-channel to obtain the corrected I-channel data, and the Q-channel filtered data can be corrected according to the average value of the Q-channel to obtain the corrected Q-channel data. That is to say, the influence of noise can be removed from the I-channel filtered data to obtain the true corrected I-channel data, and the influence of noise can be removed from the Q-channel filtered data to obtain the true corrected Q-channel data.

[0083] In one implementation, the I-channel filtered data and the Q-channel filtered data can be corrected according to the following steps: when the average value of the I-channel is greater than zero, the difference between the I-channel filtered data and the average value of the I-channel is used as the corrected I-channel data; when the average value of the I-channel is less than zero, the sum of the I-channel filtered data and the average value of the I-channel is used as the corrected I-channel data; when the average value of the I-channel is equal to zero, the I-channel filtered data is used as the corrected I-channel data; when the average value of the Q-channel is greater than zero, the difference between the Q-channel filtered data and the average value of the Q-channel is used as the corrected Q-channel data; when the average value of the Q-channel is less than zero, the sum of the Q-channel filtered data and the average value of the Q-channel is used as the corrected Q-channel data; when the average value of the Q-channel is equal to zero, the Q-channel filtered data is used as the corrected Q-channel data.

[0084] S360: Perform a modulo operation on the corrected I-channel data and the corrected Q-channel data to obtain the second harmonic absorption characteristics corresponding to the gas to be measured.

[0085] After the above steps are processed, the noise influence can be removed from the I-channel filtered data to obtain the true I-channel corrected data, and the noise influence can be removed from the Q-channel filtered data to obtain the true Q-channel corrected data. In this case, by performing a modulo operation on the I-channel corrected data and the Q-channel corrected data, the second harmonic absorption characteristics corresponding to the gas to be measured can be obtained.

[0086] Specifically, the second harmonic absorption characteristics of obvious gas absorption can be calculated according to the following formula:

[0087] Figure 2 In the example shown, after gas concentration detection is performed in the manner provided by the embodiment of the present application, the obtained second harmonic absorption characteristics are as Figure 4 shown. It can be seen that compared with Figure 2 , Figure 4 the second harmonic absorption characteristics in

[0088] are obvious, and the accuracy of gas concentration detection has been significantly improved. Figure 4 On the basis of

[0089] extracting the characteristic parameters in interval 1, the concentration of the gas in the multi-pass absorption cell can be reflected. The above characteristic parameters may include: peak value, area, etc., and the embodiment of the present application does not limit this.

[0090] Next, a specific embodiment is combined to illustrate the gas concentration detection method based on quadrature phase-locked provided by the embodiment of the present application. The method may include the following steps:

[0091] 1. The laser temperature control circuit can set the working temperature of the laser to make the working temperature constant at T±0.0001°C.

[0092] 2. A sawtooth wave scanning signal with a period of 20 ms and a peak amplitude of 0.25 V is loaded between the LD+ and LD- pins of the laser, so that the laser wavelength scanning width is 2-3 times the complete absorption line width of the gas and covers the complete gas absorption line; the sawtooth signal can be controlled by the MCU.

[0093] 3. A digital frequency synthesizer DDS generates a frequency of ω0 , a first sine signal with an amplitude of V1, which is superimposed on a sawtooth scanning signal to modulate the wavelength emitted by the laser; the expression of the first sine signal is: V1·sin[2π·ω 0 ·t], where ω 0 = 10 kHz, V1 = 100 mV can both be controlled by the MCU, and t is a time series with a step size equal to the following AD acquisition interval.

[0094] 4. The modulated laser passes through a multi-pass absorption cell containing the CH 4 gas to be measured and is received by a high-speed optoelectronic conversion detector. The received signal is amplified by an operational amplifier.

[0095] 5. An AD acquisition chip with a sampling rate S = 500 k and a resolution of 16 bits is responsible for converting (receiving and amplifying) the signal into an analog-to-digital conversion and temporarily storing the converted original data in the buffer of the MCU control chip; the original data is represented by Raw_data.

[0096] 6. The MCU control chip is not only responsible for the coordinated control of the entire system, but also for the demodulation operation of the original data and the output of the results.

[0097] 6.1. The MCU generates two reference signals with the same length as the original data, a frequency of 2ω 0 , an amplitude of A = 1 and orthogonal to each other (with a phase difference of 90°), and their expressions are: Ref1 = A·sin[2π·(2ω 0 )·t]; Ref2 = A·cos[2π·(2ω 0 )·t]; t is a time series with a step size equal to the AD sampling interval.

[0098] 6.2. The MCU reads the original data in the buffer and performs a multiplication operation with the reference signal to obtain the original data I' and Q' of the I channel and the Q channel:

[0099] I' = Raw_data·Ref1;

[0100] Q' = Raw_data·Ref2;

[0101] 6.3. Use a low-pass digital filter to perform low-pass filtering on I' and Q'. At this time, the obtained is the amplitude I and Q of the second harmonic of each data point. Here, a 3rd-order Butterworth digital filter is selected, and the cut-off frequency f 0 = 300 Hz.

[0102] 6.4. As described in Article 2, the laser wavelength scanning width is 2 - 3 times the gas complete absorption line. The data within one period is divided into two parts, namely the gas-free absorption interval 0 and the gas absorption interval 1.

[0103] 6.5. Calculate the average values of the data in the gas absorption-free intervals of the I-channel and Q-channel respectively:

[0104] If the average value is greater than 0: Subtract the average value from the corresponding channel data;

[0105] If the average value is less than 0: Add the absolute value of the average value to the corresponding channel data;

[0106] If the average value is equal to 0: Do not perform any processing on the corresponding channel data.

[0107] 6.6. Perform a modulo operation on the data of the two channels after the processing in step 6.5 Obtain the second harmonic absorption characteristics of obvious gas absorption, such as Figure 4 shown.

[0108] 6.7. Extract the characteristic parameters in interval 1, and the gas concentration in the multi-pass absorption cell can be reflected.

[0109] Such as Figure 5 shown, which shows a gas concentration detection device based on orthogonal phase-locking provided by an embodiment of the present application. The device includes:

[0110] A data acquisition module 510, configured to acquire original data, and respectively generate a first reference signal and a second reference signal that are orthogonal to each other based on the original data; the original data is the data obtained after the modulated laser passes through the gas to be measured, is received and amplified, and undergoes analog-to-digital conversion;

[0111] A data processing module 520, configured to perform a multiplication operation on the original data and the first reference signal to obtain I-channel original data, and perform a multiplication operation on the original data and the second reference signal to obtain Q-channel original data;

[0112] A data filtering module 530, configured to perform low-pass filtering on the I-channel original data and the Q-channel original data based on a preset low-pass digital filter to obtain I-channel filtered data and Q-channel filtered data;

[0113] An average value calculation module 540, configured to obtain a preset gas absorption-free interval and a gas absorption interval, and respectively calculate the I-channel average value of the I-channel filtered data in the gas absorption-free interval and the Q-channel average value of the Q-channel filtered data in the gas absorption-free interval;

[0114] A data correction module 550, configured to correct the I-channel filtered data according to the I-channel average value to obtain I-channel corrected data, and correct the Q-channel filtered data according to the Q-channel average value to obtain Q-channel corrected data;

[0115] A modulo operation module 560, configured to perform a modulo operation on the I-channel correction data and the Q-channel correction data to obtain the second harmonic absorption characteristics corresponding to the gas to be measured.

[0116] Optionally, the data correction module 550 is specifically configured to:

[0117] When the average value of the I channel is greater than zero, the difference between the filtered data of the I channel and the average value of the I channel is used as the I-channel correction data; when the average value of the I channel is less than zero, the sum of the filtered data of the I channel and the average value of the I channel is used as the I-channel correction data; when the average value of the I channel is equal to zero, the filtered data of the I channel is used as the I-channel correction data;

[0118] When the average value of the Q channel is greater than zero, the difference between the filtered data of the Q channel and the average value of the Q channel is used as the Q-channel correction data; when the average value of the Q channel is less than zero, the sum of the filtered data of the Q channel and the average value of the Q channel is used as the Q-channel correction data; when the average value of the Q channel is equal to zero, the filtered data of the Q channel is used as the Q-channel correction data.

[0119] Optionally, the data acquisition module 510 is specifically configured to:

[0120] Generate a first reference signal Ref1 and a second reference signal Ref2 respectively according to the following formulas:

[0121] Ref1 = A·sin[2π·(2ω 0 )·t]

[0122] Ref2 = A·cos[2π·(2ω 0 )·t];

[0123] where A is the amplitude, ω 0 is the frequency of the original data, and t is the time series.

[0124] Optionally, the cut-off frequency of the low-pass digital filter is less than the frequency ω 0 of the original signal.

[0125] Optionally, the apparatus further includes:

[0126] A parameter calculation module, configured to calculate characteristic parameters corresponding to the gas to be measured according to the second harmonic absorption characteristics corresponding to the gas to be measured;

[0127] A concentration calculation module, configured to calculate the gas concentration of the gas to be measured according to the characteristic parameters.

[0128] In the embodiments of the present application, after filtering the I-channel data and Q-channel data based on a low-pass filter, the average values of the I-channel data and Q-channel data in the gas absorption-free interval can be calculated. That is to say, the noise levels corresponding to the filtered data can be calculated separately. Further, after correcting the I-channel data and Q-channel data respectively according to the corresponding average values and then performing a modulo operation, the influence of noise on the data can be effectively reduced, so that the gas concentration can be truly reflected. Even when the gas concentration is low, the gas concentration can be effectively detected, improving the accuracy of gas concentration detection.

[0129] Next, a computer device provided by the embodiments of the present application will be introduced. Please refer to Figure 6 , Figure 6 which is a schematic structural diagram of the computer device provided by the embodiments of the present application. The computer device includes:

[0130] One or more processors 40;

[0131] The processor 40 is coupled to the storage device 41, and the storage device 41 is used to store one or more programs.

[0132] When the one or more programs are executed by the one or more processors 40, the electronic device realizes the technical solution of Figure 3 a gas concentration detection method based on orthogonal phase-locking as described above.

[0133] The embodiments of the present application also provide a computer-readable storage medium, on which a computer program is stored. When the program is executed by a processor, the technical solution of Figure 3 a gas concentration detection method based on orthogonal phase-locking as described above is realized.

[0134] The present application provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the technical solution of Figure 3 a gas concentration detection method based on orthogonal phase-locking as described above is realized.

[0135] Those of ordinary skill in the art can understand that the drawings are only schematic diagrams of an embodiment, and the modules or processes in the drawings are not necessarily essential for implementing the present application.

[0136] Those of ordinary skill in the art can understand that the modules in the device in the embodiment can be distributed in the device in the embodiment as described in the embodiment, or can be correspondingly changed and located in one or more devices different from this embodiment. The modules in the above embodiments can be combined into one module, or can be further split into multiple sub-modules.

[0137] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than limiting them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A gas concentration detection method based on orthogonal phase locking, characterized in that: The method comprises: Acquire raw data, and based on the raw data, respectively generate a first reference signal and a second reference signal that are orthogonal to each other; the raw data is data obtained after the modulated laser passes through the gas to be measured, is received, amplified, and analog-to-digital converted; Multiplying the original data by the first reference signal to obtain I channel original data, and multiplying the original data by the second reference signal to obtain Q channel original data; Performing low-pass filtering on the I channel raw data and the Q channel raw data based on a preset low-pass digital filter to obtain I channel filtered data and Q channel filtered data; Obtaining a preset gas absorption-free interval and a gas absorption interval, and respectively calculating an I channel average value of the I channel filtered data in the gas absorption-free interval and a Q channel average value of the Q channel filtered data in the gas absorption-free interval; The I channel filter data is corrected according to the I channel average value to obtain I channel corrected data, and the Q channel filter data is corrected according to the Q channel average value to obtain Q channel corrected data; A modulo operation is performed on the I channel correction data and the Q channel correction data to obtain the second harmonic absorption characteristics corresponding to the gas to be measured.

2. The method according to claim 1, characterized in that The steps of correcting the I channel filtered data according to the I channel average value to obtain I channel corrected data, and correcting the Q channel filtered data according to the Q channel average value to obtain Q channel corrected data include: When the I-channel average value is greater than zero, the difference between the I-channel filtered data and the I-channel average value is used as the I-channel corrected data; when the I-channel average value is less than zero, the sum of the I-channel filtered data and the I-channel average value is used as the I-channel corrected data; when the I-channel average value is equal to zero, the I-channel filtered data is used as the I-channel corrected data; When the Q channel average value is greater than zero, the difference between the Q channel filtered data and the Q channel average value is used as the Q channel correction data; when the Q channel average value is less than zero, the sum of the Q channel filtered data and the Q channel average value is used as the Q channel correction data; when the Q channel average value is equal to zero, the Q channel filtered data is used as the Q channel correction data.

3. The method according to claim 1, characterized in that The step of generating a mutually orthogonal first reference signal and a second reference signal based on the original data comprises: The first reference signal Ref1 and the second reference signal Ref2 are generated according to the following formulas: Ref1=A·sin[2π·(2ω0)·t] Ref2=A·cos[2π·(2ω0)·t]; Wherein, A is the amplitude, ω0 is the frequency of the original data, and t is the time series.

4. The method according to claim 3, characterized in that The cut-off frequency of the low-pass digital filter is less than the frequency ω0 of the original signal.

5. The method according to any one of claims 1 to 3, characterized in that: The method further comprises: Calculating characteristic parameters corresponding to the gas to be measured according to the second harmonic absorption characteristics corresponding to the gas to be measured; The gas concentration of the gas to be measured is calculated according to the characteristic parameters.

6. A gas concentration detection device based on orthogonal phase locking, characterized in that: The device comprises: A data acquisition module is used to acquire raw data, and based on the raw data, generate a first reference signal and a second reference signal which are mutually orthogonal; the raw data is the data obtained after the modulated laser passes through the gas to be measured, is received, amplified and analog-to-digital converted; A data processing module, configured to multiply the original data by the first reference signal to obtain I channel original data, and multiply the original data by the second reference signal to obtain Q channel original data; A data filtering module, used for performing low-pass filtering on the I channel raw data and the Q channel raw data based on a preset low-pass digital filter to obtain I channel filtered data and Q channel filtered data; An average value calculation module, used to obtain a preset gas absorption-free interval and a gas absorption interval, and respectively calculate an I channel average value of the I channel filtered data in the gas absorption-free interval and a Q channel average value of the Q channel filtered data in the gas absorption-free interval; A data correction module, used for correcting the I channel filtered data according to the I channel average value to obtain I channel corrected data, and correcting the Q channel filtered data according to the Q channel average value to obtain Q channel corrected data; The modulo operation module is used to perform a modulo operation on the I channel correction data and the Q channel correction data to obtain the second harmonic absorption characteristics corresponding to the gas to be measured.

7. The device according to claim 6, characterized in that The data correction module is specifically used for: When the I-channel average value is greater than zero, the difference between the I-channel filtered data and the I-channel average value is used as the I-channel corrected data; when the I-channel average value is less than zero, the sum of the I-channel filtered data and the I-channel average value is used as the I-channel corrected data; when the I-channel average value is equal to zero, the I-channel filtered data is used as the I-channel corrected data; When the Q channel average value is greater than zero, the difference between the Q channel filtered data and the Q channel average value is used as the Q channel correction data; when the Q channel average value is less than zero, the sum of the Q channel filtered data and the Q channel average value is used as the Q channel correction data; when the Q channel average value is equal to zero, the Q channel filtered data is used as the Q channel correction data.

8. The device according to claim 6, characterized in that The data acquisition module is specifically used for: The first reference signal Ref1 and the second reference signal Ref2 are generated according to the following formulas: Ref1=A·sin[2π·(2ω0)·t] Ref2=A·cos[2π·(2ω0)·t]; Wherein, A is the amplitude, ω0 is the frequency of the original data, and t is the time series.

9. The device according to claim 8, characterized in that The cut-off frequency of the low-pass digital filter is less than the frequency ω0 of the original signal.

10. The device according to any one of claims 6 to 8, characterized in that: The device also includes: A parameter calculation module, used to calculate characteristic parameters corresponding to the gas to be measured according to the second harmonic absorption characteristics corresponding to the gas to be measured; The concentration calculation module is used to calculate the gas concentration of the gas to be measured according to the characteristic parameters.

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