Gas concentration measuring method and gas concentration measuring device

Abstract

The invention discloses a gas concentration measuring method and device. The gas concentration measuring method comprises the steps that a control module controls a driving module to output scanning driving signals of at least two scanning periods to a laser; the laser emits an optical signal according to the scanning driving signal; the photoelectric detector receives the attenuated light signal absorbed by the gas to be detected and converts the attenuated light signal into an electric signal; the control module determines the concentration of the to-be-detected gas in the first scanning period according to the electric signal of the first scanning period; when the concentration of the to-be-detected gas in the first scanning period is smaller than a first set threshold value, the concentration of the to-be-detected gas in the second scanning period is determined according to the electric signal in the second scanning period on the basis of the wavelength modulation spectrum WMS technology, and when the concentration of the to-be-detected gas in the first scanning period is larger than or equal to the first set threshold value, the to-be-detected gas is detected. And determining the concentration of the to-be-detected gas in the second scanning period based on a direct absorption spectrum (DAS) technology according to the electric signal in the second scanning period. According to the invention, the problem that high sensitivity and full scale are difficult to consider in the existing gas detection technology can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of gas detection, and in particular, to a method and a device for measuring gas concentration. Background Art

[0002] With the adjustment of the national energy structure, the application of clean energy is increasing. However, the safety accidents caused by the leakage of hydrocarbon gases are also emerging in an endless stream, and the safety situation is becoming increasingly urgent. When hydrocarbon gases leak, there are both tiny leaks and high-concentration leaks, which not only cause economic losses and environmental pollution, but also endanger the safety of people's lives and property.

[0003] Common methods for detecting hydrocarbon gas concentration include electrochemistry method, catalytic combustion method, solid electrolyte method, infrared absorption spectroscopy method, etc. However, the existing gas concentration detection methods have the problem that it is difficult to balance high sensitivity and full range. Summary of the Invention

[0004] The present invention provides a method and a device for measuring gas concentration to solve the problem that it is difficult to balance high sensitivity and full range in the existing gas detection technology.

[0005] In a first aspect, an embodiment of the present invention provides a method for measuring gas concentration, including: a control module controls a driving module to output a scanning driving signal to a laser for at least two scanning cycles; the at least two scanning cycles include a first scanning cycle and a second scanning cycle, and the second scanning cycle is after the first scanning cycle; the laser emits an optical signal according to the scanning driving signal; a photodetector receives the attenuated optical signal absorbed by the gas to be measured and converts the attenuated optical signal into an electrical signal; the control module determines the concentration of the gas to be measured in the first scanning cycle according to the electrical signal of the first scanning cycle; when the concentration of the gas to be measured in the first scanning cycle is less than a first set threshold, the concentration of the gas to be measured in the second scanning cycle is determined based on the wavelength modulation spectroscopy (WMS) technology according to the electrical signal of the second scanning cycle, and when the concentration of the gas to be measured in the first scanning cycle is greater than or equal to the first set threshold, the concentration of the gas to be measured in the second scanning cycle is determined based on the direct absorption spectroscopy (DAS) technology according to the electrical signal of the second scanning cycle.

[0006] Second aspect, an embodiment of the present invention provides a gas concentration measurement device. The measurement device is used to execute the gas concentration measurement method provided by any embodiment of the present invention. The measurement device includes: a driving module, a laser, a photodetector, and a control module; the control module is connected to the driving module and is used to control the driving module to output a scanning driving signal to the laser; at least two scanning periods include a first scanning period and a second scanning period, and the second scanning period is after the first scanning period; the laser is connected to the driving module and is used to emit an optical signal according to the scanning driving signal; the photodetector is arranged on the optical path of the optical signal emitted by the laser, the photodetector is electrically connected to the control module, and the photodetector is used to receive the attenuated optical signal absorbed by the gas to be measured and convert the attenuated optical signal into an electrical signal; the control module is further used to determine the concentration of the gas to be measured in the first scanning period according to the electrical signal in the first scanning period; when the concentration of the gas to be measured in the first scanning period is less than the first set threshold, determine the concentration of the gas to be measured in the second scanning period based on the wavelength modulation spectroscopy (WMS) technology according to the electrical signal in the second scanning period, and when the concentration of the gas to be measured in the first scanning period is greater than or equal to the first set threshold, determine the concentration of the gas to be measured in the second scanning period based on the direct absorption spectroscopy (DAS) technology according to the electrical signal in the second scanning period.

[0007] The gas concentration measurement method provided by the embodiment of the present invention determines the concentration of the gas to be measured in the first scanning period according to the electrical signal in the first scanning period. When the concentration of the gas to be measured in the first scanning period is less than the first set threshold (i.e., in the low concentration range), the WMS technology is used to process the electrical signal in the second scanning period. This enables the measurement method to fully utilize the high sensitivity characteristic of the WMS technology in the low concentration range, effectively detect low concentration gases, and avoid the problem of inaccurate measurement due to too low concentration. When the concentration of the gas to be measured in the first scanning period is greater than or equal to the first set threshold (i.e., in the high concentration range), the DAS technology is used to analyze the electrical signal in the second scanning period. This enables the measurement method to utilize the advantages of directly and accurately measuring high concentration gases by the DAS technology in the high concentration range, and achieve reliable detection of the high concentration part in the full range measurement.

[0008] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. Description of the Drawings

[0009] To more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the accompanying drawings required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0010] Figure 1 is an absorption curve diagram obtained by using the direct absorption spectroscopy technique when detecting methane gas, provided by an embodiment of the present invention;

[0011] Figure 2 is an absorption curve diagram obtained by using the wavelength modulation spectroscopy technique when detecting methane gas, provided by an embodiment of the present invention;

[0012] Figure 3 is a curve diagram of the absorption signal obtained when detecting low-concentration methane gas, provided by an embodiment of the present invention;

[0013] Figure 4 is a curve diagram of the second harmonic signal obtained when detecting concentration methane gas, provided by an embodiment of the present invention;

[0014] Figure 5 is a curve diagram of the concentration absorption signal obtained when detecting high-concentration methane gas, provided by an embodiment of the present invention;

[0015] Figure 6 is a curve diagram of the second harmonic signal obtained when detecting high-concentration methane gas, provided by an embodiment of the present invention;

[0016] Figure 7 is a measuring device for gas concentration, provided by an embodiment of the present invention;

[0017] Figure 8 is a flowchart of a method for measuring gas concentration, provided by an embodiment of the present invention;

[0018] Figure 9 is a flowchart of another method for measuring gas concentration, provided by an embodiment of the present invention;

[0019] Figure 10 is a flowchart of another method for measuring gas concentration, provided by an embodiment of the present invention;

[0020] Figure 11 is a waveform diagram of a first scanning drive signal, provided by an embodiment of the present invention;

[0021] Figure 12 is the concentration absorption signal after the gas of the WMS+DAS combination method;

[0022] Figure 13are the second harmonic signals demodulated by the WMS and the concentration absorption peaks extracted by the DAS;

[0023] Figure 14 is a flowchart of another method for measuring gas concentration provided by an embodiment of the present invention;

[0024] Figure 15 is a waveform diagram of a second scan driving signal provided by an embodiment of the present invention;

[0025] Figure 16 is a waveform diagram of a third scan driving signal provided by an embodiment of the present invention;

[0026] Figure 17 is a flowchart of another method for measuring gas concentration provided by an embodiment of the present invention;

[0027] Figure 18 is a waveform diagram of a fourth scan driving signal provided by an embodiment of the present invention;

[0028] Figure 19 is a schematic structural diagram of another gas concentration measuring device provided by an embodiment of the present invention. Detailed Embodiments

[0029] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0030] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above drawings are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units does not necessarily need to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0031] As described in the background art, in the prior art, there is a problem that it is difficult to balance high sensitivity and full range in the existing gas concentration detection methods. After research by the inventor, it is found that the reason for the above problem is:

[0032] Current gas concentration detection technologies all use a single DAS technology or WMS technology. When only using DAS, it is impossible to detect lower detection limits and higher sensitivities; when only using WMS, due to the non-linear problem of high concentrations, it is impossible to detect methane gas in the full range. This invention will be described by taking the detection of methane gas concentration as an example.

[0033] Methane molecules have an absorption effect on light of a specific wavelength, and they have the best absorption effect on monochromatic light with a wavelength of about 1653.7 nm. DAS modulates the scanning drive current of the laser to make the laser emit laser light with a scanning wavelength of 1653.7 nm ± 0.3 nm. When the laser passes through methane gas, the laser light with a wavelength of 1653.7 nm will be absorbed, resulting in attenuation of its light intensity. The attenuated laser light is received by a photodetector and converted into an electrical signal. The electrical signal near 1653.7 nm will generate an absorption peak due to the absorption effect. The concentration of methane is measured by analyzing the proportional relationship between the concentration and the absorption peak parameters through the Lambert-Beer law. The direct absorption method can simply and directly measure the concentration of methane. Its simple and direct characteristics make DAS vulnerable to various noise sources, such as laser intensity fluctuations, laser wavelength fluctuations, detector noise, shot noise (photon noise), etc. When measuring low-concentration gases, DAS is easily interfered by noise. When the concentration of the absorbing gas is high enough and the absorption line is strong enough, it can provide a sufficient signal-to-noise ratio (SNR) for the absorption signal, and the DAS technology can accurately measure the gas concentration.

[0034] The WMS technology modulates the scanning drive signal of the laser in the DAS technology by superimposing a high-frequency carrier wave (a sine wave of ten to dozens of kHz), and transfers the detection of DAS to a higher-frequency range with better SNR, which can effectively suppress low-frequency noise or mechanical noise in the laser emission to the receiving link. The photodetector converts the high-frequency modulated light signal absorbed by the gas into an electrical signal, and applies the lock-in amplification technology for quadrature double-channel demodulation. The two channels respectively use high-frequency sine wave signals and cosine signals to modulate the absorption signal, amplify the absorption signal, and then pass through a low-pass filter and double-channel signal merging to demodulate the second harmonic. The concentration of methane is measured by analyzing the proportional relationship between the concentration and the second harmonic parameters through the Lambert-Beer law. The WMS technology can effectively reduce the detection limit of methane and improve the sensitivity of methane detection, but it is prone to exhibit a non-linear absorption process under high-concentration conditions.

[0035] Figure 1 It is an absorption curve diagram obtained by using the direct absorption spectroscopy technology when detecting methane gas provided by an embodiment of the present invention. Figure 2 It is an absorption curve diagram obtained by using the wavelength modulation spectroscopy technology when detecting methane gas provided by an embodiment of the present invention.

[0036] Reference Figure 1 and Figure 2 , for example, the abscissa represents the sampling time, and the ordinate represents the energy intensity of the laser. Both technical routes are based on the absorption of light with a specific wavelength by methane molecules, and the proportional relationship between the absorption peak and the concentration is inverted through the Lambert-Beer law. As Figure 1 shown, DAS directly inverses the concentration through the absorption peak; as Figure 2 shown, WMS modulates the emission signal of the laser with a high-frequency sine wave, demodulates the gas absorption signal received by the photodetector through the phase-locked amplification technology, removes the low-frequency noise interference and amplifies the absorption signal, demodulates the second harmonic of the gas absorption signal, and inverses the concentration of the absorption gas.

[0037] Figure 3 is a graph of the absorption signal obtained when detecting low-concentration methane gas provided by an embodiment of the present invention. Figure 4 is a graph of the second harmonic signal obtained when detecting low-concentration methane gas provided by an embodiment of the present invention.

[0038] Combined with Figure 3 and Figure 4 , for example, the abscissa represents the sampling time, and the ordinate represents the energy intensity of the laser. The dark blue solid line #1 represents that the current concentration of methane gas is 50 ppm, the red solid line #2 represents that the current concentration of methane gas is 100 ppm, the yellow solid line #3 represents that the current concentration of methane gas is 500 ppm, and the green solid line #4 represents that the current concentration of methane gas is 1000 ppm. At low concentrations (such as 50 ppm - 1000 ppm), from the ordinate ratio, it can be seen that the second harmonic demodulated by the wavelength modulation method has more obvious absorption characteristics, and the peak spacing ratio of different concentrations is much larger than that of the direct absorption method, which enables the wavelength modulation method to detect a lower detection limit and obtain higher sensitivity. Since in the actual process, the environment, laser, photoelectric converter, readout circuit, etc. will generate some noise signals, in order to ensure the reliability of methane concentration detection, generally the lowest detection limit requires a signal-to-noise ratio greater than 3.

[0039] Taking a phase-locked gain of 30 times as an example in an embodiment of the present invention, the absorption peaks and second harmonics of DAS and WMS methods at low and high concentrations are compared. The second harmonic of WMS is about 1.6 times the peak of the absorption peak of DAS, and the sensitivity of WMS is also increased by 1.6 times, and the detection limit can be reduced by 0.8 times. The wavelength modulation method uses high-frequency signal modulation and phase-locked amplification technology, which can avoid the interference of noise signals and amplify the absorption signal. By controlling the phase-locked gain, it can detect lower concentrations with higher sensitivity.

[0040] Figure 5The present invention provides a curve diagram of a concentration absorption signal obtained when detecting high-concentration methane gas. Figure 6 The graph is a graph of a second harmonic signal obtained when detecting high-concentration methane gas, provided by an embodiment of the present invention.

[0041] Combination Figure 5 and Figure 6 , for example, the horizontal axis represents the sampling time, and the vertical axis represents the energy intensity of the laser. The light blue solid line #5 represents that the current methane gas concentration is 10000ppm, the dark blue solid line #6 represents that the current methane gas concentration is 20000ppm, the purple solid line #7 represents that the current methane gas concentration is 30000ppm, and the pink solid line #8 represents that the current methane gas concentration is 40000ppm. At high concentrations (such as 10000ppm-40000ppm), the DAS peak value has a good linear relationship with the gas concentration; WMS shows a nonlinear relationship at high concentrations, which does not conform to the Lambert-Beer law.

[0042] In summary, using a single DAS cannot reach a lower detection limit and has lower sensitivity than WMS; using a single WMS can achieve a lower detection limit and higher sensitivity, but it is nonlinear at high concentrations and cannot meet the full range of use.

[0043] In order to solve the problems in the prior art, an embodiment of the present invention provides a method and a device for measuring gas concentration. The following first introduces a device for measuring gas concentration using the method for measuring gas concentration provided by an embodiment of the present invention.

[0044] Figure 7 A gas concentration measuring device provided by an embodiment of the present invention. Figure 7 The measuring device includes: a driving module 11, a laser 12, a photodetector 13 and a control module 14.

[0045] The control module 14 is connected to the driving module 11 , the laser 12 is connected to the driving module 11 , the photodetector 13 is disposed on an optical path of an optical signal emitted by the laser 12 , and the photodetector 13 is electrically connected to the control module 14 .

[0046] Figure 8 1 is a flow chart of a method for measuring gas concentration provided by an embodiment of the present invention. This embodiment is applicable to the measurement of gas concentration. The method can be performed by a gas concentration measurement device. Figure 7 and Figure 8 , the method comprising:

[0047] S101 , a control module controls a driving module to output a scanning driving signal of at least two scanning cycles to a laser.

[0048] Specifically, at least two scanning periods include a first scanning period and a second scanning period, and the second scanning period is after the first scanning period.

[0049] The driving module 11 at least includes a triangular wave signal generator and a sine wave signal generator.

[0050] The control module 14 may include a micro control unit. Optionally, the control module 14 may include a single-chip microcomputer, and may also include a Digital Signal Processor (DSP) or a Field Programmable Gate Array (FPGA).

[0051] In some embodiments, the control module 14 sends a control signal to the driving module 11 to control the driving module 11 to generate a scanning driving signal.

[0052] S102. The laser emits an optical signal according to the scanning driving signal.

[0053] According to the scanning driving signal provided by the driving module 11, the laser 12 can accurately emit a specific wavelength optical signal that matches the absorption spectrum of the gas to be measured. Different gas molecules have selectivity for the absorption of light. Only when the wavelength of the light emitted by the laser is consistent with the absorption peak wavelength of the gas molecules, the gas molecules will strongly absorb the light. For example, when measuring the concentration of methane gas, the laser 12 will emit an optical signal with a wavelength near the absorption peak of methane (such as 1653.7 nm, etc.) to ensure that the absorption of light by methane carbon can be effectively detected.

[0054] S103. The photodetector receives the attenuated optical signal after being absorbed by the gas to be measured and converts the attenuated optical signal into an electrical signal.

[0055] Specifically, when the optical signal emitted by the laser 12 passes through the gas to be measured, the molecules in the gas to be measured will absorb the light of a specific wavelength, resulting in attenuation of the optical signal. The photodetector 13 is located on the propagation path of the optical signal, can receive the attenuated optical signal, and converts it into an electrical signal using principles such as the photoelectric effect. The overall shape of the electrical signal is consistent with the modulation wave signal of the laser, and the attenuation of the optical signal after gas absorption is reflected as absorption dips on both sides of the triangular wave.

[0056] Optionally, the gas concentration measuring device further includes: a gas chamber 15, and the gas chamber 15 is located between the laser 12 and the photodetector 13; the gas chamber 15 is filled with the gas to be measured.

[0057] S104. The control module determines the concentration of the gas to be measured in the first scanning period according to the electrical signal in the first scanning period; when the concentration of the gas to be measured in the first scanning period is less than the first set threshold, the concentration of the gas to be measured in the second scanning period is determined based on the wavelength modulation spectroscopy (WMS) technology according to the electrical signal in the second scanning period. When the concentration of the gas to be measured in the first scanning period is greater than or equal to the first set threshold, the concentration of the gas to be measured in the second scanning period is determined based on the direct absorption spectroscopy (DAS) technology according to the electrical signal in the second scanning period.

[0058] Specifically, the first scanning period is used to preliminarily determine the concentration range of the gas to be measured. By analyzing the electrical signal in the first scanning period, the control module can quickly understand the approximate level of the current concentration of the gas to be measured, providing a basis for selecting an appropriate detection technology subsequently. This way of first judging the concentration range makes the whole measurement process more targeted, avoiding the problem of inaccurate detection that may be caused by blindly using a single technology.

[0059] After obtaining the electrical signal in the first scanning period, the control module calculates the concentration of the gas to be measured in the first scanning period through a pre-set algorithm and model, combined with the DAS technology or the WMS technology. Then, the concentration in the first scanning period is compared with the first set threshold. If it is less than the first set threshold, it means that the concentration of the gas to be measured is low. At this time, the wavelength modulation spectroscopy (WMS) technology is used in the second scanning period because this technology has higher sensitivity in low-concentration measurements. If it is greater than or equal to the first set threshold, it means that the concentration of the gas to be measured is high. In the second scanning period, the direct absorption spectroscopy (DAS) technology is used. The DAS technology can more accurately determine the concentration in high-concentration measurements. Based on the concentration judgment result in the first scanning period, the corresponding WMS or DAS technology is selected in the second scanning period for accurate measurement. This strategy of double scanning periods and adapting the technology according to the concentration range enables the measurement method to achieve the best detection performance in different concentration intervals, thus taking into account the measurement requirements of both high sensitivity and full range.

[0060] The steps for determining the concentration of the gas to be measured based on the direct absorption spectroscopy (DAS) technology include: the control module performs a baseline fitting operation on the electrical signal to determine the baseline level of the electrical signal, and then removes the baseline; performs an absorption peak fitting on the electrical signal after removing the baseline, and extracts the parameters of the absorption peak; determines the concentration of the gas to be measured according to the extracted absorption peak parameters, combined with the Lambert-Beer law.

[0061] The steps for determining the concentration of the gas to be measured based on the wavelength modulation spectroscopy (WMS) technology include: amplifying and demodulating the electrical signal transmitted from the photodetector to obtain a second harmonic signal; analyzing the demodulated second harmonic signal and extracting the parameters of the second harmonic signal; inversely calculating the concentration of the gas to be measured according to the parameters of the second harmonic signal.

[0062] It should be noted that in the actual use process, the switching first setting threshold of the two methods can be comprehensively considered according to factors such as the measurement environment, signal parameters, measurement equipment, optical path, WMS modulation coefficient, and WMS modulation frequency.

[0063] The gas concentration measurement method provided by the embodiments of the present invention determines the concentration of the gas to be measured in the first scan period through the electrical signal in the first scan period. When the concentration of the gas to be measured in the first scan period is less than the first setting threshold (i.e., in the low concentration range), the WMS technology is used to process the electrical signal in the second scan period. This enables the measurement method to fully utilize the high-sensitivity characteristic of the WMS technology in the low concentration range, effectively detect low concentration gases, and avoid the problem of inaccurate measurement due to too low concentration. When the concentration of the gas to be measured is greater than or equal to the first setting threshold (i.e., in the high concentration range), the DAS technology is used to analyze the electrical signal in the second scan period. This enables the measurement method to utilize the advantages of directly and accurately measuring high concentration gases by the DAS technology in the high concentration range, and realizes reliable detection of the high concentration part in the full range measurement.

[0064] Optionally, the scan drive signal includes a triangular wave signal and / or a modulation wave signal, and the modulation wave signal is a superimposed signal of a triangular wave signal and a sine wave signal; the attenuated electrical signal corresponding to the triangular wave signal is the first electrical signal, and the attenuated electrical signal corresponding to the modulation wave signal is the second electrical signal.

[0065] Figure 9 It is a flowchart of another gas concentration measurement method provided by the embodiments of the present invention. As Figure 9 shown, the method includes:

[0066] S201. The control module controls the drive module to output a scan drive signal for at least two scan periods to the laser.

[0067] S202. The laser emits an optical signal according to the scan drive signal.

[0068] S203. The photodetector receives the attenuated optical signal after being absorbed by the gas to be measured, and converts the attenuated optical signal into an electrical signal.

[0069] S204. The control module determines the concentration of the gas to be measured in the first scan period based on the DAS technology according to the first electrical signal in the first scan period; or, the control module determines the concentration of the gas to be measured in the first scan period based on the WMS technology according to the second electrical signal in the first scan period.

[0070] Specifically, if the gas concentration measurement method of the embodiment of the present invention is applied to a scenario where the gas concentration changes from high to low, the control module determines the concentration of the gas to be measured in the first scanning period based on the first electrical signal in the first scanning period using the DAS technology. The DAS technology directly measures the attenuation of light intensity. When detecting high-concentration gases, the signal intensity changes significantly, enabling rapid and accurate preliminary quantification of high-concentration gases.

[0071] If the gas concentration measurement method of the embodiment of the present invention is applied to a scenario where the gas concentration changes from low to high, the control module determines the concentration of the gas to be measured in the first scanning period based on the second electrical signal in the first scanning period using the WMS technology. The WMS technology modulates the laser driver signal and demodulates the harmonic signal after gas absorption, with high sensitivity for detecting low-concentration gases.

[0072] S205. When the concentration of the gas to be measured in the first scanning period is less than the first set threshold, control the scanning drive signal output to the laser in the second scanning period to include a modulation wave signal, and determine the concentration of the gas to be measured in the second scanning period based on the second electrical signal in the second scanning period using the wavelength modulation spectroscopy (WMS) technology.

[0073] When it is determined in the first scanning period that the gas concentration is less than the first set threshold (i.e., low concentration), the scanning drive signal output to the laser in the second scanning period includes a modulation wave signal, and the concentration is determined based on the WMS technology. Because the noise interference is large at low concentrations, the harmonic detection of the WMS technology can effectively suppress noise and improve the signal-to-noise ratio. By continuing to use the WMS technology and optimizing the modulation wave signal in the second scanning period, the sensitivity for detecting low-concentration gases is improved, ensuring the accuracy of low-concentration measurements.

[0074] S206. When the concentration of the gas to be measured in the first scanning period is greater than or equal to the first set threshold, control the scanning drive signal output to the laser in the second scanning period to include a triangular wave signal, and determine the concentration of the gas to be measured in the second scanning period based on the first electrical signal in the second scanning period using the direct absorption spectroscopy (DAS) technology.

[0075] When the gas concentration in the first scanning period is greater than or equal to the first set threshold (i.e., high concentration), the scanning drive signal output in the second scanning period includes a triangular wave signal, and the concentration is determined based on the DAS technology. The triangular wave signal can make the laser output stable scanning light. The DAS technology has a good linear response and a wide dynamic range at high concentrations. Adopting this method in the second scanning period can accurately measure in the high-concentration range and meet the full-range measurement requirements.

[0076] Figure 10 is a flowchart of another gas concentration measurement method provided by the embodiment of the present invention. As Figure 10 shown, the gas concentration measurement method includes:

[0077] S301. The control module controls the driving module to output a first scanning driving signal to the laser.

[0078] Figure 11 It is a waveform diagram of a first scanning driving signal provided by an embodiment of the present invention. As Figure 11 shown, the scanning period of the first scanning driving signal includes a first sub-scanning driving signal in a first time period and a second sub-scanning driving signal in a second time period. The first sub-scanning driving signal includes a modulation wave signal, and the modulation wave signal is a superposition of a triangular wave signal and a sine wave signal. The second sub-scanning driving signal includes a triangular wave signal; the electric signal includes a second electric signal corresponding to the first sub-scanning driving signal and a first electric signal corresponding to the second sub-scanning driving signal; the control module outputs the concentration of the gas to be measured once per scanning period.

[0079] S302. The laser emits an optical signal according to the scanning driving signal.

[0080] S303. The photodetector receives the attenuated optical signal after being absorbed by the gas to be measured and converts the attenuated optical signal into an electric signal.

[0081] S304. The control module determines the concentration of the gas to be measured in the first scanning period based on the WMS technology according to the second electric signal in the first time period; or the control module determines the concentration of the gas to be measured in the first scanning period based on the DAS technology according to the first electric signal in the second time period.

[0082] S305. When the concentration of the gas to be measured in the first scanning period is less than the first set threshold, the scanning driving signal output to the laser in the second scanning period is controlled to include a modulation wave signal, and the concentration of the gas to be measured in the second scanning period is determined based on the WMS technology according to the second electric signal in the second scanning period.

[0083] S306. When the concentration of the gas to be measured in the first scanning period is greater than or equal to the first set threshold, the concentration of the gas to be measured in the second scanning period is determined based on the DAS technology according to the first electric signal in the second scanning period, and the second scanning period is after the first scanning period.

[0084] After the signal emitted by the laser is absorbed by the gas and then converted into an electric signal by the photodetector, its state is as Figure 12 and Figure 13 shown. Figure 12 It is the concentration absorption signal of the WMS+DAS combined method after passing through the gas, Figure 13 which is the second harmonic signal demodulated by WMS and the concentration absorption peak extracted by DAS. When the concentration in the first scanning period is lower than the first set threshold concentration, the output is mainly based on WMS, and when the concentration in the first scanning period is higher than the first set threshold concentration, the output is mainly based on DAS.

[0085] Figure 14 It is a flowchart of another method for measuring gas concentration provided by an embodiment of the present invention. As Figure 14 shown, the method for measuring gas concentration includes:

[0086] S401. The control module controls the driving module to output a second scanning driving signal corresponding to the WMS technology to the laser or controls the driving module to output a third scanning driving signal corresponding to the DAS technology to the laser.

[0087] Figure 15 It is a waveform diagram of a second scanning driving signal provided by an embodiment of the present invention. As Figure 15 shown, the second scanning driving signal includes a modulation wave signal of at least one scanning period, and the modulation wave signal is a superposition of a triangular wave signal and a sine wave signal.

[0088] Figure 16 It is a waveform diagram of a third scanning driving signal provided by an embodiment of the present invention. As Figure 16 shown, the third scanning driving signal includes a triangular wave signal of at least one scanning period; the electric signal corresponding to the second scanning driving signal is a second electric signal, and the electric signal corresponding to the third scanning driving signal is a first electric signal.

[0089] S402. The laser emits an optical signal according to the scanning driving signal.

[0090] S403. The photodetector receives the attenuated optical signal after being absorbed by the gas to be measured and converts the attenuated optical signal into an electric signal.

[0091] S404. The control module determines the concentration of the gas to be measured in the first scanning period through the WMS technology according to the second electric signal in the first scanning period, or the control module determines the concentration of the gas to be measured in the first scanning period through the DAS technology according to the first electric signal in the first scanning period.

[0092] S405. When the concentration of the gas to be measured in the first scanning period is less than the first set threshold, output a second scanning driving signal to the laser, and determine the concentration of the gas to be measured in the second scanning period through the WMS technology according to the second electric signal.

[0093] S406. When the concentration of the gas to be measured in the first scanning period is greater than or equal to the first set threshold, output a third scanning driving signal to the laser, and determine the concentration of the gas to be measured in the second scanning period through the DAS technology according to the first electric signal.

[0094] Figure 17 It is a flowchart of another method for measuring gas concentration provided by an embodiment of the present invention. As Figure 17 shown, the method for measuring gas concentration includes:

[0095] S501. The control module controls the driving module to output a fourth scanning driving signal to the laser.

[0096] Figure 18 It is a waveform diagram of a fourth scanning driving signal provided by an embodiment of the present invention. As Figure 18 shown, the fourth scanning driving signal includes a third sub-scanning driving signal and a fourth sub-scanning driving signal that are alternately scanned. The third sub-scanning driving signal includes a modulated wave signal of at least one scanning period, and the fourth sub-scanning driving signal includes a triangular wave signal of at least one scanning period; the modulation signal wave is a superposition of a triangular wave signal and a sine wave signal; the electric signal corresponding to the third sub-scanning driving signal is a second electric signal, and the electric signal corresponding to the fourth sub-scanning driving signal is a first electric signal.

[0097] S502. The laser emits an optical signal according to the scanning driving signal.

[0098] S503. The photodetector receives the attenuated optical signal after being absorbed by the gas to be measured, and converts the attenuated optical signal into an electric signal.

[0099] S504. The control module determines the concentration of the gas to be measured in the first scanning period through the WMS technology according to the second electric signal in the first scanning period, or the control module determines the concentration of the gas to be measured in the first scanning period through the DAS technology according to the first electric signal in the first scanning period.

[0100] S505. When the control module controls the driving module to output a third sub-scanning driving signal to the laser, and the concentration of the gas to be measured in the first scanning period is less than the first set threshold, the concentration of the gas to be measured in the second scanning period is determined through the WMS technology according to the second electric signal.

[0101] S506. When the control module controls the driving module to output a fourth sub-scanning driving signal to the laser, and the concentration of the gas to be measured in the first scanning period is greater than or equal to the first set threshold, the concentration of the gas to be measured in the second scanning period is determined through the DAS technology according to the first electric signal.

[0102] S507. When the control module controls the driving module to output a third sub-scanning driving signal to the laser, and the concentration of the gas to be measured in the first scanning period is greater than or equal to the first set threshold, the concentration of the gas to be measured in the first scanning period is used as the concentration of the gas to be measured in the second scanning period.

[0103] S508. When the control module controls the driving module to output a fourth sub-scanning driving signal to the laser, and the concentration of the gas to be measured in the first scanning period is less than the first set threshold, the concentration of the gas to be measured in the first scanning period is used as the concentration of the gas to be measured in the second scanning period.

[0104] When the third sub-scanning drive signal is output and the concentration in the first scanning period is greater than or equal to the first set threshold, and when the fourth sub-scanning drive signal is output and the concentration in the first scanning period is less than the first set threshold, the concentration in the first scanning period is used as the concentration in the second scanning period. This strategy ensures the measurement efficiency while avoiding incorrect measurement results that may be caused by inappropriate selection of detection techniques, and can give relatively reasonable concentration measurement values in different situations.

[0105] Based on the same inventive concept, an embodiment of the present invention further provides a gas concentration measurement device. The gas concentration measurement device provided by the embodiment of the present invention can execute the gas concentration measurement method provided by any embodiment of the present invention, and has corresponding functional modules and beneficial effects for executing the gas concentration measurement method.

[0106] Continue to refer to Figure 7 , the measurement device includes: a driving module 11, a laser 12, a photodetector 13, and a control module 14.

[0107] The control module 14 is connected to the driving module 11 and is used to control the driving module 11 to output a scanning drive signal to the laser 12. At least two scanning periods include a first scanning period and a second scanning period, and the second scanning period is after the first scanning period. The laser 12 is connected to the driving module 11 and is used to emit an optical signal according to the scanning drive signal. The photodetector 13 is arranged on the optical path of the optical signal emitted by the laser 12. The photodetector 13 is electrically connected to the control module 14. The photodetector 13 is used to receive the attenuated optical signal after being absorbed by the gas to be measured and convert the attenuated optical signal into an electrical signal.

[0108] The control module 14 is further used to determine the concentration of the gas to be measured in the first scanning period according to the electrical signal in the first scanning period; when the concentration of the gas to be measured in the first scanning period is less than the first set threshold, determine the concentration of the gas to be measured in the second scanning period based on the wavelength modulation spectroscopy (WMS) technology according to the electrical signal in the second scanning period, and when the concentration of the gas to be measured in the first scanning period is greater than or equal to the first set threshold, determine the concentration of the gas to be measured in the second scanning period based on the direct absorption spectroscopy (DAS) technology according to the electrical signal in the second scanning period.

[0109] It should be noted that for the similarities between the gas concentration measurement device and the gas concentration measurement method, reference can be made to the explanation of the gas concentration measurement method, and the embodiment of the present invention will not elaborate here.

[0110] On the basis of the above embodiment, optionally, continue to refer to Figure 7 , the measurement device further includes a gas chamber 15, and the gas chamber 15 is located between the laser 12 and the photodetector 13; the gas chamber 15 is filled with the gas to be measured.

[0111] The presence of the gas chamber 15 optimizes the environment for the interaction between optical signal transmission and gas. On the one hand, it can reduce the interference of external environmental factors (such as temperature, humidity, and air flow, etc.) on the optical signal, enabling the optical signal to propagate in a relatively stable environment before entering the actual gas region to be measured, thus improving the stability and repeatability of detection. On the other hand, by adjusting the state parameters of the gas in the gas chamber (such as pressure and temperature, etc.), different detection conditions can be simulated, which helps to more accurately analyze the interaction between the optical signal and the gas under different conditions, thereby improving the detection accuracy of the entire measurement device.

[0112] Figure 19 It is a schematic structural diagram of another gas concentration measurement device provided by an embodiment of the present invention. As Figure 19 shown, optionally, the gas concentration measurement device further includes an alarm module 16, and the alarm module 16 is connected to the control module 14; the control module 14 is further configured to control the alarm module 16 to give an alarm prompt when the difference between the concentration of the gas to be measured and the preset concentration is greater than a second set threshold. In actual application scenarios, this function has an important safety warning role. For example, in industrial production sites, when the concentration of harmful gases exceeds the safety preset value, the alarm module can promptly issue an alarm to remind the staff to take corresponding measures, such as starting ventilation equipment, stopping relevant production processes, etc., to avoid safety accidents caused by excessive gas concentration and ensure the safety of personnel's lives and the normal operation of production facilities.

[0113] It should be understood that various forms of the processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in the present invention can be executed in parallel, sequentially, or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and no limitations are imposed herein.

[0114] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub - combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for measuring gas concentration, characterized in that: include: The control module controls the driving module to output a scanning driving signal of at least two scanning cycles to the laser; the at least two scanning cycles include a first scanning cycle and a second scanning cycle, and the second scanning cycle is after the first scanning cycle; The laser emits a light signal according to the scanning drive signal; The photoelectric detector receives the attenuated light signal after being absorbed by the gas to be measured, and converts the attenuated light signal into an electrical signal; The control module determines the concentration of the gas to be measured in the first scanning cycle according to the electrical signal of the first scanning cycle; when the concentration of the gas to be measured in the first scanning cycle is less than the first set threshold value, the concentration of the gas to be measured in the second scanning cycle is determined based on the wavelength modulation spectroscopy WMS technology according to the electrical signal of the second scanning cycle; when the concentration of the gas to be measured in the first scanning cycle is greater than or equal to the first set threshold value, the concentration of the gas to be measured in the second scanning cycle is determined based on the direct absorption spectroscopy DAS technology according to the electrical signal of the second scanning cycle.

2. The method for measuring gas concentration according to claim 1, characterized in that: The scanning drive signal includes a triangular wave signal and / or a modulated wave signal, wherein the modulated wave signal is a superimposed signal of the triangular wave signal and a sine wave signal; the attenuated electrical signal corresponding to the triangular wave signal is a first electrical signal, and the attenuated electrical signal corresponding to the modulated wave signal is a second electrical signal; The control module determines the concentration of the gas to be measured in the first scanning cycle according to the electrical signal of the first scanning cycle; when the concentration of the gas to be measured in the first scanning cycle is less than the first set threshold, the concentration of the gas to be measured in the second scanning cycle is determined based on the wavelength modulation spectroscopy WMS technology according to the electrical signal of the second scanning cycle; when the concentration of the gas to be measured in the first scanning cycle is greater than or equal to the first set threshold, the concentration of the gas to be measured in the second scanning cycle is determined based on the direct absorption spectroscopy DAS technology according to the electrical signal of the second scanning cycle. The steps include: The control module determines the concentration of the gas to be measured in the first scanning cycle based on the DAS technology according to the first electrical signal in the first scanning cycle; or, the control module determines the concentration of the gas to be measured in the first scanning cycle based on the WMS technology according to the second electrical signal in the first scanning cycle; When the concentration of the gas to be measured in the first scanning cycle is less than the first set threshold, the scanning drive signal output to the laser in the second scanning cycle is controlled to include the modulated wave signal, and the concentration of the gas to be measured in the second scanning cycle is determined based on the wavelength modulation spectroscopy (WMS) technology according to the second electrical signal in the second scanning cycle; When the concentration of the gas to be measured in the first scanning cycle is greater than or equal to the first set threshold, the scanning drive signal output to the laser in the second scanning cycle is controlled to include the triangular wave signal, and the concentration of the gas to be measured in the second scanning cycle is determined based on the direct absorption spectroscopy DAS technology according to the first electrical signal in the second scanning cycle.

3. The method for measuring gas concentration according to claim 1 or 2, characterized in that: The step of the control module controlling the driving module to output a scanning driving signal of at least two scanning cycles to the laser comprises: The control module controls the driving module to output a first scanning driving signal to the laser; The scanning cycle of the first scanning driving signal includes a first sub-scanning driving signal in a first time period and a second sub-scanning driving signal in a second time period, the first sub-scanning driving signal includes a modulated wave signal, and the second sub-scanning driving signal includes a triangular wave signal; the electrical signal includes a second electrical signal corresponding to the first sub-scanning driving signal and a first electrical signal corresponding to the second sub-scanning driving signal; the control module outputs the concentration of the gas to be measured once in each scanning cycle; The control module determines the concentration of the gas to be measured in the first scanning cycle according to the electrical signal of the first scanning cycle; when the concentration of the gas to be measured in the first scanning cycle is less than the first set threshold, the concentration of the gas to be measured in the second scanning cycle is determined based on the wavelength modulation spectroscopy WMS technology according to the electrical signal of the second scanning cycle; when the concentration of the gas to be measured in the first scanning cycle is greater than or equal to the first set threshold, the concentration of the gas to be measured in the second scanning cycle is determined based on the direct absorption spectroscopy DAS technology according to the electrical signal of the second scanning cycle. The steps include: The control module determines the concentration of the gas to be measured in the first scanning period based on the WMS technology according to the second electrical signal in the first time period; or the control module determines the concentration of the gas to be measured in the first scanning period based on the DAS technology according to the first electrical signal in the second time period; When the concentration of the gas to be measured in the first scanning period is less than a first set threshold, determining the concentration of the gas to be measured in the second scanning period based on the WMS technology according to the second electrical signal in the second scanning period; When the concentration of the gas to be measured in the first scanning period is greater than or equal to a first set threshold, the concentration of the gas to be measured in the second scanning period is determined based on the DAS technology according to the first electrical signal in the second scanning period.

4. The method for measuring gas concentration according to claim 1 or 2, characterized in that: The step of the control module controlling the driving module to output a scanning driving signal of at least two scanning cycles to the laser comprises: The control module controls the driving module to output a second scanning driving signal to the laser or controls the driving module to output a third scanning driving signal to the laser; wherein the second scanning driving signal includes a modulated wave signal of at least one scanning cycle, the modulated wave signal is a superposition of a triangular wave signal and a sine wave signal, and the third scanning driving signal includes a triangular wave signal of at least one scanning cycle; the electrical signal corresponding to the second scanning driving signal is a second electrical signal, and the electrical signal corresponding to the third scanning driving signal is a first electrical signal; The control module determines the concentration of the gas to be measured in the first scanning cycle according to the electrical signal of the first scanning cycle; when the concentration of the gas to be measured in the first scanning cycle is less than the first set threshold, the concentration of the gas to be measured in the second scanning cycle is determined based on the wavelength modulation spectroscopy WMS technology according to the electrical signal of the second scanning cycle; when the concentration of the gas to be measured in the first scanning cycle is greater than or equal to the first set threshold, the concentration of the gas to be measured in the second scanning cycle is determined based on the direct absorption spectroscopy DAS technology according to the electrical signal of the second scanning cycle. The steps include: The control module determines the concentration of the gas to be measured in the first scanning period by the WMS technology according to the second electrical signal in the first scanning period, or the control module determines the concentration of the gas to be measured in the first scanning period by the DAS technology according to the first electrical signal in the first scanning period; When the concentration of the gas to be measured in the first scanning cycle is less than the first set threshold, outputting the second scanning drive signal to the laser, and determining the concentration of the gas to be measured in the second scanning cycle by the WMS technology according to the second electrical signal; When the concentration of the gas to be measured in the first scanning cycle is greater than or equal to the first set threshold, the third scanning drive signal is output to the laser, and the concentration of the gas to be measured in the second scanning cycle is determined by the DAS technology according to the first electrical signal.

5. The method for measuring gas concentration according to claim 1 or 2, characterized in that: The step of the control module controlling the driving module to output a scanning driving signal of at least two scanning cycles to the laser comprises: The control module controls the driving module to output a fourth scanning driving signal to the laser; wherein the fourth scanning driving signal comprises a third sub-scanning driving signal and a fourth sub-scanning driving signal which are scanned alternately, the third sub-scanning driving signal comprises a modulated wave signal of at least one scanning cycle, and the fourth sub-scanning driving signal comprises a triangular wave signal of at least one scanning cycle; the modulated signal wave is a superposition of a triangular wave signal and a sine wave signal; the electrical signal corresponding to the third sub-scanning driving signal is a second electrical signal, and the electrical signal corresponding to the fourth sub-scanning driving signal is a first electrical signal; The control module determines the concentration of the gas to be measured in the first scanning cycle according to the electrical signal of the first scanning cycle; when the concentration of the gas to be measured in the first scanning cycle is less than the first set threshold, the concentration of the gas to be measured in the second scanning cycle is determined based on the wavelength modulation spectroscopy WMS technology according to the electrical signal of the second scanning cycle; when the concentration of the gas to be measured in the first scanning cycle is greater than or equal to the first set threshold, the concentration of the gas to be measured in the second scanning cycle is determined based on the direct absorption spectroscopy DAS technology according to the electrical signal of the second scanning cycle. The steps include: The control module determines the concentration of the gas to be measured in the first scanning period by the WMS technology according to the second electrical signal in the first scanning period, or the control module determines the concentration of the gas to be measured in the first scanning period by the DAS technology according to the first electrical signal in the first scanning period; When the control module controls the driving module to output the third sub-scanning driving signal to the laser, and the concentration of the gas to be measured in the first scanning period is less than the first set threshold, the concentration of the gas to be measured in the second scanning period is determined by the WMS technology according to the second electrical signal; When the control module controls the driving module to output the fourth sub-scanning driving signal to the laser, and the concentration of the gas to be measured in the first scanning period is greater than or equal to the first set threshold, and according to the first electrical signal, the concentration of the gas to be measured in the second scanning period is determined by the DAS technology; When the control module controls the driving module to output the third sub-scanning driving signal to the laser, and the concentration of the gas to be measured in the first scanning period is greater than or equal to the first set threshold, the concentration of the gas to be measured in the first scanning period is used as the concentration of the gas to be measured in the second scanning period; When the control module controls the driving module to output the fourth sub-scanning driving signal to the laser, and the concentration of the gas to be measured in the first scanning period is less than the first set threshold, the concentration of the gas to be measured in the first scanning period is used as the concentration of the gas to be measured in the second scanning period.

6. The method for measuring gas concentration according to claim 1, characterized in that: The steps of determining the concentration of the gas to be measured based on direct absorption spectroscopy (DAS) technology include: The control module performs a baseline fitting operation on the electrical signal to determine a baseline level of the electrical signal, and then removes the baseline; Performing absorption peak fitting on the electrical signal after removing the baseline, and extracting parameters of the absorption peak; The concentration of the gas to be measured is determined according to the extracted absorption peak parameters in combination with Beer-Lambert's law.

7. The method for measuring gas concentration according to claim 1, characterized in that: The steps of determining the concentration of the gas to be measured based on wavelength modulation spectroscopy (WMS) technology include: amplifying and demodulating the electrical signal transmitted by the photodetector to obtain a second harmonic signal; Analyze the demodulated second harmonic signal and extract parameters of the second harmonic signal; The concentration of the gas to be measured is inverted according to the parameters of the second harmonic signal.

8. A gas concentration measuring device, characterized in that: The measuring device is used to perform the gas concentration measurement method according to any one of claims 1 to 7, and the measuring device comprises: a driving module, a laser, a photodetector and a control module; The control module is connected to the driving module and is used to control the driving module to output a scanning driving signal to the laser; the at least two scanning cycles include a first scanning cycle and a second scanning cycle, and the second scanning cycle is after the first scanning cycle; The laser is connected to the driving module and is used to emit a light signal according to the scanning driving signal; The photoelectric detector is arranged on the optical path of the optical signal emitted by the laser, the photoelectric detector is electrically connected to the control module, and the photoelectric detector is used to receive the attenuated optical signal after being absorbed by the gas to be measured, and convert the attenuated optical signal into an electrical signal; The control module is also used to determine the concentration of the gas to be measured in the first scanning cycle according to the electrical signal of the first scanning cycle; when the concentration of the gas to be measured in the first scanning cycle is less than a first set threshold, the concentration of the gas to be measured in the second scanning cycle is determined based on the wavelength modulation spectroscopy WMS technology according to the electrical signal of the second scanning cycle; when the concentration of the gas to be measured in the first scanning cycle is greater than or equal to the first set threshold, the concentration of the gas to be measured in the second scanning cycle is determined based on the direct absorption spectroscopy DAS technology according to the electrical signal of the second scanning cycle.

9. The gas concentration measuring device according to claim 8, characterized in that: It also includes: an alarm module; the alarm module is connected to the control module; the control module is also used to control the alarm module to issue an alarm prompt when the difference between the concentration of the gas to be tested and the preset concentration is greater than a second set threshold.

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