A dual-range H2O2 gas concentration monitoring system and method

Abstract

This application discloses a dual-range H2O2 gas concentration monitoring system and method, belonging to the field of environmental gas detection. In this dual-range H2O2 gas concentration monitoring system, a main circuit module drives a transmitting unit to emit a laser of a characteristic wavelength, wherein the driving signal includes a low-frequency modulation signal and a high-frequency modulation signal; a receiving unit receives the laser signal after it passes through the H2O2 gas to be measured and converts it into an electrical signal; the electrical signal is divided into a first path and a second path for parallel processing; in the first path, the electrical signal is processed based on wavelength modulation spectroscopy to obtain a first concentration value; in the second path, the electrical signal is processed based on direct absorption spectroscopy to obtain a second concentration value; according to a preset high / low range switching mechanism, the final gas concentration is output by combining the first and second concentration values. This system and method can achieve automatic switching between high and low ranges, ensuring high-precision measurement across the entire range.

Description

Technical Field

[0001] This application relates to the field of environmental gas detection technology, and in particular to a dual-range H2O2 gas concentration monitoring system and method. Background Technology

[0002] Hydrogen peroxide (H2O2) gas concentration monitoring is crucial in sterilization and environmental monitoring. Currently, the mainstream technology used is tunable diode laser absorption spectroscopy (TDLAS). TDLAS technology is mainly divided into direct absorption spectroscopy (DAS), wavelength modulation spectroscopy (WMS), and frequency modulation spectroscopy (FMS). Among them, FMS equipment is expensive; although DAS technology has a fast response and is suitable for high concentration measurements, its algorithm has high requirements for baseline fitting and is easily affected by changes in light intensity and low-frequency noise, resulting in low accuracy and high detection limits in low-range measurements; although WMS technology can remove noise and obtain high-precision results through lock-in amplification, harmonic signals are prone to saturation anomalies under high-concentration conditions, limiting the measurement range. Existing single-range monitoring systems cannot simultaneously meet the demands of high accuracy at low concentrations and wide measurement range at high concentrations. Especially in industrial process conditions, when the measured environment experiences sudden changes or extreme concentration variations, a single mode is insufficient for accurate measurement, easily leading to data distortion and failing to meet the monitoring needs under complex and variable conditions. Furthermore, existing range switching often uses fixed threshold values, lacking a smooth transition and affecting measurement continuity. Summary of the Invention

[0003] The purpose of this application is to overcome the shortcomings of the prior art and provide a dual-range H2O2 gas concentration monitoring system and method to achieve automatic switching between high and low ranges and ensure high-precision measurement across the entire range.

[0004] To achieve the above objectives, this application provides the following solution.

[0005] On one hand, this application provides a dual-range H2O2 gas concentration monitoring system, including: a gas detection module and a system circuit module; the gas detection module includes a reflection absorption cell, a transmitting unit and a receiving unit; the system circuit module includes a main circuit module and an auxiliary circuit module; The transmitting unit and the receiving unit are disposed on the reflection absorption cell; the transmitting unit, the receiving unit, and the auxiliary circuit module are all connected to the main circuit module; The main circuit module is used to control the emitting unit to emit laser light; the laser light passes through a reflection absorption cell containing the H2O2 gas to be measured, and is attenuated and emitted after multiple reflections; after the laser light is emitted, it is received by the receiving unit and converted into an electrical signal; the main circuit module receives the electrical signal and transmits the electrical signal to the auxiliary circuit module; The main circuit module processes the electrical signal using wavelength modulation spectroscopy to obtain a first concentration value. The auxiliary circuit module processes the electrical signal according to direct absorption spectroscopy to obtain a second concentration value, and feeds the second concentration value back to the main circuit module. The main circuit module is used to select the final output concentration based on the first concentration value and the second concentration value according to the preset high and low range switching mechanism.

[0006] Optionally, the reflection absorption cell is provided with an inlet and an outlet for introducing and discharging the H2O2 gas to be measured, respectively. The reflection absorption cell is a White cell, which includes two small mirrors and one large mirror, and is used to achieve the required optical path through multiple reflections. The transmitting unit and the receiving unit are connected at the White pool, where two circular holes are provided for emitting and receiving laser beams.

[0007] Optionally, the main circuit module includes a drive current control element, a temperature control module, a lock-in amplifier, and a main controller; The drive current control element and the temperature control module are used to control the operating current and operating temperature of the transmitting unit. The lock-in amplifier is used to perform phase-locked processing on the electrical signal and extract the second harmonic signal; The main controller calculates the first concentration value based on the second harmonic signal.

[0008] Optionally, the auxiliary circuit module includes a low-pass filter unit and an auxiliary controller; The low-pass filter unit is used to filter out the high-frequency modulation signal components in the electrical signal and retain the DC or low-frequency signal. The auxiliary controller is used to perform baseline fitting on the filtered signal and calculate the second concentration value by absorption intensity inversion based on Beer-Lambert's law.

[0009] Optionally, the main controller stores a high-low range switching mechanism; the high-low range switching mechanism calculates weights or selects thresholds based on Gaussian membership functions to achieve a smooth transition from the first concentration value to the second concentration value.

[0010] On the other hand, this application provides a dual-range H2O2 gas concentration monitoring method, applied to the aforementioned dual-range H2O2 gas concentration monitoring system, comprising the following steps: The main circuit module drives the transmitting unit to emit laser light of a characteristic wavelength, wherein the driving signal includes a low-frequency modulation signal and a high-frequency modulation signal; The receiving unit receives the laser signal after it passes through the H2O2 gas to be tested and converts it into an electrical signal. The electrical signal is divided into a first path and a second path and processed in parallel. In the first path, the electrical signal is processed based on wavelength modulation spectroscopy to obtain a first concentration value; In the second pathway, the electrical signal is processed using direct absorption spectroscopy to obtain a second concentration value; Based on the preset high and low range switching mechanism, the final gas concentration is output by combining the first concentration value and the second concentration value.

[0011] Optionally, the process of processing the electrical signal based on wavelength modulation spectroscopy to obtain the first concentration value specifically includes: The electrical signal is subjected to phase-locked processing using a lock-in amplifier to extract the second harmonic signal; wherein the reference signal of the lock-in amplifier is a harmonic of the high-frequency modulation signal. The first concentration value is calculated based on the correspondence between the signal strength of the second harmonic signal and the gas concentration.

[0012] Optionally, the relationship between the signal strength of the second harmonic signal and the gas concentration is as follows: ;in This is the first concentration value; and The signal intensities of the second harmonic signal obtained with and without H2O2 gas are shown respectively. For calibration coefficients; Optical path length; Pressure; It is a linear intensity function of temperature; Let be the values ​​of the linear function of H2O2 gas at room temperature and pressure.

[0013] Optionally, the step of processing the electrical signal based on direct absorption spectroscopy to obtain the second concentration value specifically includes: The electrical signal is subjected to low-pass filtering to remove high-frequency modulation signal components and retain DC or low-frequency signals; The filtered signal is baseline-fitted, and the second concentration value is obtained by absorption intensity inversion calculation based on the Beer-Lambert law. ;in ; The absorption strength is denoted as .

[0014] Optionally, the high-low range switching mechanism adopts the fuzzy interval threshold method and uses a Gaussian membership function to achieve a smooth transition between the first and second channels and determine the final gas concentration.

[0015] According to the specific embodiments provided in this application, the following technical effects are disclosed: This application provides a dual-range H2O2 gas concentration monitoring system and method. By setting an automatic high-low range switching mechanism, a direct absorption circuit is used to measure the high range when the concentration is high, and a wavelength modulation circuit is used to measure the low range when the concentration is low. This eliminates the low precision and high detection limit of the direct absorption method and the limited measurement range of the wavelength modulation method, and achieves effective measurement with high precision and full range. It solves the problems of being unable to measure sudden concentration changes in the measured environment and the difficulty in accurately measuring when extreme concentration changes occur under industrial process conditions. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of a dual-range H2O2 gas concentration monitoring system. Figure 2 This is a signal link diagram for a dual-range H2O2 gas concentration monitoring system. Figure 3 This is a schematic diagram of the process for a dual-range H2O2 gas concentration monitoring method. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] Tunable semiconductor laser absorption spectroscopy (TDLAS) is based on molecular absorption spectroscopy theory. When a laser beam passes through the measurement region, the light is absorbed, resulting in intensity attenuation. TDLAS technology is divided into Direct Absorption Spectroscopy (DAS), Wavelength Modulation Spectroscopy (WMS), and Frequency Modulation Spectroscopy (FMS) depending on the modulation method. FMS uses a modulation frequency equal to or greater than the linewidth, and its corresponding high-frequency detectors and other equipment are expensive, leading to higher costs. DAS concentration algorithms require a high-quality baseline and are affected by factors such as light intensity variations, low-frequency noise, and spectral interference, resulting in low accuracy in low-range measurements. However, it directly obtains gas concentration through Beer-Lambert's law inversion, offering fast response speed and significant advantages for measurements with large ranges and high concentrations. WMS, combining lock-in amplifiers and low-pass filtering techniques, can remove low-frequency noise and acquire strong harmonic signals containing absorption information. Since the measurement object is the relative change in spectral line shape, no measurement baseline needs to be determined, thus obtaining more accurate measurement results than direct absorption spectroscopy. However, in operating conditions with high concentrations, the harmonic signal is prone to saturation and other anomalies due to excessively strong absorption. Therefore, to address the problems of insufficient accuracy in high-range detection and limited detection range in low-range detection, which is prone to oversaturation and detection distortion, this application provides a dual-range H2O2 gas concentration monitoring system and method to effectively improve the accuracy and detection range of gas concentration measurement.

[0020] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] In one exemplary embodiment, this application provides a dual-range H2O2 gas concentration monitoring system, including: a gas detection module and a system circuit module. Figure 1 As shown, the gas detection module includes a reflection absorption cell, a transmitting unit, and a receiving unit; the transmitting unit and the receiving unit are disposed on the reflection absorption cell. The system circuit module includes a main circuit module, an auxiliary circuit module, and a display unit. The transmitting unit, the receiving unit, the auxiliary circuit module, and the display unit are all connected to the main circuit module. The system circuit module consists of hardware circuitry and embedded software, including a preset high / low range switching mechanism for processing signals, selecting pathways, and outputting the final concentration. .

[0022] In an exemplary embodiment, the emitting unit can be a semiconductor laser. The receiving unit can be a photodetector. The emitting unit and the receiving unit are respectively fixed to the same side of the reflection absorption cell by screws. The reflection absorption cell is a White cell, including two small reflectors and one large reflector, achieving the required optical path through multiple reflections. Two circular holes are provided at the connection between the emitting unit and the receiving unit and the White cell for emitting and receiving laser beams. The reflection absorption cell is provided with an inlet and an outlet for introducing and emitting the H2O2 gas to be measured, respectively, and the rest is sealed.

[0023] In an exemplary embodiment, the transmitting unit and the receiving unit are connected to the main circuit module via wires and connection terminals, respectively, and the auxiliary circuit module and the display unit are connected to the main circuit module via wires. The main circuit module is used to control the transmitting unit to emit a laser. The laser passes through a reflection absorption cell containing the H2O2 gas to be measured, and is attenuated before being emitted after multiple reflections. After the laser is emitted, it is received by the receiving unit and converted into an electrical signal. The main circuit module receives the electrical signal and transmits it to the auxiliary circuit module. The main circuit module processes the electrical signal according to wavelength modulation spectroscopy (WMS) technology to obtain a first concentration value. The auxiliary circuit module processes the electrical signal using direct absorption spectroscopy (DAS) technology to obtain a second concentration value. and the second concentration value Feedback is sent to the main circuit module. The main circuit module is used to, according to a preset high / low range switching mechanism, combine the first concentration value... and the second concentration value Select the final output concentration .

[0024] See further Figure 2 The main circuit module includes a drive current control element, a temperature control module, a lock-in amplifier, and a main controller. The drive current control element specifically includes a high-frequency sine wave function generator, a low-frequency sawtooth wave function generator, a subtractor, a constant current drive circuit, and a frequency multiplier. The temperature control module is mainly a temperature control circuit. The drive current control element and the temperature control module are used to control the operating current and operating temperature of the transmitting unit (laser). The lock-in amplifier is used to perform phase-locked processing on the electrical signal and extract the second harmonic signal. The main controller calculates the first concentration value based on the second harmonic signal. The auxiliary circuit module includes a low-pass filter unit and an auxiliary controller; the low-pass filter unit is used to filter out high-frequency modulation signal components in the electrical signal, retaining DC or low-frequency signals; the auxiliary controller is used to perform baseline fitting on the filtered signal and calculate the second concentration value by absorption intensity inversion based on Beer-Lambert's law. The main controller stores a high / low range switching mechanism; this mechanism calculates weights or selects thresholds based on a Gaussian membership function to achieve a smooth transition from the first concentration value to the second concentration value, thereby determining the final gas concentration. .

[0025] In an exemplary embodiment, the operation of the dual-range H2O2 gas concentration monitoring system includes S1 to S3.

[0026] S1: The H2O2 sample gas is introduced through the inlet of the reflection absorption cell, passes through the reflection absorption cell, and is then discharged through the outlet. During this process, the main circuit module controls the emitting unit to emit a laser beam. The laser beam is attenuated after multiple reflections through the reflection absorption cell containing the H2O2 gas to be measured. After the laser beam is emitted, the receiving unit receives the optical signal, which is converted into an electrical signal by a photodetector and then transmitted to the main circuit module. The main circuit module then transmits the signal to the auxiliary circuit module.

[0027] S2: The main circuit module divides the received electrical signal into two paths for processing. The main circuit module is responsible for path 1 (also known as the first path), and the auxiliary circuit module is responsible for path 2 (also known as the second path). In path 1, the main circuit module uses an STM32 to control a DDS chip, generating a high-frequency sine wave signal with a frequency of 40 kHz and an amplitude of 400 mV, and also generates a square wave signal as a reference signal for the lock-in amplifier. Simultaneously, the STM32 generates a low-frequency triangular wave signal with a scanning frequency of 10 Hz and an amplitude of 1.41 V through a DAC chip. This triangular wave signal and the aforementioned sine wave signal are superimposed by an adder, and the resulting superimposed signal is converted into a current signal by a constant current drive circuit to drive the laser. At the same time, the temperature control module regulates the laser temperature to stabilize. Through precise control of the operating current and operating temperature, the center wavelength of the laser output is adjusted to be near the target gas, and a laser beam is output. The emitted laser passes through a reflection absorption cell containing the gas to be measured. After multiple optical reflections in the reflection absorption cell containing the gas to be measured, the absorbed and attenuated laser signal is focused onto the receiving unit by a converging lens. The receiving unit uses a photodetector to receive the optical signal and performs photoelectric conversion to output a weak current signal. The signal acquisition module uses an AD8605 chip to convert the weak current signal into current / voltage (I / V) before supplying it to the subsequent circuitry for processing. In path 1, after signal processing by a lock-in amplifier based on an AD630 chip, the signal after laser transmission is obtained as shown in path 2. Component signal (i.e., second harmonic signal), obtain signal strength Finally, based on the functional relationship between harmonic signals and concentration, the first concentration value is obtained. .

[0028] The auxiliary circuit module is responsible for path 2. Since the received signal contains a weak sinusoidal signal, this application uses a low-pass filter to remove it. Because path 2 is responsible for testing high-concentration gases, the signal-to-noise ratio is very high. The influence of noise and other interference signals on the relative intensity of the spectral absorption signal can be approximately ignored. Therefore, after filtering out the weak, linear sinusoidal signal, the obtained triangular wave DC signal is still relatively strong and linear. The processed DC signal is then processed using the direct absorption method, followed by baseline fitting, and the absorption intensity is obtained by peak area inversion based on the Beer-Lambert law. The second concentration value was obtained. The data is then transmitted back to the main circuit module.

[0029] S3: Based on the preset high and low range switching mechanism, combined with the first concentration value and the second concentration value Output the final gas concentration This application provides two preset high-low range switching mechanisms. One feasible high-low range switching mechanism is: when the absorption intensity obtained by channel 2... Less than or equal to the set concentration threshold When the preset high / low range switching mechanism is applied, it switches to low range mode, defaults to channel 1, and outputs concentration. equal Otherwise, switch to high-range mode, execute path 2, and output concentration. equal Another high / low range switching mechanism employs a fuzzy interval threshold method, utilizing a Gaussian membership function to achieve a smooth transition between the first and second pathways, thereby determining the final gas concentration. .

[0030] The dual-range H2O2 gas concentration monitoring system of this application can simultaneously achieve full-range, high-precision measurement of H2O2 gas concentration, solving the problem of sacrificing one for the other in terms of low-range high-precision and high-range low-precision.

[0031] Based on the aforementioned dual-range H2O2 gas concentration monitoring system, this application also provides a dual-range H2O2 gas concentration monitoring method, see [link to relevant documentation]. Figure 3 This includes the following steps 1 to 6.

[0032] Step 1: The main circuit module drives the transmitting unit to emit laser light of a characteristic wavelength, wherein the driving signal includes a low-frequency modulation signal and a high-frequency modulation signal.

[0033] The main circuit module drives a laser at a certain operating temperature to emit laser light of a characteristic wavelength based on a preset low-frequency sawtooth wave superimposed with a high-frequency sine wave signal. At the same time, the high-frequency sine wave is used as a reference signal after being frequency-doubled.

[0034] Step 2: Receive the laser signal after it passes through the H2O2 gas to be tested through the receiving unit and convert it into an electrical signal.

[0035] The photodetector receives a laser beam that passes through the H2O2 gas being measured and obtains an electrical signal carrying information about the gas concentration.

[0036] Step 3: Divide the electrical signal into a first path and a second path for parallel processing.

[0037] Step 3 is one of the key steps in this application. The main circuit module controls the emitting unit to emit laser light through the drive current and temperature control module. The receiving unit receives the laser signal and completes photoelectric conversion. The resulting electrical signal is transmitted back to the main circuit module, where it is processed according to path 1 to obtain the concentration. Simultaneously, the electrical signal is transmitted to the auxiliary circuit module, where it is processed according to path 2 to obtain the concentration. Finally, the output concentration is selected according to the preset high and low range switching mechanism. Specifically, the acquired electrical signal is transmitted to the first path (path 1), and the signal is processed using wavelength modulation spectroscopy to obtain the second harmonic signal AC / DC, with signal strength... The first concentration value was obtained. Simultaneously, the acquired electrical signal is transmitted to the second channel (channel 2), where it is first low-pass filtered and then processed using direct absorption spectroscopy to obtain the absorption intensity. The second concentration value was calculated. .

[0038] Step 4: In the first channel, the electrical signal is processed based on wavelength modulation spectroscopy to obtain the first concentration value.

[0039] In the first path, the harmonic signal is obtained through phase-locked processing by a lock-in amplifier, and the first concentration value is further obtained. Specifically, the electrical signal is processed using a lock-in amplifier to extract the second harmonic signal; wherein the reference signal of the lock-in amplifier is a harmonic of the high-frequency modulation signal; and the first concentration value is calculated based on the correspondence between the signal strength of the second harmonic signal and the gas concentration.

[0040] The absorption of the light beam by the gas follows the Beer-Lambert law, which can be expressed as: (1); in, The intensity of transmitted light. The intensity of the incident light. For frequency, This represents the laser transmittance. The intensity of the spectral line absorbed by the gas being measured is only related to the gas temperature. It is a linear function that represents the shape of the absorption spectral line and is related to factors such as gas temperature, pressure, and composition. For pressure, For optical path, The concentration of the target gas (H2O2 gas in this application) is given.

[0041] The preset laser center frequency is The modulation amplitude is The modulation frequency is Instantaneous frequency The cosine Fourier series of laser transmittance can be expressed as: (2); in For the first The Fourier coefficients of the subharmonics are related to the modulation depth, normalized frequency, and concentration.

[0042] Therefore, the amplitude of the second harmonic can be obtained: (3).

[0043] We can obtain: (4).

[0044] Further results were obtained: (5); in To obtain the gas concentration for pathway 1, i.e., the first concentration value. To obtain the signal strength for channel 1, The signal strength is obtained when there is no target gas in channel 1. For calibration coefficients, For pressure, For optical path, It is a linear intensity function of temperature. The values ​​of the linear function relating to the target gas at room temperature and pressure are given.

[0045] Step 5: In the second pathway, the electrical signal is processed based on direct absorption spectroscopy to obtain a second concentration value.

[0046] In the second path, the obtained electrical signal is filtered by a low-pass filter to remove high-frequency modulation signal components and retain DC or low-frequency signals; the filtered signal is then further processed by baseline fitting and Lambert-Beer inversion to obtain the second concentration value. .

[0047] From Lambert-Beer's law, we get: (6); Depend on For normalization function, We can obtain: (7); in To obtain the concentration for pathway 2, i.e., the second concentration value. The intensity of the laser after passing through the gas medium. The intensity of the incident laser. denoted as spectral absorbance. Absorption strength; The absorption peak starting frequency, The frequency is the endpoint frequency of the absorption peak.

[0048] Step 6: Based on the preset high and low range switching mechanism, and combining the first concentration value and the second concentration value, output the final gas concentration.

[0049] The system circuit module of this application is equipped with a high-low range switching mechanism. The relevant parameters obtained from channels 1 and 2 are input into the preset high-low range switching mechanism. The final gas concentration is output through the fuzzy interval Gaussian membership function and the gas concentration formula. .

[0050] In an exemplary embodiment, the high-low range switching mechanism uses a fuzzy interval threshold method instead of a fixed threshold method and a Gaussian membership function instead of a normal membership function to ensure the continuity and accuracy of gas measurement, achieve a smooth transition from low to high ranges, and at the same time give the entire system the best fit, thereby obtaining continuous and accurate gas concentration.

[0051] Specifically, the high and low range switching mechanism is divided into two parts: the first part gradually transitions from the wavelength modulation algorithm range to the fuzzy transition range, and the second part gradually transitions from the fuzzy transition range to the direct absorption algorithm range.

[0052] Specifically, the first part includes a semi-Gaussian Z-type membership function: (8); in, The first concentration value obtained for pathway 1, width Let the standard deviation be the Gaussian Z-type membership function. This represents the lower bound of the fuzzy interval.

[0053] The latter part includes the semi-Gaussian S-shaped membership function: (9); in, To obtain a second concentration value for pathway 2, the width Let the standard deviation be the Gaussian S-type membership function. This is the upper bound of the fuzzy interval.

[0054] The specific formula for selecting the final output concentration using the high / low range switching mechanism is as follows: (10); income That is, the final gas concentration. .

[0055] The width of the Gaussian Z-type membership function and central value First, set it to 50% of the saturation range when the preset low range is used. The acceptable boundary of the concept, 60% of the range, is considered as a point with a membership degree of approximately 0.5. Based on this, the width is calculated using the formula. For the width of the Gaussian sigmoid membership function and central value First, set the saturation range to 90% based on the preset low range. The acceptable boundary of the concept is considered as 80% of the range, with a membership degree of approximately 0.5. Based on this, the width is calculated using the formula. Then, standard gases of different concentration gradients were introduced into the monitoring system to observe for any jump values ​​or outliers. Record the values ​​at 10%, 25%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 110%, and 120% of the saturated range for the low-range concentration gradient, and at 20%, 50%, 80%, and 100% of the full-scale range for the high-range gradient. Repeat the test 10 times, and calculate the mean, root mean square error, and dispersion. Repeat the above steps, recording the values. Finally, based on the principle of global optimization, the concentration is obtained. The optimal fuzzy interval is defined by the lower and upper bounds of the minimum root mean square error and the best fit. .

[0056] The dual-range H2O2 gas concentration monitoring method of this application, based on existing technologies, transmits the obtained signal to two pathways centered on wavelength modulation spectroscopy and direct absorption spectroscopy to obtain the concentration. and concentration Furthermore, through a preset automatic high- and low-range switching mechanism, a direct absorption circuit is used to measure the high-range concentration, while a wavelength modulation circuit is used to measure the low-range concentration. This achieves high-precision and full-range effective measurement of H2O2 gas concentration, ultimately outputting an accurate gas concentration. .

[0057] It should be noted that the information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data must comply with relevant regulations.

[0058] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0059] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A dual-range H2O2 gas concentration monitoring system, characterized in that, include: Gas detection module and system circuit module; the gas detection module includes a reflection absorption cell, a transmitting unit and a receiving unit; The system circuit module includes a main circuit module and an auxiliary circuit module; The transmitting unit and the receiving unit are disposed on the reflection absorption cell; the transmitting unit, the receiving unit, and the auxiliary circuit module are all connected to the main circuit module; The main circuit module is used to control the emitting unit to emit laser light; the laser light passes through a reflection absorption cell containing the H2O2 gas to be measured, and is attenuated and emitted after multiple reflections; after the laser light is emitted, it is received by the receiving unit and converted into an electrical signal; the main circuit module receives the electrical signal and transmits the electrical signal to the auxiliary circuit module; The main circuit module processes the electrical signal using wavelength modulation spectroscopy to obtain a first concentration value. The auxiliary circuit module processes the electrical signal according to direct absorption spectroscopy to obtain a second concentration value, and feeds the second concentration value back to the main circuit module. The main circuit module is used to select the final output concentration based on the first concentration value and the second concentration value according to the preset high and low range switching mechanism.

2. The dual-range H2O2 gas concentration monitoring system according to claim 1, characterized in that, The reflection absorption cell is provided with an air inlet and an air outlet, which are used to introduce and discharge the H2O2 gas to be measured, respectively. The reflection absorption cell is a White cell, which includes two small mirrors and one large mirror, and is used to achieve the required optical path through multiple reflections. The transmitting unit and the receiving unit are connected at the White pool, where two circular holes are provided for emitting and receiving laser beams.

3. The dual-range H2O2 gas concentration monitoring system according to claim 1, characterized in that, The main circuit module includes a drive current control element, a temperature control module, a lock-in amplifier, and a main controller; The drive current control element and the temperature control module are used to control the operating current and operating temperature of the transmitting unit. The lock-in amplifier is used to perform phase-locked processing on the electrical signal and extract the second harmonic signal; The main controller calculates the first concentration value based on the second harmonic signal.

4. The dual-range H2O2 gas concentration monitoring system according to claim 1, characterized in that, The auxiliary circuit module includes a low-pass filter unit and an auxiliary controller; The low-pass filter unit is used to filter out the high-frequency modulation signal components in the electrical signal and retain the DC or low-frequency signal. The auxiliary controller is used to perform baseline fitting on the filtered signal and calculate the second concentration value by absorption intensity inversion based on Beer-Lambert's law.

5. The dual-range H2O2 gas concentration monitoring system according to claim 3, characterized in that, The main controller stores a high-low range switching mechanism; the high-low range switching mechanism calculates weights or selects thresholds based on Gaussian membership functions to achieve a smooth transition from the first concentration value to the second concentration value.

6. A method for monitoring H2O2 gas concentration with dual ranges, characterized in that, The dual-range H2O2 gas concentration monitoring system applied to any one of claims 1 to 5 includes the following steps: The main circuit module drives the transmitting unit to emit laser light of a characteristic wavelength, wherein the driving signal includes a low-frequency modulation signal and a high-frequency modulation signal; The receiving unit receives the laser signal after it passes through the H2O2 gas to be tested and converts it into an electrical signal. The electrical signal is divided into a first path and a second path and processed in parallel. In the first path, the electrical signal is processed based on wavelength modulation spectroscopy to obtain a first concentration value; In the second pathway, the electrical signal is processed using direct absorption spectroscopy to obtain a second concentration value; Based on the preset high and low range switching mechanism, the final gas concentration is output by combining the first concentration value and the second concentration value.

7. The dual-range H2O2 gas concentration monitoring method according to claim 6, characterized in that, The process of processing the electrical signal based on wavelength modulation spectroscopy to obtain the first concentration value specifically includes: The electrical signal is subjected to phase-locked processing using a lock-in amplifier to extract the second harmonic signal; wherein the reference signal of the lock-in amplifier is a harmonic of the high-frequency modulation signal. The first concentration value is calculated based on the correspondence between the signal strength of the second harmonic signal and the gas concentration.

8. The dual-range H2O2 gas concentration monitoring method according to claim 7, characterized in that, The relationship between the signal strength of the second harmonic signal and the gas concentration is as follows: ;in This is the first concentration value; and The signal intensities of the second harmonic signal obtained with and without H2O2 gas are shown respectively. For calibration coefficients; Optical path length; Pressure; It is a linear intensity function of temperature; Let be the values ​​of the linear function of H2O2 gas at room temperature and pressure.

9. The dual-range H2O2 gas concentration monitoring method according to claim 8, characterized in that, The process of processing the electrical signal based on direct absorption spectroscopy to obtain the second concentration value specifically includes: The electrical signal is subjected to low-pass filtering to remove high-frequency modulation signal components and retain DC or low-frequency signals; The filtered signal is baseline-fitted, and the second concentration value is obtained by absorption intensity inversion calculation based on the Beer-Lambert law. ;in ; The absorption strength is denoted as .

10. The dual-range H2O2 gas concentration monitoring method according to claim 9, characterized in that, The high and low range switching mechanism adopts the fuzzy interval threshold method and uses a Gaussian membership function to achieve a smooth transition between the first and second channels and determine the final gas concentration.

Images