A CO2 detection device based on optical fiber FP cavity sensing and embedded system

Abstract

The present invention discloses a CO2 detection device based on fiber optic F-P cavity sensing and an embedded system, which includes a signal detection and processing module, an embedded control module, a power supply voltage stabilization module, and a sensing module. The sensing module includes an incident light source, an incident conduction optical fiber, a photoelectric sensor, a reflective fiber optic jumper, and a fiber optic F-P cavity CO2 sensor. The control signal of the embedded control module is supplied to the incident light source after being stabilized by the power supply voltage stabilization module. The incident light enters the fiber optic F-P cavity CO2 sensor through the incident conduction optical fiber, and the reflected light signal is transmitted to the photoelectric sensor by the reflective fiber optic jumper to be converted into an electrical signal, and then fed back to the signal detection and processing module for processing. This device can achieve intelligent and automatic detection, effectively improve the detection efficiency and accuracy, reduce manual intervention and errors, and has a low cost and is easy to industrialize.

Description

Technical Field

[0001] The invention belongs to the technical field of CO2 detection, and relates to a CO2 detection device, in particular to a CO2 detection device based on optical fiber FP cavity sensing and an embedded system. Background Art

[0002] With the acceleration of global industrialization and urbanization, carbon dioxide (CO2), as one of the main greenhouse gases, has seen a sharp increase in emissions, leading to an increasingly serious global warming problem. Climate change not only affects natural ecosystems, but also poses a major threat to the sustainable development of human society. Accurate and timely detection of CO2 has become an important means to respond to global climate change and protect the earth's environment. Accurately measuring the concentration of CO2 in the air not only provides key data for climate change research, but also is related to the formulation of environmental protection policies and the evaluation of their implementation effects. Therefore, the development of efficient and reliable CO2 detection methods has become a top priority.

[0003] CO2 detection technology can provide accurate data on CO2 concentration in the atmosphere, which is an important basis for evaluating climate change trends and formulating environmental protection policies. Through CO2 detection, environmental protection agencies can grasp the CO2 emissions in various regions in real time, analyze the distribution and intensity of pollution sources, and provide data support for formulating scientific emission reduction targets and environmental protection policies.

[0004] However, many existing CO2 detection devices have the defects of high cost, high difficulty in system integration, poor environmental adaptability, or significantly reduced detection-related performance under the premise of meeting certain performance. For example, CN116242971A discloses a collection device for collecting carbon dioxide, which uses carbon dioxide detection elements to expose and contact the air to detect carbon dioxide content. It aims at the problem that a single airflow impacts the detection element, the carbon dioxide content is low, and the measurement result is unstable. It proposes to control multiple airflows to impact the detection element evenly, which improves the overall detection effect. However, the device has a certain effect in collecting CO2, but the detection ability needs to be improved; CN118603894A improves the traditional photoacoustic spectroscopy gas sensor. Since the sound wave is generated in a closed photoacoustic pool, and the traditional photoacoustic pool needs to resonate with the excitation light source and the sound wave sensor, the overall photoacoustic spectroscopy gas sensor has a large volume, which makes it difficult to achieve high-sensitivity detection. Therefore, the invention improves the sensitivity of detecting sound pressure to improve the sensitivity of the photoacoustic spectroscopy gas detection device. However, the integration of the invention is not good enough, and the cost is high. It cannot be mass-produced and cannot be applied to productization. The subsequent development difficulty is high, and the application ability of related inventions is weak. CN116026778A discloses a sky-ground based integrated monitoring system and method for carbon emissions in a park. The system includes a regional division module, a data acquisition module and a processing and analysis module. The regional division module is used to divide the park. The data acquisition module and the processing and analysis module are used to realize real-time monitoring of various areas in the park. However, there are still some defects: for example, the scheme only realizes monitoring of various areas in the park by simply dividing the park. However, in order to judge whether the carbon dioxide emissions of the park exceed the standard, it is necessary to compare the carbon dioxide emissions of the park with the carbon dioxide emission standard. At the same time, the area is generally divided into construction land and non-construction land. The construction land is the park, and the non-construction land refers to grassland, forest land and cultivated land. The non-construction land absorbs the carbon dioxide discharged by the construction land. Therefore, in order to obtain a more accurate carbon dioxide emission of the park, it is necessary to consider the influence of grassland, forest land and cultivated land around the park on carbon dioxide. Therefore, the measurement result of the invention is not accurate enough, is easily affected by environmental factors, has poor anti-interference ability, and the response speed needs to be improved.

[0005] It can be seen that there is still a lot of room for improvement in the field of portable, high-performance and low-cost CO2 detection. Summary of the invention

[0006] The purpose of the present invention is to provide a CO2 detection device based on optical fiber FP cavity sensing and embedded system to address the deficiencies of the prior art. The device can realize intelligent and automated detection, effectively improve detection efficiency and accuracy, reduce manual intervention and errors, and is low-cost and easy to industrialize.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A CO2 detection device based on optical fiber FP cavity sensing and embedded system comprises a signal detection and processing module, an embedded control module, a power supply voltage stabilization module and a sensing module. The sensing module comprises an incident light source, an incident conductive optical fiber, a photoelectric sensor, a reflective optical fiber jumper and an optical fiber FP cavity CO2 sensor. The control signal of the embedded control module is stabilized by the power supply voltage stabilization module to supply energy to the incident light source. The incident light enters the optical fiber FP cavity CO2 sensor through the incident conductive optical fiber. The reflective optical fiber jumper transmits the outgoing light signal to the photoelectric sensor to convert it into an electrical signal, and feeds it back to the signal detection and processing module for processing.

[0009] In the above technical scheme, further, the optical fiber FP cavity CO2 sensor includes a single-mode optical fiber, a hollow-core optical fiber, and a hollow-core capillary sleeve. One end of the single-mode optical fiber is fused with the hollow-core optical fiber to form an integrated structure. UV glue is coated on the fusion end face of the optical fiber, and a reflective gold foil film is provided at the other end of the hollow-core optical fiber. The hollow-core capillary sleeve is placed outside the integrated structure of the single-mode optical fiber and the hollow-core optical fiber, and an air inlet and an air outlet are opened at the hollow-core optical fiber to communicate with the inside of the hollow-core optical fiber. The air inlet and the air outlet can be controlled to open and close.

[0010] Furthermore, the signal detection and processing module and the power supply voltage stabilization module are integrated into the embedded control module and are electrically connected to the sensor module via a connector.

[0011] Furthermore, the fiber FP cavity CO2 sensor is very sensitive to temperature changes, which may lead to deviations in the measurement results and affect the accuracy of CO2 detection. To address this problem, a temperature compensation mechanism is designed, which combines the embedded system to monitor the ambient temperature in real time and adjust the sensor output through an algorithm. For example, a mathematical model of temperature and sensor CO2 concentration can be established after the actual measurement of the sensor, and the model can be imported into the embedded control module, i.e., the main control. The embedded system is responsible for reading the real-time temperature through the temperature sensor (thermocouple type, thermal resistor, infrared type) and compensating the output value according to the mathematical model, and finally displaying the compensated and calibrated data.

[0012] Furthermore, the sensitivity of the fiber FP cavity CO2 sensor is affected by the cavity length and the fiber refractive index, and may not meet the needs of high-precision or wide-range CO2 detection. By optimizing the structural design of the fiber FP cavity, such as adjusting the cavity length and using high-refractive-index optical fiber, the sensitivity and measurement range of the sensor can be improved. According to experience, the cavity length is better within 200um, and the cavity length should not be too long, otherwise the quality of the optical signal will be affected. At the same time, by utilizing the high-precision data processing capabilities of the embedded system, the sensor output is finely adjusted and analyzed by adjusting the frequency of the digital-analog acquisition signal and filtering the acquired data.

[0013] Furthermore, a signal processing algorithm is provided in the signal detection and processing module to filter and suppress interference signals. The signal processing algorithm may adopt existing filtering algorithms such as mean filtering, peak filtering, etc., or may adopt a self-developed and designed algorithm, or may perform data compensation and stray signal filtering through the acquisition data model calculated by data fitting, and adjust according to the required effect. This part may be continuously developed. For example, for the waveform processing after the FP cavity is converted from an optical signal to an electrical signal, a compensation value filter may be used. Based on the construction of the mathematical model, data may be selectively corrected according to the waveform trend (including supplementing the data length, smoothing signal glitches, etc.). The specific processing ideas may include the following:

[0014] 1) When the converted electrical signal is accompanied by impulse signal glitches and clutter, a low-pass filter is first used to filter out the glitches in the electrical signal;

[0015] 2) If the converted signal is a waveform with peaks and valleys, such as a sine wave or a triangle wave, the mathematical model is used to determine whether the peak value and the minimum value meet the requirements. If the waveform meets the requirements, it will pass. If the waveform does not meet the requirements, it will be judged and a limit (threshold) of no more than 5% of the peak error will be set. The values ​​exceeding the limit will be weighted averaged to meet the allowable error range.

[0016] 3) Store a large number of waveforms, such as hundreds of them, and perform smoothing and filtering on the data contained in these waveforms. Some non-burr noise signals (which destroy the integrity of the waveform and make the data disorganized) are discarded through mathematical model judgment, and the remaining part after discarding is filled with the expected value of the mathematical model (at this time, this set of data is equivalent to filling after discarding, and the filled data is also averaged from the original data, and the average waveform value is filled in the missing part to keep the data length unchanged);

[0017] 4) If the data is similar to a curve signal, threshold limiting is still performed according to the mathematical model, and the data exceeding the threshold is weighted averaged. The data is corrected with 100 data points sampled as a cycle, and finally the filtered waveform is output for the system to read.

[0018] Furthermore, the embedded control module measures the light source input angle and the installation angle by means of a gyroscope arranged at the incident light source, and determines whether the maximum incident angle is met to satisfy the condition of total reflection in the optical fiber.

[0019] Furthermore, if the device is offset at the connection or installation due to wear and tear, the embedded control module determines the angle range that should be met between the light source and the incident optical fiber through the offset angle feedback from the gyroscope, and issues an alarm if the angle range is not met.

[0020] The beneficial effects of the present invention are:

[0021] The present invention constructs a Fabry-Perot cavity (FP) structure and combines the optical fiber interference structure with the CO2 sensor. Through structural design and optimization, and combined with embedded system technology, the whole device has high precision and sensitivity, is less affected by the environment, has high stability and accuracy, and has excellent anti-electromagnetic interference and corrosion resistance. It can realize intelligent and automated detection, has low cost and is easy to promote and apply. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the structure of the optical fiber FP cavity CO2 sensor in the device of the present invention;

[0023] Figure 2 It is a schematic diagram of the structure of the device of the present invention. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0025] According to a specific embodiment of the present invention, a CO2 detection device based on optical fiber FP cavity sensing and embedded system provided by the present invention is implemented based on a uniquely designed optical fiber FP cavity CO2 sensor combined with an embedded system. Figure 1 and Figure 2 As shown, the device includes an embedded control module 9, a signal detection and processing module 8, a power supply voltage stabilizing module 10, and a sensor module 14. The signal detection and processing module 8 and the power supply voltage stabilizing module 10 can be directly integrated into the embedded control module 9. The sensor module 14 includes an incident light source 12, an incident transmission optical fiber 13, a photoelectric sensor 15, a reflective optical fiber jumper 16, and an optical fiber FP cavity CO2 sensor 17. An external power supply supplies energy to the embedded control module 9. The control signal of the embedded control module 9 is stabilized by the power supply voltage stabilizing module 10 to supply energy to the incident light source 12. The incident light source generates an excitation light signal, and its wavelength is usually 2.7μm or 4.26μm. It enters the optical fiber FP cavity CO2 sensor 17 through the incident transmission optical fiber 13. The feedback light signal of the optical fiber FP cavity CO2 sensor is transmitted by the reflective optical fiber jumper 16 to the photoelectric sensor 15, converted into an electrical signal, and fed back to the signal detection and processing module 8 for processing.

[0026] like Figure 1In the example, the optical fiber FP cavity CO2 sensor includes a single-mode optical fiber, a hollow-core optical fiber 6, and a hollow-core capillary sleeve 2. One end of the single-mode optical fiber (including the core 3 and the cladding 1) is fused with the hollow-core optical fiber 6 to form an integrated structure. UV glue is coated on the fusion end face of the optical fiber. A reflective gold foil film 7 is provided at the other end of the hollow-core optical fiber 6. The hollow-core capillary sleeve 2 is placed outside the integrated structure of the single-mode optical fiber and the hollow-core optical fiber, and an air inlet 4 and an air outlet 5 are provided at the hollow-core optical fiber to communicate with the hollow-core optical fiber. The air inlet 4 and the air outlet 5 can be opened and closed, and the opening and closing of the air inlet and the air outlet can be controlled by respectively setting a movable outer shell cover outside the hollow-core capillary sleeve 2 and the air inlet 4 and the air outlet 5. Before testing the gas to be tested, the influence of the gas that may be contained in the cavity must be eliminated. Therefore, the gas to be tested must be introduced for a certain period of time. When the cavity is filled with the gas to be tested, the gas outlet is closed, that is, the CO2 to be tested is injected into the cavity through the gas inlet. After a certain period of time, the gas outlet is closed, and then the gas inlet is closed. The incident light enters the optical fiber FP cavity CO2 sensor through the incident optical fiber. The light is reflected in the cavity by the FP cavity composed of the optical fiber fusion end face and the reflective gold foil film. Different concentrations of CO2 will correspond to different reflection transmittances, so that the spectrum of the reflected and transmitted optical signal has corresponding differences. The reflective optical fiber jumper transmits the optical signal to the photoelectric sensor and converts it into an electrical signal, which is fed back to the embedded module for further processing and displays the corresponding results in real time.

[0027] The ideal raw data model of the sensor involved in the present invention satisfies the following: the maximum incident angle between the inner core and the normal line of the optical fiber end face at which the total internal reflection derived from Snell's law can occur:

[0028] Ɵ=arcsin[(n²-n1²)^1 / 2]

[0029] Where n is the refractive index of the fiber core, and n1 is the refractive index of the fiber cladding. That is, the installation position of the light source is determined by the incident light angle. The embedded system can use a gyroscope placed on the light source to measure whether the input angle of the light source and the installation angle meet the above incident light angle to meet the condition of total reflection in the optical fiber. If the angle of the connection or installation point is offset due to loss in use, the angle range can be set in the embedded system, and an alarm will be issued if it is not met.

[0030] Transmitted light errors are filtered out using a narrow bandwidth of transmitted light separated by a frequency inversely proportional to the FP resonant cavity length L:

[0031] △V=C / 2L

[0032] where C is the speed of light.

[0033] Calculate the reflected light intensity to obtain the intensity of the final input photoelectric sensor light signal. The reflected light intensity IR is:

[0034] IR =R1I0 +ηR2I0 +2 ηR1R2I0cos(φ0 +Δφ)

[0035] Among them, R1 and R2 are the reflectivities of the front and rear end faces of the FP cavity, respectively. The front end is the air end face where the FP cavity connects with the incident optical fiber, and the rear end is the reflective gold foil film; I0 is the incident light intensity; η is the coupling efficiency of light from the single-mode optical fiber into the hollow-core optical fiber and then coupled back to the single-mode optical fiber; φ0 is the inherent phase difference of the FP resonant cavity, and Δφ is the phase change.

[0036] In a specific example of the present invention, the FP cavity length L in the photoelectric FP cavity CO2 sensor can be controlled within 200um, and the FP cavity is composed of an air gap formed between the end faces of the optical fiber. Its size (such as cavity length) has an important influence on the sensitivity and measurement range of the sensor. The embedded control module can be integrated with a microprocessor STM32F103C8T6, a power supply voltage regulator module, a signal detection and processing module, a memory, an interface circuit, etc., which are used to control the operation of the entire detection device. Among them, the specific model of the external power supply of the device can be JOA (H) series 100W-200W, and the power supply voltage regulator module part adopts linear voltage regulator chips AMS1117-3.3 and AMS1117-5.0 series. When an infrared light source in a spectral range suitable for detecting CO2 is selected, the light source is powered, and the power supply stability of the entire embedded system is guaranteed. The signal detection and processing module may include a signal amplifier (AD623), an analog-to-digital converter (ADS1256), an LCD display, an LED indicator, a wireless communication module (ESP32), etc., which are used to amplify, filter, and process the converted electrical signal output by the optical fiber FP cavity sensor, display the detected concentration value of CO2, and transmit the detection result to a host computer or other equipment. The present invention realizes the combination of optical fiber sensor and embedded system application by converting light intensity and frequency signals into voltage and current signals to collect analog electrical signals, and then converting them into digital signals for collection.

[0037] The above-described embodiments are only some of the preferred solutions of the present invention, but they are not intended to limit the present invention. A person skilled in the relevant technical field may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A CO2 detection device based on optical fiber FP cavity sensing and embedded system, characterized in that: include: A signal detection and processing module, an embedded control module, a power supply voltage stabilization module, and a sensor module. The sensor module includes an incident light source, an incident transmission optical fiber, a photoelectric sensor, a reflective optical fiber jumper, and an optical fiber FP cavity CO2 sensor. The control signal of the embedded control module is stabilized by the power supply voltage stabilization module to supply energy to the incident light source. The incident light enters the optical fiber FP cavity CO2 sensor through the incident transmission optical fiber. The reflective optical fiber jumper transmits the outgoing light signal to the photoelectric sensor to convert it into an electrical signal, and feeds it back to the signal detection and processing module for processing; The embedded control module measures the input angle of the light source and the installation angle by using a gyroscope arranged at the incident light source to determine whether the maximum incident angle is met to satisfy the condition of total reflection in the optical fiber; The optical fiber FP cavity CO2 sensor comprises a single-mode optical fiber, a hollow-core optical fiber, and a hollow-core capillary sleeve. One end of the single-mode optical fiber is fused with the hollow-core optical fiber to form an integrated structure. UV glue is coated on the fusion end face of the optical fiber. A reflective gold foil film is provided on the other end of the hollow-core optical fiber. The hollow-core capillary sleeve is placed outside the integrated structure of the single-mode optical fiber and the hollow-core optical fiber, and an air inlet and an air outlet are provided at the hollow-core optical fiber to communicate with the hollow-core optical fiber. The air inlet and the air outlet can be controlled to open and close. The embedded control module monitors the ambient temperature in real time, and adjusts the device output through a temperature compensation algorithm to compensate for the deviation of the optical fiber FP cavity CO2 sensor caused by temperature.

2. The CO2 detection device based on optical fiber FP cavity sensing and embedded system according to claim 1 is characterized in that: The signal detection and processing module and the power supply voltage stabilization module are integrated in the embedded control module and are electrically connected to the sensor module via a connector.

3. The CO2 detection device based on optical fiber FP cavity sensing and embedded system according to claim 1 is characterized in that: The cavity length of the optical fiber FP cavity in the optical fiber FP cavity CO2 sensor is within 200 um.

4. The CO2 detection device based on optical fiber FP cavity sensing and embedded system according to claim 1, characterized in that: A signal processing algorithm is provided in the signal detection and processing module for filtering and suppressing interference signals.

5. The CO2 detection device based on optical fiber FP cavity sensing and embedded system according to claim 1, characterized in that: If the device is worn out and the angle of the connection or installation point is offset, the embedded control module determines the angle range that should be satisfied between the light source and the incident optical fiber through the offset angle fed back by the gyroscope, and alarms if the angle range is not satisfied.

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