A dynamic anti-interference method for infrared gas sensor

Abstract

This invention discloses a dynamic anti-interference method for infrared gas sensors in the field of gas detection technology. Based on the sampling data of the current sampling period and the sampling data of the previous sampling period, a dynamic baseline equation is determined. Based on the dynamic baseline equation, baseline disturbances in the current sampling period are eliminated, and the voltage signal output by the detector in the current sampling period is determined. The detected value of the infrared gas sensor is then calculated. This invention overcomes the interference caused by the dynamic fluctuation of the reference baseline during signal acquisition. Furthermore, the entire process requires no complex hardware support, simplifying the data processing. The self-referencing method further improves the accuracy of data calculation.

Description

Technical Field

[0001] This invention relates to the field of gas detection technology, and more specifically, to a dynamic anti-interference method for infrared gas sensors. Background Technology

[0002] Infrared gas sensors utilize the relationship between gas concentration and absorbed light intensity (Lambert-Beer Law), offering advantages such as fast response, high measurement accuracy, and long service life. They are widely used in petrochemical, metallurgical, and mining industries. However, the detection results of infrared gas sensors are affected by numerous factors, including the environmental conditions surrounding the sensor and the materials used, all of which can impact their accuracy.

[0003] The baseline of the sampling points in a gas sensor is a crucial indicator in the gas detection process. The signal value acquired by the infrared gas sensor is calculated using this baseline. In actual operation, infrared gas sensors are susceptible to interference from stray light and infrared radiation from the human body. This causes the sampling reference baseline to fluctuate in real time, leading to data distortion and ultimately, inaccurate test results. Traditional infrared gas sensor sampling methods do not consider the impact of baseline changes on the data. To improve the anti-interference capability of infrared gas sensors, hardware or software anti-interference measures are typically employed.

[0004] In hardware implementation, virtual sensors and calibration instruments are often used for data acquisition and reference, with corrections made based on the difference between the reference and acquired values. This approach involves significant hardware investment and high costs, resulting in bulky equipment. Furthermore, it doesn't adequately investigate whether the offset of the reference structure matches the offset of the acquisition structure, leading to data results being significantly affected by the different structures' responsiveness to interference.

[0005] In software implementation, baseline fitting is required to obtain a more accurate reference baseline. For example, invention patent CN117747008A discloses a baseline fitting and noise reduction method for gas laser absorption spectra. This method requires establishing a baseline fitting neural network, training and testing the neural network using a dataset, and then training and testing it against noise and other influencing factors using another dataset for signal noise reduction. This data processing is quite extensive, affecting signal detection efficiency, and requires collecting a large amount of data. Different datasets have varying resistance to interference factors, leading to significant result deviations.

[0006] The aforementioned shortcomings deserve to be addressed. Summary of the Invention

[0007] To overcome the shortcomings of existing technologies, this invention provides a dynamic anti-interference method for infrared gas sensors, which can overcome the interference caused by the dynamic fluctuation of the reference baseline during signal acquisition. Furthermore, the entire process does not require complex hardware support, simplifies the data processing, and the self-reference method can further improve the accuracy of data calculation.

[0008] The technical solution of this invention is as follows:

[0009] A dynamic anti-interference method for infrared gas sensors, characterized by comprising:

[0010] Based on the sampling signal values ​​of the current sampling period and the sampling signal values ​​of the previous sampling period, the dynamic baseline equation is determined.

[0011] Based on the dynamic baseline equation, the voltage signal output by the detector in the current sampling period is determined, and then the detection value of the infrared gas sensor is calculated.

[0012] According to the present invention based on the above scheme, the dynamic baseline equation is calculated based on the average value of the current sampling period and the average value of the previous sampling period.

[0013] According to the present invention based on the above scheme, the characteristic is that, in the process of determining the dynamic baseline equation:

[0014] (1) Construct a coordinate system for sampling signal value and sampling number: First, obtain the sampling number of the current sampling period and the previous sampling period, and the sampling signal value of each sampling point. Use the sampling number of the current sampling period and the previous sampling period as the horizontal axis, the sampling signal value of each sampling point as the vertical axis, and the middle position of the sampling point in the previous sampling period as the zero point of the horizontal axis to establish a coordinate system.

[0015] (2) Determine the dynamic baseline equation:

[0016]

[0017] Where Ai is the signal value corresponding to the i-th sampling point on the dynamic baseline in the current sampling period, ni is the position of the i-th sampling point in the current sampling period, i is a positive integer, and 1≤i≤N, N is the number of sampling points in each sampling period, A1 is the average value of the previous sampling period, and A2 is the average value of the current sampling period.

[0018] According to the present invention based on the above scheme, the voltage signal output by the detector is calculated using the peak method or the area method based on the dynamic baseline equation.

[0019] Furthermore, in the current sampling period, when the sampling signal value Vi corresponding to the i-th sampling point is not less than the signal value Ai of that sampling point on the dynamic baseline, the sum of all sampling signal values ​​Vi is denoted as ∑Vb; when the sampling signal value Vi corresponding to the i-th sampling point is less than the signal value Ai of that sampling point on the dynamic baseline, the sum of all sampling signal values ​​Vi is denoted as ∑Vs. The voltage signal output by the detector in the current sampling period is obtained using the following formula, and this formula is used to characterize the change in the dynamic baseline due to interference factors in the current sampling period:

[0020] V = ∑Vb - ∑Vs.

[0021] Furthermore, for a single-channel detector, after obtaining the voltage signal V output by the single-channel detector, an expression is established after normalization to correspond to the relevant gas concentration C.

[0022] For detectors with two or more channels, after obtaining the voltage signal V for each channel, the voltage signal of one channel is used as the reference signal V. REF The voltage signals of the remaining channels are the probe signals VDi, where i≥1, determined by V. REF After performing differential operations on VDi and normalizing it, an expression is established to correspond to the relevant gas concentration Ci.

[0023] According to the present invention described above, the infrared gas sensor includes an optical chamber. An incident parabolic reflective surface, a plurality of edge planar reflective surfaces, and an exit parabolic reflective surface are sequentially arranged on the inner wall of the optical chamber. One or more optical path extension planar reflective surfaces are further arranged between the exit parabolic reflective surface and the incident parabolic reflective surface, and the optical path extension planar reflective surface is located on the opposite side of the edge planar reflective surfaces.

[0024] One of the optical path extension plane reflectors is used to receive light from one of the edge plane reflectors and reflect it to another edge plane reflector to increase the optical path length of the light in the optical chamber.

[0025] According to the above-described scheme, the beneficial effects of this invention are as follows: This invention uses the sampling signals from two adjacent cycles to determine a dynamic baseline, and then compares the sampling signal values ​​with the dynamic baseline to determine the calculated results of the sampling signal values, thereby obtaining the detection results of the infrared gas sensor. The dynamic baseline of this invention floats in real time, eliminating the influence of external stray light, infrared radiation from the human body, and other interference. Compared with traditional sampling methods, this invention provides more accurate detection results under interference conditions, and the entire process requires no complex hardware support, simplifying the data processing. Attached Figure Description

[0026] Figure 1This is a waveform sampling diagram for anti-interference in this invention;

[0027] Figure 2 This is an exploded view of the infrared gas sensor in this invention;

[0028] Figure 3 This is a schematic diagram of the optical gas chamber portion of the infrared gas sensor in this invention;

[0029] Figure 4 This is the theoretical optical path diagram of the infrared gas sensor in this invention;

[0030] Figure 5 This is the optical path tracing diagram of the infrared gas sensor in this invention;

[0031] Figure 6 This is an optical path tracing diagram of an infrared gas sensor in the prior art;

[0032] Figure 7 This is the optical path diagram of another infrared gas sensor in the prior art.

[0033] In the diagram, the labels are as follows:

[0034] 1. Optical air cell; 101. First parabolic reflecting surface; 102. First planar reflecting surface; 103. Second planar reflecting surface; 104. Third planar reflecting surface; 105. Fourth planar reflecting surface; 106. Fifth planar reflecting surface; 107. Second parabolic reflecting surface; 108. Third parabolic reflecting surface;

[0035] 2. Cover plate; 201. First cover plate through hole; 202. Second cover plate through hole;

[0036] 3. Signal acquisition circuit module; 301. Infrared light source; 302. Detector; 303. Signal acquisition circuit board. Detailed Implementation

[0037] The present invention will now be further described with reference to the accompanying drawings and embodiments:

[0038] To address the issues of interference from stray light and human infrared radiation during gas detection, which can cause fluctuations in the reference baseline and distortion of sampled data points, leading to errors in test results, this invention proposes a dynamic anti-interference method for infrared gas sensors. When there is no interference, the reference baseline remains unchanged, and the sampled data is consistent with conventional sampling methods. However, when the infrared gas sensor is subjected to interference from stray light or human infrared radiation, a dynamic reference baseline is used for anti-interference, ensuring that the sampled data from the infrared gas sensor can still accurately obtain signal values. Compared to traditional sampling methods, this invention provides more accurate test results even under interference conditions.

[0039] like Figure 1 As shown, in this invention, a dynamic anti-interference method for an infrared gas sensor first obtains the dynamic baseline equation after fluctuations caused by interference factors, then determines the output voltage signal of the detector based on the dynamic baseline equation, and finally obtains the detection value of the infrared gas sensor.

[0040] S1. Based on the sampling data of the current sampling period and the sampling data of the previous sampling period, determine the dynamic baseline equation.

[0041] In this embodiment, the previous sampling period precedes the current sampling period, and the current sampling period and the previous sampling period are two adjacent sampling periods. Within these two adjacent sampling periods, the previous sampling period characterizes the changes in the current sampling period. Since the change in the reference baseline is uncertain when using different periods as a reference (for example, compared to period 1, the baseline is rising in period 2; compared to period 2, the reference baseline is falling in period 3; therefore, the rise and fall of the reference baseline compared to period 1 cannot reflect its true fluctuation), using sampling data from intervals as a reference may distort the calculated data. This invention determines the sampling data within the current sampling period by using two adjacent periods, making the data more accurate. Furthermore, the current sampling period, compared to the previous sampling period, can more accurately indicate the dynamic changes in the data within the current sampling period, resulting in higher precision.

[0042] This embodiment calculates the dynamic baseline equation based on the average value of the current sampling period and the average value of the previous sampling period. The average value of the current sampling period refers to the average value of multiple data collected in the current sampling period, and the average value of the previous sampling period refers to the average value of multiple data collected in the previous sampling period. Using the average value method can more accurately reflect the situation of all sampling data in each sampling period.

[0043] The relationship between the average sampling value of the current sampling period and the average sampling value of the previous sampling period is determined: If the average sampling value of the current sampling period is equal to the average sampling value of the previous sampling period, then the dynamic baseline is determined to be stable, and the sampling signal value in the current sampling period is equal to both the average sampling value of the current and previous sampling periods. In this case, there is no difference between using the dynamic baseline and using the reference baseline for data calculation. However, if the average sampling value of the current sampling period is unequal to the average sampling value of the previous sampling period, then using the reference baseline will obviously cause data distortion. In this case, using the dynamic baseline for data calculation is significantly more accurate than using the reference baseline. Therefore, the dynamic anti-interference method described in this invention is applicable to various situations and has wider adaptability.

[0044] During the process of acquiring the infrared light signal intensity within the current sampling period:

[0045] (1) Construct a coordinate system for the signal values ​​and the number of sampling points:

[0046] First, obtain the number of sampling points in the current sampling period and the previous sampling period, and the sampling signal value of each sampling point. Then, use the middle position of the sampling points in the previous sampling period as the zero point of the horizontal coordinate to construct a coordinate system of sampling signal value and sampling point number.

[0047] In the process of constructing the coordinate system, first obtain the number of sampling points in two adjacent cycles and the corresponding sampling signal value of each sampling point. Then, establish the coordinate system with the number of sampling points in the current sampling cycle and the previous sampling cycle as the horizontal axis and the sampling signal value of each sampling point as the vertical axis.

[0048] To facilitate the calculation of the optical signal intensity in the current cycle, the median value of the number of sampling points in the previous cycle is used as the horizontal zero point when constructing the coordinate system. The number of sampling points in each cycle is used as the horizontal axis, and the sampling signal value is used as the vertical axis. Data calculations for the current sampling cycle are then performed using these two cycles. For example, in... Figure 1 In the embodiment shown, the horizontal axis n is the number of sampling points in each cycle, the vertical axis is the sampling signal value corresponding to each sampling point, and the horizontal axis 0 is the median value of the number of sampling points in the previous sampling cycle T1.

[0049] In this embodiment, the original reference baseline is set to 2000, the modulation period is 640ms, and the ADC sampling period is 2ms. Therefore, 320 data points are collected in each sampling period. That is, the sampling signal value obtained by the i-th sampling point in each period is Vi, where i takes the integer value from 1 to 320. Figure 1In the illustrated embodiment, when constructing the coordinate system, the 160th sampling point of the previous sampling period T1 is used as the horizontal coordinate 0. The curves in the figure show the sampling signal values ​​of the 320 sampling points in the previous sampling period T1 and the 320 sampling points in the current sampling period T2, respectively.

[0050] (2) Determine the dynamic baseline equation

[0051] The dynamic baseline, as the corrected reference baseline, appears as a straight line in the coordinate system. Therefore, when determining the dynamic baseline equation, two points that can represent the dynamic baseline are first identified. Specifically, the midpoint of the sampling point in the previous sampling period and the average value of the sampling signal for the entire period, and the midpoint of the sampling point in the current sampling period and the average value of the sampling signal for the entire period are selected as two representative points.

[0052] (2.1) Determine representative locations

[0053] Within the previous sampling period T1, the average value A1 of several sampling signal values ​​is calculated; within the current sampling period T2, the average value A2 of several sampling signal values ​​is calculated. That is, the first representative point is (0, A1), and the second representative point is (N / 2 + N / 2, A2).

[0054]

[0055] In equation (1), V T1-i V represents the sampling signal value corresponding to the i-th sampling point within the previous sampling period T1. T2-i Let N be the sampling signal value corresponding to the i-th sampling point within the current sampling period T2, and N be the number of sampling points within each sampling period.

[0056] (2.2) Determine the dynamic baseline equation based on two representative points

[0057] Based on two established representative points (0, A1) and (N / 2+N / 2, A2), the dynamic baseline A1A2 and its corresponding equation are determined, as shown in the following equation. According to this equation, the signal value Ai corresponding to the i-th sampling point on the dynamic baseline A1A2 in the current sampling cycle can be calculated:

[0058]

[0059] In equation (2), Ai is the signal value of the i-th sampling point on the dynamic baseline in the current sampling period, ni is the position of the i-th sampling point in the current sampling period, i is a positive integer, and 1≤i≤N.

[0060] by Figure 1Taking the illustrated embodiment as an example: Ai refers to the signal value corresponding to the i-th sampling point on the dynamic baseline A1A2 in the current sampling period T2; A1 is the average value of the signal values ​​of 320 sampling points in the previous sampling period T1; A2 is the average value of the signal values ​​of 320 sampling points in the current sampling period T2; N is the number of sampling points in the previous sampling period T1 and the current sampling period T2, i.e., N = 320. This yields... Figure 1 In the illustrated embodiment, the signal value Ai corresponding to the i-th sampling point on the dynamic baseline A1A2 within the current sampling period T2 is:

[0061]

[0062] In equation (3), The slope of the dynamic baseline A1A2 is represented by (ni+160), which represents the position of the i-th sampling point in the entire horizontal coordinate in the current sampling period T2 (the number of sampling points in the second half of the previous sampling period T1, i.e., 160, needs to be added).

[0063] S2. Based on the dynamic baseline equation, eliminate the baseline disturbance of the current sampling period, determine the voltage signal output by the detector in the current sampling period, and then calculate the detection value of the infrared gas sensor.

[0064] During the calculation process, the voltage signal output by the detector can be calculated using the peak method based on the dynamic baseline equation; alternatively, it can be calculated using the area method based on the dynamic baseline equation. The following examples demonstrate the calculation of the sampling data using the area method.

[0065] In the calculation based on the area method, the voltage signal V output by the detector in the current sampling period is obtained using the following formula, which also characterizes the change in the dynamic baseline due to interference factors in the current sampling period:

[0066] V=∑Vb-∑Vs (4)

[0067] In the current sampling period, when the sampling signal value Vi corresponding to the i-th sampling point is not less than the signal value Ai of that sampling point on the dynamic baseline, the sum of all sampling signal values ​​Vi is denoted as ΣVb; when the sampling signal value Vi corresponding to the i-th sampling point is less than the signal value Ai of that sampling point on the dynamic baseline, the sum of all sampling signal values ​​Vi is denoted as ∑Vs.

[0068] The principle of this invention for eliminating interference using dynamic baseline is as follows: External interference signals affect the reference baseline, causing it to change, resulting in the reference baseline rising or falling. If the traditional calculation method is used (based on the original reference baseline, such as 2000 mentioned in the above embodiment), the data point Vi with a signal value Ai of the i-th sampling point that is not less than the original reference baseline belongs to set Vb, and the data point Vi with a signal value Ai of the i-th sampling point that is less than the original reference baseline belongs to set Vs. The result obtained by using the method of calculating using set Vb and set Vs has a large deviation.

[0069] According to Beer-Lambert's law, the higher the gas concentration, the stronger the absorption of infrared light by the gas, and consequently, the weaker the optical signal received by the detector and the electrical signal converted by the detector. In other words, the detector's output sampling signal is negatively correlated with the gas concentration. Based on the sampling signal value curve, among the sampling signal values ​​above the reference baseline, the sampling signal values ​​for high-concentration gases are lower than those for low-concentration gases; while among the sampling signal values ​​below the reference baseline, the sampling signal values ​​for high-concentration gases are higher than those for low-concentration gases.

[0070] Therefore, based on this principle, this invention uses a dynamic baseline as a reference. If the sampling signal value Vi of the i-th sampling point is located on or above the dynamic baseline A1A2, and the gas concentration changes from low to high, its sampling signal value Vi decreases (the data point in the coordinate system changes from high to low). If the sampling signal value Vi of the i-th sampling point is located below the dynamic baseline A1A2, and the gas concentration changes from low to high, its sampling signal value Vi increases (the data point in the coordinate system changes from low to high). Then ∑Vb-∑Vs reflects the change in the sampling signal value caused by the gas concentration within the current sampling period, thereby eliminating the influence of reference baseline disturbances caused by external interference factors.

[0071] For a single-channel detector, the voltage signal V obtained by equation (4) is normalized and then processed to establish an expression corresponding to the relevant gas concentration C. For dual-channel and multi-channel detectors, the voltage signal Vj (j is the number of channels, j is an integer, and j≥1) can be obtained from each channel using equation (4), where the voltage signal of one channel is used as the reference signal V. REF The voltage signals of the remaining channels are the probe signals VDi (i is an integer, and 1≤i≤j), determined by V... REF After performing differential operations on VDi and normalizing it, an expression is established to correspond to the relevant gas concentration Ci.

[0072] Preferably, in the infrared gas sensor, the detector used to receive the infrared light signal is a dual-channel detector, wherein the voltage signal output by the detection channel is called the DAD value, and the voltage signal output by the reference channel is called the RAD value. After calculating the DAD value and the RAD value, the gas concentration value detected by the dual-channel detector can be obtained by performing a difference operation between the RAD value and the DAD value.

[0073] Both RAD and DAD values ​​can be calculated using the above formula, and the calculated RAD and DAD values ​​eliminate baseline disturbances caused by external interference. During data processing:

[0074] (1) First, calculate the output values ​​of the detection channel and the reference channel in the dual-channel detector respectively:

[0075] V DAD =∑Vb DAD -∑Vs DAD (5)

[0076] V RAD =ΣVb RAD -ΣVs RAD (6)

[0077] In equations (5) and (6), V DAD To detect the voltage signal after removing baseline disturbances in the detection channel, during the current sampling period of the detection channel, when the sampling signal value V corresponding to the i-th sampling point... DADi Not less than the signal value A of the sampling point on the dynamic baseline DADi At that time, all sampled signal values ​​V DADi The sum is denoted as ΣVb DAD When the sampling signal value V corresponding to the i-th sampling point DADi The signal value A at that sampling point on the dynamic baseline is less than DADi At that time, all sampled signal values ​​V DADi The sum is denoted as ΣVs DAD ;

[0078] V RAD For the voltage signal of the reference channel after removing baseline disturbances, in the current sampling period of the reference channel, when the sampling signal value V corresponding to the i-th sampling point... RADi Not less than the signal value A of the sampling point on the dynamic baseline RADi At that time, all sampled signal values ​​V RADi The sum is denoted as ΣVb DAD When the sampling signal value V corresponding to the i-th sampling point RADi The signal value A at that sampling point on the dynamic baseline is less than RADi At that time, all sampled signal values ​​V RADi The sum is denoted as ΣVs RAD;

[0079] (2) Reuse V RAD Value and V DAD The values ​​are differentially processed to obtain a differential signal representing the gas concentration value detected by the infrared gas sensor.

[0080] Using the above method, the calculation of the voltage signal DAD value of the detection channel and the voltage signal RAD value of the reference channel can eliminate the disturbance of the reference baseline caused by external interference, thus ensuring a more accurate calculation result. In this invention, under stable operating conditions of the infrared gas sensor, the baseline equation Ai = A1 = A2, at which point the baseline of the infrared gas sensor is consistent with that of traditional sensors during acquisition and calculation. When the infrared gas sensor experiences baseline fluctuations due to external interference, the calculated V... RAD Value and V DAD The value can cover baseline variations. Therefore, regardless of the application situation, the data calculation results of this invention are reliable and more accurate.

[0081] like Figures 2 to 7 As shown, in order to achieve the above-mentioned dynamic anti-interference method, the present invention also provides an infrared gas sensor, which includes an optical gas chamber 1, a cover plate 2, and a signal acquisition circuit module 3. The cover plate 2 and the signal acquisition circuit module 3 are located at the lower opening of the optical gas chamber 1, so that the cover plate 2 can isolate the electronic components of the signal acquisition circuit module 3 from the optical gas chamber 1.

[0082] The signal acquisition circuit module 3 includes a signal acquisition circuit board 303 and an infrared light source 301 and a detector 302 located on the signal acquisition circuit board 303. The cover plate 2 is provided with a first cover plate through hole 201 and a second cover plate through hole 202. The infrared light source 301 extends into the optical gas chamber 1 through the first cover plate through hole 201, and the detector 302 extends into the optical gas chamber 1 through the second cover plate through hole 202. This allows the light emitted by the infrared light source 301 to be reflected multiple times in the optical gas chamber 1 and interact with the gas in the optical gas chamber 1 before being received by the detector 302.

[0083] Preferably, the infrared light source 301 adopts a blackbody radiation infrared light source, which has advantages such as high emissivity, wide wavelength range, precise temperature control, miniaturization and high output power, and is less affected by external interference factors.

[0084] like Figure 2 , Figure 3As shown, the optical chamber 1 has a hollow structure in the middle and an air hole at its top. In order to increase the optical path length of infrared light inside the optical chamber 1 and to make more effective use of the space inside the optical chamber 1, the optical chamber 1 in this invention is provided with an incident parabolic reflector, multiple edge plane reflectors, and an exit parabolic reflector in sequence inside. One or more optical path extension plane reflectors are also provided between the exit parabolic reflector and the incident parabolic reflector, and the optical path extension plane reflectors are located on the opposite side of the edge plane reflectors, so that after one optical path extension plane reflector receives light from one edge plane reflector, it reflects it to another edge plane reflector, thereby increasing the optical path length of light inside the optical chamber.

[0085] This invention extends the optical path so that the planar reflective surface can cooperate with the opposite edge planar reflective surface, making full use of the space in the middle part of the optical chamber 1 to increase the optical path length. This allows for full interaction between the gas to be tested and the light within the optical chamber 1, thereby improving the accuracy of gas detection.

[0086] In one specific embodiment, the edge planar reflective surface includes a first parabolic reflective surface 101, a first planar reflective surface 102, a second planar reflective surface 103, a third planar reflective surface 104, and a fourth planar reflective surface 105 arranged sequentially. The incident parabolic reflective surface is the first parabolic reflective surface 101, and the optical path extension planar reflective surface is the fifth planar reflective surface 106. The fifth planar reflective surface 106 is disposed between the first parabolic reflective surface 101 and the outgoing parabolic reflective surface, and the fifth planar reflective surface 106 is located on the opposite side of the second planar reflective surface 103 and the third planar reflective surface 104, such that the first parabolic reflective surface 101, the first planar reflective surface 102, the second planar reflective surface 103, the third planar reflective surface 104, the fourth planar reflective surface 105, the outgoing parabolic reflective surface, and the fifth planar reflective surface 106 are sequentially connected to form an annulus and located on the outer wall of the optical air chamber 1.

[0087] In this embodiment, by setting the fifth planar reflective surface 106, the space inside the optical gas chamber 1 can be fully utilized while minimizing energy loss caused by multiple reflections of light, thus making full use of light energy for gas detection.

[0088] In this embodiment, the outgoing parabolic reflector includes a second parabolic reflector 107 and a third parabolic reflector 108, such that the light reflected from the fourth planar reflector 105 (or in other embodiments, a light path extension planar reflector) to the second parabolic reflector 107 is focused by the second parabolic reflector 107 and reflected to the third parabolic reflector 108.

[0089] like Figure 3 , Figure 4As shown, the light emitted by the infrared light source 301 passes sequentially through the first parabolic reflector 101, the first planar reflector 102, the third planar reflector 104, the fifth planar reflector 106, the second planar reflector 103, the fourth planar reflector 105, the second parabolic reflector 107, and the third parabolic reflector 108 before being received by the detector 302.

[0090] The infrared light source 301 is located at the focal point of the first parabolic reflector 101, allowing the first parabolic reflector 101 to transmit the light emitted by the infrared light source 301 from its bottom position upwards to the middle region of the optical chamber 1, collimating the light into parallel light and reflecting it to the first planar reflector 102. The fifth planar reflector 106 receives the light from the third planar reflector 104 and reflects it to the second planar reflector 103. Furthermore, the fifth planar reflector 106 can fully utilize the space within the optical chamber 1, allowing the third planar reflector 104 to reflect the light to the fifth planar reflector. The light rays from the fifth planar reflector 106 and the light rays reflected from the fifth planar reflector 106 to the second planar reflector 103 can pass through the central region inside the optical chamber 1, making full use of this region to increase the optical path length and avoid the stacking of light rays; the second parabolic reflector 107 is used to focus the light rays reflected from the fourth planar reflector 105 and reflect them to the third parabolic reflector 108. The detector 302 is located at the focal point of the third parabolic reflector 108, so that the light rays reflected from the third parabolic reflector 108 can be reflected to the bottom of the optical chamber 1 and focused at the detector 302.

[0091] Preferably, the second parabolic reflector 107 and the third parabolic reflector 108 are in a common focal plane, that is, the focal point of the second parabolic reflector 107 and the focal point of the third parabolic reflector 108 are located on the same vertical axis.

[0092] like Figure 6 , Figure 7 The optical path states for light reflection in optical air cells in two existing technologies are given. Figure 6 In the illustrated embodiment, the light undergoes multiple reflections and accumulates at the edge of the optical chamber, while the space in the central region of the optical chamber remains unused, resulting in wasted space. Figure 7 In the embodiment shown, light is reflected from the right side to the detector on the left. In order to ensure the light effect, the lateral volume of the entire optical chamber is maximized. The increase in chamber volume directly affects the response time of the sensor, while the internal space utilization is low.

[0093] like Figure 4 , Figure 5As shown, the optical gas cell design of the infrared gas sensor in this invention can make full use of the internal space of the optical gas cell to achieve multiple cross reflections, increase the optical path length of a single reflection, and thus increase the total optical path length; and the number of reflections is less compared to the spiral gas cell channel, reducing reflection loss.

[0094] In one embodiment, it is applied to products of the same external dimensions (standard 7 series). Figure 6 The optical cell structure shown in the figure can achieve an optical path length of 6cm compared to the optical cell structure of the present invention, while the present invention can achieve an optical path length of 10cm, thus greatly improving the overall optical path length.

[0095] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

[0096] The present invention has been described above with reference to the accompanying drawings. Obviously, the implementation of the present invention is not limited to the above-described manner. Any improvements made using the inventive concept and technical solution of the present invention, or the direct application of the inventive concept and technical solution of the present invention to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A dynamic anti-interference method for infrared gas sensors, characterized in that, include: The dynamic baseline equation is determined based on the sampling signal values ​​of the current sampling period and the sampling signal values ​​of the previous sampling period. The voltage signal output by the detector in the current sampling period is determined based on the dynamic baseline equation, and then the detection value of the infrared gas sensor is calculated. In determining the dynamic baseline equations: (1) Construct a coordinate system for sampling signal value and sampling number: First, obtain the sampling number of the current sampling period and the previous sampling period, and the sampling signal value of each sampling point. Use the sampling number of the current sampling period and the previous sampling period as the horizontal axis, the sampling signal value of each sampling point as the vertical axis, and the middle position of the sampling point in the previous sampling period as the zero point of the horizontal axis to establish a coordinate system. (2) Determine the dynamic baseline equation: Where Ai is the signal value corresponding to the i-th sampling point on the dynamic baseline in the current sampling period, ni is the position of the i-th sampling point in the current sampling period, i is a positive integer, and 1≤i≤N, N is the number of sampling points in each sampling period, A1 is the average value of the previous sampling period, and A2 is the average value of the current sampling period.

2. The dynamic anti-interference method for an infrared gas sensor according to claim 1, characterized in that, The dynamic baseline equation is calculated based on the average value of the current sampling period and the average value of the previous sampling period.

3. The dynamic anti-interference method for an infrared gas sensor according to claim 1, characterized in that, Based on the dynamic baseline equation, the voltage signal output by the detector is calculated using either the peak method or the area method.

4. The dynamic anti-interference method for an infrared gas sensor according to claim 3, characterized in that, In the current sampling period, when the sampling signal value Vi corresponding to the i-th sampling point is not less than the signal value Ai of that sampling point on the dynamic baseline, the sum of all sampling signal values ​​Vi is denoted as ∑Vb. When the sampling signal value Vi corresponding to the i-th sampling point is less than the signal value Ai of that sampling point on the dynamic baseline, the sum of all sampling signal values ​​Vi is denoted as ∑Vs. The voltage signal output by the detector in the current sampling period is obtained using the following formula, which characterizes the change of the dynamic baseline due to interference factors in the current sampling period: V = ∑Vb - ∑Vs.

5. The dynamic anti-interference method for an infrared gas sensor according to claim 4, characterized in that, For a single-channel detector, after obtaining the voltage signal V output by the single-channel detector, an expression is established after normalization to correspond to the relevant gas concentration C. For detectors with two or more channels, after obtaining the voltage signal V for each channel, the voltage signal of one channel is used as the reference signal V. REF The voltage signals of the remaining channels are the probe signals VDi, where i≥1, determined by V. REF After performing differential operations on VDi and normalizing it, an expression is established to correspond to the relevant gas concentration Ci.

6. The dynamic anti-interference method for an infrared gas sensor according to claim 1, characterized in that, The infrared gas sensor includes an optical chamber. The inner wall of the optical chamber is sequentially provided with an incident parabolic reflective surface, multiple edge planar reflective surfaces, and an exit parabolic reflective surface. One or more optical path extension planar reflective surfaces are also provided between the exit parabolic reflective surface and the incident parabolic reflective surface, and the optical path extension planar reflective surface is located on the opposite side of the edge planar reflective surfaces. One of the optical path extension plane reflectors is used to receive light from one of the edge plane reflectors and reflect it to another edge plane reflector to increase the optical path length of the light in the optical chamber.

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