Dynamic anti-interference method for infrared gas sensor

Abstract

The invention discloses a dynamic anti-interference method for an infrared gas sensor in the technical field of gas detection, which comprises the following steps of: determining a dynamic baseline equation based on sampling point data of a current sampling point period and sampling point data of a previous sampling point period; and based on the dynamic baseline equation, eliminating baseline disturbance of the current sampling point period, determining a voltage signal output by the detector in the current sampling point period, and then calculating to obtain a detection value of the infrared gas sensor. The interference influence caused by dynamic floating of the reference baseline in the signal acquisition process can be overcome, complex hardware support is not needed in the whole process, the data processing process is simplified, and the accuracy of data calculation can be further improved through the self-reference mode.

Description

Technical Field

[0001] The invention relates to the technical field of gas detection, and in particular to a dynamic anti-interference method for an infrared gas sensor. Background Art

[0002] Infrared gas sensors use the relationship between gas concentration and absorbed light intensity (Lambert-Beer law) and have the advantages of fast response speed, high measurement accuracy, and long service life. They are widely used in petrochemical, metallurgical, industrial and mining industries. The detection results of infrared gas sensors are affected by many factors, such as the environmental factors where the infrared gas sensor is located and the materials used by the sensor, which will affect the detection accuracy of the infrared gas sensor.

[0003] The baseline of the sampling point in the gas sensor is an important indicator in the gas detection process. The signal value of the data acquisition of the infrared gas sensor is calculated by referring to the baseline. In the actual working process, the infrared gas sensor is easily interfered by external stray light, infrared radiation from the human body, etc., which causes the reference baseline of the sampling point of the infrared gas sensor to be not constant. It will float in real time, which can easily cause the data of the sampling point to be distorted, and then lead to errors in the test results. The traditional sampling method of infrared gas sensors does not consider the impact of changes in the sampling reference baseline on the data. In order to improve the anti-interference ability of infrared gas sensors, hardware or software methods are usually used for anti-interference.

[0004] In the process of hardware implementation, virtual sensors and calibration instrument lights are often used for data collection reference, and the difference between the reference value and the collected value is used for correction. This method requires large hardware investment and high cost, and the entire device is large in size. In addition, there is not much exploration of whether the offset of the reference structure is consistent with the offset of the collection structure, resulting in the data results being greatly affected by the response ability of different structures to interference factors.

[0005] In the process of software implementation, it is necessary to perform data fitting on the baseline to obtain a more accurate reference baseline. For example, the invention patent with publication number CN117747008A discloses a baseline fitting and noise reduction method for gas laser absorption spectrum, which requires the establishment of a baseline fitting neural network, and the use of a data set to train and test the baseline fitting neural network, and then use another data set to train and test the influencing factors such as noise to perform signal noise reduction. The above data processing process is relatively large, which affects the efficiency of signal detection, and requires the collection of relatively large amounts of data. Different data have different anti-interference capabilities for interference factors, resulting in large deviations in the results.

[0006] The above defects are worth solving. Summary of the invention

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

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

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

[0010] Determine the dynamic baseline equation based on the sampling signal value of the current sampling cycle and the sampling signal value of the previous sampling cycle;

[0011] 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.

[0012] The present invention according to the above scheme is characterized in that the dynamic baseline equation is calculated based on the average value of the current sampling cycle and the average value of the previous sampling cycle.

[0013] The present invention according to the above scheme is characterized in that, in the process of determining the dynamic baseline equation:

[0014] (1) Constructing a coordinate system of sampling point signal values ​​and sampling point numbers: first obtain the sampling point numbers of the current sampling point cycle and the previous sampling point cycle, and the sampling point signal value of each sampling point, and establish a coordinate system with the sampling point numbers of the current sampling point cycle and the previous sampling point cycle as the horizontal coordinate, the sampling point signal value of each sampling point as the vertical coordinate, and the middle position of the sampling point in the previous sampling point cycle as the horizontal coordinate zero point;

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

[0016]

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

[0018] The present invention according to the above scheme is characterized in that, based on the dynamic baseline equation, a peak method or an area method is used to calculate the voltage signal output by the detector.

[0019] Furthermore, in the current sampling cycle, when the sampling signal value Vi corresponding to the ith sampling point is not less than the signal value Ai of the sampling point on the dynamic baseline, the sum of all the sampling signal values ​​Vi is recorded as ∑Vb, and when the sampling signal value Vi corresponding to the ith sampling point is less than the signal value Ai of the sampling point on the dynamic baseline, the sum of all the sampling signal values ​​Vi is recorded as ∑Vs. The voltage signal output by the detector in the current sampling cycle is obtained by the following formula, and the change of the dynamic baseline affected by interference factors in the current sampling cycle is characterized by this formula:

[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 corresponding to the relevant gas concentration C is established after normalization;

[0022] For detectors with more than two channels, after obtaining the voltage signal V of each channel, the voltage signal of one channel is used as the reference signal V REF , the voltage signals of the other channels are detection signals VDi, where i≥1, and V REF After performing differential operation on VDi and normalizing it, an expression corresponding to the relevant gas concentration Ci is established.

[0023] The present invention according to the above scheme is characterized in that the infrared gas sensor includes an optical gas chamber, and an incident parabolic reflection surface, a plurality of edge plane reflection surfaces, and an exit parabolic reflection surface are sequentially arranged on the inner wall of the optical gas chamber, and one or more optical path extension plane reflection surfaces are further arranged between the exit parabolic reflection surface and the incident parabolic reflection surface, and the optical path extension plane reflection surface is located on the opposite side of the edge plane reflection surface,

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

[0025] The present invention according to the above scheme has the beneficial effect that the present invention uses the sampling point signals of two adjacent cycles to determine the dynamic baseline, and then uses the sampling point signal value to compare with the dynamic baseline to determine the calculation result of the sampling point signal value, thereby obtaining the detection result of the infrared gas sensor. The dynamic baseline of the present invention floats in real time, which can eliminate the influence of interference such as external stray light and infrared radiation from the human body. Compared with the traditional sampling method, the present invention has more accurate detection results under interference conditions, and the whole process does not require complex hardware support, and can also simplify the data processing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1This is a sampling diagram of the anti-interference waveform in the present invention;

[0027] Figure 2 This is a structural exploded view of the mid-infrared gas sensor of the present invention;

[0028] Figure 3 Schematic diagram of the optical gas chamber portion of the mid-infrared gas sensor of the present invention;

[0029] Figure 4 The theoretical optical path diagram of the infrared gas sensor of the present invention;

[0030] Figure 5 This is a light path tracing diagram of the mid-infrared gas sensor of the present invention;

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

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

[0033] In the figure, the labels are:

[0034] 1. Optical air chamber; 101. First parabolic reflection surface; 102. First plane reflection surface; 103. Second plane reflection surface; 104. Third plane reflection surface; 105. Fourth plane reflection surface; 106. Fifth plane reflection surface; 107. Second parabolic reflection surface; 108. Third parabolic reflection surface;

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

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

[0037] The present invention is further described below in conjunction with the accompanying drawings and embodiments:

[0038] In order to solve the problem that the infrared gas sensor is easily disturbed by external stray light, human infrared radiation and the like during gas detection, causing the reference baseline of the infrared gas sensor sampling points to float, the sampling data points to be distorted, and the like, thereby causing errors in the test results, the present invention proposes a dynamic anti-interference method for the infrared gas sensor. When the infrared gas sensor is not interfered with, the reference baseline does not change, and the sampling point data is consistent with the conventional sampling method. When the infrared gas sensor is interfered with by external stray light, human infrared radiation and the like, a dynamic reference baseline method is used for anti-interference, so that the sampling point data of the infrared gas sensor can still accurately obtain signal values. Compared with the traditional sampling method, the test result of the present invention is more accurate under interference conditions.

[0039] like Figure 1 As shown, in the present invention, a dynamic anti-interference method for an infrared gas sensor first obtains a dynamic baseline equation after the interference factor fluctuates, and then determines the output voltage signal of the detector based on the dynamic baseline equation, thereby obtaining the detection value of the infrared gas sensor.

[0040] S1. Determine a dynamic baseline equation based on the sampling data of the current sampling cycle and the sampling data of the previous sampling cycle.

[0041] In this embodiment, the previous sampling cycle is located before the current sampling cycle, and the current sampling cycle and the previous sampling cycle are two adjacent sampling cycles. In the two adjacent sampling cycles, the previous sampling cycle characterizes the changes in the current sampling cycle. Since the change of the reference baseline is uncertain when different cycles are used as references (for example: compared with cycle 1, the baseline of cycle 2 is in an upward state; compared with cycle 2, the reference baseline of cycle 3 is in a downward state; therefore, compared with cycle 1, the rising and falling state of the reference baseline of cycle 3 cannot reflect its true fluctuation), therefore, using the sampling data of the interval cycle as a reference, the calculated data may be distorted. The present invention determines the sampling data in the current sampling cycle through two adjacent cycles, which can make the data more accurate, and the current sampling cycle can more accurately indicate the changing dynamics of the data in the current sampling cycle compared with the previous sampling cycle, and the accuracy is higher.

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

[0043] Determine the size relationship between the sampling average value of the current sampling cycle and the sampling average value of the previous sampling cycle: if the sampling average value of the current sampling cycle is equal to the sampling average value of the previous sampling cycle, then it is determined that the dynamic baseline has no fluctuations, and the sampling signal value in the current sampling cycle is equal to the sampling average value of the current sampling cycle and the sampling average value of the previous sampling cycle. At this time, there is no difference between using the dynamic baseline for data calculation and using the reference baseline for data calculation; but if the sampling average value of the current sampling cycle is not equal to the sampling average value of the previous sampling cycle, then using the reference baseline method will obviously cause data distortion. At this time, using the dynamic baseline method for data calculation is obviously more accurate than the original method of using the reference baseline. It can also be seen that the dynamic anti-interference method described in the present invention can be applied to various different occasions and has a wider adaptability.

[0044] In the process of obtaining the infrared light signal strength in the current sampling period:

[0045] (1) Construct the coordinate system of sampling point signal value and sampling point number:

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

[0047] In the process of constructing the coordinate system, the number of sampling points of two adjacent periods and the sampling signal value corresponding to each sampling point are first obtained, and then the coordinate system is established with the number of sampling points in the current sampling period and the previous sampling period as the horizontal coordinate, the sampling signal value of each sampling point as the vertical coordinate, the number of sampling points as the horizontal coordinate, and the sampling signal value corresponding to each sampling point as the vertical coordinate.

[0048] In order to more conveniently calculate the optical signal strength of the current cycle, the middle value of the number of sampling points in the previous cycle is used as the horizontal 0 point when constructing the coordinate system. The number of sampling points in each cycle is used as the horizontal coordinate, and the sampling point signal value is used as the vertical coordinate, and these two cycles are used to calculate the data of the current sampling cycle. For example, Figure 1 In the illustrated embodiment, the horizontal axis n is the number of sampling points in each cycle, the vertical axis is the sampling point signal value corresponding to each sampling point, and the horizontal axis 0 is the middle 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. Then, 320 data 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 is an integer from 1 to 320. Figure 1When constructing the coordinate system in the illustrated embodiment, the 160th sampling point in the previous sampling period T1 is used as the horizontal coordinate value 0. The curves in the figure respectively 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.

[0050] (2) Determine the dynamic baseline equation

[0051] The dynamic baseline is a corrected reference baseline, which is a straight line in the coordinate system. Therefore, when determining the dynamic baseline equation, two points that can represent the dynamic baseline are first determined. Specifically, the middle position of the sampling point in the previous sampling cycle and the average value of the sampling point signal of the entire cycle, and the middle position of the sampling point in the current sampling cycle and the average value of the sampling point signal of the entire cycle are selected as two representative points.

[0052] (2.1) Determine representative points

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

[0054]

[0055] In formula (1), V T1-i is the sampling signal value corresponding to the i-th sampling point in the previous sampling period T1, V T2-i is the sampling signal value corresponding to the ith sampling point in the current sampling cycle T2, and N is the number of sampling points in each sampling cycle.

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

[0057] Based on two determined representative points (0, A1) and (N / 2+N / 2, A2), the dynamic baseline A1A2 and the equation corresponding to the dynamic baseline A1A2 are determined as shown in the following formula. According to the following formula, 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 formula (2), Ai is the signal value corresponding to the i-th sampling point on the dynamic baseline in the current sampling cycle, ni is the position of the i-th sampling point in the current sampling cycle, i is a positive integer, and 1≤i≤N.

[0060] by Figure 1Take the embodiment shown 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 cycle T2; A1 is the average value of the signal values ​​of 320 sampling points in the previous sampling cycle T1; A2 is the average value of the signal values ​​of 320 sampling points in the current sampling cycle T2; N is the number of sampling points in the previous sampling cycle T1 and the current sampling cycle T2, that is, N = 320. Figure 1 In the embodiment shown, the signal value Ai corresponding to the i-th sampling point on the dynamic baseline A1A2 in the current sampling period T2 is:

[0061]

[0062] In formula (3), represents the slope of the dynamic baseline A1A2, (ni+160) represents the position of the ith sampling point in the entire horizontal axis in the current sampling period T2 (the number of sampling points in the second half of the previous sampling period T1 needs to be added, that is, 160).

[0063] S2. Eliminate the baseline disturbance of the current sampling period based on the dynamic baseline equation, 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] In the calculation process, the voltage signal output by the detector can be calculated by the peak method based on the dynamic baseline equation; or the voltage signal output by the detector can be calculated by the area method based on the dynamic baseline equation. The following embodiments calculate the sampling point data based on the area method.

[0065] In the process of calculation based on the area method, the voltage signal V output by the detector in the current sampling cycle is obtained using the following formula, and the change of the dynamic baseline affected by interference factors in the current sampling cycle is characterized by this formula:

[0066] V=∑Vb-∑Vs (4)

[0067] Among them, in the current sampling cycle, when the sampling point signal value Vi corresponding to the i-th sampling point is not less than the signal value Ai of the sampling point on the dynamic baseline, the sum of all sampling point signal values ​​Vi is recorded as ΣVb; when the sampling point signal value Vi corresponding to the i-th sampling point is less than the signal value Ai of the sampling point on the dynamic baseline, the sum of all sampling point signal values ​​Vi is recorded as ΣVs.

[0068] The principle of the present invention using dynamic baseline to eliminate interference is: the external interference signal affects the reference baseline and causes the reference baseline to change, causing the reference baseline to rise or fall. If the traditional calculation method (using the original reference baseline, such as 2000 mentioned in the above embodiment) is used for calculation, the data point Vi whose signal value Ai of the i-th sampling point is not less than the original reference baseline belongs to the set Vb, and the data point Vi whose signal value Ai of the i-th sampling point is less than the original reference baseline belongs to the set Vs. The result obtained by using the set Vb and the set Vs for calculation will have a large deviation.

[0069] According to Lambert-Beer's law, the higher the gas concentration, the stronger the gas's absorption of infrared light, and the weaker the optical signal received by the detector and the electrical signal converted by the detector, that is, the sampling point signal output by the detector is negatively correlated with the gas concentration. Based on the curve of the sampling point signal value, in the sampling point signal value located above the reference baseline, the sampling point signal value of the high-concentration gas is lower than the sampling point signal value of the low-concentration gas; and in the sampling point signal value located below the reference baseline, the sampling point signal value of the high-concentration gas is higher than the sampling point signal value of the low-concentration gas.

[0070] Therefore, based on this principle, the present invention uses the dynamic baseline as a reference benchmark. If the sampling signal value Vi of the i-th sampling point is located on the dynamic baseline A1A2 or on the upper side of the dynamic baseline A1A2, when the detection gas concentration changes from low to high, its sampling signal value Vi changes from large to small (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 on the lower side of the dynamic baseline A1A2, when the detection gas concentration changes from low to high, its sampling signal value Vi changes from small to large (the data point in the coordinate system changes from low to high). Then ∑Vb-∑Vs reflects the changes in the sampling signal value affected by the gas concentration in the current sampling cycle, thereby eliminating the influence of the reference baseline disturbance caused by external interference factors.

[0071] For a single-channel detector, the voltage signal V obtained by formula (4) is normalized and processed to establish an expression corresponding to the relevant gas concentration C; for a dual-channel detector or a multi-channel detector, the voltage signal Vj (j is the number of channels, j is an integer, and j ≥ 1) can be obtained from each channel using formula (4), and the voltage signal of one channel is used as the reference signal V REF , the voltage signals of the other channels are detection signals VDi (i is an integer, and 1≤i≤j), and V REF After performing differential operation on VDi and normalizing it, an expression corresponding to the relevant gas concentration Ci is established.

[0072] Preferably, in the infrared gas sensor, the detector for receiving 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 the DAD value and the RAD value are calculated, the gas concentration value detected by the dual-channel detector can be obtained by performing a differential operation between the RAD value and the DAD value.

[0073] Both the RAD value and the DAD value can be calculated using the above formula, and the RAD value and the DAD value calculated using the above formula exclude the baseline disturbance caused by external interference. In the data processing process:

[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] Among them, in formula (5) and formula (6), V DAD is the voltage signal of the detection channel after removing the baseline disturbance factor. In the current sampling cycle 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 When all sampling point signal values ​​V DADi The sum of DAD , when the sampling point signal value V corresponding to the i-th sampling point DADi Less than the signal value A of the sampling point on the dynamic baseline DADi When all sampling point signal values ​​V DADi The sum of DAD ;

[0078] V RAD is the voltage signal of the reference channel after removing the baseline disturbance factor. In the current sampling cycle 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 When all sampling point signal values ​​V RADi The sum of DAD , when the sampling point signal value V corresponding to the i-th sampling point RADi Less than the signal value A of the sampling point on the dynamic baseline RADi When all sampling point signal values ​​V RADi The sum of RAD;

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

[0080] By using the above method, the voltage signal DAD value of the detection channel and the voltage signal RAD value of the reference channel can be calculated to eliminate the disturbance of the reference baseline caused by external interference, thereby ensuring that the entire calculation result is more accurate. In the present invention, when the infrared gas sensor is in a stable working state, the baseline equation Ai=A1=A2, at this time, the infrared gas sensor is consistent with the baseline in the traditional sensor acquisition and calculation process; when the infrared gas sensor is disturbed by the outside world and the baseline fluctuates, the calculated V RAD Value and V DAD The value can cover the situation of baseline changes. Therefore, no matter in which state the present invention is applied, the data calculation result is reliable and the data calculation is more accurate.

[0081] like Figures 2 to 7 As shown, in order to realize 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 end 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 air chamber 1 through the first cover plate through hole 201, and the detector 302 extends into the optical air chamber 1 through the second cover plate through hole 202, so that the light emitted by the infrared light source 301 is reflected multiple times in the optical air chamber 1 and reacts with the gas in the optical air chamber 1 before being received by the detector 302.

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

[0084] like Figure 2 , Figure 3As shown, the optical air chamber 1 is a structure with a hollow middle portion, and an air hole is provided at the top thereof. In order to increase the optical path length of infrared light in the optical air chamber 1 and more effectively utilize the space in the optical air chamber 1, the optical air chamber 1 in the present invention is provided with an incident parabolic reflection surface, a plurality of edge plane reflection surfaces, and an exit parabolic reflection surface in sequence, and one or more optical path extension plane reflection surfaces are further provided between the exit parabolic reflection surface and the incident parabolic reflection surface, and the optical path extension plane reflection surface is located on the opposite side of the edge plane reflection surface, so that after one optical path extension plane reflection surface receives light from one edge plane reflection surface, it reflects it to another edge plane reflection surface, so as to increase the optical path length of light in the optical air chamber.

[0085] The present invention can cooperate with the opposite edge plane reflective surface through the optical path extension plane reflective surface, fully utilize the middle part of the space in the optical gas chamber 1 to increase the optical path length, and further realize the full interaction between the gas to be measured and the light in the optical gas chamber 1, thereby improving the accuracy of gas detection.

[0086] In a specific embodiment, the edge plane reflection surface includes a first parabolic reflection surface 101, a first plane reflection surface 102, a second plane reflection surface 103, a third plane reflection surface 104, and a fourth plane reflection surface 105 which are arranged in sequence. The incident parabolic reflection surface is the first parabolic reflection surface 101, and the optical path extension plane reflection surface is the fifth plane reflection surface 106. The fifth plane reflection surface 106 is arranged between the first parabolic reflection surface 101 and the exit parabolic reflection surface, and the fifth plane reflection surface 106 is located on the opposite side of the second plane reflection surface 103 and the third plane reflection surface 104, so that the first parabolic reflection surface 101, the first plane reflection surface 102, the second plane reflection surface 103, the third plane reflection surface 104, the fourth plane reflection surface 105, the exit parabolic reflection surface, and the fifth plane reflection surface 106 are connected in sequence to form a ring and are located on the outer wall of the optical air chamber 1.

[0087] Through the provision of the fifth planar reflective surface 106 , this embodiment can fully utilize the space in the optical gas chamber 1 while minimizing the energy loss caused by multiple reflections of light, thereby fully utilizing light energy for gas detection.

[0088] In this embodiment, the outgoing parabolic reflection surface includes a second parabolic reflection surface 107 and a third parabolic reflection surface 108, so that the light reflected by the fourth plane reflection surface 105 (which can also be set as a plane reflection surface extending the light path in other embodiments) to the second parabolic reflection surface 107 is focused by the second parabolic reflection surface 107 and reflected to the third parabolic reflection surface 108.

[0089] like Figure 3 , Figure 4As shown, the light emitted by the infrared light source 301 passes through the first parabolic reflection surface 101, the first plane reflection surface 102, the third plane reflection surface 104, the fifth plane reflection surface 106, the second plane reflection surface 103, the fourth plane reflection surface 105, the second parabolic reflection surface 107 and the third parabolic reflection surface 108 in sequence and is then received by the detector 302.

[0090] The infrared light source 301 is located at the focal position of the first parabolic reflective surface 101, so that the first parabolic reflective surface 101 transmits the light emitted by the infrared light source 301 from the bottom position upward to the middle area of ​​the optical air chamber 1, and collimates the light into parallel light and reflects it to the first plane reflective surface 102; the fifth plane reflective surface 106 is used to receive the light of the third plane reflective surface 104 and reflect it to the second plane reflective surface 103, and the fifth plane reflective surface 106 can also make full use of the space in the optical air chamber 1, so that the third plane reflective surface 104 is reflected to the fifth plane reflective surface The light from the fifth plane reflection surface 106 and the light reflected from the fifth plane reflection surface 106 to the second plane reflection surface 103 can pass through the middle area in the optical air chamber 1, and this area is fully utilized to increase the optical path length and avoid the stacking of light. The second parabolic reflection surface 107 is used to focus the light reflected from the fourth plane reflection surface 105 and reflect it to the third parabolic reflection surface 108. The detector 302 is located at the focal position of the third parabolic reflection surface 108, so that the light reflected from the third parabolic reflection surface 108 can be reflected to the bottom of the optical air chamber 1 and focused to the detector 302.

[0091] Preferably, the second parabolic reflecting surface 107 and the third parabolic reflecting surface 108 are in the same focal plane, that is, the focus of the second parabolic reflecting surface 107 and the focus of the third parabolic reflecting surface 108 are located on the same longitudinal axis.

[0092] like Figure 6 , Figure 7 Two optical path states of optical air chambers for light reflection in the prior art are given. Figure 6 In the embodiment shown, the light is reflected multiple times and accumulates at the edge of the optical air chamber, while the space of the optical air chamber in the middle area is not utilized, resulting in a waste of space. Figure 7 In the embodiment shown, the light is reflected from the right side to the detector on the left side. In order to ensure the light effect, the lateral volume of the entire optical air chamber is increased as much as possible. The increase in the air chamber volume directly affects the response time of the sensor, and the internal space utilization rate is low.

[0093] like Figure 4 , Figure 5As shown, the optical gas chamber design of the infrared gas sensor of the present invention can make full use of the internal space of the optical gas chamber to achieve multiple cross reflections, increase the optical path length of the single-path reflection, and thus increase the total optical path length; and the number of reflections is less than that of the spiral gas chamber channel, thereby reducing reflection losses.

[0094] In one embodiment, the same size (standard 7) is applied to the products. Figure 6 The optical air chamber structure shown and the optical air chamber structure of the present invention can achieve an optical path length of 6 cm in comparison, while the present invention can achieve an optical path length of 10 cm, and the entire optical path length is greatly improved.

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

[0096] The above is an exemplary description of the present invention in conjunction with the accompanying drawings. It is obvious that the implementation of the present invention is not limited to the above-mentioned method. As long as various improvements are made by adopting the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A dynamic anti-interference method for an infrared gas sensor, characterized in that: include: Determine the dynamic baseline equation based on the sampling signal value of the current sampling cycle and the sampling signal value of the previous sampling cycle; 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.

2. The dynamic anti-interference method for 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 cycle and the average value of the previous sampling cycle.

3. The dynamic anti-interference method for infrared gas sensor according to claim 1 or 2, characterized in that: In determining the dynamic baseline equation: (1) Constructing a coordinate system of sampling point signal values ​​and sampling point numbers: first obtain the sampling point numbers of the current sampling point cycle and the previous sampling point cycle, and the sampling point signal value of each sampling point, and establish a coordinate system with the sampling point numbers of the current sampling point cycle and the previous sampling point cycle as the horizontal coordinate, the sampling point signal value of each sampling point as the vertical coordinate, and the middle position of the sampling point in the previous sampling point cycle as the horizontal coordinate zero point; (2) Determine the dynamic baseline equation: Among them, Ai is the signal value corresponding to the i-th sampling point in the current sampling cycle on the dynamic baseline, ni is the position of the i-th sampling point in the current sampling cycle, i is a positive integer, and 1≤i≤N, N is the number of sampling points in each sampling cycle, A1 is the average value of the previous sampling cycle, and A2 is the average value of the current sampling cycle.

4. The dynamic anti-interference method for 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 a peak value method or an area method.

5. The dynamic anti-interference method for infrared gas sensor according to claim 4, characterized in that: In the current sampling cycle, when the sampling signal value Vi corresponding to the ith sampling point is not less than the signal value Ai of the sampling point on the dynamic baseline, the sum of all the sampling signal values ​​Vi is recorded as ΣVb; when the sampling signal value Vi corresponding to the ith sampling point is less than the signal value Ai of the sampling point on the dynamic baseline, the sum of all the sampling signal values ​​Vi is recorded as ΣVs. The voltage signal output by the detector in the current sampling cycle is obtained using the following formula, and the change of the dynamic baseline affected by interference factors in the current sampling cycle is characterized: V = ΣVb-ΣVs.

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

7. The dynamic anti-interference method for infrared gas sensor according to claim 1, characterized in that: The infrared gas sensor comprises an optical gas chamber, wherein an incident parabolic reflection surface, a plurality of edge plane reflection surfaces, and an exit parabolic reflection surface are sequentially arranged on the inner wall of the optical gas chamber, and one or more optical path extension plane reflection surfaces are arranged between the exit parabolic reflection surface and the incident parabolic reflection surface, and the optical path extension plane reflection surface is located on the opposite side of the edge plane reflection surface. One of the optical path extension plane reflection surfaces is used to receive light from one of the edge plane reflection surfaces and reflect it to another edge plane reflection surface to increase the optical path length of the light in the optical air chamber.

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