CN114486796A - NDIR multi-component gas detection module - Google Patents
NDIR multi-component gas detection module Download PDFInfo
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Abstract
The invention discloses an NDIR multi-component gas detection module, which adopts a thermal detector with a plurality of detection units based on an optical antenna, wherein each detection unit adopts optical antenna structures with different sizes, has the functions of narrow-band absorbers with different wave bands, and can simultaneously realize the detection of various gases; the light with specific wavelength is selectively absorbed by the gas and reaches the narrow-band absorber of the optical antenna, the narrow-band absorber generates heat after absorbing the light, and then the light is detected by the lower heat detector and converted into a voltage signal, and the corresponding gas concentration is obtained according to the signal. The thermal detector based on the optical antenna adopts an antenna array structure, so that the whole volume of the detector can be greatly reduced, and the detection precision is improved; different antenna arrays correspond to different wavelength channels, so that the cost difference is small, and the cost can be well saved; the arrayed structure can simultaneously realize real-time measurement of the multi-component gas and is suitable for real-time analysis of the multi-component gas.
Description
Technical Field
The invention belongs to the field of gas detection, and particularly relates to an NDIR multi-component gas detection module.
Background
The Non-dispersive infrared (NDIR) technology utilizes infrared light for detection, and has the advantages of real-time monitoring, wide detection range, low maintenance cost, long service life and the like, so that the method is widely applied. The traditional NDIR detection system mainly comprises a wide-spectrum light source, an air chamber, an optical filter, a detector and a signal processing circuit. The principle is mainly that the optical filter is used for filtering out light with specific wavelength absorbed by gas, and then the thermal detector generates corresponding response. The response is proportional to the gas concentration according to the Belrongbo law, and the gas concentration can be obtained through certain algorithm processing.
The traditional multi-gas detector adopts a mode that narrow-band filters with different wave bands are placed at the TO pipe cap in front of the detector TO filter out light with specific wavelength. The optical filter has certain limitations, such as angle sensitivity, and needs to operate at a specific incident angle, because the principle of the optical filter is an optical thin film interference effect. If the incident angle is changed, the problems of resonant wavelength drift, filter channel widening, transmittance reduction and the like can be caused, so that the detection precision is influenced; the whole volume of the module can be increased due to the separated design, and integration is not facilitated; in addition, due to the design principle limitation of the narrow-band filter, the price difference between different filters is large, which causes the increase of production cost.
Disclosure of Invention
Aiming at the defects or the improvement requirements of the prior art, the invention provides the NDIR multi-component gas detection module, so that the technical problems that the detection precision of the conventional multi-gas detector is easily influenced, the size is large, the integration is not facilitated and the cost is high are solved.
To achieve the above object, according to one aspect of the present invention, there is provided an NDIR multi-component gas detection module, comprising: the device comprises a light source, an air chamber, a thermal detector based on an optical antenna and a signal processing unit;
the air chamber is arranged in the emergent light direction of the light source;
the thermal detector is used for receiving the light beams emitted from the air chamber and comprises a plurality of detection units distributed in an array manner, wherein the absorption wave bands of the optical antennas in the detection units are different;
the signal processing unit is connected with the heat detector and used for processing output signals of the heat detector to obtain the type and concentration of the gas to be detected.
Preferably, the gas cell comprises a first through hole, an optical channel and a second through hole; the optical channel comprises a first arc reflecting groove, a second arc reflecting groove and a third arc reflecting groove;
emergent light of the light source enters the optical channel through the first through hole to be reflected for multiple times and then is emitted through the second through hole.
Preferably, the detection unit comprises an optical antenna, a thermal detector and a substrate layer from top to bottom.
Preferably, the gas cell further comprises at least one gas conducting channel connected to the optical channel.
Preferably, the thermal detector is a thermopile detector, a pyroelectric detector or a microbolometer.
Preferably, the air chamber is made of brass or resin; the inner wall of the air chamber is plated with polytetrafluoroethylene, barium sulfate or magnesium oxide, and the inner surface of the air chamber is polished.
Preferably, the optical antenna based thermal detector further comprises at least one reference unit, and the reference unit comprises a thermal detector and a substrate layer from top to bottom.
Preferably, a heat insulation groove is arranged between the detection units.
Preferably, the light source is a MEMS infrared light source.
Preferably, the optical antenna is of a disc type or a cross type.
In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:
1. the NDIR multi-component gas detection module provided by the invention adopts a thermal detector with a plurality of detection units based on an optical antenna, and when the detection units adopt optical antenna structures with different sizes, the detection modules have the functions of narrow-band absorbers with different wave bands, and can simultaneously realize the detection of various gases; the light with specific wavelength selectively absorbed by the gas reaches the optical antenna narrow-band absorber, the narrow-band absorber absorbs the light and generates heat, the heat is detected by the heat detector below and converted into a voltage signal, and the corresponding gas concentration is obtained through subsequent signal processing. Compared with the defects of complex design, increased volume, unfavorable overall integration of a system, high manufacturing cost and the like caused by the mode that narrow-band filters with different wave bands are placed at the TO pipe cap in front of the detector in the traditional multi-gas detector, the NDIR multi-component gas detection module provided by the invention adopts an optical antenna-based thermal detector and an antenna array structure, so that the overall volume of the detector can be greatly reduced, and the detection precision is improved; different antenna arrays correspond to different wavelength channels, so that the cost difference is small, and the cost can be well saved; the arrayed structure can simultaneously realize real-time measurement of the multi-component gas and is suitable for real-time analysis of the multi-component gas.
2. According to the NDIR multi-component gas detection module, the reference channel is introduced into the thermal detector based on the optical antenna, the reference channel is the thermal detector without the antenna array, a new reference channel compensation mode is provided, influences caused by factors such as environment temperature change and air disturbance are basically consistent for all detectors, and the detectors without the antenna array cannot respond to light with specific wavelength. Therefore, the influence of other noises on the system can be reduced by increasing the reference channel, the measurement accuracy and sensitivity of the whole system can be further improved by algorithm processing, and the influence of relevant noises such as environment and the like is reduced.
3. According to the NDIR multi-component gas detection module, the three-folding type gas chamber is designed based on the principle of the integrating sphere type gas chamber, and the optical path of the gas chamber can be greatly prolonged. According to the Law of Erronbo, the long-optical-path gas chamber is more favorable for realizing the detection of low-concentration gas, and the long-optical-path gas chamber can realize lower detection lower limit; in addition, the optical antenna thermopile detector provided by the invention has good angular insensitivity, and the influence of light incidence at different angles on the detector is small. Therefore, the three-folding type air chamber provided by the invention can improve the detection limit lower limit of the whole system, is beneficial to the miniaturization and integration of the NDIR module, and can correspondingly change the relevant parameters of the optical antenna according to the gas to be detected, so that the module can be applied to more scenes.
Drawings
FIG. 1 is a schematic diagram of a NDIR-based multi-component gas detection module according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of an optical antenna based thermal detector according to an embodiment of the present invention;
FIG. 3 is an enlarged view of a single detection unit of the optical antenna based thermal detector provided in an embodiment of the present invention;
FIG. 4 is a cross-sectional view of a plenum provided by an embodiment of the present invention;
FIG. 5 is one of the top views of a plenum provided by embodiments of the present invention;
FIG. 6 is a second top view of the air chamber provided in the embodiment of the present invention;
fig. 7 is a third top view of the air chamber according to the embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
An embodiment of the present invention provides an NDIR multi-component gas detection module, as shown in fig. 1, including: the device comprises a light source 1, a gas chamber, a heat detector 2 based on an optical antenna and a signal processing unit.
Specifically, the NDIR module proposed by the present invention is composed of four parts: a light source, a gas cell, an optical antenna based thermal detector 2 (i.e. a multi-channel optical antenna narrowband thermal detector), a signal processing circuit.
The wave band emitted by the light source covers the absorption spectrum line of the detected gas, and the incident light is an infrared wave band.
Preferably, the light source is a MEMS infrared light source.
Specifically, the light source is an MEMS infrared light source, and the MEMS light source has good stability and long service life and can work for a long time. Meanwhile, the MEMS light source can also be modulated, and the pyroelectric detector and the thermopile detector can be adapted simultaneously. The light-gathering device is arranged around the light source, so that the emitted light can be collimated.
The air chamber is arranged in the emergent light direction of the light source;
the thermal detector is used for receiving the light beams emitted from the air chamber and comprises a plurality of detection units distributed in an array manner, wherein the absorption wave bands of the optical antennas in the detection units are different;
the signal processing unit is connected with the heat detector and used for processing output signals of the heat detector to obtain the type and concentration of the gas to be detected.
Specifically, light rays reach the inner wall of the air chamber after being emitted from the light source, the air chamber is reserved with a light inlet and a light outlet, the air chamber is internally plated with a Lambertian material, and the entering light is subjected to diffuse reflection, so that the optical path increase of a large degree is realized, and the absorption of the gas in the air chamber is increased.
The detector is an optical antenna heat detector with an array structure, and the type and the concentration of the gas to be detected are obtained by performing data processing on the signal processing unit after the infrared light is responded.
The thermal detector based on the optical antenna is used for receiving light beams emitted from the air chamber and comprises a plurality of detection units distributed in an array mode, wherein the absorption wave bands of the optical antenna in the detection units are different.
Specifically, the adopted detector is an array type optical antenna narrow-band heat detector, and can be used for detecting various target gases at the same time. The sensitive source of the heat detector is covered with an optical antenna. The optical antenna functions as a narrow-band absorption, i.e., has selective transmittance for light of a specific wavelength. The size of the antenna is adjusted to realize the absorption of light with different wavelengths, so that the concentration detection of different gases is realized, and the type and the concentration of the gas to be detected are obtained after the electric signal generated by the detector is subjected to signal processing.
The optical antenna is a resonant optical antenna, namely an optical resonant cavity, namely an optical antenna is an electromagnetic wave antenna with an optical frequency band; the optical antennas are arranged in an array mode and used for absorbing light, and absorption wave bands of the optical antenna arrays are different.
The optical antenna of each detection unit is used for realizing the function of narrow-band absorption, thereby realizing the detection effect on the light with the specific wavelength. Because the absorption wave bands of the optical antennas in the detection units are different, the thermal detector based on the optical antennas (namely, the multi-channel optical antenna narrow-band thermal detector) provided by the invention can realize the response to various gases.
Preferably, the detection unit comprises an optical antenna, a thermal detector and a substrate layer from top to bottom.
Preferably, the optical antenna based thermal detector further comprises at least one reference unit, and the reference unit comprises a thermal detector and a substrate layer from top to bottom.
Specifically, taking 3 × 3 optical antenna array as an example, as shown in fig. 2, the optical antenna narrowband thermal detector has 8 detection units, and the absorption wavelength bands of the optical antennas in the detection units are different, so that detection of 8 different gases can be realized, that is, 8-channel gas detectors respectively correspond to eight different gases.
Taking the detection unit 22 as an example, the detection unit includes an optical antenna, a thermal detector and a substrate layer from top to bottom.
By designing optical antennas with different parameters, the period (namely the distance between the two cross antennas), the length, the width and the like of the cross structure are adjusted, the optical antennas can realize narrow-band absorption effects with different wavelengths, and a heat detector such as a thermopile or pyroelectric detector is arranged below each optical antenna. The substrate with the heat insulating groove is arranged below the detector, and a metal material can be used.
Preferably, as shown in fig. 3, the detection units have heat insulation slots therebetween.
A plurality of heat insulation slots, such as the heat insulation slot 23, are distributed around the detection unit 22, and mainly play a role in isolating heat and reducing crosstalk.
While a reference channel (i.e. reference unit) 24 without an optical antenna is placed, i.e. the reference channel 24 is not covered by an optical antenna structure. Because the optical antenna structure is not designed, the optical antenna structure has no wavelength sensitivity, and the main reason influencing the signal is interference factors such as environment and the like, so the channel can be used as a reference channel, and the stability of the whole system is improved. When the NDIR module is operating, ambient temperature changes, airflow disturbances, etc. all contribute noise to the system, which affects the reference channel and the remaining eight gas channels equally. And the final gas corresponding concentration can be obtained by combining the reference channel and the target gas channel for data processing, so that the overall accuracy of the system can be increased.
In addition, different channels of the detector can be mutually used as reference channels, so that the accuracy of single gas detection can be improved while the simultaneous measurement of multiple gases is realized, the interference of factors such as environment and the like can be favorably eliminated, and the stability of the whole system is improved.
The signal processing unit is connected with the heat detector and used for processing output signals of the heat detector to obtain the type and concentration of the gas to be detected.
Specifically, the signal processing unit performs filtering amplification, ADC data acquisition and MCU signal processing on the voltage response generated by the thermal detector to obtain the corresponding gas type and gas concentration.
Preferably, the thermal detector is a thermopile detector, a pyroelectric detector or a microbolometer.
Further, the thermal detector based on the optical antenna provided by the embodiment of the invention adopts a TO package, thereby playing a role in protecting the interior of the detector. The window of the package is made of materials with high transmittance for infrared bands, such as sapphire, silicon dioxide or a high-pass filter.
Furthermore, a thermistor is arranged near the detector chip, and the detected temperature and the algorithm play a role in temperature compensation.
According to the NDIR multi-component gas detection module provided by the embodiment of the invention, the angle-insensitive optical antenna detector is adopted, and a plurality of detection units are integrated on the surface of the detector, so that gases with various components can be synchronously analyzed in real time, and the NDIR multi-component gas detection module is suitable for multi-component gas analysis; the detector is additionally provided with a reference channel, and the influence of noise such as environment and the like can be reduced through the reference channel, so that a more accurate gas concentration analysis result is finally obtained.
Most conventional NDIR gas detection modules employ filters to filter out light of a specific wavelength. Because the optical filter has angular sensitivity, a certain incident angle needs to be maintained, otherwise, the conditions of wavelength drift, passing rate reduction and the like caused by interference effect occur. Therefore, the miniaturized NDIR module mostly adopts a straight-through type air chamber or a single reflection type air chamber to ensure that light rays are mostly vertical incidence, the optical path corresponding to the designed air chamber is small, the detection lower limit of the whole system is limited, the detection lower limit of the NDIR module is greatly influenced by the optical path, and the module with the short optical path can only be used for detecting high-concentration gas.
To this end, preferably, the gas cell includes a first through hole, an optical channel, and a second through hole; the optical channel comprises a first arc reflecting groove, a second arc reflecting groove and a third arc reflecting groove;
emergent light of the light source enters the optical channel through the first through hole to be reflected for multiple times and then is emitted through the second through hole.
Specifically, wide spectrum light source light is from light source 1, and inside reaching the air chamber after first through-hole 3, the air chamber is inside to be plated with lambert material polytetrafluoroethylene, can realize the diffuse reflection to light, and light gets into and can produce diffuse reflection on its inner wall after the air chamber promptly, and optical path is prolonged greatly. The diffuse reflection broad spectrum light is continuously reflected in the gas chamber, the light with specific wavelength is absorbed by corresponding gas, finally, the signal light reaches the multichannel optical antenna thermal detector through the second through hole 4 to generate corresponding voltage response, and the signal processing unit carries out filtering amplification, ADC data acquisition and MCU signal processing on the voltage response to obtain corresponding gas types and gas concentrations.
Preferably, the light source is fixed on the first through hole 3 by gluing or adding a sealing ring.
Further, as shown in fig. 1, the overall shape of the gas cell is rectangular, and the shape of the internal optical channel is a triple-folding type, so as to realize multiple reflections of light and extend the optical path.
The radiuses of the three arc-shaped reflecting grooves can be the same or different; as shown in fig. 4-5, the radii of the three circular arc-shaped reflecting grooves are the same; as shown in fig. 6, the radii of the three circular arc-shaped reflecting grooves are different, wherein the radii of the two circular arc-shaped reflecting grooves positioned at the outer side are smaller than the radius of the circular arc-shaped reflecting groove positioned at the middle part; it is understood that the radii of the three circular arc-shaped reflecting grooves may be different from each other.
Further, as shown in fig. 4, light emitted from the light source enters the air chamber from the first through hole 3, the air chamber is a three-fold air chamber, and a first arc reflecting groove 19, a second arc reflecting groove 20 and a third arc reflecting groove 21 are arranged in the air chamber; the first arc reflecting groove 19 and the third arc reflecting groove 21 are arranged on the same side, and the second arc reflecting groove 20 and the first arc reflecting groove 19 are arranged oppositely; the three reflecting grooves can enable incident light to be reflected and finally reach the detector through the second through hole 4, and the effect of prolonging the optical path can be achieved. Through light path software simulation, the air chamber can achieve the effect of prolonging the process by more than 6 times compared with a straight-through air chamber with the same length, and the detection precision of the NDIR module is favorably improved.
An infrared wide-spectrum light source is adopted, and modulated light is generated and enters the air chamber through MCU control. The modulated light enters the air chamber to generate diffuse reflection, and the air chamber made of the lambo material can greatly prolong the optical path, so that the detection lower limit of the whole module is improved. The detector is an angle insensitive optical antenna narrow-band heat detector, and light is selectively absorbed by corresponding gas through the gas chamber. After reaching the optical antenna narrow-band absorber, light with a specific wavelength is absorbed by a specific detection chip, converted into heat and then converted into an electrical signal. And (3) amplifying and filtering through the front end, performing AD conversion, then obtaining the gas concentration through signal processing, and calculating by using the corrected Belrongbo law.
Preferably, the light source and the detector are mounted on the same side of the gas cell.
The light with specific wavelength is selectively absorbed by the corresponding gas to generate attenuation in the process that the wide-spectrum light emitted by the light source is continuously emitted in the gas chamber, and finally reaches the narrow-band heat detector of the optical antenna to generate a corresponding voltage signal.
Preferably, the gas cell further comprises at least one gas conducting channel connected to the optical channel.
Specifically, the gas chamber cavity has designed the air guide passageway, as gas diffusion groove (be the air guide groove) for exchange with between the external gas, the one end of air guide groove with the cavity of air chamber is connected, and the other end is connected with the external world for guide gas that awaits measuring gets into the air chamber, with detect its kind and concentration.
Preferably, a waterproof breathable film is arranged at one end, connected with the outside, of the air guide channel, so that the air chamber and the outside are subjected to gas exchange, and meanwhile, water vapor is prevented from entering the air chamber to generate interference on a detection result.
Taking the air chamber shown in fig. 1 as an example, the air chamber has four air guide channels, i.e., a first air guide channel to a fourth air guide channel 15-18. Waterproof breathable films 13 and 14 are respectively arranged at the ends of the first air guide channel 15 and the fourth air guide channel 18 connected with the outside, and waterproof breathable films, not shown, are also respectively arranged at the ends of the second air guide channel 16 and the third air guide channel 17 connected with the outside.
Preferably, as shown in fig. 4-7, the air guide channel is inclined to reduce the loss of the light source.
Preferably, the air chamber is made of brass or resin; the inner wall of the air chamber is plated with polytetrafluoroethylene, barium sulfate or magnesium oxide, and the inner surface of the air chamber is polished.
Specifically, the inner surface of the air chamber is polished and plated with polytetrafluoroethylene, barium sulfate, magnesium oxide or other Lanbo materials, so that diffuse reflection of incident light can be realized, and the optical path can be greatly prolonged.
In order to facilitate the internal coating treatment of the gas chamber, as shown in fig. 2, the gas chamber is integrally divided into an upper part and a lower part, which can be 3D printed by using resin or made of brass, and the coating treatment is performed after the preparation. The bottom of the upper half part is plated with Lanbo materials, and four corners of the upper half part are respectively provided with a first fixing column to a fourth fixing column 5-8; the lower part is internally plated with a Lunebo material and has first to fourth fixing holes 9-12 corresponding to the fixing posts of the upper part. The upper and lower parts can be glued after the coating is finished. The gas conduction groove is arranged at the lower half part.
Preferably, the optical antenna is of a disc type or a cross type.
Specifically, the antenna structure used is metal; the adopted optical antenna can be a disk type or cross type optical antenna which is independent of polarization and insensitive to angle
According to the NDIR multi-component gas detection module provided by the embodiment of the invention, the three-folding type gas chamber is designed based on the integrating sphere type gas chamber principle, so that the optical path can be greatly prolonged, the detection lower limit of the whole module is increased, and the detection precision and sensitivity are improved.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (10)
1. An NDIR multi-component gas detection module, comprising: the device comprises a light source, an air chamber, a thermal detector based on an optical antenna and a signal processing unit;
the air chamber is arranged in the emergent light direction of the light source;
the thermal detector is used for receiving the light beams emitted from the air chamber and comprises a plurality of detection units distributed in an array manner, wherein the absorption wave bands of the optical antennas in the detection units are different;
the signal processing unit is connected with the heat detector and used for processing output signals of the heat detector to obtain the type and concentration of the gas to be detected.
2. The NDIR multi-component gas detection module of claim 1, wherein said gas chamber comprises a first through hole, an optical channel, and a second through hole; the optical channel comprises a first arc reflecting groove, a second arc reflecting groove and a third arc reflecting groove;
emergent light of the light source enters the optical channel through the first through hole to be reflected for multiple times and then is emitted through the second through hole.
3. The NDIR multi-component gas detection module of claim 2, wherein said detection unit comprises a top-down optical antenna, a thermal detector and a substrate layer.
4. The NDIR multi-component gas detection module of claim 2, wherein said gas chamber further comprises at least one gas-conducting channel connected to said optical channel.
5. The NDIR multi-component gas detection module of claim 2, wherein the thermal detector is a thermopile detector, a pyroelectric detector, or a microbolometer.
6. The NDIR multi-component gas detection module of claim 2, wherein the gas chamber is made of brass or resin; the inner wall of the air chamber is plated with any one of polytetrafluoroethylene, barium sulfate or magnesium oxide, and the inner surface of the air chamber is polished.
7. The NDIR multi-component gas detection module of claim 1, wherein the optical antenna based thermal detector further comprises at least one reference cell, the reference cell comprising a top-to-bottom thermal detector and a substrate layer.
8. The NDIR multi-component gas detection module according to claim 1 or 7, wherein there is a thermally insulating tank between each detection unit.
9. The NDIR multi-component gas detection module of claim 1, wherein the light source is a MEMS infrared light source.
10. The NDIR multi-component gas detection module of claim 1, wherein the optical antenna is disk-shaped or cross-shaped.
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| CN116879215A (en) * | 2023-07-18 | 2023-10-13 | 上海苏萨电子科技有限公司 | Non-dispersive infrared gas sensor |
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| CN116879215A (en) * | 2023-07-18 | 2023-10-13 | 上海苏萨电子科技有限公司 | Non-dispersive infrared gas sensor |
| CN116879215B (en) * | 2023-07-18 | 2024-04-09 | 上海苏萨电子科技有限公司 | Non-dispersive infrared gas sensor |
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