A small infrared gas sensor and its working method

Abstract

The present invention relates to the technical field of gas sensors, and discloses a small infrared gas sensor and a working method. It includes an optical path upper cover, a bottom of the optical path upper cover is provided with an optical path bottom cover, a bottom of the optical path bottom cover is provided with a signal amplification circuit board, a bottom of the signal amplification circuit board is provided with a signal processing circuit board. A groove optical path is opened at the bottom of the optical path upper cover, and an optical path upper cover air vent one, an optical path upper cover air vent two, an optical path upper cover air vent three and an optical path upper cover air vent four are opened inside the groove optical path. An optical path threaded fixing hole one and an optical path threaded fixing hole two are opened on an outer side wall of the optical path upper cover. This small infrared gas sensor can achieve a large optical path with a small volume, so that the infrared light emitted by an infrared light source at one end can be reflected and converged to the infrared pyroelectric probe as much as possible, achieving the purposes of miniaturization, low power consumption and high precision of the sensor.

Description

Technical Field

[0001] The present invention relates to the technical field of gas sensors, and in particular to a small infrared gas sensor and a working method thereof. Background Art

[0002] With the development of society, industrial gases are more and more widely used, and the demand for gas sensors is also continuously expanding. In the traditional coal mine and oil field industries, there is a high possibility of the existence of natural toxic and explosive gases such as methane and carbon monoxide. If the concentration exceeds the standard, it will pose a great threat to the lives of workers. Therefore, a large number of gas sensors are equipped to monitor the working environment to ensure the safety of personnel. At the same time, in order to detect gas leakage, more and more chemical plants and residential houses are also beginning to be equipped with various gas sensors to ensure safety. As an important guarantee for environmental safety, gas sensors have a huge market demand and are gradually developing towards the direction of being small and low-power. Currently, the commonly used gas sensors mainly have measurement principles such as catalytic combustion type, electrochemistry type, non-dispersive infrared type, etc.

[0003] Catalytic combustion type sensors mainly measure the target gas based on the Wheatstone bridge principle. When the sensor is in the air, the bridge is balanced and the output voltage is 0. When combustible gas is introduced, a special resistance wire will undergo a catalytic combustion reaction to break the bridge balance and the output voltage increases. Such sensors have a relatively low cost, but the readings are easily affected by temperature and humidity, high-resolution measurement cannot be performed, and regular calibration is required. At the same time, all combustible gases can undergo catalytic combustion reactions, so the sensor cannot distinguish the types of gases.

[0004] Electrochemical gas sensors mainly generate an electrochemical reaction between the target gas and the internal chemical electrolyte to generate a tiny voltage for detection purposes. Such sensors have good gas selectivity, but are prone to zero drift and require regular calibration. At the same time, the lifespan of the sensor is not long, generally about 2 years.

[0005] Non-dispersive infrared gas sensor (NDIR gas sensor) mainly measures the target gas based on Lambert-Beer law. The sensor mainly consists of an optical path, an infrared light source, an infrared receiving probe and an amplification circuit board. The target gas to be measured should be non-polar gas (such as methane, carbon monoxide, carbon dioxide, etc.). Such gases have an absorption effect on infrared light of a fixed band. When the target gas exists, the light intensity of the infrared light relative to the band will be weakened. The working principle process of such a sensor is as follows: The infrared light source and the infrared receiving probe are installed in the optical path module. The inside of the optical path module is gold-plated and has a special channel structure. The infrared light emitted by the infrared light source can be reflected and conducted in the optical path to the infrared receiving probe. The receiving probe integrates a filter for the absorption band of the target gas, ensuring that the probe only receives the infrared light intensity at the absorption peak of the target gas. The probe converts the light intensity into a voltage signal and amplifies and calculates the gas concentration by the amplification circuit board. Due to the narrow-band filter of the probe, such a sensor has the best selectivity for the target gas, and the measurement result will not be affected by other gases. At the same time, it has better anti-interference ability than the catalytic combustion type sensor and is not affected by temperature and humidity. The theoretical service life is more than 5 years, and it is currently the gas sensor with the best comprehensive performance.

[0006] In the current field of infrared gas sensing, in order to obtain accurate measurement results, it is often necessary to increase the amplification factor and improve the signal voltage output by the circuit. However, increasing the amplification factor also amplifies the noise, resulting in a decline in the performance of the sensor. Therefore, it is necessary to improve the output of the infrared probe from the source. The most direct way to improve the probe output is to increase the supply voltage of the infrared light source to generate stronger infrared light. However, the greater the luminous intensity, the greater the power consumption, which does not conform to the current development trend of low-power sensors. At the same time, the internal heat accumulation problem will also affect the long-term stability of the sensor. Another way to improve the probe output is to modify and optimize the optical path structure. The longer the optical path, the more obvious the gas absorption effect, but multiple reflections will increase the loss of infrared light. Therefore, designing a long optical path structure under the limitation of small volume to ensure that as much infrared light as possible converges on the infrared probe is the most important design difficulty of the current infrared gas sensor. For this reason, a small infrared gas sensor is proposed to solve the problems existing in the above background. Summary of the Invention

[0007] The purpose of the present invention is to provide a small infrared gas sensor and its working method to solve the problems put forward in the above background technology.

[0008] To solve the above technical problems, the present invention provides the following technical solution: A small infrared gas sensor includes an optical path upper cover. The bottom of the optical path upper cover is provided with an optical path bottom cover. The bottom of the optical path bottom cover is provided with a signal amplification circuit board. The bottom of the signal amplification circuit board is provided with a signal processing circuit board;

[0009] A groove optical path is provided at the bottom of the upper cover of the optical path. Inside the groove optical path, a first air vent hole of the upper cover of the optical path, a second air vent hole of the upper cover of the optical path, a third air vent hole of the upper cover of the optical path, and a fourth air vent hole of the upper cover of the optical path are provided. A first threaded fixing hole of the optical path and a second threaded fixing hole of the optical path are provided on the outer side wall of the upper cover of the optical path;

[0010] An infrared pyroelectric probe fixing hole is provided at the bottom of the bottom cover of the optical path. A third threaded fixing hole of the optical path and a fourth threaded fixing hole of the optical path are provided on the outer side wall of the bottom cover of the optical path. An infrared light source fixing hole is also provided on the outer side wall of the bottom cover of the optical path;

[0011] An infrared light source is fixedly connected to the top of the signal amplification circuit board. An infrared pyroelectric probe is also fixedly connected to the top of the signal amplification circuit board. A reference infrared band filter and a target gas infrared band filter are respectively fixedly connected to the top of the infrared pyroelectric probe. The reference infrared band filter is a 3.95um band filter, and the target gas infrared band filter is a 3.5um band filter. The infrared light source and the infrared pyroelectric probe are located at both ends of the groove optical path;

[0012] A first circuit board connection terminal and a second circuit board connection terminal are respectively fixedly connected to the top of the signal processing circuit board. A debugging connection terminal, a power supply and data transmission connection terminal, and a power supply and signal processing circuit element are respectively fixedly connected to the bottom of the signal processing circuit board. The signal amplification circuit board and the signal processing circuit board are fixedly connected by combining the first circuit board connection terminal and the second circuit board connection terminal.

[0013] Preferably, the first threaded fixing hole of the optical path and the second threaded fixing hole of the optical path are respectively arranged corresponding to the third threaded fixing hole of the optical path and the fourth threaded fixing hole of the optical path. The first threaded fixing hole of the optical path and the third threaded fixing hole of the optical path, and the second threaded fixing hole of the optical path and the fourth threaded fixing hole of the optical path are connected by bolts.

[0014] Preferably, the infrared light source fixing hole is adapted to the infrared light source. The infrared light source is inserted into the infrared light source fixing hole and extends above the infrared light source fixing hole, and the top end of the infrared light source is adapted to one end of the groove optical path.

[0015] Preferably, the infrared pyroelectric probe fixing hole is adapted to the infrared pyroelectric probe. The infrared pyroelectric probe is inserted into the infrared pyroelectric probe fixing hole.

[0016] A working method of a small infrared gas sensor is as follows:

[0017] S1. The signal processing circuit board emits a signal to drive the infrared light source to work. The infrared light source and the pyroelectric infrared detector are located at both ends of the groove optical path. When the infrared light source emits infrared light, the infrared light is concentrated and reflected in the groove optical path and conducted to the location of the pyroelectric infrared detector at the other end.

[0018] S2. The pyroelectric infrared detector has two input windows for receiving infrared light, and a filter with a specific wavelength band is provided on each window. The reference infrared band filter is a 3.95um band filter, and the target gas infrared band filter is a 3.5um band filter. The target gas is methane.

[0019] S3. The infrared light source emits broadband infrared light with a wavelength range of 3um - 5um. After being reflected and conducted through the groove optical path, the light irradiates on the pyroelectric infrared detector. Due to the effect of the two-channel filters, only the 3.95um infrared light is received by the reference channel, and only the 3.5um infrared light is received by the measurement channel.

[0020] S4. After receiving the infrared light, the pyroelectric infrared detector converts the light signal into an electrical signal, which is amplified by the components of the signal amplification circuit board and transmitted to the signal processing circuit board through the circuit board connection terminal 1 for signal processing and analysis.

[0021] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0022] First, the internal of the present invention is an arc-shaped groove optical path, which can achieve a large optical path in a small volume, so that the infrared light emitted by the infrared light source at one end is reflected and converged to the pyroelectric infrared detector as much as possible. Using a low-power light source effectively enhances the original signal of the pyroelectric infrared detector, achieving the purpose of miniaturization, low power consumption, and high precision of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic diagram of the overall structure of the present invention;

[0024] Figure 2 is an exploded schematic diagram of the upper view structure of the present invention;

[0025] Figure 3 is an exploded schematic diagram of the lower view structure of the present invention;

[0026] Figure 4 is a schematic diagram of the optical path bottom plate structure of the present invention

[0027] Figure 5 is a schematic diagram of the optical path upper cover structure of the present invention.

[0028] Wherein: 10, upper optical path cover; 11, first upper optical path cover ventilation hole; 12, first optical path threaded fixing hole; 13, second optical path threaded fixing hole; 14, groove optical path; 15, second upper optical path cover ventilation hole; 16, third upper optical path cover ventilation hole; 17, fourth upper optical path cover ventilation hole; 20, lower optical path cover; 21, infrared pyroelectric probe fixing hole; 22, third optical path threaded fixing hole; 23, fourth optical path threaded fixing hole; 24, infrared light source fixing hole; 30, signal amplification circuit board; 31, infrared light source; 32, infrared pyroelectric probe; 321, reference infrared band filter; 322, target gas infrared band filter; 40, signal processing circuit board; 41, first circuit board connection terminal; 42, second circuit board connection terminal; 43, debugging connection terminal; 44, power supply and data transmission connection terminal; 45, power supply and signal processing circuit components. Specific Embodiment

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0030] Embodiment 1

[0031] This embodiment is a specific implementation manner of a small infrared gas sensor.

[0032] Please refer to Figures 1-5 , a small infrared gas sensor, including an upper optical path cover 10, a lower optical path cover 20 is provided at the bottom of the upper optical path cover 10, a signal amplification circuit board 30 is provided at the bottom of the lower optical path cover 20, and a signal processing circuit board 40 is provided at the bottom of the signal amplification circuit board 30;

[0033] A groove optical path 14 is opened at the bottom of the upper optical path cover 10. A first upper optical path cover ventilation hole 11, a second upper optical path cover ventilation hole 15, a third upper optical path cover ventilation hole 16, and a fourth upper optical path cover ventilation hole 17 are opened inside the groove optical path 14. A first optical path threaded fixing hole 12 and a second optical path threaded fixing hole 13 are opened on the outer side wall of the upper optical path cover 10;

[0034] An infrared pyroelectric probe fixing hole 21 is opened at the bottom of the lower optical path cover 20. A third optical path threaded fixing hole 22 and a fourth optical path threaded fixing hole 23 are opened on the outer side wall of the lower optical path cover 20. An infrared light source fixing hole 24 is also opened on the outer side wall of the lower optical path cover 20;

[0035] An infrared light source 31 is fixedly connected to the top of the signal amplification circuit board 30. An infrared pyroelectric detector 32 is also fixedly connected to the top of the signal amplification circuit board 30. A reference infrared band filter 321 and a target gas infrared band filter 322 are respectively fixedly connected to the top of the infrared pyroelectric detector 32. The reference infrared band filter 321 is a 3.95um band filter, while the target gas infrared band filter 322 is a 3.5um band filter. The infrared light source 31 and the infrared pyroelectric detector 32 are located at both ends of the groove optical path 14;

[0036] A circuit board connection terminal one 41 and a circuit board connection terminal two 42 are respectively fixedly connected to the top of the signal processing circuit board 40. A debugging connection terminal 43, a power supply and data transmission connection terminal 44, and a power supply and signal processing circuit element 45 are respectively fixedly connected to the bottom of the signal processing circuit board 40. The signal amplification circuit board 30 and the signal processing circuit board 40 are fixedly connected by combining the circuit board connection terminal one 41 and the circuit board connection terminal two 42.

[0037] The signal processing circuit board 40 and the signal amplification circuit board 30 are connected by combining the circuit board connection terminal one 41 and the circuit board connection terminal two 42, which is used for the signal processing circuit board 40 to supply power to the signal amplification circuit board 30, drive the infrared light source to work, and transmit the signal of 930 to the signal processing circuit board 40 for analysis and processing.

[0038] Through the above technical solution, the optical path upper cover 10, the optical path bottom cover 20, and the signal amplification circuit board 30 are fixed through the circuit board and the optical path thread fixing holes one 12, optical path thread fixing holes two 13, optical path thread fixing holes three 22, and optical path thread fixing holes four 23 on the optical path to form a whole. In this way, the groove optical path 14 on the optical path upper cover 10 and the optical path bottom cover 20 are combined to form a closed optical reflection path for gas detection. The groove optical path 14 is a spherical groove with a radius of 1.25mm and a length of 4.3cm. The arc-shaped groove structure is conducive to the convergence and conduction of infrared light. At the same time, both the optical path upper cover 10 and the optical path bottom cover 20 adopt a gold plating process, which improves the light reflectivity and the corrosion resistance of the optical path structure.

[0039] Specifically, the optical path thread fixing holes one 12 and optical path thread fixing holes two 13 are respectively arranged corresponding to the optical path thread fixing holes three 22 and optical path thread fixing holes four 23. The optical path thread fixing holes one 12 and optical path thread fixing holes three 22, as well as the optical path thread fixing holes two 13 and optical path thread fixing holes four 23, are connected by bolts.

[0040] Specifically, the infrared light source fixing hole 24 is adapted to the infrared light source 31. The infrared light source 31 is inserted into the infrared light source fixing hole 24 and extends above the infrared light source fixing hole 24, and the top end of the infrared light source 31 is adapted to one end of the groove optical path 14.

[0041] Specifically, the fixing hole 21 for the pyroelectric infrared detector is adapted to the pyroelectric infrared detector 32, and the pyroelectric infrared detector 32 is inserted into the fixing hole 21 for the pyroelectric infrared detector.

[0042] Embodiment 2

[0043] This embodiment is a specific implementation manner of the working method of a small infrared gas sensor.

[0044] A working method of a small infrared gas sensor has the following process:

[0045] S1. The signal processing circuit board 40 sends a signal to drive the infrared light source to drive the infrared light source 31 to work. The infrared light source 31 and the pyroelectric infrared detector 32 are located at both ends of the groove optical path 14. When the infrared light source 31 emits infrared light, the infrared light is concentrated and reflected in the groove optical path 14 and conducted to the location of the other pyroelectric infrared detector 32.

[0046] S2. The pyroelectric infrared detector 32 has two input windows for receiving infrared light, and a filter with a specific wavelength band is provided on each window. The reference infrared band filter 321 is a filter with a wavelength band of 3.95 um, and the target gas infrared band filter 322 is a filter with a wavelength band of 3.5 um. The target gas is methane.

[0047] S3. The infrared light source 31 emits broadband infrared light with a wavelength range of 3 um - 5 um. After being reflected and conducted in the groove optical path 14, the light irradiates the pyroelectric infrared detector 32. Due to the action of the two-channel filters, only the infrared light with a wavelength of 3.95 um is received by the reference channel, and only the infrared light with a wavelength of 3.5 um is received by the measurement channel.

[0048] S4. After receiving the infrared light, the pyroelectric infrared detector 32 converts the optical signal into an electrical signal, which is amplified by the components of the signal amplification circuit board 30 and transmitted to the signal processing circuit board 40 through the circuit board connection terminal 41 for signal processing and analysis.

[0049] Through the above technical solution, when the target gas exists in the environment, the target gas enters the groove optical path 14 through the first optical path cover ventilation hole 11, the second optical path cover ventilation hole 15, the third optical path cover ventilation hole 16, and the fourth optical path cover ventilation hole 17 of the optical path cover 10, and can absorb the infrared light in the filter band of the corresponding measurement channel filter. Taking methane gas as an example, the gas will absorb the infrared light of 3.5um, resulting in a decrease in the intensity of the 3.5um infrared light received by the measurement channel of the infrared pyroelectric probe 32. Furthermore, the amplified voltage signal decreases, and the decreased voltage signal will be transmitted to the signal processing circuit board 40 for analysis and processing, thereby calculating the current gas concentration. During use, connect the power supply and data transmission terminal 44 on the signal processing circuit board 40 to an external TTL communication module, and the real-time target gas concentration data calculated by this device can be received.

[0050] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device.

[0051] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A small infrared gas sensor, comprising an optical path upper cover (10), Characterized in that: An optical path bottom cover (20) is provided at the bottom of the above-mentioned optical path upper cover (10), a signal amplification circuit board (30) is provided at the bottom of the above-mentioned optical path bottom cover (20), and a signal processing circuit board (40) is provided at the bottom of the above-mentioned signal amplification circuit board (30); A groove optical path (14) is opened at the bottom of the optical path upper cover (10), and an optical path upper cover ventilation hole one (11), an optical path upper cover ventilation hole two (15), an optical path upper cover ventilation hole three (16) and an optical path upper cover ventilation hole four (17) are opened inside the groove optical path (14), and an optical path thread fixing hole one (12) and an optical path thread fixing hole two (13) are opened on the outer side wall of the optical path upper cover (10); An infrared pyroelectric probe fixing hole (21) is opened at the bottom of the optical path bottom cover (20), an optical path thread fixing hole three (22) and an optical path thread fixing hole four (23) are opened on the outer side wall of the optical path bottom cover (20), and an infrared light source fixing hole (24) is also opened on the outer side wall of the optical path bottom cover (20); An infrared light source (31) is fixedly connected to the top of the signal amplification circuit board (30), and an infrared pyroelectric probe (32) is also fixedly connected to the top of the signal amplification circuit board (30). A reference infrared band filter (321) and a target gas infrared band filter (322) are respectively fixedly connected to the top of the infrared pyroelectric probe (32). The reference infrared band filter (321) is a 3.95um band filter, and the target gas infrared band filter (322) is a 3.5um band filter. The infrared light source (31) and the infrared pyroelectric probe (32) are located at both ends of the groove optical path (14); A circuit board connection terminal one (41) and a circuit board connection terminal two (42) are respectively fixedly connected to the top of the signal processing circuit board (40), a debugging connection terminal (43), a power supply and data transmission connection terminal (44) and a power supply and signal processing circuit element (45) are respectively fixedly connected to the bottom of the signal processing circuit board (40), and the signal amplification circuit board (30) and the signal processing circuit board (40) are fixedly connected by combining and connecting through the circuit board connection terminal one (41) and the circuit board connection terminal two (42).

2. A small infrared gas sensor according to claim 1, Characterized in that: The optical path thread fixing hole one (12) and the optical path thread fixing hole two (13) are respectively arranged corresponding to the optical path thread fixing hole three (22) and the optical path thread fixing hole four (23), and the optical path thread fixing hole one (12) and the optical path thread fixing hole three (22) as well as the optical path thread fixing hole two (13) and the optical path thread fixing hole four (23) are connected by bolts.

3. A small infrared gas sensor according to claim 1, Characterized in that: The infrared light source fixing hole (24) is adapted to the infrared light source (31). The infrared light source (31) is inserted into the interior of the infrared light source fixing hole (24) and extends above the infrared light source fixing hole (24), and the top end of the infrared light source (31) is adapted to one end of the groove optical path (14).

4. A small infrared gas sensor according to claim 1, characterized in that: The pyroelectric infrared detector fixing hole (21) is adapted to the pyroelectric infrared detector (32), and the pyroelectric infrared detector (32) is inserted into the pyroelectric infrared detector fixing hole (21).

5. A working method of a small infrared gas sensor according to any one of claims 1-4, characterized in that: The process is as follows: S1. The signal processing circuit board (40) sends a signal to drive the infrared light source to drive the infrared light source (31) to work. The infrared light source (31) and the pyroelectric infrared detector (32) are located at both ends of the groove optical path (14). When the infrared light source (31) emits infrared light, the infrared light is gathered and reflected in the groove optical path (14) and conducted to the location of the other pyroelectric infrared detector (32). S2. The pyroelectric infrared detector (32) has two input windows for receiving infrared light, and a filter of a specific wavelength band is provided on each window. The reference infrared band filter (321) is a 3.95um band filter, and the target gas infrared band filter (322) is a 3.5um band filter, and the target gas is methane. S3. The infrared light source (31) emits broad-spectrum infrared light with a wavelength range of 3um-5um. After being reflected and conducted by the groove optical path (14), the light irradiates the pyroelectric infrared detector (32). Due to the action of the two-channel filters, only the infrared light of 3.95um is received by the reference channel, and only the infrared light of 3.5um is received by the measurement channel. S4. After receiving the infrared light, the pyroelectric infrared detector (32) converts the optical signal into an electrical signal, which is amplified by the components of the signal amplification circuit board (30) and transmitted to the signal processing circuit board (40) through the circuit board connection terminal 1 (41) for signal processing and analysis.

Images