Gas detection device

Abstract

The invention discloses a gas detection device, relates to the technical field of gas concentration detection, and aims to solve the problem that the detection precision of a sensor is reduced due to water vapor condensation caused by overhigh environment humidity. The substrate is provided with a first surface and a second surface which are opposite to each other, and a middle layer is arranged between the first surface and the second surface; the gas sensor is arranged on the first surface of the substrate; the heating part is embedded in the base middle layer; the temperature measuring component is arranged on the first surface and is used for detecting temperature information of the substrate; the shell covers the first surface of the substrate; the control circuit is arranged on the second surface of the substrate, the heating component, the temperature measuring component and the gas sensor are all electrically connected with the control circuit, and the control circuit is used for controlling the heating power of the heating component according to the temperature information. The temperature of the gas sensor and the interior of the shell is controlled to be proper through the heating component and the temperature measuring component, the temperature drift of the gas sensor is reduced, meanwhile, the influence of water vapor condensation on the performance of the gas sensor caused by overhigh environment humidity and temperature change is avoided, and the detection precision of the gas sensor is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of gas concentration detection, and in particular to a gas detection device. Background Art

[0002] The current mainstream gas detection technologies include electrochemical (EC), infrared (IR), metal oxide semiconductor (MOS), thermal conductivity (TC) and catalytic combustion gas sensors. Among them, thermal conductivity gas sensors based on MEMS technology are widely used in the fields of methane, hydrogen and other combustible gas leakage detection, SF6 and other industrial gas monitoring due to their small size, simple and stable structure, long life, integration and mass production.

[0003] Due to the working principle of the thermal conductivity gas sensor itself, the sensitive structure of the sensor is a temperature-sensitive element. When the ambient temperature and humidity change, the output signal of the thermal conductivity gas sensor will be affected by the ambient temperature and humidity, which will cause the drift of the detection result. Therefore, compensation for ambient temperature and humidity is particularly important; on the other hand, in extreme environments, the internal structure of the thermal conductivity gas sensor will be deformed due to the thermal stress caused by a large range of temperature changes, or water vapor condensation around the thermal conductivity gas sensor in a high humidity environment may cause the output signal of the thermal conductivity gas sensor to be abnormal, or even damage the chip of the thermal conductivity gas sensor. Summary of the invention

[0004] The object of the present invention is to provide a gas detection device for reducing the signal drift of the gas sensor caused by the change of the ambient temperature and improving the detection accuracy.

[0005] In order to achieve the above object, the present invention provides the following technical solution: a gas detection device, comprising:

[0006] A substrate having a first surface and a second surface opposite to each other, with an intermediate layer between the first surface and the second surface;

[0007] A gas sensor is disposed on the first surface of the substrate;

[0008] A heating component is embedded in the middle layer of the substrate;

[0009] A temperature measuring component is disposed on the first surface of the substrate, and is used to detect temperature information of the substrate;

[0010] A housing, which is covered on the first surface of the substrate;

[0011] The control circuit is arranged on the second surface of the substrate. The heating component, the temperature measuring component and the gas sensor are all electrically connected to the control circuit. The control circuit is used to control the heating power of the heating component according to the temperature information.

[0012] Optionally, in the above-mentioned gas detection device, the control circuit includes:

[0013] A power source connected to the heating component to form a heating circuit;

[0014] NMOS tube, connected to the heating circuit;

[0015] A flexible circuit board is arranged on the second surface of the substrate;

[0016] The main circuit board, the heating component, the gas sensor and the temperature measuring component are all connected to the main circuit board through the flexible circuit board, and the detection signals of the temperature measuring component and the gas sensor are transmitted through the flexible circuit board and the main circuit board in turn;

[0017] The controller is electrically connected to the main circuit board. The controller controls the on-off of the heating circuit according to the detection signal, and controls the heating power of the heating component to the substrate by outputting PWM waves with different duty cycles until the detection signal of the temperature measuring component stabilizes to the target temperature value.

[0018] Optionally, in the above-mentioned gas detection device, the substrate is provided with a plurality of through holes, and the gas detection device further comprises leads, which pass through the through holes to connect the heating component, the temperature measuring component and the gas sensor to the flexible circuit board.

[0019] Optionally, in the above-mentioned gas detection device, a window is formed on a first surface of the shell away from the substrate, and the gas detection device further comprises a filter element, which covers the window and is used to prevent liquid from diffusing into the shell.

[0020] Optionally, in the above-mentioned gas detection device, the projection area of ​​the window on the substrate accounts for 0.3 to 0.6 of the supporting area of ​​the substrate;

[0021] And / or, the distance between the window and the first surface of the substrate is 2 to 5 times the height of the gas sensor.

[0022] Optionally, in the above-mentioned gas detection device, the heating component is distributed in a rectangular folded and coiled shape inside the substrate;

[0023] Alternatively, the heating elements are arranged in a spiral shape in the substrate.

[0024] Optionally, in the above-mentioned gas detection device, the temperature measuring component includes a thermistor or a temperature sensitive diode.

[0025] Optionally, in the above-mentioned gas detection device, the temperature measuring component and the gas sensor are located on the same isotherm on the substrate.

[0026] Optionally, in the above-mentioned gas detection device, the substrate includes a ceramic board, a PCB board or a silicon substrate.

[0027] Optionally, in the above gas detection device, the material of the shell includes metal, ceramic or plastic.

[0028] Compared with the prior art, when the above technical solution is adopted, the control circuit is started, and the control circuit controls the heating power of the heating component located in the middle layer of the substrate by receiving the temperature information detected in real time by the temperature measuring component, so that the gas sensor located inside the shell is heated and controlled at the target temperature value. When the ambient temperature inside the shell is lower than the temperature controlled by the gas sensor, the change in ambient temperature will not affect the output signal of the temperature-controlled gas sensor. At the same time, the ambient humidity only needs to be compensated at the temperature control point and above, which effectively reduces the temperature and humidity calibration work of the gas sensor, and reduces the temperature and humidity compensation range of the gas sensor, thereby improving the detection accuracy of the gas sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0030] Figure 1 A schematic diagram of the structure of a gas detection device provided in an embodiment of the present invention without a control circuit;

[0031] Figure 2 for Figure 1 A schematic diagram of the structure of the gas detection device including a flexible circuit board;

[0032] Figure 3 A circuit diagram of a gas detection device provided in an embodiment of the present invention;

[0033] Figure 4 A schematic structural diagram of a first surface of a substrate in a gas detection device provided in an embodiment of the present invention;

[0034] Figure 5 A schematic structural diagram of an intermediate layer of a substrate in a gas detection device provided in an embodiment of the present invention;

[0035] Figure 6 It is a schematic structural diagram of the second surface of a substrate in a gas detection device provided in an embodiment of the present invention.

[0036] Reference numerals:

[0037] 1-substrate; 11-through hole; 2-gas sensor; 3-heating component; 4-temperature measuring component; 5-housing; 51-window; 52-filter element; 6-control circuit; 61-NMOS tube; 62-flexible circuit board; 63-controller; 64-power supply; 7-lead; 8-soldering pad. DETAILED DESCRIPTION

[0038] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0039] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0040] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined. The meaning of "several" is one or more, unless otherwise clearly and specifically defined.

[0041] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by the terms "up", "down", "front", "back", "left", "right", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0042] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0043] like Figure 1-Figure 6 As shown, a gas detection device provided by an embodiment of the present invention includes: a substrate 1, a gas sensor 2, a heating component 3, a temperature measuring component 4, a shell 5 and a control circuit 6.

[0044] Among them, the substrate 1 has a first surface and a second surface relative to each other, and an intermediate layer is provided between the first surface and the second surface; the gas sensor 2 is arranged on the first surface of the substrate 1; the heating component 3 is embedded in the intermediate layer of the substrate 1; the temperature measuring component 4 is arranged on the first surface of the substrate 1, and the temperature measuring component 4 is used to detect the temperature information of the substrate 1; the shell 5 is covered on the first surface of the substrate 1; the control circuit 6 is arranged on the second surface of the substrate 1, and the heating component 3, the temperature measuring component 4 and the gas sensor 2 are all electrically connected to the control circuit 6, and the control circuit 6 is used to control the heating power of the heating component 3 according to the temperature information.

[0045] When implementing it, Figure 1 As shown, the control circuit 6 is started. The control circuit 6 controls the heating power of the heating component 3 located in the middle layer of the substrate 1 by receiving the temperature information detected in real time by the temperature measuring component 4, so that the gas sensor 2 located inside the shell 5 is heated and controlled at the target temperature value. When the ambient temperature in the shell 5 is lower than the temperature controlled by the gas sensor 2, the change in ambient temperature will not affect the output signal of the temperature-controlled gas sensor 2. At the same time, the ambient humidity only needs to be compensated at and above the temperature control point, which effectively reduces the temperature and humidity calibration work of the gas sensor 2, and reduces the temperature and humidity compensation range of the gas sensor 2, thereby improving the detection accuracy of the gas sensor 2.

[0046] It should be noted that the gas sensor 2 may be a thermal conductivity gas sensor, or an electrochemical gas sensor, an infrared gas sensor or other types of gas sensors, which are not specifically limited here.

[0047] like Figure 3 As shown, specifically, in this embodiment, the control circuit 6 includes: a power supply 64, an NMOS tube 61, a flexible circuit board 62, a main circuit board, and a controller 63. The power supply 64 is connected to the heating component 3 to form a heating circuit, the NMOS tube 61 is connected to the heating circuit, the flexible circuit board 62 is arranged on the second surface of the substrate 1, the heating component 3, the gas sensor 2 and the temperature measuring component 4 are all connected to the main circuit board through the flexible circuit board 62, and the detection signals of the temperature measuring component 4 and the gas sensor 2 are transmitted through the flexible circuit board 62 and the main circuit board in turn. The controller 63 is electrically connected to the main circuit board, and the controller 63 controls the on and off of the heating circuit according to the detection signal, and controls the heating power of the heating component 3 to the substrate 1 by outputting PWM waves with different duty cycles until the detection signal of the temperature measuring component 4 stabilizes to the target temperature value.

[0048] When working, turn on the power supply 64 to power the heating component 3, the temperature measuring component 4, the gas sensor 2 and the controller 63 located in the middle layer of the substrate 1. The signals of the temperature measuring component 4 and the gas sensor 2 on the substrate 1 are all led out through the flexible circuit board 62 and transmitted to the controller 63 on the main circuit board, such as MCU, and the PWM wave is output by the IO pin of the controller 63. The controller 63 can adjust the heating power of the heating component 3 in the heating circuit to the substrate 1 by controlling the duty cycle of the PWM wave, that is, the temperature of the substrate 1 is detected by the temperature measuring component 4 on the first surface and transmitted to the controller 63 through the flexible circuit board 62, and the temperature value of the temperature measuring component 4 is used as the feedback. The feedback signal is written into the PID temperature control algorithm in the controller 63, and the heating power of the heating component 3 located in the middle layer of the substrate 1 is controlled by outputting PWM waves with different duty cycles. At the same time, the NMOS tube 61 is connected to the heating circuit, and the PWM wave is output by the controller 63 to control the on or off state of the NMOS tube 61, so as to realize the control of the working state of the heating circuit until the temperature signal of the temperature measuring component 4 is stabilized at the target temperature value, so as to realize the temperature control of the heating gas sensor 2. The internal ambient temperature of the shell 5 is kept constant by heating, thereby avoiding the influence of water vapor condensation caused by the temperature change inside the shell 5 on the performance of the gas sensor 2.

[0049] It should be noted that the threshold voltage of the NMOS tube 61 is written into the controller 63. When the actual temperature value fed back to the controller 63 by the temperature signal of the temperature measuring component 4 is lower than the target temperature value, the controller 63 controls the voltage input into the NMOS tube 61 so that the gate voltage is higher than the threshold voltage. At this time, the electronic channel in the NMOS tube 61 is turned on, and the control circuit 6 is turned on. At this time, the heating component 3 works to heat the substrate 1, so that the temperature of the substrate 1 increases until the temperature signal detected by the temperature measuring component 4 reaches the target temperature value; when the actual temperature value detected by the temperature measuring component 4 is higher than the target temperature value, the controller 63 controls the voltage input into the NMOS tube 61 so that the gate voltage is lower than the threshold voltage. At this time, the electronic channel in the NMOS tube 61 is closed, the control circuit 6 is disconnected, and the heating component 3 no longer heats the substrate 1. In addition, the gas sensor 2 has a MEMS gas sensor chip. In order to ensure that the measuring component can accurately measure the temperature of the MEMS gas sensor chip, the MEMS gas sensor chip and the temperature measuring component 4 should be mounted as much as possible in the central area of ​​the first surface of the substrate 1 and located on the same isotherm.

[0050] like Figure 5As shown, specifically, in this embodiment, the substrate 1 is provided with a plurality of through holes 11 , and the gas detection device further comprises leads 7 , which pass through the through holes 11 to connect the heating component 3 , the temperature measuring component 4 and the gas sensor 2 to the flexible circuit board 62 . The operator can mount the MEMS gas sensor chip and the temperature measuring component 4 of the gas sensor 2 on the substrate 1, and use the lead 7 to lead the signal of the gas sensor 2 through the through hole 11 to the pad on the second side of the substrate 1. The two end pins of the heating component 3 located in the middle layer of the substrate 1 and the pins of the MEMS gas sensor chip and the temperature measuring component 4 of the gas sensor 2 are all led to the second side of the substrate 1 through the through hole 11, and then welded to the flexible circuit board 62 through the pad on the second side of the substrate 1, so that the output signal of the gas sensor 2 is connected to the main circuit board through the flexible circuit board 62. At this time, the power supply 64 is used to conduct the heating circuit, so that the heating component 3 works to heat the entire substrate 1. At this time, the substrate 1 is used as a surface heat source to heat the MEMS gas sensor chip of the gas sensor 2, which is convenient for fixing and installing the gas sensor 2 and the temperature measuring component 4, reducing the signal cross interference between the components, and ensuring the accuracy and stability of data transmission. Among them, the flexible circuit board 62 can be an FPC soft board or other circuit boards, which are not specifically limited here, as long as the flexible circuit board 62 can be electrically connected to the main circuit board.

[0051] It should be noted that the second surface of the substrate 1 has a solder pad 8 , and the solder pad 8 is used for electrical connection between each component on the first surface of the substrate 1 and the flexible printed circuit board 62 .

[0052] like Figure 1 and Figure 2 As shown, specifically, in this embodiment, a window is provided on the first surface of the shell 5 away from the substrate 1, and the gas detection device further includes a filter element 52, which covers the window 51, and is used to prevent liquid from diffusing into the shell 5. When water vapor saturates and condenses in an environment with excessive relative humidity, since the temperature around the gas sensor 2 is higher than the ambient temperature, the relative humidity will be lower than the humidity of the environment, and the water vapor is still in an unsaturated state. The window 51 on the shell 5 facilitates gas circulation between the external environment and the inside of the shell 5, thereby avoiding the influence of condensation of water vapor on the output signal of the gas sensor 2 and improving the detection accuracy. Among them, the filter element 52 is a porous capillary mesh structure, and the filter element 52 can be made of metal, alloy or other materials, which is not specifically limited here, as long as the filter element 52 has the function of being waterproof and breathable, and can prevent liquid in the external environment from entering the shell 5 and damaging the gas sensor 2.

[0053] Specifically, in this embodiment, the shape of the window 51 includes a circle or a rectangle. Of course, the window 51 can also adopt other shapes, which are not specifically limited here, as long as the window 51 can facilitate the diffusion of external environmental gas into the housing 5.

[0054] like Figure 1 and Figure 2 As shown, specifically, in this embodiment, the projection area of ​​the window 51 on the substrate 1 accounts for 0.3 to 0.6 of the supporting area of ​​the substrate 1; and / or, the distance between the window 51 and the first surface of the substrate 1 is 2 to 5 times the height of the gas sensor 2. Exemplarily, the ratio between the projection area of ​​the window 51 on the substrate 1 and the supporting area of ​​the substrate 1 can be 0.3, 0.35, 0.42, 0.5, 0.6, etc., and the projection area of ​​the window 51 on the substrate 1 is not specifically limited, as long as the shape and size of the window 51 meet the gas diffusion between the external environment and the inside of the shell 5; the distance between the window 51 and the first surface of the substrate 1 can be 2 times, 3.6 times, 4 times, 4.5 times, 5 times, etc., of the height of the gas sensor 2, and the distance between the window 51 and the first surface of the substrate 1 is not specifically limited, as long as the setting height of the window 51 on the shell 5 meets the gas diffusion between the external environment and the inside of the shell 5.

[0055] like Figure 3 and Figure 5 As shown, specifically, in this embodiment, the heating component 3 is arranged in a rectangular folded coil inside the substrate 1; or, the heating component 3 is arranged in a spiral coil inside the substrate 1. The heating component 3 may also adopt other coiled distribution modes, which are not specifically limited here, as long as the heating component 3 is evenly distributed in the middle layer of the substrate 1, so that each area on the surface of the substrate 1 is heated evenly. Exemplarily, the heating component 3 may be a heating resistor wire or other structure with a heating function, which is not specifically limited here, as long as the heating component 3 can evenly heat each area on the surface of the substrate 1.

[0056] Specifically, in this embodiment, the temperature measuring component 4 includes a thermistor or a temperature-sensitive diode. Both the thermistor and the temperature-sensitive diode are components that work based on the temperature sensitivity of the material, and both can convert temperature into a resistance value or a voltage signal. Of course, the temperature measuring component 4 can also use other components with temperature measurement functions, which are not specifically limited here.

[0057] Specifically, in this embodiment, the temperature measuring component 4 and the gas sensor 2 are located on the same isotherm on the substrate 1. On the same isotherm of the heating component 3, the temperature measuring component 4 and the gas sensor 2 can receive the same heating temperature, ensuring the accuracy and reliability of the temperature measuring component 4 detecting the working environment temperature of the gas sensor 2.

[0058] Specifically, in this embodiment, the substrate 1 includes a ceramic board, a PCB board or a silicon substrate. The ceramic board has good thermal conductivity and can withstand high power density; the PCB board reduces the volume of electronic products and has low product cost. Of course, the substrate 1 can also be a silicon substrate or a substrate 1 of other materials. The material of the substrate 1 is not specifically limited here, as long as the substrate 1 has good thermal conductivity, so that the substrate 1 can transfer heat to the temperature measuring component 4 and the gas sensor 2 through the heating component 3 of the middle layer.

[0059] Specifically, in this embodiment, the material of the shell 5 includes metal, ceramic or plastic. Ceramics have good insulation and thermal stability and can work stably in a high-temperature oxidizing environment. Of course, the shell 5 can also be made of metal, plastic or other materials. The material of the shell 5 is not specifically limited here, as long as the shell 5 can provide a stable gas detection environment for the gas sensor 2 and the temperature measuring component 4. Among them, the shell 5 can be welded, mounted or other fixed connection methods with the first side of the substrate 1, which is not specifically limited here, as long as the shell 5 and the substrate 1 are tightly connected.

[0060] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

[0061] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A gas detection device, characterized in that: include: A substrate having a first surface and a second surface opposite to each other, wherein an intermediate layer is provided between the first surface and the second surface; A gas sensor is disposed on the first surface of the substrate; A heating component embedded in the middle layer of the substrate; A temperature measuring component is disposed on the first surface of the substrate, and is used to detect temperature information of the substrate; A housing, which is disposed on the first surface of the substrate; A control circuit is arranged on the second surface of the substrate. The heating component, the temperature measuring component and the gas sensor are all electrically connected to the control circuit. The control circuit is used to control the heating power of the heating component according to the temperature information.

2. The gas detection device according to claim 1, characterized in that: The control circuit comprises: A power source connected to the heating component to form a heating circuit; NMOS tube, connected to the heating circuit; A flexible circuit board is arranged on the second surface of the substrate; A main circuit board, wherein the heating component, the gas sensor and the temperature measuring component are all connected to the main circuit board through the flexible circuit board, and the detection signals of the temperature measuring component and the gas sensor are transmitted through the flexible circuit board and the main circuit board in sequence; A controller is electrically connected to the main circuit board. The controller controls the on and off of the heating circuit according to the detection signal, and controls the heating power of the heating component to the substrate by outputting PWM waves with different duty cycles until the detection signal of the temperature measuring component stabilizes to a target temperature value.

3. The gas detection device according to claim 2, characterized in that: The substrate is provided with a plurality of through holes, and the gas detection device further comprises leads, which pass through the through holes to connect the heating component, the temperature measuring component and the gas sensor to the flexible circuit board.

4. The gas detection device according to claim 1, characterized in that: A window is formed on a first surface of the shell away from the substrate. The gas detection device further comprises a filter element, which covers the window and is used to prevent liquid from diffusing into the shell.

5. The gas detection device according to claim 4, characterized in that: The projection area of ​​the window on the substrate accounts for 0.3 to 0.6 of the supporting area of ​​the substrate; And / or, the distance between the window and the first surface of the substrate is 2 to 5 times the height of the gas sensor.

6. The gas detection device according to claim 1, characterized in that: The heating component is distributed in the substrate in a rectangular folded and coiled shape; Alternatively, the heating component is distributed in the substrate in a spiral shape.

7. The gas detection device according to claim 1, characterized in that: The temperature measuring component includes a thermistor or a temperature sensitive diode.

8. The gas detection device according to claim 1, characterized in that: The temperature measuring component and the gas sensor are located on the same isotherm on the substrate.

9. The gas detection device according to claim 1, characterized in that: The substrate includes a ceramic board, a PCB board or a silicon substrate.

10. The gas detection device according to claim 1, characterized in that: The material of the housing includes metal, ceramic or plastic.

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