Thermal conductivity type gas measuring device and thermal conductivity type gas sensor thereof

Abstract

The invention provides a heat conduction type gas measuring device. The heat conduction type gas measuring device comprises a mounting seat, a heat sensor and a heating platinum wire, the thermal sensor and the heating platinum wire are sealed in a thermal conductive material to form a detection head, and the detection head is fixedly arranged on the mounting seat; the heat sensor is located above the heating platinum wire, and the heat sensor and the heating platinum wire are electrically connected with external equipment through leads. Through the above structure, the heating platinum wire and the thermal sensor are sealed through the thermal conductive material to form the detection head, and the heating platinum wire does not need to be in contact with the detected gas, so that the heating platinum wire can be effectively prevented from being attached by impurities, and the heating platinum wire does not need to be stretched, so that the heating platinum wire is high in structural stability and relatively high in vibration resistance; therefore, the final detection precision and sensitivity are effectively ensured.

Description

Technical Field

[0001] This invention relates to the field of gas sensors, and more particularly to a thermal conductivity gas measuring device and its thermal conductivity gas sensor. Background Technology

[0002] Thermal conductivity gas sensors are widely used in gas concentration measurement. In existing technologies, thermal conductivity gas sensors use platinum wire as the sensing element, with the platinum wire forming both the measuring arm and the reference arm. The principle is as follows: Figure 4 As shown: A constant voltage source E drives a bridge circuit consisting of fixed resistors R1 and R2, a reference arm, and a measuring arm. The reference arm contains a zero-point gas (reference gas), and the measuring arm is supplied with sample gas. The circuit outputs a voltage signal V characterizing the concentration of the sample gas. O When the measured gas has a high thermal conductivity, more heat is conducted, the temperature at the platinum wire decreases, and the resistance of the platinum wire decreases. Consequently, the voltage signal VO output by the bridge changes, and the reference arm has a compensating effect for environmental changes.

[0003] In existing technologies, for thermal conductivity gas-sensitive sensor structures, such as Figure 5 As shown: Thermally conductive platinum wire elements come in various shapes, including straight and spiral. The platinum wire is made of... Figure 5 The structure provides support, including V-shapes, straight lines, and arc shapes; during measurement, such as... Figure 6 As shown, regardless of the type used, the heating platinum wire is always in a stretched state. To ensure measurement sensitivity, the heating platinum wire needs to be as thin and long as possible, usually exceeding 20mm in length. This results in low vibration resistance of the sensor, as vibration can easily cause the heating platinum wire to stretch and deform, leading to larger errors. Furthermore, when the gas being measured comes into contact with the heating platinum wire, impurities in the gas can easily adhere to the surface of the platinum wire, affecting the detection accuracy over time. Moreover, the structure of the existing technology makes the entire sensor highly sensitive to environmental conditions and has poor anti-interference capabilities.

[0004] Therefore, in order to solve the above-mentioned technical problems, it is urgent to propose a new technical approach. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a thermal conductivity gas measuring device and its thermal conductivity gas sensor. By sealing the heating platinum wire and the thermal sensor with a thermally conductive material to form a detection head, the heating platinum wire no longer needs to contact the gas being measured, thereby effectively preventing impurities from adhering to the heating platinum wire. Furthermore, there is no need to stretch the heating platinum wire, resulting in strong structural stability and strong vibration resistance, thus effectively ensuring the final detection accuracy.

[0006] The present invention provides a thermal conductivity gas measuring device, comprising a mounting base, a thermal sensor, and a heating platinum wire;

[0007] The thermal sensor and the heating platinum wire are sealed in a thermally conductive material to form a detection head, which is fixedly mounted on a mounting base. The thermal sensor is located above the heating platinum wire, and the thermal sensor and the heating platinum wire are electrically connected to an external device via leads.

[0008] Furthermore, the heating platinum wire is bent to form a U-shaped structure, with the apex of the inverted U-shaped structure of the heating platinum wire facing the thermal sensor.

[0009] Furthermore, the thermal sensor is a negative temperature coefficient thermistor.

[0010] Furthermore, the apex of the inverted U-shaped structure formed by the heating platinum wire is close to the thermal sensor and maintains a set gap.

[0011] Furthermore, the thermally conductive material is thermally conductive glass.

[0012] Accordingly, the present invention also provides a thermal conductivity gas sensor, including a base, a reference unit, and a measurement unit;

[0013] The base is provided with an airflow channel, and the base is provided with two mounting holes for mounting the reference unit and the measuring unit, the mounting holes being connected to the airflow channel;

[0014] The reference unit and the measuring unit are embedded in the mounting hole;

[0015] Both the reference unit and the measuring unit are equipped with the aforementioned thermal conductivity gas measuring device.

[0016] Furthermore, both the reference unit and the measuring unit are provided with cylindrical housings;

[0017] The front end of the cylindrical shell of the reference unit is a closed structure, and the reference unit is sealed with reference gas.

[0018] The front end of the cylindrical housing of the measuring unit is connected to the airflow channel;

[0019] Both the reference unit and the measuring unit have annular seals at their tail ends, which are located between the mounting base and the inner wall of the cylindrical housing.

[0020] Furthermore, a sealing block is provided at the tail end of the mounting hole.

[0021] The beneficial effects of this invention are as follows: By sealing the heating platinum wire and the thermal sensor together with a thermally conductive material to form a detection head, the heating platinum wire no longer needs to come into contact with the gas being measured, thus effectively preventing impurities from adhering to the heating platinum wire. Furthermore, the heating platinum wire does not need to be stretched, resulting in strong structural stability and strong vibration resistance, thereby effectively ensuring the final detection accuracy. Attached Figure Description

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0023] Figure 1 This is a schematic diagram of the thermal conductivity gas measuring device of the present invention.

[0024] Figure 2 This is a schematic diagram of the thermal conductivity gas measuring device of the present invention as a reference unit.

[0025] Figure 3 This is a schematic diagram of the thermal conductivity gas sensor structure of the present invention.

[0026] Figure 4 This is a schematic diagram of the measurement principle of an existing thermal conductivity gas sensor.

[0027] Figure 5 This is a schematic diagram of the heating platinum wire structure of an existing thermal conductivity gas sensor.

[0028] Figure 6 This is a schematic diagram of a measurement using an existing thermal conductivity gas sensor. Detailed Implementation

[0029] The present invention will be further described in detail below:

[0030] The present invention provides a thermal conductivity gas measuring device, comprising a mounting base 4, a thermal sensor 12, and a heating platinum wire 11;

[0031] The thermal sensor 12 and the heating platinum wire 11 are sealed within a thermally conductive material 14 to form a detection head, which is fixedly mounted on the mounting base 4. The thermal sensor is located above the heating platinum wire, and the thermal sensor and the heating platinum wire are electrically connected to an external device via a lead wire 3. With this structure, by sealing the heating platinum wire and the thermal sensor within the thermally conductive material to form the detection head, the heating platinum wire no longer needs to come into contact with the gas being measured, effectively preventing impurities from adhering to the heating platinum wire. Furthermore, there is no need to stretch the heating platinum wire, resulting in strong structural stability and excellent vibration resistance, thus effectively ensuring the final detection accuracy and sensitivity.

[0032] In this embodiment, the heating platinum wire 11 is bent to form a U-shaped structure, with the apex of the inverted U-shaped structure of the heating platinum wire 11 facing the thermal sensor 12. Through the above structure, the vibration resistance of the entire sensor can be effectively improved. Compared with the prior art, the entire heating platinum wire is shorter and more stable. The apex of the inverted U-shaped structure formed by the heating platinum wire is close to the thermal sensor and maintains a set gap. That is to say, the apex of the heating platinum wire should be as close as possible to the thermal sensor, but not in direct contact, thus having a gap to prevent the current of the heating platinum wire from causing damage or other negative effects to the thermal sensor.

[0033] In this embodiment, the thermal sensor 12 is a negative temperature coefficient thermistor. Because of its high temperature coefficient, the thermistor has good sensitivity. Figure 3 The existing measurement structure allows us to determine the change in the concentration of the gas being measured by observing a change in the resistance value.

[0034] In this embodiment, the thermally conductive material 11 is thermally conductive glass. Through thermally conductive glass, the corrosion of the thermal sensor by the gas can be avoided and the corrosion of itself can be avoided. Moreover, it has good thermal conductivity, and the heat carried away by the gas being measured can be sensed by the thermal sensor, thereby forming a corresponding detection signal.

[0035] Accordingly, the present invention also provides a thermal conductivity gas sensor, including a base 1, a reference unit, and a measurement unit;

[0036] The base 1 is provided with an airflow channel 9 and two mounting holes (8, 13) for mounting the reference unit and the measuring unit. The mounting holes (8, 13) are connected to the airflow channel 9. The gas to be measured flows through the airflow channel (either the left or right side can be the airflow inlet). The gas to be measured enters the cylindrical housing of the measuring unit, thereby carrying away the heat generated by the heating platinum wire, thus changing the resistance of the thermistor. The reference unit contains a standard reference gas. The reference unit and the measuring unit have the same current when they are working, and the heating platinum wire has the same specifications.

[0037] The reference unit and the measuring unit are embedded in the mounting holes (8, 13);

[0038] Both the reference unit and the measuring unit are equipped with the aforementioned thermal conductivity gas measuring device.

[0039] Wherein: both the reference unit and the measuring unit are provided with cylindrical housings (6,7);

[0040] The front end of the cylindrical shell 7 of the reference unit is a closed structure, and the reference unit is sealed with reference gas.

[0041] The front end of the cylindrical housing 6 of the measuring unit is connected to the airflow channel 9;

[0042] Both the reference unit and the measuring unit have annular seals 5 at their tail ends, which are located between the mounting base 4 and the inner wall of the cylindrical housing.

[0043] A sealing block 2 is provided at the end of the mounting hole (8,13). The sealing block is also made of glass material for sealing. Using glass sealing can reduce the possibility of corrosion of the sealing block. The existing laser local heating sealing process is used for sealing.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A thermal conductivity gas measuring device, characterized in that: Includes mounting base, thermal sensor and heating platinum wire; The thermal sensor and the heating platinum wire are sealed in a thermally conductive material to form a detection head, which is fixedly mounted on a mounting base. The thermal sensor is located above the heating platinum wire, and the thermal sensor and the heating platinum wire are electrically connected to an external device via leads.

2. The thermal conductivity gas measuring device according to claim 1, characterized in that: The heating platinum wire is bent to form a U-shaped structure, with the apex of the inverted U-shaped structure of the heating platinum wire facing the thermal sensor.

3. The thermal conductivity gas measuring device according to claim 1, characterized in that: The thermal sensor is a negative temperature coefficient thermistor.

4. The thermal conductivity gas measuring device according to claim 2, characterized in that: The apex of the inverted U-shaped structure formed by the heating platinum wire is close to the thermal sensor and maintains a set gap.

5. The thermal conductivity gas measuring device according to claim 1, characterized in that: The thermally conductive material is thermally conductive glass.

6. A thermal conductivity gas sensor, characterized in that: Includes a base, a reference unit, and a measurement unit; The base is provided with an airflow channel, and the base is provided with two mounting holes for mounting the reference unit and the measuring unit, the mounting holes being connected to the airflow channel; The reference unit and the measuring unit are embedded in the mounting hole; Both the reference unit and the measuring unit are equipped with the thermal conductivity gas measuring device as described in any one of claims 1-5.

7. The thermal conductivity gas sensor according to claim 6, characterized in that: Both the reference unit and the measuring unit are provided with cylindrical housings; The front end of the cylindrical shell of the reference unit is a closed structure, and the reference unit is sealed with reference gas. The front end of the cylindrical housing of the measuring unit is connected to the airflow channel; Both the reference unit and the measuring unit have annular seals at their tail ends, which are located between the mounting base and the inner wall of the cylindrical housing.

8. The thermal conductivity gas sensor according to claim 7, characterized in that: A sealing block is provided at the tail end of the mounting hole.

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