Vacuum box air bag sampling device and method for gas flow and volume metering

Abstract

The invention relates to the technical field of metering and sampling, and provides a vacuum box air bag sampling device and method for gas flow and volume metering, and the device comprises a vacuum box, an air bag, a flow sensor, a sucking pump and a single chip microcomputer. The flow sensor is installed in front of an air inlet of the air bag and communicated with a sampling source, the air bag is arranged in the vacuum box, and the air inlet nozzle is connected with an air outlet of the flow sensor to form a channel for air to enter the air bag. The air suction nozzle is connected with an air suction pump, and the pressure detection nozzle in the vacuum box is connected with a pressure sensor. The single-chip microcomputer is in communication connection with all the sensors, controls the rotating speed of the sucking pump so as to keep the constant flow of gas entering the gas bag, and calculates the flow and the volume of the gas entering the gas bag. The method comprises the steps of initializing setting, forming negative pressure, adjusting the rotating speed of the sucking pump in real time to keep constant flow, calculating gas flow and volume and storing or outputting data. According to the invention, the flow sensor is arranged in a normal pressure environment, so that the accuracy of flow measurement is improved, and sampling requirements under different environmental conditions can be met.

Description

Technical Field

[0001] The invention relates to the technical field of metering and sampling, and in particular to a vacuum box air bag sampling device and method for gas flow and volume measurement. Background Art

[0002] A metering sampler is a special device that can accurately measure and collect the flow and volume of gas samples. Figure 2 As shown, the flow sensor is installed before the vacuum pump to measure the gas flow discharged from the vacuum box. However, this flow value does not represent the actual flow value of the gas entering the air bag. Because the pressure state (negative pressure) in the vacuum box is inconsistent with the state (normal pressure) when the flow sensor is calibrated, the flow sensor does not measure the flow entering the air bag. The flow value of the flow sensor used in the negative pressure state in the vacuum box cannot be directly calibrated in the actual use environment. If the normal pressure state is used when calibrating the flow sensor, then in the actual negative pressure sampling process, the flow measurement value will have a large deviation, and the accuracy of the sampling data cannot be guaranteed. Due to the inaccurate flow measurement and the inability to effectively calibrate, there is a large deviation between the gas flow value collected in the air bag and the gas volume value, which in turn affects the reliability of the subsequent analysis results. This is a significant disadvantage for application scenarios that require high-precision gas flow and volume measurement. The prior art adjusts the flow rate by controlling the speed of the vacuum pump through a single-chip microcomputer, but due to the inaccuracy of the flow measurement itself, it is difficult for the single-chip microcomputer to achieve an accurate constant flow rate when controlling the vacuum pump. This limits the actual application effect of the technology, especially in situations where high flow control requirements are required.

[0003] Therefore, it is of great significance to design a vacuum box air bag sampling device and method for gas flow and volume measurement to solve the above problems. Summary of the invention

[0004] In order to solve the problems existing in the background technology, the present invention provides a vacuum box air bag sampling device for gas flow and volume measurement, which includes a vacuum box, an air bag, a flow sensor, an air pump and a single-chip microcomputer, wherein:

[0005] The air inlet of the flow sensor is communicated with the sampling source, and the air outlet end of the flow sensor is connected with the air inlet nozzle of the air bag.

[0006] The vacuum box is provided with a vacuum box pressure detection nozzle, an air inlet nozzle and an air extraction nozzle. An air bag is installed in the vacuum box. One end of the air inlet nozzle of the air bag is connected to the air outlet of the flow sensor to form a channel for gas to enter the air bag.

[0007] The vacuum nozzle of the vacuum box is connected to the vacuum pump, and the gas in the vacuum box is pumped out by the air pump;

[0008] The vacuum box internal pressure detection nozzle is connected to a vacuum box internal pressure sensor for detecting the pressure value in the vacuum box;

[0009] The single chip microcomputer is connected in communication with the flow sensor, the pressure sensor in the vacuum box and the air pump.

[0010] Furthermore, an atmospheric pressure sensor and an ambient temperature sensor are provided which are communicatively connected with the single-chip microcomputer and are used to detect the atmospheric pressure and the ambient temperature.

[0011] A method for measuring and sampling using a vacuum box air bag sampling device for measuring gas flow and volume comprises the following steps:

[0012] S1, correctly connect the vacuum box, air bag, flow sensor, and air pump and initialize the settings, and each sensor sends initial data to the microcontroller;

[0013] S2, the single chip microcomputer controls the vacuum pump to form a negative pressure in the vacuum box. At the same time, the gas sample enters the air bag through the flow sensor, and adjusts the speed of the vacuum pump in real time to maintain a constant flow rate, and calculates the gas flow rate and volume;

[0014] S3, the single chip microcomputer saves the collected gas flow value, volume value, atmospheric pressure, and ambient temperature parameters to a storage device or outputs the collected data to an external device or system through a communication interface.

[0015] Further, the specific process of step S1 includes:

[0016] S11, place the air bag in a sealed vacuum box, and ensure that the air inlet of the air bag is sealed and connected to the air inlet nozzle of the vacuum box in the vacuum box; the air inlet of the flow sensor is connected to the sampling source to form a channel for the gas to enter the air bag; the air extraction nozzle is connected to the air extraction pump to extract the gas in the vacuum box to form a negative pressure inside the vacuum box; the pressure detection nozzle in the vacuum box is connected to the pressure sensor in the vacuum box to detect the pressure value in the vacuum box; the atmospheric pressure sensor and the ambient temperature sensor are respectively connected to the single-chip microcomputer for communication to detect the atmospheric pressure and ambient temperature;

[0017] S12, start the single chip microcomputer and perform initialization settings, including setting the sampling flow rate and sampling time parameters; the flow sensor, the pressure sensor in the vacuum box, the atmospheric pressure sensor and the ambient temperature sensor send initial data to the single chip microcomputer respectively.

[0018] Further, the specific process of step S2 includes:

[0019] S21, under the control of the single chip microcomputer, the vacuum pump starts to work, and the gas in the vacuum box is extracted through the vacuum nozzle, causing the pressure in the vacuum box to gradually decrease, forming a negative pressure state. Under the action of the atmospheric pressure difference, the gas sample passes through the flow sensor and the air inlet nozzle and enters the air bag;

[0020] S22, when the gas flows through the flow sensor, the flow sensor transmits the flow value signal to the single chip microcomputer;

[0021] S23, the single chip microcomputer receives the flow value signal of the flow sensor, the pressure value signal of the pressure sensor in the vacuum box, the pressure value signal of the atmospheric pressure sensor and the temperature value signal of the ambient temperature sensor;

[0022] S24, according to the set sampling flow, the single chip microcomputer calculates the difference between the current sampling flow and the set sampling flow in real time;

[0023] S241, when the sampling flow rate is greater than the set sampling flow rate, the single chip microcomputer controls the speed of the vacuum pump to decrease, thereby reducing the flow rate of gas entering the air bag until the sampling flow rate reaches the set value;

[0024] S242, when the sampling flow rate is less than the set sampling flow rate, the single chip microcomputer controls the speed of the vacuum pump to increase, thereby increasing the flow rate of gas entering the air bag until the sampling flow rate reaches the set value;

[0025] S25, based on the flow value of the flow sensor, the pressure value in the vacuum box, the atmospheric pressure value and the ambient temperature value, the single chip microcomputer calculates the accurate flow value and volume value of the gas entering the air bag; during the entire sampling process, the single chip microcomputer continuously receives and processes the data of each sensor to ensure that the sampling flow rate is stable at the set value;

[0026] S26, when the set sampling time is reached or the set volume of gas sample is collected, the single chip microcomputer controls the vacuum pump to stop working.

[0027] The beneficial effects achieved by the present invention are:

[0028] First, the present invention installs the flow sensor in front of the air inlet nozzle of the air bag to ensure that its sampling flow is the flow of gas entering the air bag, thereby avoiding the influence of negative pressure on the flow measurement and improving the accuracy of flow measurement. The data of the flow sensor is received in real time through the single-chip microcomputer, and real-time adjustment is made according to the set sampling flow to ensure that the sampling flow is stable at the set sampling flow value, further improving the accuracy of flow measurement.

[0029] Second, the present invention uses the flow value of the flow sensor, the pressure value in the vacuum box, the atmospheric pressure value and the ambient temperature value to calculate the accurate flow value and volume value of the gas entering the air bag through the single-chip microcomputer, thereby ensuring the reliability of the sampling data. During the sampling process, the single-chip microcomputer continuously receives and processes the data of each sensor to ensure that the sampling flow is stable at the set value, effectively reducing the accumulation of errors and improving the accuracy of the sampling data.

[0030] Third, the present invention can detect the atmospheric pressure and ambient temperature in real time by setting an atmospheric pressure sensor and an ambient temperature sensor, so that the device can adapt to the sampling requirements under different environmental conditions, thereby improving the accuracy of flow measurement and the reliability of sampling data. The device and method of the present invention are particularly suitable for application scenarios with high requirements for flow control and high-precision gas flow and volume measurement, such as environmental monitoring, industrial gas analysis and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0032] Figure 2 It is a structural schematic diagram of a metering sampling device in the prior art.

[0033] Numbers in the figure:

[0034] 1. Air inlet nozzle; 2. Vacuum box; 3. Air bag; 4. Air extraction nozzle; 5. Flow sensor; 6. Air extraction pump; 7. Single chip microcomputer; 8. Atmospheric pressure sensor; 9. Ambient temperature sensor; 10. Pressure detection nozzle inside the vacuum box; 11. Pressure sensor inside the vacuum box. DETAILED DESCRIPTION

[0035] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the present invention. In addition, the forms of the various structures recorded in the following embodiments are merely illustrative, and the present invention is not limited to the various structures recorded in the following embodiments. All other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0036] In the prior art, Figure 2 As shown, the method of metering sampling measurement is mainly based on the combined use of vacuum box 2 and air bag 3, and the control and measurement of gas flow are realized by means of flow sensor 5, air pump 6 and single chip microcomputer 7. The specific description is as follows:

[0037] The air bag 3 is placed in the sealed vacuum box 2. The air inlet nozzle 1 of the air bag 3 is directly connected to the atmosphere, which means that in the initial state, the air bag 3 does not form a sealed gas passage with other parts in the vacuum box 2.

[0038] When the system starts working, the vacuum pump 6 starts. Under the action of the vacuum pump 6, the gas in the vacuum box 2 begins to be extracted, passes through the vacuum nozzle 4 and the flow sensor 5, and is finally discharged into the atmosphere. When the gas flows through the flow sensor 5, the sensor will capture the current flow value and transmit the flow value signal to the single-chip microcomputer 7. After receiving the signal from the flow sensor 5, the single-chip microcomputer 7 compares the current flow value with the set sampling flow value.

[0039] If the current sampling flow value is greater than the set sampling flow value, the single chip microcomputer 7 will send an instruction to reduce the speed of the air pump 6 to reduce the amount of gas extracted so that the flow gradually approaches the set value. On the contrary, if the current flow value is less than the set extraction flow, the single chip microcomputer 7 will increase the speed of the air pump 6 to increase the amount of gas extracted until the set flow is reached.

[0040] In this prior art, the flow sensor 5 measures the flow value of the gas discharged from the vacuum box 2, rather than the actual flow value of the gas entering the air bag 3. This results in the actual measurement and control results being flow values ​​and volume values ​​at different temperatures and pressures than the flow and volume of the gas entering the air bag. As we all know, the volume of gas under different temperature and pressure conditions cannot be compared. The flow value of the flow sensor 5 is calibrated under ambient temperature, atmospheric pressure and other conditions, but the state during use (i.e., the negative pressure state in the vacuum box 2) is inconsistent with the pressure and temperature state during calibration. Therefore, the gas flow value measured by this method is not the flow value of the gas entering the air bag.

[0041] A vacuum box 2 sampling device for gas flow and volume measurement of the present invention is as follows: it includes a vacuum box 2, a flow sensor 5, an air pump 6 and a single-chip microcomputer 7, wherein the flow sensor 5 is installed on the outside of the vacuum box 2, and is provided with an air inlet and an air outlet, and the air inlet of the flow sensor 5 is communicated with a sampling source; a vacuum box internal pressure detection nozzle 10, an air inlet nozzle 1 and an air suction nozzle 4 are provided on the vacuum box 2, and an air bag 3 is installed in the vacuum box 2, one end of the air inlet nozzle 1 is communicated with the air outlet of the flow sensor 5, and the other end is sealed and connected with the air inlet of the air bag 3 in the vacuum box 2, forming a channel for gas to enter the air bag 3; the air suction nozzle 4 is connected to the air suction pump 6, and the gas in the vacuum box 2 is extracted by the air pump; the vacuum box internal pressure detection nozzle 10 is connected to a vacuum box internal pressure sensor 11 for detecting the pressure value in the vacuum box 2; the single-chip microcomputer 7 is communicatively connected with the flow sensor 5, the vacuum box internal pressure sensor 11 and the air suction pump 6. An atmospheric pressure sensor 8 and an ambient temperature sensor 9 are also provided which are communicatively connected to the single chip computer 7 and are used to detect the atmospheric pressure and the ambient temperature.

[0042] The present invention utilizes constant current sampling, and its working principle is to utilize a single chip microcomputer 7, an air pump 6, a vacuum box 2, a flow sensor 5, an air bag 3 and other equipment to realize constant current collection of gas samples by accurately controlling the sampling flow rate. The single chip microcomputer 7 controls the operation of the vacuum pump 6 according to the set sampling flow rate. Since the interior of the vacuum box 2 is sealed and isolated from the outside air, under the action of the vacuum pump 6, the gas in the vacuum box 2 is discharged into the atmosphere, resulting in a negative pressure state in the vacuum box 2. Under the action of atmospheric pressure, the sampled gas sample enters the air bag 3 through the flow sensor 5 and the air inlet nozzle 1 of the vacuum box 2. When the gas flows through the flow sensor 5, the flow signal of the flow sensor 5 is transmitted to the single chip microcomputer 7. The single chip microcomputer 7 controls the rotation speed of the vacuum pump 6 according to the set flow value, so that the flow value flowing through the flow sensor 5 reaches the set sampling flow value. When the sampling flow is greater than the set flow value, the single chip microcomputer 7 controls the rotation speed of the vacuum pump 6 to decrease, so that the sampling flow reaches the set value; when the sampling flow is less than the set flow value, the single chip microcomputer 7 controls the rotation speed of the vacuum pump 6 to increase, so that the sampling flow reaches the set value, thereby achieving the purpose of constant flow sampling using the vacuum box 2 and the air bag 3.

[0043] The flow meter is installed in front of the air inlet of the air bag 3. The flow value and volume value of the gas entering the air bag 3 are the flow value and volume value under the working condition, and the data is accurate and reliable. The flow value calibration of the flow sensor 5 is consistent with the state value at the time of sampling, which ensures the authenticity of the flow value and gas volume value collected by the gas sample from the perspective of quality assurance of sample collection and credibility of quality control.

[0044] The following are the specific steps: A method for measuring and sampling a vacuum box 2 sampling device for gas flow and volume measurement, which includes the following steps:

[0045] S1, correctly connect the vacuum box 2, the air bag 3, the flow sensor 5, and the air pump 6 and initialize the settings, and each sensor sends initial data to the single chip computer 7; the specific process of step S1 includes:

[0046] S11, place the air bag 3 in the sealed vacuum box 2, and ensure that the air inlet of the air bag 3 is sealed and connected with the air inlet nozzle 1 of the vacuum box 2 in the vacuum box 2; the air inlet of the flow sensor 5 is connected with the sampling source to form a channel for the gas to enter the air bag 3; the suction nozzle 4 is connected with the suction pump 6 to extract the gas in the vacuum box 2; the pressure detection nozzle 10 in the vacuum box is connected with the pressure sensor 11 in the vacuum box to detect the pressure value in the vacuum box 2; the atmospheric pressure sensor 8 and the ambient temperature sensor 9 are respectively connected to the single-chip microcomputer 7 for detecting the atmospheric pressure and the ambient temperature;

[0047] S12, start the single-chip microcomputer 7 and perform initialization settings, including setting the sampling flow rate and sampling time parameters; the flow sensor 5, the vacuum box pressure sensor 11, the atmospheric pressure sensor 8 and the ambient temperature sensor 9 send initial data to the single-chip microcomputer 7 respectively;

[0048] S2, the single chip computer 7 controls the vacuum pump 6 to form a negative pressure, so that the gas sample enters the air bag 3 through the flow sensor 5, and adjusts the speed of the vacuum pump 6 in real time to maintain a constant flow rate, and calculates the gas flow rate and volume at the same time; the specific process of step S2 includes:

[0049] S21, under the control of the single chip microcomputer 7, the vacuum pump 6 starts to work, and the gas in the vacuum box 2 is extracted through the vacuum nozzle 4, causing the pressure in the vacuum box 2 to gradually decrease, forming a negative pressure state. Under the action of the atmospheric pressure difference, the gas sample passes through the flow sensor 5 and the air inlet nozzle 1 and enters the air bag 3;

[0050] S22, when the gas flows through the flow sensor 5, the flow sensor 5 transmits the flow value signal to the single chip computer 7;

[0051] S23, the single chip microcomputer 7 receives the flow value signal of the flow sensor 5, the pressure value signal of the pressure sensor 11 in the vacuum box, the pressure value signal of the atmospheric pressure sensor 8 and the temperature value signal of the ambient temperature sensor 9;

[0052] S24, according to the set sampling flow, the single chip microcomputer 7 calculates the difference between the current sampling flow and the set sampling flow in real time;

[0053] S241, when the sampling flow rate is greater than the set sampling flow rate, the single chip microcomputer 7 controls the speed of the air pump 6 to decrease, thereby reducing the flow rate of gas entering the air bag 3 until the sampling flow rate reaches the set value;

[0054] S242, when the sampling flow rate is less than the set sampling flow rate, the single chip microcomputer 7 controls the speed of the vacuum pump 6 to increase, thereby increasing the flow rate of gas entering the air bag 3 until the sampling flow rate reaches the set value;

[0055] S25, based on the flow value of the flow sensor 5, the pressure value in the vacuum box 2, the atmospheric pressure value and the ambient temperature value, the single chip microcomputer 7 calculates the accurate flow value and volume value of the gas entering the air bag 3; during the entire sampling process, the single chip microcomputer 7 continuously receives and processes the data of each sensor to ensure that the sampling flow rate is stable at the set value;

[0056] S26, when the set sampling time is reached or enough gas samples are collected, the single chip microcomputer 7 controls the air pump 6 to stop working.

[0057] S3, the single chip microcomputer 7 saves the collected gas flow value, volume value, atmospheric pressure, and ambient temperature parameters to a storage device or outputs the collected data to an external device or system through a communication interface.

[0058] Embodiment 1: This embodiment introduces a vacuum box 2 sampling device and method for gas flow and volume measurement of the present invention through a specific application case.

[0059] In this embodiment, a gas bag 3 with a volume of 1L is used to collect 1000mL of a gas sample (hourly average sampling) in the ambient air for 1 hour;

[0060] The goal of this example is to use a vacuum box 2 sampling device to collect 1000mL of gas sample from ambient air within 1 hour, and the set sampling flow rate value is 16.67mL / min. Follow the steps below:

[0061] 1. Device preparation and initialization:

[0062] The device includes a vacuum box 2, an air bag 3 (1L volume), a flow sensor 5, an air pump 6, a single-chip computer 7, an atmospheric pressure sensor 8, an ambient temperature sensor 9, and a pressure sensor 11 inside the vacuum box.

[0063] Place the air bag 3 in a sealed vacuum box 2, and ensure that the air inlet of the air bag 3 is sealed and connected to the air inlet nozzle 1 of the vacuum box 2 in the vacuum box 2. The air inlet of the flow sensor 5 is connected to the sampling source, and the air outlet is connected to the air inlet nozzle 1 of the vacuum box 2. The suction nozzle 4 is connected to the suction pump 6, which is used to extract the gas in the vacuum box 2. The pressure detection nozzle 10 in the vacuum box is connected to the pressure sensor 11 in the vacuum box, which is used to detect the pressure value in the vacuum box 2. The atmospheric pressure sensor 8 and the ambient temperature sensor 9 are respectively connected to the single-chip microcomputer 7 for communication, and are used to detect the atmospheric pressure and ambient temperature. Start the single-chip microcomputer 7, and perform initialization settings, including setting the sampling flow rate to 16.67mL / min and the sampling time to 1 hour. Each sensor sends initial data to the single-chip microcomputer 7.

[0064] 2. Sampling process:

[0065] Under the control of the single chip microcomputer 7, the vacuum pump 6 starts to work, and the gas in the vacuum box 2 is extracted through the vacuum nozzle 4, causing the pressure in the vacuum box 2 to gradually decrease, forming a negative pressure state. Under the action of the atmospheric pressure difference, the ambient air enters the air bag 3 through the flow sensor 5 and the air inlet nozzle 1. When the gas flows through the flow sensor 5, the flow sensor 5 transmits the flow value signal to the single chip microcomputer 7. The single chip microcomputer 7 receives the flow value signal of the flow sensor 5, the pressure value signal of the pressure sensor 11 in the vacuum box, the pressure value signal of the atmospheric pressure sensor 8, and the temperature value signal of the ambient temperature sensor 9.

[0066] According to the set sampling flow rate (16.67mL / min), the single chip microcomputer 7 calculates the difference between the current sampling flow rate and the set sampling flow rate in real time:

[0067] When the sampling flow rate is greater than the set sampling flow rate, the single chip microcomputer 7 controls the rotation speed of the vacuum pump 6 to decrease, thereby reducing the flow rate of gas entering the air bag 3 until the sampling flow rate reaches the set value.

[0068] When the sampling flow rate is less than the set sampling flow rate, the single chip microcomputer 7 controls the rotation speed of the vacuum pump 6 to increase, thereby increasing the flow rate of gas entering the air bag 3 until the sampling flow rate reaches the set value.

[0069] The single chip microcomputer 7 calculates the accurate flow value and volume value of the gas entering the air bag 3 according to the flow value of the flow sensor 5, the pressure value in the vacuum box 2, the atmospheric pressure value and the ambient temperature value. During the whole sampling process, the single chip microcomputer 7 continuously receives and processes the data of each sensor to ensure that the sampling flow is stable at the set value, effectively reducing the accumulation of errors.

[0070] 3. Sampling ends:

[0071] When the set sampling time (1 hour) is reached or 1000 mL of gas sample is collected, the single chip microcomputer 7 controls the air pump 6 to stop working. The single chip microcomputer 7 saves the collected gas flow value, volume value, atmospheric pressure, ambient temperature and other environmental parameters to a storage device, or outputs them to an external device or system through a communication interface.

[0072] 4. Result verification:

[0073] Through the above process, this embodiment collects 1000 mL of gas sample from the ambient air within 1 hour, and the sampling flow rate is constant at 16.67 mL / min, achieving the purpose of constant flow sampling.

[0074] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A vacuum box air bag sampling device for gas flow and volume measurement, comprising a vacuum box, an air bag, a flow sensor, an air pump and a single chip microcomputer, wherein: The air inlet of the flow sensor is connected to the sampling source, and the air outlet of the flow sensor is connected to the air inlet nozzle of the air bag; The vacuum box is provided with a vacuum box pressure detection nozzle, an air inlet nozzle and an air extraction nozzle. An air bag is installed in the vacuum box. One end of the air inlet nozzle of the air bag is connected to the air outlet of the flow sensor to form a channel for gas to enter the air bag. The vacuum nozzle of the vacuum box is connected to the vacuum pump, and the gas in the vacuum box is pumped out by the air pump; The vacuum box internal pressure detection nozzle is connected to a vacuum box internal pressure sensor for detecting the pressure value in the vacuum box; The single chip microcomputer is connected in communication with the flow sensor, the pressure sensor in the vacuum box and the air pump.

2. A vacuum box air bag sampling device for gas flow and volume measurement according to claim 1, characterized in that: An atmospheric pressure sensor and an ambient temperature sensor which are connected to the single chip microcomputer for detecting the atmospheric pressure and the ambient temperature are also provided.

3. A method for measuring and sampling using the vacuum box air bag sampling device for gas flow and volume measurement as claimed in claim 2, characterized in that: It includes the following steps: S1, correctly connect the vacuum box, air bag, flow sensor, and air pump and initialize the settings, and each sensor sends initial data to the microcontroller; S2, the single chip microcomputer controls the vacuum pump to form a negative pressure in the vacuum box. At the same time, the gas sample enters the air bag through the flow sensor, and adjusts the speed of the vacuum pump in real time to maintain a constant flow rate, and calculates the gas flow rate and volume; S3, the single chip microcomputer saves the collected gas flow value, volume value, atmospheric pressure, and ambient temperature parameters to a storage device or outputs the collected data to an external device or system through a communication interface. Further, the specific process of step S1 includes: S11, place the air bag in a sealed vacuum box, and ensure that the air inlet of the air bag is sealed and connected to the air inlet nozzle of the vacuum box in the vacuum box; the air inlet of the flow sensor is connected to the sampling source to form a channel for the gas to enter the air bag; the air extraction nozzle is connected to the air extraction pump to extract the gas in the vacuum box to form a negative pressure inside the vacuum box; the pressure detection nozzle in the vacuum box is connected to the pressure sensor in the vacuum box to detect the pressure value in the vacuum box; the atmospheric pressure sensor and the ambient temperature sensor are respectively connected to the single-chip microcomputer for communication to detect the atmospheric pressure and ambient temperature; S12, start the single chip microcomputer and perform initialization settings, including setting the sampling flow rate and sampling time parameters; the flow sensor, the pressure sensor in the vacuum box, the atmospheric pressure sensor and the ambient temperature sensor send initial data to the single chip microcomputer respectively.

4. The method according to claim 3, characterized in that The specific process of step S2 includes: S21, under the control of the single chip microcomputer, the vacuum pump starts to work, and the gas in the vacuum box is extracted through the vacuum nozzle, causing the pressure in the vacuum box to gradually decrease, forming a negative pressure state. Under the action of the atmospheric pressure difference, the gas sample passes through the flow sensor and the air inlet nozzle and enters the air bag; S22, when the gas flows through the flow sensor, the flow sensor transmits the flow value signal to the single chip microcomputer; S23, the single chip microcomputer receives the flow value signal of the flow sensor, the pressure value signal of the pressure sensor in the vacuum box, the pressure value signal of the atmospheric pressure sensor and the temperature value signal of the ambient temperature sensor; S24, according to the set sampling flow, the single chip microcomputer calculates the difference between the current sampling flow and the set sampling flow in real time; S241, when the sampling flow rate is greater than the set sampling flow rate, the single chip microcomputer controls the speed of the vacuum pump to decrease, thereby reducing the flow rate of gas entering the air bag until the sampling flow rate reaches the set value; S242, when the sampling flow rate is less than the set sampling flow rate, the single chip microcomputer controls the speed of the vacuum pump to increase, thereby increasing the flow rate of gas entering the air bag until the sampling flow rate reaches the set value; S25, based on the flow value of the flow sensor, the pressure value in the vacuum box, the atmospheric pressure value and the ambient temperature value, the single chip microcomputer calculates the accurate flow value and volume value of the gas entering the air bag; during the entire sampling process, the single chip microcomputer continuously receives and processes the data of each sensor to ensure that the sampling flow rate is stable at the set value; S26, when the set sampling time is reached or the set volume of gas sample is collected, the single chip microcomputer controls the vacuum pump to stop working.

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