Target gas concentration change measuring device and lung dispersion testing equipment

Abstract

The embodiment of the invention belongs to the technical field of gas concentration measurement, and relates to a target gas concentration change measuring device which comprises a gas supply module, a gas sensor, a gas flow interface, a pressure sensor and a main control processing module, the gas supply module and the gas sensor are communicated with the gas flow interface through a gas path; the main control processing module is used for controlling the gas supply module to output a test gas with a first pressure to the gas flow interface, wherein the test gas contains a target gas component with a first concentration; detecting the concentration of the gas flow output from the gas flow interface through a gas sensor to obtain the actually measured concentration, and detecting the pressure of the gas flow flowing through the gas sensor through a pressure sensor to obtain the gas path pressure; according to the ratio of the first pressure to the gas path pressure, correcting the actually measured concentration into a second concentration under the first pressure; and determining the concentration variation of the target gas according to the first concentration and the second concentration. Therefore, the concentration variation of the target gas in the whole test process can be measured more accurately.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of gas concentration measurement, and in particular to a target gas concentration change measurement device and a lung diffusion test device. BACKGROUND

[0002] In some scenarios of applying system identification methods for testing based on target gas concentration changes, standard gas containing a set concentration of target gas is introduced into the measured system, which can absorb or convert the target gas due to its characteristics, and then the measured concentration of the target gas in the measured gas output by the measured system is detected. By determining the change amount of the measured concentration and the set concentration, some characteristics of the measured system can be determined. However, in some cases, the pressure of the measured gas output by the measured system may be different from the pressure of the input standard gas. If this pressure fluctuation is not corrected, it will affect the accuracy of the finally measured target gas concentration change, thereby affecting the final test result. Specifically, taking the lung diffusion test scenario as an example:

[0003] Lung diffusion function test is one of the core examinations for evaluating the gas exchange capacity of the lung, mainly measuring the ability of a certain alveolar gas to diffuse from the alveolus to the capillary through the alveolus-capillary membrane and combine with hemoglobin (Hb) in red blood cells. It is an important means for diagnosing and evaluating respiratory diseases. The core of lung diffusion function is the diffusion of gas, i.e. the natural diffusion of gas from a high concentration area to a low concentration area. Carbon monoxide (CO) is used as a diffusion gas in the test to simulate the diffusion process of oxygen, and the absorption amount of carbon monoxide in the inhaled gas is measured to reflect the diffusion function.

[0004] Currently, in the lung diffusion function test, a one-breath diffusion test method is used, and a non-dispersive infrared (NDIR) module is used to detect the concentration of tracer gas and diffusion gas (CO) in real time to calculate diffusion parameters. The tracer gas can be methane (CH4) or helium (He). Specifically, in the one-breath test, there are three processes: inhalation, breath holding and exhalation. The subject first inhales test gas containing standard concentration of tracer gas and CO, then holds breath for a period of time, and then exhales quickly and completely. During the exhalation process, the NDIR gas detector automatically measures the concentrations of CO and tracer gas in the exhaled gas. Then, according to the concentration changes of CO and tracer gas in the inhaled and exhaled gas, the diffusing capacity of the lung for carbon monoxide (DLCO), alveolar ventilation (VA) and other lung diffusion function parameters are automatically calculated by formula.

[0005] However, in existing lung diffusion testing equipment, the pressure at the sampling tube connected to the breathing interface fluctuates due to factors such as subject cooperation and breathing rhythm during the test. Furthermore, the NDIR module used for diffusion typically employs an extraction scheme, further leading to significant changes in the airway pressure exiting the NDIR module. Since the NDIR module is sensitive to airway pressure changes when measuring gas concentration, these fluctuations alter the concentrations of CO and tracer gas in the gas flowing through the NDIR module. If these changes in CO and tracer gas concentrations caused by airway pressure fluctuations are not corrected, they will significantly affect the final calculated values ​​of CO and tracer gas concentration changes in inhaled and exhaled gases, resulting in inaccurate measurements of lung diffusion function parameters.

[0006] Based on the above discussion, how to avoid concentration change errors caused by gas path pressure fluctuations in test scenarios such as lung diffusion tests, and accurately measure the concentration change of a target gas throughout the entire test process, is a technical problem that still needs to be solved. Summary of the Invention

[0007] The purpose of this application is to provide a target gas concentration change measuring device, which can be used in test scenarios such as lung diffusion tests to avoid concentration change errors caused by gas path pressure fluctuations and accurately measure the concentration change of a target gas throughout the entire test process.

[0008] To address the aforementioned technical problems, the first aspect of this application provides a device for measuring changes in the concentration of a target gas, employing the technical solution described below:

[0009] Gas supply module, gas sensor, airflow interface, pressure sensor and main control processing module;

[0010] The gas supply module and the gas sensor are both connected to the gas flow interface through the gas path;

[0011] The main control processing module is used to execute the following test methods:

[0012] The gas supply module is controlled to output test gas at a first pressure to the airflow interface, and the test gas contains a target gas component at a first concentration;

[0013] The concentration of the gas flow output from the gas flow interface is detected by the gas sensor to obtain the measured concentration, which is the concentration of the target gas in the gas to be tested. The pressure of the gas flow passing through the gas sensor is detected by the pressure sensor to obtain the gas path pressure.

[0014] Based on the ratio of the first pressure to the gas path pressure, the measured concentration is corrected to a second concentration at the first pressure;

[0015] The concentration change of the target gas is determined based on the first concentration and the second concentration.

[0016] In some possible implementations, the pressure sensor includes a differential pressure sensor and an ambient pressure sensor. The differential pressure sensor is disposed in the gas path at the outlet of the gas sensor. The step of detecting the pressure of the gas flow passing through the gas sensor to obtain the gas path pressure includes:

[0017] The differential pressure value is obtained through the differential pressure sensor, and the current ambient pressure is obtained through the ambient pressure sensor.

[0018] The gas path pressure is determined based on the pressure difference value and the ambient pressure.

[0019] In some possible implementations, the main control processing module is also used to perform the following steps:

[0020] Determine whether both the differential pressure and the ambient pressure are within the set range, and issue an alarm if they exceed the set range.

[0021] In some possible implementations, the step of detecting the concentration of the gas flow output from the gas flow interface using the gas sensor to obtain the measured concentration includes:

[0022] The concentration of the gas flow output from the gas flow interface is detected by the gas sensor, and the first output signal of the gas sensor is obtained.

[0023] The measured concentration is determined based on the first output signal and the preset mapping relationship.

[0024] In some possible implementations, the gas supply module is connected to the gas sensor via a gas path, and the main control processing module is also used to perform the following gas sensor calibration method:

[0025] The gas supply module is controlled to output calibration gas at a third pressure to the gas sensor, and the calibration gas contains a target gas component at a third concentration;

[0026] Acquire the second output signal of the gas sensor and detect the gas path pressure through the pressure sensor;

[0027] Based on the ratio of the third pressure to the gas path pressure, the third concentration is calibrated to the fourth concentration under the gas path pressure;

[0028] The mapping relationship is determined based on the fourth concentration and the second output signal.

[0029] In some possible implementations, the measuring device further includes a vacuum pump, which is disposed in the gas path at the outlet of the gas sensor, and the main control processing module is also used to control the vacuum pump to draw gas.

[0030] To address the aforementioned technical problems, a second aspect of this application also provides a lung diffusion testing device, which employs the technical solution described below. The lung diffusion testing device includes:

[0031] The target gas concentration change measuring device as described in the first aspect and any possible implementation thereof, wherein the airflow interface is a breathing interface and the gas sensor is an NDIR gas sensor;

[0032] The gas supply module is connected to the breathing interface through a test gas path, and the gas sensor is connected to the breathing interface through a sampling gas path;

[0033] The target gas includes carbon monoxide and a tracer gas, wherein the tracer gas is methane or helium;

[0034] The main control processing module is also used to calculate lung diffusion parameters based on the change in the concentration of the target gas.

[0035] In some possible implementations, the step of determining the mapping relationship based on the fourth concentration and the second output signal includes:

[0036] The relative absorption rate is determined based on the second output signal and the zero-point output signal, wherein the zero-point output signal is the output signal of the NDIR gas sensor when air is pre-ventilated to the NDIR gas sensor;

[0037] The mapping relationship is determined based on the relative absorption rate and the fourth concentration.

[0038] In some possible implementations, the lung diffusion testing device further includes a flow sensor disposed at the breathing interface, and the main control processing module is further used to determine the subject's breathing status based on the flow sensor.

[0039] The step of controlling the gas supply module to output test gas at a first pressure to the airflow interface, wherein the test gas contains a target gas component at a first concentration, includes:

[0040] When the subject is detected to be in an inhalation state, the gas supply module is controlled to output test gas at a first pressure to the breathing interface, and the test gas contains a first concentration of target gas components;

[0041] The step of detecting the concentration of the airflow output from the airflow interface using the gas sensor to obtain the measured concentration includes:

[0042] When the subject is detected to be in an exhalation state, the concentration of the airflow output from the breathing interface is detected by the gas sensor to obtain the measured concentration.

[0043] In some possible implementations, the NDIR gas sensor includes a measuring chamber with an inlet and an outlet. The inlet of the measuring chamber is connected to both the breathing interface and the gas supply module, and the pressure sensor is disposed on the gas path at the outlet.

[0044] Compared with the prior art, the embodiments of this application have the following main advantages:

[0045] The target gas concentration change measuring device in this application measures the gas path pressure of a gas sensor using a pressure sensor. After the gas sensor detects the actual concentration of the target gas output from the gas flow interface, it corrects the actual concentration of the gas sensor to a second concentration under the same gas pressure as the test gas. Then, it compares the first concentration of the target gas in the test gas with this second concentration to determine the amount of concentration change of the target gas throughout the entire test process. This avoids the error caused by fluctuations in the gas path pressure of the gas sensor, thus enabling a more accurate measurement of the concentration change of the target gas throughout the entire test process. Attached Figure Description

[0046] To more clearly illustrate the solutions in this application, the accompanying drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a schematic diagram of the architecture of the target gas concentration change measuring device in Embodiment 1 of this application;

[0048] Figure 2 A flowchart of an embodiment of the test method executed by the main control processing module in Embodiment 1 of this application;

[0049] Figure 3 A flowchart of an embodiment of the gas path pressure monitoring method executed by the main control processing module in Embodiment 1 of this application;

[0050] Figure 4 A flowchart of an embodiment of the calibration method executed by the main control processing module in Embodiment 1 of this application;

[0051] Figure 5 This is a schematic diagram of the architecture of the lung diffusion testing device in Embodiment 12 of this application. Detailed Implementation

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having," and any variations thereof, in the specification, claims, and foregoing drawings of this application, are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the specification, claims, or foregoing drawings of this application are used to distinguish different objects, not to describe a particular order.

[0053] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0054] The concepts involved in the embodiments of this application will be further explained below:

[0055] Lung diffusion capacity refers to the ability of a certain alveolar gas to diffuse across the alveolar-capillary membrane from the alveoli into the bloodstream and bind to hemoglobin (Hb) in red blood cells. The gases exchanged in the alveolar-capillary membrane are primarily oxygen (O2) and carbon dioxide (CO2). Directly calculating oxygen diffusion is complex; however, carbon monoxide (CO) binds to hemoglobin 210 times more strongly than oxygen, and the carbon monoxide content in the blood plasma of normal individuals is almost zero (except for heavy smokers), making it convenient to calculate carbon monoxide intake during testing. Furthermore, carbon monoxide dissolves very little in blood plasma during transport; therefore, DLCO (diluted carbon dioxide) is currently the most commonly used method for lung diffusion capacity testing.

[0056] DLCO test: This test measures the efficiency of gas exchange in the lungs based on the ability of carbon monoxide (CO) to pass through the alveolar-capillary membrane. It is commonly used to diagnose and monitor certain respiratory diseases, such as interstitial lung disease and emphysema. During the DLCO test, the patient inhales gas containing a certain concentration of carbon monoxide and then exhales. By measuring the change in carbon monoxide concentration in the exhaled air, the diffusing capacity of carbon monoxide is calculated, thereby inferring the functional status of lung gas exchange. This method utilizes the high affinity of carbon monoxide for hemoglobin, making it an ideal gas for assessing lung diffusion capacity.

[0057] NDIR gas detection technology is a detection method based on the theory of gas absorption. Its basic principle is to identify and measure the concentration of gases by utilizing the absorption characteristics of different gases to specific wavelengths of infrared light. Each gas has its unique absorption spectrum, meaning it absorbs only within a specific range of infrared wavelengths. Therefore, by measuring the degree to which a gas sample absorbs these specific wavelengths of infrared light, the concentration of the gas can be calculated.

[0058] An NDIR gas detection module typically includes an infrared light source, a gas chamber, and an infrared detector. The infrared light source emits infrared light of a specific frequency, which shines onto the infrared detector after passing through the gas chamber. The gas chamber is used to introduce the gas to be tested. The infrared detector senses changes in the intensity of the infrared light after it passes through the gas chamber. When the gas to be tested contains a target gas component that can absorb infrared light of that specific frequency, the infrared light of that frequency will be lost due to absorption after passing through the gas chamber. Therefore, whether the gas to be tested contains a target gas component that can absorb infrared light of that specific frequency, and the concentration of that target gas component, will cause different output results from the infrared detector. This output result is mapped to the concentration of the target gas component in the gas to be tested. This mapping relationship is based on the Lambert-Beer law and combined with system design. Therefore, by obtaining the output value of the infrared detector and substituting it into the mapping relationship, the concentration of the target gas component can be determined.

[0059] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0060] Example 1

[0061] Specific reference Figure 1 , Figure 1 A schematic diagram of the architecture of a target gas concentration change measuring device according to an embodiment of this application is disclosed, wherein the target gas concentration change measuring device includes:

[0062] Gas supply module 110, gas sensor 120, airflow interface 130, pressure sensor 140 and main control processing module 150;

[0063] The gas supply module 110 and the gas sensor 120 are both connected to the gas flow interface 130 through the gas path.

[0064] The main control processing module 150 is used to implement functions such as data acquisition and processing and hardware control. It can be one or more processors, one or more controllers, or one or more controllers and processors. The controller can be a micro-controller unit (MCU).

[0065] The gas supply module 110, gas sensor 120, and pressure sensor 140 are all electrically connected to the main control processing module 150, and can receive control commands from the main control processing module 150 and upload data to the main control processing module 150.

[0066] The gas supply module 110 includes a gas source, valves, a pressure regulating unit, and a gas mixing unit. The valves and gas mixing unit control the gas source to output a mixed gas containing a set target gas concentration, and the pressure regulating unit outputs the gas flow at a set pressure. The gas source includes one or more high-pressure gas cylinders. In some cases, multiple high-pressure gas cylinders are used, each containing a single-component gas. By controlling the valves and gas mixing unit, the gases output from different high-pressure gas cylinders are mixed to obtain mixed gases with different set concentrations, facilitating the calibration of the gas sensor 120 using various mixed gas concentrations. In other cases, one or more high-pressure gas cylinders may also contain mixed gases with known component concentrations, thereby reducing the gas mixing operation and improving efficiency.

[0067] The airflow interface 130 serves as the airflow test port for this measuring device. It is connected to the air supply module 110 via a test air path and to the gas sensor 120 via a sampling air path. The testing unit can receive the airflow output from the air supply module 110 via the test air path through the airflow interface 130, and also output airflow to the gas sensor 120 via the sampling air path through the airflow interface 130. The airflow interface 130 can be a single gas interface, or it can include separate input and output airflow ports. The input airflow port is connected to the air supply module 110, and the output airflow port is connected to the gas sensor 120.

[0068] Pressure sensor 140 is installed in the gas path through gas sensor 120 to detect the pressure of gas flowing through gas sensor 120.

[0069] The gas sensor 120 can be an electrochemical gas sensor, an NDIR gas sensor, or other types of gas sensors, depending on the type of target gas and the detection requirements. The NDIR gas sensor includes a measuring chamber with an inlet and an outlet. The inlet is connected to the gas flow interface 130 via a sampling gas path, and the pressure sensor 140 can be installed within the gas path at the outlet.

[0070] based onFigure 1 The architecture shown is as follows: Figure 2 As shown, the main control processing module 150 is used to execute the following test methods:

[0071] S210, Control the gas supply module to output test gas at a first pressure to the airflow interface, the test gas containing the target gas component at a first concentration.

[0072] In this embodiment, the target gas is the sensitive gas of the gas sensor 120. Before executing step S210, the main control processing module 150 is also used to open the test gas path and close the sampling gas path. Then, it controls the gas supply module 110 to output the test gas to the gas flow interface 130 within a set time period.

[0073] S220. The concentration of the airflow output from the airflow interface is detected by a gas sensor to obtain the measured concentration, which is the concentration of the target gas in the gas to be measured. The pressure of the airflow flowing through the gas sensor is detected by a pressure sensor to obtain the gas path pressure.

[0074] In this embodiment, when the airflow interface 130 outputs airflow, the main control processing module 150 can issue a command to the gas sensor 120 to monitor the concentration of the airflow output from the airflow interface 130, and determine the measured concentration of the target gas in the output airflow. The unit of the measured concentration is mol / L or g / L. Simultaneously, the main control processing module 150 uses the gas sensor 120 to detect the pressure of the airflow flowing through the gas sensor 120 to obtain the gas path pressure. The airflow flowing through the gas sensor 120 is the gas actually detected by the gas sensor 120.

[0075] S230. Based on the ratio of the first pressure to the gas path pressure, correct the measured concentration to the second concentration under the first pressure.

[0076] In this embodiment, during testing, the testing environment is kept as constant as possible, so that the temperature of the test gas and the gas output from the gas flow interface 130 and flowing to the gas sensor 120 through the sampling gas path are the same or close. Thus, according to the ideal gas law PV=nRT, where P is pressure, V is volume, R is a constant, T is temperature, and n is the amount of substance, we can obtain P=cRT, c=n / V, which is the molar concentration in mol / L. That is, under constant temperature, the molar concentration is directly proportional to the gas pressure.

[0077] Therefore, after obtaining the measured concentration, the second concentration at the first pressure can be obtained by correcting the measured concentration using the equation P = cRT. Specifically, C2 = C1 * (P2 / P1), where C1 refers to the measured concentration, P1 refers to the gas path pressure, C2 refers to the second concentration, and P2 refers to the first pressure.

[0078] S240. Determine the change in the concentration of the target gas based on the first concentration and the second concentration.

[0079] In this embodiment, the measured concentration is corrected to the second concentration under the first pressure, and then the concentration change of the target gas during the entire test process is determined based on the difference between the first concentration and the second concentration.

[0080] Compared with the prior art, the embodiments of this application have the following main advantages:

[0081] The target gas concentration change measuring device in this application measures the gas path pressure of gas sensor 120 using a pressure sensor 140. After gas sensor 120 detects the actual concentration of the target gas output from gas flow interface 130, the actual concentration of gas sensor 120 is corrected to a second concentration under the same gas pressure as the test gas. Then, the first concentration of the target gas in the test gas is compared with the second concentration to determine the concentration change of the target gas throughout the entire test process. This avoids the error caused by gas path pressure fluctuations of gas sensor 120 affecting the target gas concentration change, thus allowing for a more accurate measurement of the concentration change of the target gas throughout the entire test process.

[0082] In some optional implementations of this embodiment, the pressure sensor 140 includes a differential pressure sensor and an ambient pressure sensor 140. The differential pressure sensor is disposed in the gas path at the outlet of the gas sensor 120. The step of detecting the pressure of the gas flow passing through the gas sensor 120 by the pressure sensor 140 to obtain the gas path pressure includes:

[0083] The differential pressure value is obtained through the differential pressure sensor, and the current ambient pressure is obtained through the ambient pressure sensor 140.

[0084] The gas path pressure is determined based on the pressure difference and ambient pressure.

[0085] In this embodiment, the pressure sensor 140 includes a differential pressure sensor and an ambient pressure sensor 140. The differential pressure sensor is installed in the gas path at the gas flow outlet of the gas sensor 120 and is used to detect the pressure difference value relative to the environment in the gas path. The main control processing module 150 superimposes the differential pressure value of the differential pressure sensor and the ambient pressure of the ambient sensor to determine the gas path pressure.

[0086] Specifically, when the gas sensor 120 is an NDIR gas sensor, the differential pressure sensor can be installed in the gas path at the outlet of the measuring gas chamber. The gas path pressure is marked as Pndir, the differential pressure value is marked as ΔP, and the ambient pressure value is P0. Then, Pndir = ΔP + P0. When the gas path pressure is negative relative to the ambient pressure, ΔP is a negative number.

[0087] In some optional implementations of this embodiment, the main control processing module 150 is further configured to perform the following steps:

[0088] It determines whether the differential pressure and ambient pressure are both within the set range, and issues an alarm when they exceed the set range.

[0089] Specifically, since air pressure has a significant impact on the concentration detection of gas sensor 120, it is usually necessary to perform pressure detection on the gas path of gas sensor 120. Existing gas path pressure detection typically uses an absolute pressure sensor 140 installed in the gas path for pressure measurement. However, the pressure value detected by the absolute pressure sensor changes with atmospheric pressure, making it impossible to calculate the pressure difference between the gas path and the environment, thus failing to identify some abnormal operating states of the gas path. Common abnormal gas path states include gas path blockage (increased negative pressure) and gas path leakage (decreased negative pressure) caused by blockage, loosening, or cracking of the sampling gas path, as well as abnormal gas path pressure caused by abnormal operation of the extraction pump 160 if extraction is used (excessive extraction power leads to excessively high negative pressure in the gas path; insufficient extraction power leads to excessively low negative pressure in the gas path).

[0090] In this embodiment, to detect the gas path pressure and to monitor the aforementioned abnormalities in the gas path, the pressure sensor 140 is designed to include a differential pressure sensor and an ambient pressure sensor 140, such as... Figure 3 As shown, the main control processing module 150 is also used to perform the following gas path pressure monitoring method:

[0091] S310. Obtain the ambient pressure value through an ambient pressure sensor;

[0092] S320. Determine whether the ambient pressure value is within the preset operating range of the gas sensor;

[0093] S330. When the ambient pressure value is within the operating range of the gas sensor, acquire the differential pressure value detected by the differential pressure sensor;

[0094] S340. Determine whether the differential pressure value is within the preset gas path design range;

[0095] S350. When the differential pressure value is within the gas circuit design range, the gas circuit status is determined to be normal.

[0096] S360 generates an error message when the ambient pressure value deviates from the operating range of the gas sensor, or when the differential pressure value deviates from the gas path design range.

[0097] In some optional implementations of this embodiment, the step of detecting the concentration of the gas flow output from the gas flow interface 130 using the gas sensor 120 to obtain the measured concentration includes:

[0098] The concentration of the gas flow output from the gas flow interface 130 is detected by the gas sensor 120, and the first output signal of the gas sensor 120 is obtained.

[0099] The measured concentration is determined based on the first output signal and the preset mapping relationship.

[0100] In this embodiment, the gas sensor 120 needs to be calibrated and standardized before concentration detection, and the mapping relationship between the output signal of the gas sensor 120 and the measured concentration value needs to be determined. The output signal can be a current signal or a voltage signal. Therefore, when performing concentration detection subsequently, the first output signal is substituted into the preset mapping relationship, thereby determining the measured concentration value.

[0101] For example, taking gas sensor 120 as an NDIR gas sensor and CO and CH4 as target gases, the process of gas concentration measurement will be explained.

[0102] The step of determining the measured concentration based on the first output signal and a preset mapping relationship specifically includes:

[0103] The relative absorption rate is determined based on the first output signal and the zero-point output signal, wherein the zero-point output signal is the output signal of the NDIR gas sensor when air is pre-ventilated to the NDIR gas sensor;

[0104] The measured concentration is determined based on the relative absorbance and the preset mapping relationship.

[0105] If the NDIR gas sensor is configured to have three detection channels—a CO channel, a CH4 channel, and a reference channel—then its specific detection process is as follows:

[0106] (1) Zero point calibration

[0107] Under ventilated conditions, the AD values ​​of the NDIR gas sensor were collected. The collected data included the AD values ​​of the CO channel, CH4 channel, and reference channel, which were labeled as ADco0, ADch40, and ADref0, respectively.

[0108] (2) Signal Acquisition

[0109] In measurement mode, the gas to be measured is input into the NDIR gas sensor, and the AD value of the NDIR gas sensor is collected. The collected data includes the AD value of the CO channel, the AD value of the CH4 channel, and the AD value of the reference channel, which are labeled as ADco, ADch4, and ADref, respectively.

[0110] (3) Calculate the relative absorption rate

[0111] The relative absorption rate of the CO channel is given by ABSco = ADco / ADref*ADco0 / ADref0.

[0112] The relative absorption rate of the CH4 channel is given by: ABSch4 = ADch4 / ADref * ADch40 / ADref0.

[0113] (4) Calculate the concentration of the target gas based on the preset mapping relationship.

[0114] The mapping relationship of the NDIR gas sensor is based on Beer-Lambert's absorption law. For example, for the CO concentration value Cco=[(ln(1-ABSco / wco_cal i)) / (-bco)]^(1 / nco), wco_cal i, bco, and nco are all parameters of the preset mapping relationship obtained by the CO channel according to Beer-Lambert's absorption law. For the CH4 concentration value Cch4=[(ln(1-ABSch4 / wch4_cali)) / (-bch4)]^(1 / nch4), wch4_cal i, bch4, and nch4o are all parameters of the preset mapping relationship obtained by the CH4 channel according to Beer-Lambert's absorption law.

[0115] In some optional implementations of this embodiment, based on Figure 1 The architecture shown is as follows: Figure 4 As shown, the main control processing module 150 is also used to perform the following gas sensor 120 calibration method:

[0116] S410, Control the gas supply module to output calibration gas at a third pressure to the gas sensor, the calibration gas containing the target gas component at a third concentration;

[0117] S420: Acquire the second output signal of the gas sensor and detect the gas path pressure through the pressure sensor 140;

[0118] S430. Based on the ratio of the third pressure to the gas path pressure, calibrate the third concentration to the fourth concentration under the gas path pressure.

[0119] S440. Determine the mapping relationship based on the fourth concentration and the second output signal.

[0120] In this embodiment, the gas supply module 110 is also connected to the gas sensor 120 through a calibration gas path. When calibrating the gas sensor 120 of the measuring device, the gas supply module 110 can be controlled to output a calibration gas with a third pressure and a target gas concentration of the third concentration to the gas sensor 120. The gas sensor 120 is calibrated with the calibration gas to determine the mapping relationship between the output signal of the gas sensor 120 and the concentration measurement value.

[0121] Considering that the calibration gas needs to pass through the calibration gas path, the gas pressure of the gas flow through the gas sensor 120 may differ significantly from the pressure of the calibration gas. This pressure difference will cause the concentration of the target gas in the gas actually detected by the gas sensor 120 to be different from the third concentration. Therefore, if the third concentration is directly used to calibrate the gas sensor 120, the set input (i.e., the third concentration) will not correspond to the actual output (the second output signal). As a result, the mapping relationship calculated by back-calculation based on the set input and the actual output will also be inaccurate.

[0122] Based on the above description, in this embodiment, during the process of controlling the gas supply module 110 to output calibration gas to the gas sensor 120, the main control processing module 150 also detects the pressure of the airflow passing through the gas sensor 120 through the pressure sensor 140 to obtain the gas path pressure. The method for detecting the gas path pressure can refer to the aforementioned content. Then, based on the ratio of the third pressure to the gas path pressure, the third concentration is calibrated to the fourth concentration under that gas path pressure. After obtaining the second output signal output by the gas sensor 120, the mapping relationship is determined by reverse calculation based on the fourth concentration and the second output signal.

[0123] In a specific embodiment, step S440, determining the mapping relationship based on the fourth concentration and the second output signal, specifically includes:

[0124] The relative absorption rate is determined based on the second output signal and the zero-point output signal, wherein the zero-point output signal is the output signal of the NDIR gas sensor when air is pre-ventilated to the NDIR gas sensor;

[0125] The mapping relationship is determined based on the relative absorption rate and the fourth concentration.

[0126] For example, the NDIR gas sensor described above will be used as an example for illustration.

[0127] The mapping relationship of NDIR gas sensors follows Lambert-Beer's law. According to Lambert-Beer's law, the relationship between gas concentration and absorbance is as follows: Where ABS is the absorption rate, c is the concentration, b and n are the parameters of the formula, whose values ​​are related to the structure and coordination of the gas chamber, light source and sensor, and w is the environmental parameter, which is related to environmental temperature, humidity, environmental pressure and other parameters.

[0128] Given a fixed structure and hardware for the NDIR gas sensor, the values ​​of b and n do not change over time, while the value of w varies with environmental temperature, humidity, and pressure. Therefore, the calibration of an NDIR gas sensor typically involves two stages: calibration and full-scale calibration. Calibration primarily determines parameters b and n, while full-scale calibration primarily determines parameter w and needs to be performed as needed, such as each time the measuring device is powered on or when there are significant changes in the testing environment.

[0129] For example, the calibration process is as follows:

[0130] (1) Under the condition of air circulation, the AD value detected by the NDIR gas sensor is collected. The collected data includes the AD value of the CO channel, the AD value of the CH4 channel, and the AD value of the reference channel, which are labeled as ADco0, ADch40, and ADref0, respectively.

[0131] (2) Test gas 1, test gas 2 and test gas 3 with three concentrations of CO and CH4 are output to the NDIR gas sensor in sequence, and the AD value of the infrared gas detector is collected. The collected data includes the AD value of the CO channel, the AD value of the CH4 channel and the AD value of the reference channel. The results output for test gas 1 are labeled as ADco1, ADch41 and ADref1, respectively; the results output for test gas 2 are labeled as ADco2, ADch42 and ADref2, respectively; and the results output for test gas 3 are labeled as ADco3, ADch43 and ADref3, respectively.

[0132] (3) Based on the AD value, calculate the relative absorptivity of infrared light at different concentrations. The definition of relative absorptivity is:

[0133] The relative absorption rate of the CO channel is given by: ABSco = ADco / ADref * ADco0 / ADref0;

[0134] The relative absorption rate of the CH4 channel is given by: ABSch4 = ADch4 / ADref * ADch40 / ADref0.

[0135] Therefore, the CO channel can yield ABSco1, ABSco2, and ABSco3 for the three test gases. The CH4 channel can yield ABSch41, BSch42, and ABSch4 for the three test gases.

[0136] (4) Calculate the parameter coefficients of the gas concentration-relative absorption rate equation.

[0137] in accordance with By fitting the equations based on multiple concentration-relative absorption rates, the coefficients wco, bco, and nco for CO, and the coefficients wch4, bch4, and nch4 for CH4 can be obtained.

[0138] It should be noted that since the calibration process mainly involves calculating parameters b and n, and b and n are related to the structural fit of the gas chamber, light source, and sensor, it is not necessary to calibrate the concentrations of test gas 1, test gas 2, and test gas 3 to their concentrations under the gas path pressure during the calibration process, thus improving the efficiency of the calibration process.

[0139] After calibration, the w parameter in the mapping relationship can be determined. However, the w parameter is greatly affected by ambient temperature and humidity, so full-scale calibration is usually required as needed based on environmental conditions. For example, the full-scale calibration process is as follows:

[0140] (1) Under the condition of air being supplied to the NDIR gas sensor, the AD value of the infrared gas detector is collected. The collected data includes the AD value of the CO channel, the AD value of the CH4 channel, and the AD value of the reference channel, which are labeled as ADco0, ADch40, and ADref0, respectively.

[0141] (2) When the NDIR gas sensor is purged with a full-scale calibration test gas, the AD values ​​of the infrared gas detector are collected. The collected data include the AD values ​​of the CO channel, CH4 channel, and reference channel, which are labeled as ADcofull, ADch4full, and ADreffull, respectively. Among them, the CO concentration and CH4 concentration in the full-scale calibration test gas are labeled as Ccofull and Cch4full, respectively, and the pressure of the test gas is labeled as Pfull.

[0142] (3) During the execution of step (2), the gas path pressure of the NDIR gas sensor is acquired synchronously and recorded as Pndir.

[0143] (4) Based on the AD value, calculate the relative absorbance of the CO and CH4 channels at full-scale concentration. The definition of relative absorbance is:

[0144] CO channel, ABScoful l = ADcoful l / ADrefful l * ADco0 / ADref0;

[0145] CH4 channel, ABSch4ful l=ADch4ful l / ADrefful l*ADch40 / ADref0.

[0146] (5) According to Boyle's law, Ccofull and Cch4full are calibrated to the gas path pressure at the NDIR gas sensor, and the following is obtained:

[0147] The concentration of Ccofull at Pndir is Ccofull_cali = Pndir / Pfull * Ccofull, and the concentration of Cch4full at Pndir is Cch4full_cali = Pndir / Pfull * Cch4full.

[0148] (6) Based on the expression between gas concentration and absorption rate Calculate the calibration coefficients. Here, b and n are related to the fit between the gas chamber, light source, and sensor structure; they are fixed at the factory and require no adjustment. The only parameter that needs recalculation is w. wco_cal i and wch4_cal i can be calculated based on Ccofull_cal i, ABScofull, Cch4full_cali, and ABSch4full.

[0149]

[0150] (7) The new concentration-relative absorbance expression is obtained as follows:

[0151] These are the mapping relationships for the CO channel and the CH4 channel, respectively.

[0152] In some optional implementations of this embodiment, please refer to the following for details. Figure 1 The measuring device may also include a vacuum pump 160, which is installed in the gas path at the outlet of the gas sensor 120. The main control processing module 150 is also used to control the vacuum pump 160 to draw air.

[0153] In this embodiment, the measuring device may further include a vacuum pump 160, which is installed in the gas path at the outlet of the gas sensor 120. For the NDIR gas sensor, it may be installed in the gas path at the outlet of the measuring gas chamber. The vacuum pump 160 is electrically connected to the main control processing module 150. When the gas sensor 120 needs to be activated for calibration or gas concentration measurement, the main control processing module 150 can control the vacuum pump 160 to draw air, so that the airflow quickly reaches the gas sensor 120.

[0154] Example 2

[0155] Specific reference Figure 5 , Figure 5 This application provides a schematic diagram of the architecture of a lung diffusion testing device according to an embodiment of the present application, wherein the lung diffusion testing device includes:

[0156] like Figure 1 and Figure 1 In the optional embodiment, the target gas concentration change measuring device includes an airflow interface 130 which is a breathing interface 510 and a gas sensor 120 which is an NDIR gas sensor 520.

[0157] The gas supply module 110 is connected to the breathing interface 510 through the test gas path, and the gas sensor 120 is connected to the breathing interface 510 through the sampling gas path.

[0158] The target gas includes carbon monoxide and a tracer gas, which is either methane or helium.

[0159] The main control processing module 150 is also used to calculate lung diffusion parameters based on the change in the concentration of the target gas.

[0160] In this embodiment, one end of the breathing interface 510 for lung diffusion testing is connected to the gas supply module 110 through the test gas path, and the other end is used to receive the subject's breathing. The gas path at the breathing interface 510 is also provided with a sampling interface. One end of the sampling gas path is connected to the sampling interface, and the other end is connected to the air inlet of the measuring gas chamber of the NDIR gas sensor 520. The test gas is a standard gas with lung diffusion function.

[0161] During the lung diffusion test, the test airway is open and the sampling airway is closed during the inhalation phase. The subject inhales the standard gas output from the gas supply module 110 through the test airway. During the breath-hold phase, both the test airway and the sampling airway are closed. After the breath-hold phase ends, the sampling airway is opened, and the subject exhales. The exhaled airflow enters the test air chamber of the NDIR gas sensor 520 through the sampling airway.

[0162] Then the main control processing module 150 according to... Figure 2 The test method shown determines the changes in CO and CH4 concentrations in the subject during a lung diffusion test, and then calculates lung diffusion parameters based on these changes. The calculation process for the lung diffusion parameters is consistent with existing techniques and will not be elaborated here.

[0163] Compared with the prior art, the embodiments of this application have the following main advantages:

[0164] The lung diffusion testing device in this application measures the gas path pressure of the NDIR gas sensor 520 using a pressure sensor 140. After the NDIR gas sensor 520 detects the actual concentration of the test gas output from the breathing interface 510, it corrects this actual concentration to a second concentration under the same gas pressure as the test gas. Then, it compares the first concentration of the target gas in the test gas with this second concentration to determine the concentration change of the target gas throughout the entire testing process. This avoids the error caused by fluctuations in the gas path pressure at the NDIR gas sensor 520, which leads to more accurate measurement of the concentration change of the target gas throughout the testing process, thus making the lung diffusion parameter calculation results more accurate.

[0165] In some optional implementations of this embodiment, refer to Figure 5 As shown, the lung diffusion testing device also includes a flow sensor 530, which is located at the breathing interface 510. The main control processing module 150 is also used to determine the subject's breathing status based on the flow sensor 530.

[0166] The step of controlling the gas supply module 110 to output test gas at a first pressure to the airflow interface 130, wherein the test gas contains a target gas component at a first concentration, includes:

[0167] When the subject is detected to be in an inhalation state, the gas supply module 110 is controlled to output test gas at a first pressure to the breathing interface 510. The test gas contains a target gas component at a first concentration.

[0168] The step of detecting the concentration of the gas flow output from the gas flow interface 130 using the gas sensor 120 to obtain the measured concentration includes:

[0169] When the subject is detected to be in an exhalation state, the concentration of the airflow output from the breathing interface 510 is detected by the gas sensor 120 to obtain the measured concentration.

[0170] In this embodiment, the lung diffusion testing device includes a gas path switching module, which includes a gas path switching valve. The gas path switching module has at least three interfaces: one connected to the gas source 110 via a test gas path, another connected to the NDIR gas sensor 520 via a sampling gas path, and the third connected to the breathing interface 510. The gas path switching module is communicatively connected to the main control processing module 150 and can selectively switch and open / close the connection status between the breathing interface 510 and the gas source 110 and the NDIR gas sensor 520. A flow sensor 530 is disposed on the gas path between the breathing interface 510 and the gas path switching module to detect the airflow rate through the breathing interface 510. The flow sensor 530 can be an ultrasonic flow sensor or a differential pressure flow sensor. The main control processing module 150 can acquire the detection signal of the flow sensor 530, determine the flow rate at the breathing interface 510, and generate a breathing velocity profile. Based on the direction of the flow velocity, the breathing state of the subject is determined. Thus, when the subject inhales, the test gas path is opened and the sampling gas path is closed, and the gas supply module 110 is controlled to output test gas to the breathing interface. When the subject exhales, the test gas path is closed and the sampling gas path is opened, so that the exhaled airflow of the subject enters the measuring chamber of the NDIR gas sensor 520.

[0171] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. This computer program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the methods described above. The aforementioned storage medium can be a non-volatile storage medium such as a magnetic disk, optical disk, or read-only memory (ROM), or random access memory (RAM).

[0172] It should be understood that although the steps in the flowcharts of the accompanying figures are shown sequentially as indicated by the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the accompanying figures may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the sub-steps or stages of other steps.

[0173] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk), and includes several instructions to cause a terminal device (which may be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in the various embodiments of this application.

[0174] Obviously, the embodiments described above are only some embodiments of this application, not all embodiments. The accompanying drawings show preferred embodiments of this application, but do not limit the patent scope of this application. This application can be implemented in many different forms; rather, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the disclosure of this application. Although this application 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 specific embodiments, or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this application's specification and drawings, directly or indirectly applied to other related technical fields, are similarly within the scope of patent protection of this application.

Claims

1. A device for measuring changes in the concentration of a target gas, characterized in that, include: Gas supply module, gas sensor, airflow interface, pressure sensor and main control processing module; The gas supply module and the gas sensor are both connected to the gas flow interface through the gas path; The main control processing module is used to execute the following test methods: The gas supply module is controlled to output test gas at a first pressure to the airflow interface, and the test gas contains a target gas component at a first concentration; The concentration of the gas flow output from the gas flow interface is detected by the gas sensor to obtain the measured concentration, which is the concentration of the target gas in the gas to be tested. The pressure of the gas flow passing through the gas sensor is detected by the pressure sensor to obtain the gas path pressure. Based on the ratio of the first pressure to the gas path pressure, the measured concentration is corrected to a second concentration at the first pressure; The concentration change of the target gas is determined based on the first concentration and the second concentration.

2. The measuring device according to claim 1, characterized in that: The pressure sensor includes a differential pressure sensor and an ambient pressure sensor. The differential pressure sensor is disposed in the gas path at the outlet of the gas sensor. The step of detecting the pressure of the gas flow passing through the gas sensor to obtain the gas path pressure includes: The differential pressure value is obtained through the differential pressure sensor, and the current ambient pressure is obtained through the ambient pressure sensor. The gas path pressure is determined based on the pressure difference value and the ambient pressure.

3. The measuring device according to claim 2, characterized in that, The main control processing module is also used to perform the following steps: Determine whether both the differential pressure and the ambient pressure are within the set range, and issue an alarm if they exceed the set range.

4. The measuring device according to any one of claims 1-3, characterized in that, The step of detecting the concentration of the airflow output from the airflow interface using the gas sensor to obtain the measured concentration includes: The concentration of the gas flow output from the gas flow interface is detected by the gas sensor, and the first output signal of the gas sensor is obtained. The measured concentration is determined based on the first output signal and the preset mapping relationship.

5. The measuring device according to claim 4, characterized in that, The gas supply module is connected to the gas sensor via a gas path, and the main control processing module is also used to execute the following gas sensor calibration method: The gas supply module is controlled to output calibration gas at a third pressure to the gas sensor, and the calibration gas contains a target gas component at a third concentration; Acquire the second output signal of the gas sensor and detect the gas path pressure through the pressure sensor; Based on the ratio of the third pressure to the gas path pressure, the third concentration is calibrated to the fourth concentration under the gas path pressure; The mapping relationship is determined based on the fourth concentration and the second output signal.

6. The measuring device according to claim 5, characterized in that, The measuring device also includes a vacuum pump, which is installed in the gas path at the outlet of the gas sensor. The main control processing module is also used to control the vacuum pump to draw gas.

7. A lung diffusion testing device, characterized in that, include: The device for measuring the change in target gas concentration according to any one of claims 1-6, wherein the airflow interface is a breathing interface and the gas sensor is an NDIR gas sensor; The gas supply module is connected to the breathing interface through a test gas path, and the gas sensor is connected to the breathing interface through a sampling gas path; The target gas includes carbon monoxide and a tracer gas, wherein the tracer gas is methane or helium; The main control processing module is also used to calculate lung diffusion parameters based on the change in the concentration of the target gas.

8. When claim 7 refers to claim 4, the lung diffusion testing device according to claim 7 is characterized in that, The step of determining the mapping relationship based on the fourth concentration and the second output signal includes: The relative absorption rate is determined based on the second output signal and the zero-point output signal, wherein the zero-point output signal is the output signal of the NDIR gas sensor when air is pre-ventilated to the NDIR gas sensor; The mapping relationship is determined based on the relative absorption rate and the fourth concentration.

9. The lung diffusion testing device according to claim 7, characterized in that, The lung diffusion testing device also includes a flow sensor, which is located at the breathing interface. The main control processing module is also used to determine the subject's breathing status based on the flow sensor. The step of controlling the gas supply module to output test gas at a first pressure to the airflow interface, wherein the test gas contains a target gas component at a first concentration, includes: When the subject is detected to be in an inhalation state, the gas supply module is controlled to output test gas at a first pressure to the breathing interface, and the test gas contains a first concentration of target gas components; The step of detecting the concentration of the airflow output from the airflow interface using the gas sensor to obtain the measured concentration includes: When the subject is detected to be in an exhalation state, the concentration of the airflow output from the breathing interface is detected by the gas sensor to obtain the measured concentration.

10. The lung diffusion testing device according to any one of claims 7-9, characterized in that, The NDIR gas sensor includes a measuring chamber, which has an inlet and an outlet. The inlet of the measuring chamber is connected to both the breathing interface and the gas supply module. The pressure sensor is located on the gas path at the outlet.

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