CO sensor measurement concentration correction equation determination method and CO concentration determination method

Abstract

The embodiment of the invention provides a CO sensor measurement concentration correction equation determination method and a CO concentration determination method. The method for determining the correction equation of the measured concentration of the CO sensor comprises the following steps of: sequentially preparing mixed gas of various set oxygen contents and set CO concentration combinations in a pressure maintaining gas tank by adopting a gas distribution system, and obtaining the measured CO concentration obtained by measuring the mixed gas by the CO sensor; and combining the set oxygen content, the set CO concentration and the corresponding measured CO concentration into a data pair, and performing data fitting calculation based on the data pair to determine a measured concentration correction equation. In subsequent use, the actually measured CO concentration can be corrected based on the measured concentration correction equation to obtain the relatively accurate environmental CO concentration.

Description

Technical Field

[0001] The present disclosure relates to the technical field of sensor calibration, and particularly to a method for determining a measurement concentration correction equation of a CO sensor and a method for determining a CO concentration. Background Art

[0002] Since sensors for monitoring CO concentration based on redox reactions have problems such as short service life and being easily interfered by impurity gases and producing a "poisoning" effect in a closed environment, the prior art designs a new type of CO sensor based on the principle of light absorption. The new type of CO sensor is based on the principle that the light absorption ability of CO for a specific wavelength band is positively correlated with the CO concentration, and the CO concentration in the measured ambient gas is inversely calculated according to the absorption rate of light with a specific wavelength. It is actually measured that the aforementioned new type of CO sensor has advantages in terms of response sensitivity and service life, but there is a problem of poor data accuracy during quality verification. Summary of the Invention

[0003] The solution of the embodiment of the present disclosure analyzes the reasons for the poor accuracy of the output data of the CO sensor, and proposes a method for determining a measurement concentration correction equation of a CO sensor and a method for determining a CO concentration based on the aforementioned reasons.

[0004] In a first aspect, the embodiment of the present disclosure provides a method for determining a measurement concentration correction equation of a CO sensor, which is implemented based on a gas distribution system. The gas distribution system includes a first nitrogen gas cylinder, an oxygen-containing gas cylinder, a CO gas cylinder, a gas distributor, and a pressure-holding gas tank; the first nitrogen gas cylinder, the oxygen-containing gas cylinder, and the CO gas cylinder are respectively connected to corresponding air inlets of the gas distributor; the air outlet of the gas distributor is connected to the air inlet of the pressure-holding gas tank; the determination method includes:

[0005] Using the gas distribution system to sequentially configure mixed gases with various combinations of set oxygen contents and set CO concentrations in the pressure-holding gas tank, and obtaining the measured CO concentration measured by the CO sensor for the mixed gases;

[0006] Combining the set oxygen content, the set CO concentration, and the corresponding measured CO concentration into data pairs, and performing data fitting calculation based on the data pairs to determine the measurement concentration correction equation.

[0007] Optionally, the gas distributor includes a first gas distributor and a second gas distributor whose air outlets are both connected to the air inlet of the pressure-holding gas tank; the first nitrogen gas cylinder and the oxygen-containing gas cylinder are connected to the air inlet of the first gas distributor, and form a first gas distribution branch in combination with the first gas distributor; the CO gas cylinder is connected to the air inlet of the second gas distributor, and forms a second gas distribution branch in combination with the second gas distributor;

[0008] Using the described gas distribution system, various combinations of mixed gases with set oxygen contents and set CO concentrations are sequentially configured in the pressure-holding gas tank, including:

[0009] Using the first gas distribution branch to configure a background gas with a set oxygen content in the pressure-holding gas tank;

[0010] Using the second gas distribution branch to sequentially and quantitatively inject additive gas into the pressure-holding gas tank to form a mixed gas with a relatively high set CO concentration in the pressure-holding gas tank, where the CO amount of the additive gas is set according to the existing CO amount in the pressure-holding gas tank and the relatively high set CO concentration;

[0011] Obtaining the measured CO concentration of the mixed gas measured by the CO sensor, including: after injecting the additive gas into the background gas again each time, obtaining the measured CO concentration of the new mixed gas measured by the CO sensor.

[0012] Optionally, the gas distribution system further includes a second nitrogen gas cylinder as part of the second gas distribution branch; the second nitrogen gas cylinder is communicated with the inlet of the second gas distribution instrument;

[0013] Using the second gas distribution branch to sequentially and quantitatively inject additive gas into the pressure-holding gas tank includes:

[0014] Using the second gas distribution instrument to inject a set amount of CO gas into the pressure-holding gas tank, and then using the second gas distribution instrument to inject nitrogen gas into the pressure-holding gas tank.

[0015] Optionally, before using the first gas distribution branch to configure a background gas with a target oxygen content in the pressure-holding gas tank, it further includes: performing a cleaning operation on the gas distribution system;

[0016] The cleaning operation includes: using the nitrogen gas in the first nitrogen gas cylinder to clean the first gas distribution branch, using the nitrogen gas in the second nitrogen gas cylinder to clean the second gas distribution branch, and using the nitrogen gas in the first nitrogen gas cylinder and the second nitrogen gas cylinder to clean the pressure-holding gas tank when the pressure-holding gas tank opens the gas release port.

[0017] Optionally, using the gas distribution system to sequentially configure various combinations of mixed gases with set oxygen contents and set CO concentrations in the pressure-holding gas tank, and obtaining the measured CO concentration of the mixed gas measured by the CO sensor, including:

[0018] Using the gas distribution system to configure a first calibration gas without CO in the pressure-holding gas tank, and obtaining the first measured concentration of the first calibration gas measured by the CO sensor;

[0019] Configure a second calibration gas with a full-scale CO concentration and no oxygen in the pressure-holding gas tank using a gas distribution system, and obtain a second measured concentration obtained by the CO sensor measuring the second calibration gas. The full-scale CO concentration is determined according to the designed range of the CO sensor;

[0020] Perform sensor calibration on the CO sensor using the first measured concentration, the second measured concentration, and the full-scale CO concentration to obtain a calibration equation;

[0021] Configure a mixed gas with other concentration combinations using the gas distribution system, and after obtaining the output concentration data by the CO sensor measuring the other concentration gas, process the output concentration data based on the calibration equation to obtain the corresponding measured CO concentration.

[0022] Optionally, obtaining the measured CO concentration obtained by the CO sensor measuring the mixed gas includes:

[0023] Trigger the CO sensor to perform concentration measurement after the mixed gas has been introduced for a set duration to obtain multiple measured concentrations;

[0024] Calculate the mean of the multiple measured concentrations as the corresponding measured CO concentration; or,

[0025] Start obtaining measured concentrations after the mixed gas is introduced, and calculate the concentration difference ratio between the concentration measurement data and the corresponding set CO concentration;

[0026] Calculate the mean of the multiple measured concentrations obtained after the concentration difference ratio is less than the preset difference ratio as the corresponding measured CO concentration.

[0027] Optionally, the gas distribution system further includes a pressure sensor for measuring the gas pressure in the pressure-holding gas tank;

[0028] Configuring a mixed gas with various set oxygen contents and set CO concentration combinations in the pressure-holding gas tank using the gas distribution system, and obtaining the measured CO concentration obtained by the CO sensor measuring the mixed gas includes:

[0029] Configure mixed gases with various set oxygen percentage, set CO concentration, and set pressure combinations in the pressure-holding gas tank using the gas distribution system, and obtain the measured CO concentration obtained by the CO sensor measuring the mixed gas;

[0030] Combining the set oxygen content, the set CO concentration, and the corresponding measured CO concentration into data pairs, including:

[0031] Combine the set oxygen percentage, the set CO concentration, the set pressure, and the corresponding measured CO concentration into data pairs.

[0032] Optionally, the calculating the data fitting based on the data pair to determine the measurement concentration correction equation includes:

[0033] Calculating the concentration difference between the set CO concentration and the measured CO concentration in the data pair;

[0034] For a specific set oxygen content, performing a fitting calculation with the measured CO concentration as the independent variable and the concentration difference as the dependent variable to obtain a concentration difference equation;

[0035] Constructing the measurement concentration correction equation with the concentration difference equation and the actually measured CO concentration of the CO sensor.

[0036] In a second aspect, an embodiment of the present disclosure provides a method for determining a CO concentration. The method is based on a CO sensor and an oxygen content sensor; the method includes:

[0037] Obtaining the measured CO concentration output by the CO sensor and the measured oxygen content output by the oxygen content sensor;

[0038] Based on the measured CO concentration and the measured oxygen content, obtaining a corrected concentration by using the measurement concentration correction equation, and using the corrected concentration as the environmental CO concentration.

[0039] In a third aspect, an embodiment of the present disclosure provides a method for evaluating the measurement accuracy of a CO measurement system. The evaluation method is implemented based on a gas distribution system. The gas distribution system includes a first nitrogen gas cylinder, an oxygen-containing gas cylinder, a CO gas cylinder, a gas distributor, and a pressure-holding gas tank; the first nitrogen gas cylinder, the oxygen-containing gas cylinder, and the CO gas cylinder are respectively connected to corresponding inlets of the gas distributor; the outlet of the gas distributor is connected to the inlet of the pressure-holding gas tank; the CO sensor in the CO measurement system is placed in the pressure-holding gas tank; the method includes:

[0040] Using the gas distribution system to sequentially configure a mixed gas with a set oxygen content and a set CO concentration combination in the pressure-holding gas tank, inputting the set oxygen content to the CO measurement system through an input interface, and obtaining the measured CO concentration output by the CO measurement system;

[0041] Evaluating the measurement accuracy of the CO measurement system based on the measured CO concentration and the set CO concentration.

[0042] By adopting the solution of the embodiment of the present disclosure, by constructing a mixed gas for determining the oxygen content and the CO concentration, and then using the CO sensor to measure the measured CO concentration of the foregoing mixed gas, a measurement concentration correction equation affected by the oxygen content can be obtained by using the foregoing data. During subsequent use, the actually measured CO concentration can be corrected based on the measurement concentration correction equation to obtain a relatively accurate environmental CO concentration. Description of the Drawings

[0043] The accompanying drawings herein are incorporated into and constitute a part of this specification, showing embodiments consistent with the present disclosure and, together with the specification, are used to explain the principles of the present disclosure.

[0044] To more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the following will briefly introduce the accompanying drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings, where

[0045] Figure 1 is a flowchart of a method for determining a CO sensor measurement concentration correction equation provided by an embodiment of the present disclosure;

[0046] Figure 2 is a schematic structural diagram of a gas distribution system adopted in some embodiments of the present disclosure;

[0047] Figure 3 is a schematic structural diagram of a gas distribution system adopted in some other embodiments of the present disclosure;

[0048] Figure 4 is a flowchart of a method for evaluating the measurement accuracy of a CO measurement system provided by an embodiment of the present disclosure;

[0049] Figure 5 is a flowchart of a method for determining a CO concentration provided by an embodiment of the present disclosure. Detailed Embodiments

[0050] The embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although some embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Instead, these embodiments are provided to more thoroughly and completely understand the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are only for exemplary purposes and are not used to limit the protection scope of the present disclosure.

[0051] The term "including" and its variations used herein are open-ended, that is, "including but not limited to". The term "based on" is "at least partially based on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments". The relevant definitions of other terms will be given in the following description. In this document, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

[0052] As analyzed in the background art, when verifying the quality of a CO sensor based on the principle of light absorption, there is a problem of poor accuracy of measurement data, and the foregoing problem is a systemic problem. Reviewing the in-factory calibration process and quality verification process of the CO sensor, the inventor found that the environmental characteristics of the calibration process and the quality inspection process are not exactly the same. Specifically, the environmental oxygen content is not the same. The in-factory calibration process is carried out under the condition of a relatively high environmental oxygen content, while the user verification quality test is carried out under the condition of a relatively low environmental oxygen content in the underground mine.

[0053] Considering the foregoing differences, the applicant considered whether the oxygen content of the environmental gas might affect the measurement accuracy of the foregoing type of CO sensor, and then consulted the spectral absorption characteristics of oxygen and CO and the chemical reaction mechanism in the environment, and confirmed from the physical principle that the environmental oxygen content does indeed affect the CO sensor concentration measurement. That is to say, it is necessary to consider the influence of the oxygen content of the gas to be measured on the CO sensor measurement in order to obtain a more accurate measurement of the CO concentration. And identifying the influence of the oxygen content on the CO measurement and then constructing a reasonable calibration equation are necessary considerations in the design and calibration of the CO sensor. Based on this, the embodiments of the present disclosure provide a method for determining a calibration equation for the measurement concentration of a CO sensor.

[0054] Figure 1 It is a flowchart of the method for determining the calibration equation for the measurement concentration of the CO sensor provided by the embodiments of the present disclosure. As Figure 1 shown, the calibration equation determination method provided by the embodiments of the present disclosure includes S110-S120.

[0055] The method for determining the calibration equation for the measurement concentration provided by the embodiments of the present disclosure needs to configure a mixed gas for calibration, and its implementation is based on the premise that a gas distribution system configures a mixed gas with a specific combined concentration. Therefore, before analyzing the method provided by the embodiments of the present disclosure, the gas distribution system is first introduced.

[0056] Figure 2 It is a schematic structural diagram of the gas distribution system adopted by some embodiments of the present disclosure. As Figure 2 shown, the gas distribution system 100 adopted by some embodiments of the present disclosure includes a first nitrogen gas cylinder 101, an oxygen-containing gas cylinder 102, a CO gas cylinder 103, a gas distributor 104, and a pressure-holding gas tank 105.

[0057] The first nitrogen gas cylinder 101 is a gas cylinder for storing pure nitrogen (the pure nitrogen concentration mentioned here reaches 99.9%, which has little influence on the oxygen content and CO concentration in the configured mixed gas).

[0058] The oxygen-containing gas cylinder 102 is a gas cylinder storing gas containing oxygen. In specific implementations, the gas stored in the oxygen-containing gas cylinder 102 can be pure oxygen or air. Considering that in the usage scenarios of the CO sensor, it is mostly in a conventional open atmosphere environment scenario or an underground low oxygen concentration scenario, and the maximum oxygen content percentage in the foregoing scenarios is the oxygen content percentage in air, so the oxygen content percentage stored in the oxygen-containing gas cylinder 102 is at least the highest oxygen content percentage in the usage scenario (the oxygen content percentage of the mixed gas stored in the oxygen-containing gas cylinder 102 is at least 21%).

[0059] The CO gas cylinder 103 is a gas cylinder storing CO gas. The concentration of the CO gas stored therein is at least the maximum measurement range concentration of the CO sensor.

[0060] The gas mixer 104 is an instrument for realizing the mixing of various gases to form a mixed gas with a specific ratio combination. The gas mixer 104 in the embodiments of the present disclosure can meet the configuration of a mixed gas with a specific oxygen content and a specific CO concentration.

[0061] The pressure-holding gas tank 105 is a container for storing the mixed gas configured by the gas mixer 104. As its name implies, the pressure-holding gas tank 105 has good airtightness and will not have gas leakage during the process of storing the mixed gas, and thus will not cause the reduction of the concentration of various components of the mixed gas.

[0062] As Figure 2 shown, the air outlets of the first nitrogen gas cylinder 101, the oxygen-containing gas cylinder 102, and the CO gas cylinder 103 are respectively communicated with the corresponding air inlets of the gas mixer 104 through corresponding pipelines, and corresponding stop valves are arranged on each of the foregoing pipelines; the air outlet of the gas mixer 104 is communicated with the air inlet of the pressure-holding gas tank 105 through a pipeline; the detection end of the CO sensor 106 and the pressure sensor 107 are communicated with the inner cavity of the pressure-holding gas tank 105 and are connected to an external power supply line and a data processor through wires. By using the foregoing gas distribution system 100, according to the oxygen content, CO concentration, nitrogen concentration in the low-pressure nitrogen gas cylinder, oxygen concentration in the oxygen-containing gas cylinder, and CO concentration of the CO gas cylinder 103 of the mixed gas to be configured, as well as the required air pressure condition and the internal volume of the pressure-holding gas tank 105, the gas consumption of various gas sources required is determined, and the gas flow rate of the corresponding gas sources is measured through an internal metering pump to form a mixed gas with a set oxygen content and a set CO concentration.

[0063] The following analyzes the method for determining the CO sensor measurement concentration correction equation in the embodiments of the present application.

[0064] S110: Use the gas distribution system to sequentially configure mixed gases with various combinations of set oxygen content and set CO concentration in the pressure-holding gas tank, and obtain the measured CO concentration measured by the CO sensor for the mixed gas.

[0065] In order to determine the actual output characteristics of the CO sensor in various possible application scenarios, it is necessary to prepare a mixed gas with corresponding characteristics of oxygen content and CO concentration according to the actual application scenario, and then use the CO sensor set in the above-mentioned mixed gas environment to measure the concentration, so as to obtain the measured CO concentration representing the CO concentration in the mixed gas.

[0066] In the embodiments of the present disclosure, a gas distribution system is used to sequentially configure mixed gases with various combinations of set oxygen content and set CO concentration, store the above-mentioned gases in a pressure-maintaining gas tank, and trigger the CO sensor to measure to obtain the measured CO concentration.

[0067] In specific implementation, after the gases from various gas sources are introduced into the pressure-maintaining gas tank, it is necessary to wait for the gases of various types to diffuse evenly before a mixed gas with uniform concentration can be formed. Only in this case can the measured CO concentration obtained by the CO sensor measuring the mixed gas be obtained.

[0068] In specific implementation, the following method can be used to obtain the measured CO concentration.

[0069] The first method: Trigger the CO sensor to measure the concentration after a set duration of introducing the mixed gas, and obtain multiple measured concentrations; then calculate the average value of the multiple measured concentrations as the corresponding measured CO concentration.

[0070] In a specific application, each time the mixed gas is configured and introduced into the pressure-maintaining gas tank, the pressure-maintaining gas tank maintains pressure for 30 minutes, and the CO sensor is triggered to measure the concentration in the last 5 minutes of the above-mentioned 30 minutes to obtain the measured concentration. If the working cycle of the CO sensor is 1 s, 300 measured concentrations can be obtained by using the above method. Summing and averaging the above 300 measured concentrations can obtain the corresponding measured CO concentration.

[0071] In another specific application, when it has been determined through preliminary experiments that the gases in the mixed gas have diffused evenly, the difference between the measured concentration output by the CO sensor and the actual CO concentration will not exceed 5%. Therefore, the data acquisition rule can be determined based on the above 5%. Specifically, the CO sensor is triggered to measure immediately after the mixed gas is introduced into the pressure-maintaining gas tank, and the measured concentration is obtained. After the difference between the measured concentration and the set CO concentration is less than 5%, the subsequent measured concentrations can be started to be recorded, and the recording is carried out for 5 minutes. If the working cycle of the CO sensor is 1 s, the number of measured concentrations obtained by using the above method is also 300. Summing and averaging the above 300 data can also obtain the corresponding measured CO concentration.

[0072] S120: Combine the set oxygen content, the set CO concentration and the corresponding measured CO concentration into data pairs, and perform data fitting calculation based on the data pairs to determine the measured concentration correction equation.

[0073] As analyzed above, the CO concentration is measured for a mixed gas with a set oxygen content and a set CO concentration. Therefore, the set oxygen content, the set CO concentration, and the corresponding measured CO concentration can be combined into data pairs, and a multi-point data fitting operation can be performed based on the foregoing data pairs to obtain a measured concentration correction equation for obtaining the actual CO concentration from the measured CO concentration at a specific oxygen content.

[0074] In specific implementation, existing regression processing tools can be used to process the data in the foregoing data pairs to obtain a measured concentration correction equation.

[0075] By adopting the solution of the embodiment of the present disclosure, by constructing a mixed gas determined by the oxygen content and the CO concentration, and then using a CO sensor to measure the measured CO concentration of the foregoing mixed gas, a measured concentration correction equation affected by the oxygen content can be obtained using the foregoing data. In subsequent use, the actual measured CO concentration can be corrected based on the measured concentration correction equation to obtain a more accurate ambient CO concentration.

[0076] In some embodiments, the foregoing set oxygen content and the corresponding measured CO concentration are used as independent variables of the measured concentration correction equation, and the foregoing set CO concentration is used as the dependent variable of the measured concentration correction equation for regression analysis to obtain the fitting analytical formula and various coefficients of the concentration correction equation.

[0077] In some other examples, the measured concentration correction equation is obtained by adopting the following S121-S123.

[0078] S121: Calculate the concentration difference between the set CO concentration and the measured CO concentration in the data pair;

[0079] S122: For a specific set oxygen content, perform a fitting calculation with the measured CO concentration as the independent variable and the concentration difference as the dependent variable to obtain a concentration difference equation;

[0080] S123: Construct a measured concentration correction equation with the concentration difference equation and the actually measured CO concentration of the CO sensor.

[0081] Through the discovery of the previous data, at a specific CO concentration, the magnitude of the oxygen content directly affects the oxidation-reduction reaction of some CO. That is to say, the oxygen content mainly causes the concentration deviation between the set CO and the measured CO concentration. Based on this, in some embodiments, first calculate the concentration difference between the set CO concentration and the measured CO concentration, and for various CO concentration data and concentration differences at a specific oxygen content, perform a fitting with the measured CO concentration as the independent variable and the concentration difference as the dependent variable to obtain a concentration difference equation characterizing the characteristics of the oxygen content and causing the characteristics of the CO concentration difference, and then add the concentration difference equation and the measured CO concentration to obtain a measured concentration correction equation.

[0082] In specific implementation, the CO sensor is applied to monitor the CO concentration in the gob area of the underground mine. The oxygen content in the air of the gob area of the underground mine is between 0% and 21% (about 100 KPa under normal underground air pressure). Under normal circumstances, the maximum CO concentration is about 400 ppm. Based on the foregoing conditions, it is determined that the set oxygen content is characterized by the proportion of oxygen under normal underground air pressure, which are 0%, 5%, 10%, 15% and 21% respectively, and the set CO concentrations are 100 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, 350 ppm and 400 ppm respectively. Subsequently, 35 kinds of mixed gases with combinations of set oxygen content and set CO concentration are configured according to the foregoing method, 35 data pairs are obtained, and then data fitting is performed based on the foregoing 35 data to obtain a measurement concentration correction equation.

[0083] Table 1 is a table of concentration difference equations under various set oxygen contents obtained in an application. Table 1 shows the polynomial fitting equations under various oxygen content ratios under normal underground air pressure conditions, and the concentration difference equations under each oxygen content ratio are all greater than 0.63. Therefore, it can be determined that the concentration difference equations under various oxygen contents all have good fitting performance.

[0084] Table 1 Table of concentration difference equations under various set oxygen contents

[0085] Oxygen content (%) Concentration difference equation (x represents the measured CO concentration, Y represents the concentration difference) <![CDATA[R 2 > 0 <![CDATA[Y = -2.92143 E-5 x + 0.01944]]> 0.81 5 <![CDATA[Y = -4.09286 E-5 x + 0.0326]]> 0.78 10 <![CDATA[Y = -6 E-5 x + 0.04404]]> 0.69 15 <![CDATA[Y = -6.45 E-5 x + 0.05]]> 0.84 21 <![CDATA[Y = -5.77857 E-5 x + 0.05515]]> 0.79

[0086] There may be the following doubts here: If only the concentration difference equations under several set oxygen contents are obtained, the CO concentration differences under other oxygen contents and CO concentrations cannot be determined. It should be noted by the applicant that because the influence of oxygen content on the CO concentration difference has a positive correlation with the oxygen content, the CO difference under a specific oxygen content can be determined based on the difference method.

[0087] For example, if the actually measured oxygen content is 8%, and the adjacent set oxygen contents are 5% and 10%, the first difference and the second difference corresponding to the CO concentration can be calculated respectively by using the concentration difference equations under the foregoing two set oxygen contents, and weighted weights are set for the foregoing first difference and second difference, and the first difference and the second difference are processed by addition using the weighted weights to obtain the CO concentration difference under this oxygen content. When the difference method is linear difference, if the first difference is the difference calculated at 5% oxygen content and the second difference is the difference calculated at 10% oxygen content, the weighted weight corresponding to the first difference is 0.4 ((10% - 8%) / (10% - 5%)), and the weighted weight corresponding to the second difference is 0.6 ((8% - 5%) / (10% - 5%)).

[0088] Figure 3 It is a schematic structural diagram of a gas distribution system adopted in other embodiments of the present disclosure. As Figure 3 shown, compared withFigure 2 The gas distribution system shown. In some other embodiments, the gas distribution system 100 adopted uses two gas distributors, namely the first gas distributor 104A and the second gas distributor 104B. The outlets of the first nitrogen gas cylinder 101 and the oxygen-containing gas cylinder 102 are connected to the first gas distributor 104A through pipelines and corresponding stop valves. The first nitrogen gas cylinder 101, the oxygen-containing gas cylinder 102 and the first gas distributor 104A form a first gas distribution branch 100A. The outlet of the CO gas cylinder 103 is connected to the inlet of the second gas distributor 103B. The CO gas cylinder 104 and the second gas distributor 103B form a second gas distribution branch 100B. The above two gas distribution branches can independently perform gas distribution operations.

[0089] When Figure 3 performing gas distribution operations using the gas distribution system shown, the above S110 using the gas distribution system to sequentially configure mixed gases with various combinations of set oxygen contents and set CO concentrations in the pressure-holding gas tank may specifically include S111 - S112.

[0090] S111: Configure a background gas with a set oxygen content in the pressure-holding gas tank using the first gas distribution branch.

[0091] S112: Sequentially and quantitatively inject additive gases into the pressure-holding gas tank using the second gas distribution branch to form a mixed gas with a relatively high set CO concentration in the pressure-holding gas tank.

[0092] In specific implementation, configuring a background gas with a set oxygen content in the pressure-holding gas tank using the first gas distribution branch is to determine the required amount of nitrogen gas and the amount of oxygen-containing gas according to the volume of the pressure-holding gas tank, the nitrogen concentration of the first nitrogen gas cylinder, the proportion of oxygen content in the oxygen-containing gas cylinder, the proportion of oxygen content in the background gas to be configured, and the pressure (the two determine the oxygen content), and fill the above-mentioned quantified gases into the pressure-holding gas tank to form a background gas with a set oxygen content.

[0093] As shown in the data in the previous text, the CO concentration in the actual application environment gas is much lower than the concentrations of oxygen and nitrogen. When changing the CO gas concentration (increasing) in the mixed gas, the oxygen content (proportion) in the mixed gas only changes very slightly (the above change may not be detectable by existing oxygen sensors).

[0094] In order to reduce the time consumption of configuring the mixed gas, a background gas with a set oxygen content can be configured first, and then a mixed gas with a gradually increasing CO concentration can be formed by gradually increasing the amount of CO in the mixed gas, so as to obtain mixed gases with various set CO concentrations by injecting the background gas once, thereby saving the preparation time of the background gas.

[0095] As Figure 3As shown, in some embodiments, the gas distribution system 100 further includes a second nitrogen cylinder 108 as part of the second gas distribution branch 100B, and the second nitrogen cylinder 106 is communicated with the air inlet of the second gas distributor 104B.

[0096] In specific implementation, during the execution of the foregoing S112, after injecting a set amount of CO gas into the pressure maintaining gas tank by using the second gas distributor, nitrogen can be injected into the pressure maintaining gas tank by using the second gas distributor.

[0097] In practical applications, the CO concentration in the CO gas cylinder is much higher than the CO concentration of the mixed gas to be configured. If only the second gas distributor is used to control the amount of gas injected from the CO gas cylinder into the pressure maintaining gas tank, a small amount of CO gas remaining in the pipeline of the second gas distributor will have a great impact on the actual CO in the pressure maintaining gas tank. By setting a second nitrogen cylinder in the second gas distribution branch, after injecting a set amount of CO gas into the pressure maintaining gas tank first, and then injecting the nitrogen in the second nitrogen cylinder into the pressure maintaining gas tank through the second gas distributor, the nitrogen in the second nitrogen cylinder can be used to flush the pipeline of the second gas distributor, so that the CO in the pipeline is all filled into the pressure maintaining gas tank, thereby avoiding the problem of inaccurate actual gas concentration caused by CO residue.

[0098] If the gas is prepared according to the foregoing S111 - S112 method, before obtaining a mixed gas with a certain set oxygen content and various set CO concentrations, in order to avoid the influence of the residual gas in the first gas distribution branch, the second gas distribution branch and the pressure maintaining gas tank on the subsequent oxygen content and CO concentration, before executing S111, the gas distribution system should also be cleaned. The cleaning operation specifically includes cleaning the first gas distribution branch with the nitrogen in the first nitrogen cylinder, cleaning the second gas distribution branch with the nitrogen in the second nitrogen cylinder, and cleaning the pressure maintaining gas tank with the nitrogen in the first nitrogen cylinder and the second nitrogen cylinder when the pressure maintaining gas tank opens the air outlet. The foregoing cleaning operation makes the oxygen and CO contents in the first gas distribution branch, the second gas distribution branch and the pressure maintaining gas tank as low as possible, so as to avoid affecting the subsequent gas configuration.

[0099] As analyzed above, the CO sensor determines the CO concentration based on the intensity detection of light with a specific wavelength, and it needs to use a photoelectric sensor. And the photoelectric sensor needs to be calibrated before use to determine the performance of the light emitting light source and the photoelectric receiver therein, that is, the CO sensor itself needs to be calibrated. In specific implementation, the calibration is performed by two-point calibration, and the two-point calibration includes zero-point calibration and pole calibration. To implement the calibration of the CO sensor, the foregoing S110 may further include S113 - S114.

[0100] S113: Use the gas distribution system to configure a first calibration gas that does not contain CO in the pressure-holding gas tank, and obtain the first measured concentration obtained by the CO sensor measuring the first calibration gas.

[0101] S114: Use the gas distribution system to configure a second calibration gas with a full-scale CO concentration and no oxygen in the pressure-holding gas tank, and obtain the second measured concentration obtained by the CO sensor measuring the second calibration gas.

[0102] The full-scale CO concentration is determined according to the designed range of the CO sensor. For example, in some embodiments, if it is determined that the maximum range of the CO sensor is 1000 ppm, the CO concentration in the second calibration gas is set to 1000 ppm.

[0103] In the case of performing the foregoing S113 - S114 of the actuator, the CO sensor can be calibrated using the first measured concentration, the second measured concentration, and the full-scale CO concentration to obtain a calibration equation. Correspondingly, after using the gas distribution system to configure a mixed gas with other concentration combinations and obtaining the output concentration data measured by the CO sensor for other concentration gases, the corresponding measured CO concentration can be obtained by processing the output concentration data based on the calibration equation.

[0104] It should be noted that the foregoing oxygen content is characterized in percentage. In practical applications, the specific meaning of oxygen for the same percentage of oxygen content at different pressures is different, and the corresponding oxidation-reduction reaction between oxygen and CO, as well as the influence of oxygen on the measurement of CO concentration, are also different. To solve this problem, in some embodiments, during the process of using the gas distribution system to mix the mixed gas, when using the gas distribution system to configure a mixed gas with a set oxygen content in the pressure-holding gas tank, the specific oxygen content is characterized by the oxygen content percentage and the pressure, that is, mixed gases with various combinations of set oxygen content percentages, set CO concentrations, and set pressures are configured in sequence, and the measured CO concentration obtained by the CO sensor measuring the mixed gas is obtained. Subsequently, the set oxygen content percentage, the set CO concentration, the set pressure, and the corresponding measured CO concentration are combined into data pairs, and the measured concentration correction equation is obtained by fitting the foregoing data. For the improvement of the foregoing method, the gas distribution system not only requires the foregoing first gas distribution branch, second gas distribution branch, and pressure-holding gas tank, but also includes a pressure sensor for measuring the gas pressure in the pressure-holding gas tank.

[0105] As analyzed above, since the absolute content of oxygen affects the measurement error of the CO concentration, the concentration difference between the set CO concentration and the measured CO concentration in the data pair can be calculated first. Subsequently, for a specific set oxygen content percentage and set pressure, with the measured CO concentration as the independent variable and the concentration difference as the dependent variable, fitting calculations are performed to obtain a concentration difference equation. Finally, the measured concentration correction equation is constructed using the concentration difference equation and the CO concentration actually measured by the CO sensor.

[0106] To more clearly understand the method for determining the CO sensor measurement concentration correction equation, the following analyzes the determination of the concentration correction equation using the gas distribution system shown in Figure 3 in a specific application, including the following A - E.

[0107] A. Before performing the gas distribution operation, test the tightness of the entire gas distribution system, specifically the tightness of the pressure - maintaining gas tank. First, close the outlet of the pressure - maintaining gas tank and check that the data shown on the pressure gauge is less than 0.03 Kpa. Subsequently, inflate the pressure - maintaining gas tank at a set air pressure of 200 KPa (the air supply pressure from each gas cylinder to the gas distributor) and a speed of 1000 mL / min until the pressure of the pressure - maintaining gas tank rises to 100.5 KPa, and then let it stand for 30 min. If the decrease in the pressure gauge reading is less than 0.1 KPa within 30 min, it is determined that the airtightness of the pressure - maintaining gas tank is qualified.

[0108] B. Turn on the CO sensor for prediction for 5 min, and measure the measured CO concentration in the pressure - maintaining gas tank filled with only nitrogen to obtain the zero - point calibration value. Subsequently, inject CO gas into the pressure - maintaining gas tank so that the CO concentration in the pressure - maintaining gas tank is 1000 ppm, and use the CO sensor to measure the full - scale measured CO concentration. Use the aforementioned zero - point calibration value and the full - scale measured CO concentration to calibrate the CO sensor to obtain the calibration equation.

[0109] C. Purge the entire gas distribution system with nitrogen from the first nitrogen cylinder and the second nitrogen cylinder. After purging, use the first gas distribution branch to configure background gas with a set oxygen percentage and a set pressure in the pressure - maintaining gas tank; use the second gas distribution branch to gradually inject CO gas into the background gas to obtain mixed gases with various set CO concentrations. After the mixed gas is fully mixed, read the CO sensor data and use the calibration equation to obtain the measured CO concentration; repeat the aforementioned step of injecting CO gas until the maximum CO concentration is obtained, and then repeat this step according to the next set oxygen concentration. In this way, the measured CO concentrations of actual CO concentrations from 100 ppm to 400 ppm at 0%, 5%, 10%, 15%, and 21% oxygen percentages under a specific pressure condition are obtained.

[0110] In performing the aforementioned steps, the deflation pressures of the first nitrogen cylinder, the second nitrogen cylinder, and the carbon monoxide gas cylinder are set at 2.0 Mpa, and the deflation pressure of the oxygen - containing gas cylinder is 0.4 Mpa.

[0111] D. Combine the set oxygen percentage, set pressure, set CO concentration, and the corresponding measured CO concentration into data pairs, and perform data fitting calculations based on the data pairs to determine the measurement concentration correction equation.

[0112] In addition to providing the method for determining the CO sensor measurement concentration correction equation described above, an embodiment of the present disclosure also provides a method for evaluating the measurement accuracy of a CO measurement system. The accuracy evaluation method is also implemented using the gas distribution system described above, and the structure of the gas distribution system will not be analyzed here. Figure 4 is a flowchart of the method for evaluating the measurement accuracy of the CO measurement system provided by an embodiment of the present disclosure. As Figure 4 shown, the measurement accuracy evaluation method includes S210 - S220. It should be noted here that in addition to the CO sensor, the CO measurement system also includes a data processor.

[0113] S210: Use the gas distribution system to sequentially configure a mixed gas with a set oxygen content and a set CO concentration combination in the pressure - maintaining gas tank, input the set oxygen content into the CO measurement system through the input interface, and obtain the measured CO concentration of the mixed gas measured by the CO measurement system.

[0114] Among them, the process of configuring the mixed gas and obtaining the measured CO concentration using the CO sensor is as analyzed above and will not be elaborated here. Different from the previous method, it is also necessary to input the set oxygen content into the data processor of the CO measurement system through the input interface, and the data processor calculates the measured CO concentration based on the sensor detection data and the set oxygen content.

[0115] S220: Evaluate the measurement accuracy of the CO measurement system based on the measured CO concentration and the set CO concentration.

[0116] In some specific implementations, the corresponding measured CO concentration and the set CO concentration can be subtracted to obtain a CO concentration difference, and the CO concentration difference is used to characterize the measurement accuracy.

[0117] Table 2 is a measurement accuracy data table of a type of CO sensor

[0118]

[0119] Referring to Table 2, it shows the measurement accuracy of a type of CO sensor at different oxygen contents in the form of a percentage of the concentration difference under a specific pressure. The larger the percentage of the concentration difference, the worse the measurement accuracy.

[0120] In specific implementations, considering that temperature will affect the measurement accuracy, the temperature condition can also be added for testing to determine the measurement accuracy.

[0121] An embodiment of the present disclosure also provides a method for determining the CO concentration. In addition to the aforementioned CO sensor, the method for determining the CO concentration also requires an oxygen content sensor. Figure 5 is a flowchart of the method for determining the CO concentration provided by an embodiment of the present disclosure, as Figure 5As shown, the CO concentration determination method includes S310 - S320.

[0122] S310: Obtain the measured CO concentration output by the CO sensor and the measured oxygen content output by the oxygen content sensor.

[0123] S320: Based on the measured CO concentration and the measured oxygen content, use the measured concentration correction equation to obtain the corrected concentration, and take the corrected concentration as the ambient CO concentration.

[0124] For example, for the method of constructing the measured concentration correction equation described above, in specific implementation, the concentration difference equation to be used can be determined based on the measured oxygen concentration. Subsequently, the measured CO concentration is processed using the concentration difference equation to obtain the difference CO concentration. Finally, the difference CO concentration and the measured CO concentration are added together to obtain the ambient CO concentration.

[0125] In specific implementation, if the independent variables in the measured concentration correction equation also include parameters such as ambient temperature, corresponding sensors can also be used to measure the corresponding ambient parameters and substitute them into the measured concentration correction equation to obtain the ambient CO concentration.

[0126] The above are only specific implementation manners of the present disclosure, enabling those skilled in the art to understand or implement the present disclosure. Various modifications to these embodiments will be obvious to those skilled in the art. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure will not be limited to these embodiments herein, but rather will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for determining the calibration equation of the CO sensor measurement concentration, which is implemented based on the gas distribution system, is characterized in that The gas distribution system includes a first nitrogen cylinder, an oxygen-containing gas cylinder, a CO gas cylinder, a gas distributor, and a pressure-holding gas tank; the first nitrogen cylinder, the oxygen-containing gas cylinder, and the CO gas cylinder are respectively communicated with corresponding air inlets of the gas distributor; an air outlet of the gas distributor is communicated with an air inlet of the pressure-holding gas tank; the determination method includes: Using the gas distribution system to sequentially configure mixed gases with various combinations of set oxygen contents and set CO concentrations in the pressure-holding gas tank, and obtaining the measured CO concentration of the mixed gas measured by the CO sensor; Combining the set oxygen content, the set CO concentration, and the corresponding measured CO concentration into a data pair, and performing data fitting calculation based on the data pair to determine a measured concentration correction equation.

2. The determination method according to claim 1, wherein The gas distributor includes a first gas distributor and a second gas distributor with air outlets both communicated with the air inlet of the pressure-holding gas tank; the first nitrogen cylinder and the oxygen-containing gas cylinder are communicated with the air inlets of the first gas distributor, and form a first gas distribution branch combined with the first gas distributor; the CO gas cylinder is communicated with the air inlet of the second gas distributor, and forms a second gas distribution branch combined with the second gas distributor; Using the gas distribution system to sequentially configure mixed gases with various combinations of set oxygen contents and set CO concentrations in the pressure-holding gas tank includes: Using the first gas distribution branch to configure a background gas with a set oxygen content in the pressure-holding gas tank; Using the second gas distribution branch to sequentially and quantitatively inject additive gas into the pressure-holding gas tank to form a mixed gas with a relatively high set CO concentration in the pressure-holding gas tank, and the CO amount of the additive gas is set according to the existing CO amount in the pressure-holding gas tank and the relatively high set CO concentration; Obtaining the measured CO concentration of the mixed gas measured by the CO sensor includes: after injecting the additive gas into the background gas again each time, obtaining the measured CO concentration of the new mixed gas measured by the CO sensor.

3. The determination method according to claim 2, characterized in that The gas distribution system further includes a second nitrogen cylinder as part of the second gas distribution branch; the second nitrogen cylinder is communicated with the air inlet of the second gas distributor; Using the second gas distribution branch to sequentially and quantitatively inject additive gas into the pressure-holding gas tank includes: Using the second gas distributor to inject a set amount of CO gas into the pressure-holding gas tank, and then using the second gas distributor to inject nitrogen into the pressure-holding gas tank.

4. The determination method according to claim 3, characterized in that, Before using the first gas distribution branch to configure a background gas with a target oxygen content in the pressure-holding gas tank, it further includes: performing a cleaning operation on the gas distribution system; The cleaning operation includes: using the nitrogen in the first nitrogen cylinder to clean the first gas distribution branch, using the nitrogen in the second nitrogen cylinder to clean the second gas distribution branch, and using the nitrogen in the first nitrogen cylinder and the second nitrogen cylinder to clean the pressure-holding gas tank when the pressure-holding gas tank opens the air release port.

5. The method according to claim 1 or 2, characterized in that, Using the gas distribution system to sequentially configure mixed gases with various combinations of set oxygen contents and set CO concentrations in the pressure-holding gas tank, and obtaining the measured CO concentration of the mixed gas measured by the CO sensor includes: Configure a first calibration gas without CO in the pressure-holding gas tank using the described gas distribution system, and obtain a first measured concentration obtained by the CO sensor measuring the first calibration gas; Configure a second calibration gas with a full-scale CO concentration and without oxygen in the pressure-holding gas tank using the gas distribution system, and obtain a second measured concentration obtained by the CO sensor measuring the second calibration gas, where the full-scale CO concentration is determined according to the design range of the CO sensor; Perform sensor calibration on the CO sensor using the first measured concentration, the second measured concentration, and the full-scale CO concentration to obtain a calibration equation; Configure a mixed gas with other concentration combinations using the gas distribution system, and after obtaining the output concentration data by the CO sensor measuring the other concentration gas, process the output concentration data based on the calibration equation to obtain the corresponding measured CO concentration.

6. The determination method according to claim 1 or 2, characterized in that, The obtaining of the measured CO concentration obtained by the CO sensor measuring the mixed gas includes: Trigger the CO sensor to perform concentration measurement after the mixed gas has been introduced for a set duration to obtain multiple measured concentrations; Calculate the mean of the multiple measured concentrations as the corresponding measured CO concentration; or, Start obtaining measured concentrations after the mixed gas is introduced, and calculate the concentration difference ratio between the concentration measurement data and the corresponding set CO concentration; Obtain the mean of the multiple measured concentrations obtained after the concentration difference ratio is less than the preset difference ratio as the corresponding measured CO concentration.

7. The determination method according to claim 1 or 2, characterized in that, The gas distribution system further includes a pressure sensor for measuring the gas pressure in the pressure-holding gas tank; Configure mixed gases with various combinations of set oxygen content and set CO concentration in the pressure-holding gas tank using the gas distribution system, and obtain the measured CO concentration obtained by the CO sensor measuring the mixed gas, including: Configure mixed gases with various combinations of set oxygen percentage, set CO concentration, and set pressure in the pressure-holding gas tank using the gas distribution system, and obtain the measured CO concentration obtained by the CO sensor measuring the mixed gas; Combine the set oxygen content, the set CO concentration, and the corresponding measured CO concentration into data pairs, including: Combine the set oxygen percentage, the set CO concentration, the set pressure, and the corresponding measured CO concentration into data pairs.

8. The determination method according to claim 1 or 2, characterized in that, The performing of data fitting calculation based on the data pairs to determine the measured concentration correction equation includes: Calculate the concentration difference between the set CO concentration and the measured CO concentration in the data pairs; For a specific set oxygen content, perform fitting calculation with the measured CO concentration as the independent variable and the concentration difference as the dependent variable to obtain a concentration difference equation; Construct the measured concentration correction equation based on the concentration difference equation and the actually measured CO concentration of the CO sensor.

9. A method for determining the CO concentration, characterized in that, The method is based on a CO sensor and an oxygen content sensor; the method includes: Obtain the measured CO concentration output by the CO sensor and the measured oxygen content output by the oxygen content sensor; Based on the measured CO concentration and the measured oxygen content, obtain a corrected concentration using the measured concentration correction equation, and use the corrected concentration as the ambient CO concentration.

10. A method for evaluating the measurement accuracy of a CO measurement system, characterized in that, The evaluation method is implemented based on a gas distribution system, which includes a first nitrogen cylinder, an oxygen-containing gas cylinder, a CO cylinder, a gas distributor, and a pressure-holding gas tank; the first nitrogen cylinder, the oxygen-containing gas cylinder, and the CO cylinder are respectively communicated with corresponding air inlets of the gas distributor; an air outlet of the gas distributor is communicated with an air inlet of the pressure-holding gas tank; the method includes: Using the gas distribution system to sequentially configure a mixed gas with a set oxygen content and a set CO concentration combination in the pressure-holding gas tank, inputting the set oxygen content to the CO measurement system through an input interface, and obtaining a measured CO concentration output by the CO measurement system; Evaluating the measurement accuracy of the CO measurement system based on the measured CO concentration and the set CO concentration.

Images