Hydrogen detection circuit and automatic calibration method

Abstract

The application discloses a hydrogen detection circuit and an automatic calibration method, which comprise a single-chip microcomputer, a hydrogen sensor, a temperature and humidity sensor, a power module, a data storage module and an output module; the hydrogen sensor, the temperature and humidity sensor, the power module, the data storage module and the output module are connected with the single-chip microcomputer; a signal amplification circuit is connected between the hydrogen sensor and the single-chip microcomputer, so as to amplify the signal output by the hydrogen sensor and input the amplified signal into the single-chip microcomputer. The hydrogen detection circuit and the automatic calibration method amplify the weak signal of the hydrogen sensor by arranging the signal amplification circuit between the hydrogen sensor and the single-chip microcomputer, thereby realizing the detection of low-concentration hydrogen; and the automatic calibration of the calibration method can guarantee that the accuracy of the finally output hydrogen concentration data is higher.

Description

TECHNICAL FIELD

[0001] The present application relates to a hydrogen detection device, more particularly to a hydrogen detection circuit and an automatic calibration method. BACKGROUND

[0002] At present, monitoring the release of H2 in the battery during lithium battery thermal runaway is of great significance for early warning of battery thermal runaway. Many literatures have reported that H2 is detected first (639s earlier than smoke and 769s earlier than flame) in battery thermal runaway experiments, which strongly proves that introducing H2 gas sensor into the battery system is an effective strategy to prevent thermal runaway in the early stage.

[0003] The existing hydrogen detection circuit basically detects the hydrogen gas in the battery system through the hydrogen sensor. However, the detection accuracy of the hydrogen sensor is affected by the ambient temperature. Therefore, the existing technology discloses an invention patent with the publication number CN112557595A and the name of a hydrogen sensor module output automatic calibration circuit and its calibration method, which improves the output accuracy of the hydrogen sensor by setting a single-chip microcomputer to receive the signal transmitted by the hydrogen sensor and then calibrate and output the signal. However, the signal strength output by the hydrogen sensor is small when the hydrogen concentration is low, so it is easy to be recognized as an interference signal by the single-chip microcomputer and filtered out after calibration. Therefore, the existing hydrogen sensor module and calibration method have the problem of being unable to detect hydrogen with low concentration. SUMMARY

[0004] In view of the deficiencies in the prior art, the purpose of the present application is to provide a hydrogen detection circuit and an automatic calibration method that can effectively detect hydrogen with low concentration.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a hydrogen detection circuit, comprising a single-chip microcomputer, a hydrogen sensor, a temperature and humidity sensor, a power module, a data storage module and an output module, the hydrogen sensor, the temperature and humidity sensor, the power module, the data storage module and the output module are connected with the single-chip microcomputer, characterized in that: a signal amplification circuit is connected between the hydrogen sensor and the single-chip microcomputer to amplify the signal output by the hydrogen sensor and input it into the single-chip microcomputer, the single-chip microcomputer comprises:

[0006] A digital signal acquisition module connected with the temperature and humidity sensor for receiving temperature and humidity data output by the temperature and humidity sensor;

[0007] An analog signal acquisition module connected with the signal amplification circuit for receiving analog detection data output by the hydrogen sensor output by the signal amplification circuit;

[0008] The data processing module is connected with the digital signal acquisition module and the analog signal acquisition module, and is also connected with the output module, and is used for receiving the temperature and humidity data output by the digital signal acquisition module and the analog detection data output by the analog signal acquisition module, and outputting the data to the output module after automatic calibration.

[0009] The data calibration module is connected with the data storage module and the data processing module, and the data storage module stores a calibration mathematical model, so that the data calibration module calls the calibration mathematical model to the data processing module, and the data processing model executes the automatic calibration operation.

[0010] As a further improvement of the application, the output module includes a CAN communication module, a PWM output module and an analog signal output module, which are used to output the calibrated hydrogen detection signal output by the single-chip microcomputer in the form of CAN communication, PWM signal and analog signal.

[0011] As a further improvement of the application, the signal amplification circuit includes:

[0012] The operational amplifier has a non-inverting input end, an inverting input end and an output end, the non-inverting input end is connected to the hydrogen sensor, the inverting input end is connected to the ground through a resistor R3 and is also connected to the output end through a resistor R1, and the output end is connected to the single-chip microcomputer through a resistor R2 and is also connected to the ground through a capacitor C between the resistor R2 and the single-chip microcomputer.

[0013] The application also provides a calibration method for hydrogen concentration data, which specifically includes the following steps: step one, receiving the temperature and humidity data output by the temperature and humidity sensor as environmental data through the digital signal acquisition module, and receiving the analog detection data output by the hydrogen sensor as hydrogen concentration data through the analog signal acquisition module after the signal amplification circuit amplifies and outputs the analog detection data;

[0014] Step two, calling the mathematical model stored in the data storage module based on the environmental data and the hydrogen concentration data received in step one through the data calibration module, to realize automatic calibration of the hydrogen concentration data, and then outputting the calibrated hydrogen concentration data through the output module;

[0015] The mathematical model includes baseline drift processing, humidity compensation processing, response function calculation and error correction processing.

[0016] As a further improvement of the above calibration method, the specific way of the baseline drift processing in the mathematical model is as follows: first, according to the baseline resistance change rule measured for 10 weeks, the long-time deviation rule is calculated: y=0.3623x+2.2311

[0017] In the formula, X represents the number of weeks of operation, and y represents the baseline resistance.

[0018] After the single-chip microcomputer runs the time counter, the count value is set as t;

[0019]

[0020] And every 1 hour, the running time counter under the storage module is added by 1.

[0021] As a further improvement of the above calibration method, first, the baseline resistance of the hydrogen sensor under 10%-90% humidity is measured, and then the function of the baseline resistance changing with humidity is fitted:

[0022] y = (901,237) ln(x) + 7,076,279

[0023] y = (801,839) ln(x) + 6,556,941

[0024] After that, the function trend is obtained:

[0025] Rz = a ln H + b

[0026] Finally, the most accurate baseline curve changing with humidity H is obtained by calibrating the least number of points.

[0027] As a further improvement of the above calibration method, the specific way of calculating the response function in the mathematical model is: first, calculate the response value X:

[0028]

[0029] Then according to the linear relationship:

[0030] Y = AX + B

[0031] In the formula, Y is the hydrogen concentration, Rz is the baseline resistance, and Rs is the current sensor response resistance;

[0032] Then extract A and B of the response curve, and list the change relationship of A and B and humidity H:

[0033] A = 1.3789H + 21.832

[0034] B = -15.15H - 17.02

[0035] Finally, the mathematical model of hydrogen concentration Y and humidity H real-time response resistance Rs is established through the above data:

[0036]

[0037] Rz = a ln H + b

[0038] A = 1.3789H + 21.832

[0039] B = -15.15 H - 17.02.

[0040] According to the established mathematical model, the hydrogen concentration result is calculated.

[0041] As a further improvement of the application, the specific way of the total error correction processing of the mathematical model is that: taking the partial key hydrogen concentration points 50% humidity, 5ppm, 10ppm, 20ppm three concentrations, the measured hydrogen concentration results O1, O2, O3 are respectively the correction error, and the correction coefficients a, b, c are calculated:

[0042]

[0043] The three coefficients are applied to the calibration correction coefficient in all humidity ranges, specifically: taking a = 1.25, in the 0-5ppm interval, through the two hydrogen concentrations of 0 and 5ppm, (0, 1), (5, 1.25) two points to determine a correction coefficient straight line in the 0-5ppm interval:

[0044] k = 0.05x + 1

[0045] Where x represents the hydrogen concentration before correction, k represents the correction coefficient, the straight line represents the correction value in the range of 0-5ppm, and the hydrogen concentration Y after correction:

[0046] Y = k * x5-10ppm The correction coefficient b and the correction coefficient c of 10-20ppm are also corrected to the hydrogen concentration Y in the above manner.

[0047] The beneficial effects of the application are that by connecting a signal amplification circuit between the hydrogen sensor and the single-chip microcomputer, the signal amplification circuit can amplify the hydrogen concentration signal output by the hydrogen sensor, so that the single-chip microcomputer is not easy to identify the hydrogen concentration signal as an interference signal, thereby realizing the detection of hydrogen with low concentration. In addition, by setting a data calibration module in the single-chip microcomputer, information data in the data storage module can be called as calibration data, and the data processing module can further realize calibration operation. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 The module block diagram of the hydrogen detection circuit of the application;

[0049] Figure 2 The flowchart for the calibration operation of the mathematical model;

[0050] Figure 3 The schematic diagram of baseline drift change;

[0051] Figure 4A circuit diagram of a signal amplification circuit;

[0052] Figure 5 A diagram showing the change of baseline resistance with humidity;

[0053] Figure 6 A diagram showing the baseline at 10 and 90% humidity;

[0054] Figure 7 A diagram showing the baseline at 30 and 60% humidity;

[0055] Figure 8 A diagram showing the baseline at 10 and 70% humidity;

[0056] Figure 9 A diagram showing the relationship between hydrogen concentration and response value at different humidity;

[0057] Figure 10 A diagram showing the value of A;

[0058] Figure 11 A diagram showing the value of B;

[0059] Figure 12 A diagram showing the result of the correction coefficient. DETAILED DESCRIPTION

[0060] The present application will be further described in conjunction with the embodiments shown in the accompanying drawings.

[0061] Referring to Figure 1 the hydrogen detection circuit of the present embodiment comprises a single-chip microcomputer 1, a hydrogen sensor 2, a temperature and humidity sensor 6, a power module 3, a data storage module 4 and an output module 5, wherein the hydrogen sensor 2, the temperature and humidity sensor 6, the power module 3, the data storage module 4 and the output module 5 are all connected to the single-chip microcomputer 1, and characterized in that a signal amplification circuit 7 is connected between the hydrogen sensor 2 and the single-chip microcomputer 1 to amplify the signal output by the hydrogen sensor 2 and input it into the single-chip microcomputer 1, wherein the single-chip microcomputer 1 comprises a digital signal acquisition module 11 connected to the temperature and humidity sensor 6 to receive the temperature and humidity data output by the temperature and humidity sensor 6;

[0062] an analog signal acquisition module 12 connected to the signal amplification circuit 7 to receive the analog detection data output by the hydrogen sensor 2 output by the signal amplification circuit 7;

[0063] a data processing module 13 connected to the digital signal acquisition module 11 and the analog signal acquisition module 12 and also connected to the output module 5 to receive the temperature and humidity data output by the digital signal acquisition module 11 and the analog detection data output by the analog signal acquisition module 12, and output them to the output module 5 after automatic calibration;

[0064] A data calibration module 8 is connected with the data storage module 4 and the data processing module 13, the data storage module 4 stores the calibration mathematical model, the data calibration module 8 calls the calibration mathematical model to the data processing module 13, and the data processing module 13 performs the automatic calibration operation, wherein the output module 5 includes a CAN communication module 51, a PWM output module 52 and an analog signal output module 53 to realize the output of the hydrogen concentration in three ways, in the actual use process, the temperature and humidity sensor 6 obtains the environmental parameters, and the data processing module 13 calculates the influence of the environment on the sensor, the signal amplification circuit 7 processes the weak signal on the hydrogen sensor, and the single-chip microcomputer 1 collects and processes the amplified signal, so as to avoid the problem that the data processing module 13 judges the weak signal on the hydrogen sensor as an interference signal and filters it, resulting in inaccurate final hydrogen concentration data, the power module 3 mainly processes the vehicle power system, reduces the power voltage to the voltage required for the single-chip microcomputer 1 and the sensor to run, and can convert the 12-36V voltage to 3V, the data storage module 4 mainly stores the production information of the sensor module, including the production date, the model and the serial number, and stores the calibration data of the sensor, including the sensor running time, the baseline calibration data, the humidity processing data, the response function, the correction coefficient, the CAN communication module, the PWM output, the analog signal output and the automobile head unit communication, and the real-time output of the current environmental hydrogen concentration.

[0065] Further, the embodiment provides a calibration process of the data calibration module 8 as follows:

[0066] The sensor module is built, the sensor module is powered on, the hydrogen sensor 2 and the temperature and humidity sensor 6 are included, and it is determined that the communication is normal.

[0067] The baseline curve of the long-term running of the sensor is recorded in the data storage module. When the sensor module is running, the baseline resistance is corrected in real time according to the running time, and the baseline resistance value Z1 is obtained.

[0068] According to the baseline function measured under 10%-90% humidity, the related parameters of the current sensor baseline function are calibrated, and the current sensor baseline function is calculated. According to the current humidity, the baseline resistance Z2 is calculated.

[0069] The sensor response function is determined. By measuring the response values of the sensor at 30%, 50% and 70% humidity to 5ppm, 10ppm and 20ppm, a total of 9 points, the sensor response function is determined.

[0070] Each sensor has different errors, and the errors are corrected again at 50%, 5ppm, 10ppm and 20ppm, the correction coefficients a, b and c are calculated, and the three coefficients are applied to all humidity ranges.

[0071] Further, the embodiment provides a circuit structure of the signal amplification circuit 7, which comprises:

[0072] An operational amplifier has a non-inverting input connected to the hydrogen sensor 2, an inverting input connected to ground through a resistor R3 and to the output through a resistor R1, and an output connected to the single-chip microcomputer 1 through a resistor R2 and to ground through a capacitor C1. Figure 4 As shown in FIG. 1, the hydrogen sensor 2 in the embodiment is the same as in the prior art, and has a load resistor of a response resistor therein. Specifically, Figure 4 wherein RHeat is a heating wire built in the hydrogen sensor, powered by a 3V voltage, Rs is the response resistor, Rl is the load resistor, and is 5.1kΩ. The operational amplifier uses a precision operational amplifier OPA333AIDBVR from TI:

[0073] Based on the circuit structure, the operational amplifier constructs a same-direction signal amplification circuit. The amplification factor β is:

[0074]

[0075] R1 is 10kΩ, R3 is 100Ω, and the calculation result β = 101.

[0076] Amplification factor A:

[0077] A = 20 x log β

[0078] A ≈ 40

[0079] Amplified voltage Vout:

[0080] Vout = Vi x β

[0081] Taking the baseline resistance Rz as 4MΩ under 30% humidity, Rl as the load resistor, 5.1kΩ, and the circuit voltage as 3V

[0082]

[0083] Calculating Vi ≈ 1.27 x 10 -3 V

[0084] Vout ≈ 0.127V, which can be accurately collected in the 12-bit analog-to-digital converter of the single-chip microcomputer.

[0085] Therefore, the 12-bit minimum collection voltage Vin(min) is:

[0086]

[0087] The minimum collection response resistance Rz(min) is:

[0088]

[0089] Vi takes 0.03V, and β=101

[0090] Rz(min)≈1.5MΩ

[0091] The response resistance is 1.5MΩ. According to the measured response resistance of the actual sensor sample, the upper limit of the collected hydrogen concentration is about 50ppm or so.

[0092]

[0093]

[0094] Further, Figure 2 The mathematical model in the data processing module 13 is shown, including baseline drift processing, humidity compensation processing, response function calculation and error correction processing, in particular:

[0095] Baseline drift processing: After long-term operation of the sensor, the resistance value of the sensor itself will change with the running time without hydrogen response, as shown in Figure 3 . After long-term operation of the sensor, the baseline drift needs to be automatically corrected. According to the baseline resistance change rule measured for 10 weeks, the long-time deviation rule is calculated:

[0096] Y=0.3623X+2.2311

[0097] x represents the number of weeks, and y represents the baseline resistance.

[0098] The single-chip microcomputer runs the time counter, and the counter value is set as t;

[0099]

[0100] Every 1 hour, the running time counter under the storage module is increased by 1.

[0101] Humidity compensation processing: The baseline resistance of the hydrogen sensor will change regularly under different humidity. By measuring the baseline resistance of the hydrogen sensor under 10%-90% humidity as shown in Figure 5 , the function of the baseline resistance changing with humidity is fitted. Figure 5 The fitting curves of two sensors are shown in

[0102] y=(901,237)ln(x)+7,076,279

[0103] y=(801,839)ln(x)+6,556,941

[0104] Rz= a ln H + b 2 It can be seen that the overall fitting error is small, and the function trend is:

[0105] Rz= a ln H + b

[0106] To obtain the most accurate baseline curve of resistance change with humidity H by calibrating with the least number of points. By Figure 6 , 10% humidity and 90% humidity calibration, record the baseline resistance; Figure 7 , 30% humidity and 60% humidity calibration, record the baseline resistance; Figure 8 , 10% humidity and 70% humidity calibration, record the baseline resistance. It can be concluded that the 10% humidity and 70% humidity calibration baseline is the most accurate.

[0107] Response function calculation: the hydrogen sensor will have different response values for different concentrations of hydrogen. The response function is to determine the relationship between hydrogen concentration and response value at different concentrations. From Figure 9 It can be seen that when the humidity is fixed, in the range of 0-20 ppm, the response value X and the hydrogen concentration are linearly related, and the R 2 It can be seen that the linear error is small. Among them, the response value X:

[0108]

[0109] According to the linear relationship:

[0110] Y = AX + B

[0111] Y is the hydrogen concentration, Rz is the baseline resistance, and Rs is the current sensor response resistance. A and B also change according to certain rules, which will Figure 9 The A and B of the response curve at different humidities are extracted and listed to show the relationship with humidity. It is found that Figure 10 , the relationship between A and humidity H; Figure 11 , the relationship between B and humidity H.

[0112] A = 1.3789H + 21.832

[0113] B = -15.15H - 17.02

[0114] From the above data, the following mathematical model of hydrogen concentration Y and humidity H real-time response resistance Rs can be established:

[0115]

[0116] Rz= a ln H + b

[0117] A = 1.3789H + 21.832

[0118] B = -15.15H - 17.02

[0119] As can be seen from Table 1, the hydrogen concentration results have been calculated basically accurately by the mathematical model of the above steps.

[0120] Table 1

[0121]

[0122]

[0123] Due to circuit errors, sensor individual errors, etc., the calculated hydrogen concentration needs to be corrected. Take some key hydrogen concentration points at 50% humidity, 5ppm, 10ppm, and 20ppm, and the measurement results are O1, O2, and O3, respectively, to correct the error, and calculate the correction coefficients a, b, and c:

[0124]

[0125] Apply the three coefficients to the calibration correction coefficients in all humidity ranges.

[0126] Figure 12 Three points are shown in FIG. 3, which represent the correction coefficients a, b, and c. Take a = 1.25, and in the 0-5ppm range, determine a correction coefficient straight line in the 0-5ppm range by two hydrogen concentrations at 0 and 5ppm, (0, 1), and (5, 1.25):

[0127] k = 0.05x + 1

[0128] Where x represents the hydrogen concentration before correction, k represents the correction coefficient, the straight line represents the correction value in the 0-5ppm range, and Y represents the hydrogen concentration after correction:

[0129] Y = k * x

[0130] Similarly, 5-10ppm and 10-20ppm also follow this rule. The correction results are shown in Table 2.

[0131] Table 2

[0132]

[0133]

[0134] In summary, the hydrogen detection circuit and automatic calibration method of the embodiment can effectively amplify the weak signal output by the hydrogen sensor 2 through the setting of the signal amplification circuit 7, avoid the data processing module 13 in the single-chip microcomputer 1 from identifying the weak signal as an interference signal, and cause the problem of difficulty in detecting low-concentration hydrogen. Thus, quantitative measurement can be realized under low-concentration 1-20ppm hydrogen, battery thermal runaway can be predicted earlier, the novel sensor calibration method can avoid environmental interference on the sensor.

[0135] The above merely describes the preferred embodiments of the present application, and the protection scope of the present application is not limited to the above-described embodiments. Any technical solution falling within the concept of the present application shall fall within the protection scope of the present application. It should be noted that, for ordinary skilled persons in the art, some improvements and refinements without departing from the principles of the present application shall also be considered as falling within the protection scope of the present application.

Claims

1. A hydrogen detection circuit, comprising a single-chip microcomputer (1), a hydrogen sensor (2), a temperature and humidity sensor (6), a power module (3), a data storage module (4) and an output module (5), wherein the hydrogen sensor (2), the temperature and humidity sensor (6), the power module (3), the data storage module (4) and the output module (5) are all connected to the single-chip microcomputer (1), and is characterized in that: A signal amplifying circuit (7) is connected between the hydrogen sensor (2) and the single-chip microcomputer (1) to amplify the signal output by the hydrogen sensor (2) and input the amplified signal into the single-chip microcomputer (1). The single-chip microcomputer (1) comprises: a digital signal acquisition module (11), the digital signal acquisition module (11) being connected to the temperature and humidity sensor (6) and being used to receive temperature and humidity data output by the temperature and humidity sensor (6); an analog signal acquisition module (12), connected to the signal amplifying circuit (7) and configured to receive analog detection data outputted by the hydrogen sensor (2) and outputted by the signal amplifying circuit (7); The data processing module (13) is connected to the digital signal acquisition module (11) and the analog signal acquisition module (12), and is also connected to the output module (5), and is used to receive the temperature and humidity data output by the digital signal acquisition module (11) and the analog detection data output by the analog signal acquisition module (12), and output the data to the output module (5) after automatic calibration; A data calibration module (8) is connected to a data storage module (4) and a data processing module (13). The data storage module (4) stores a calibration mathematical model, so that the data calibration module (8) can retrieve the calibration mathematical model and transfer it to the data processing module (13), so that the data processing module (13) can perform an automatic calibration operation. The data processing module (13) has an automatic calibration method built in, which includes: Step 1: The temperature and humidity data output by the temperature and humidity sensor (6) is received by the digital signal acquisition module (11) as environmental data, and the analog detection data output by the hydrogen sensor (2) after amplification by the signal amplification circuit (7) is received by the analog signal acquisition module (12) as hydrogen concentration data; Step 2: The data calibration module (8) retrieves the mathematical model stored in the data storage module (4) based on the environmental data and hydrogen concentration data received in step 1, thereby automatically calibrating the hydrogen concentration data, and then outputting the calibrated hydrogen concentration data through the output module (5); Among them, the mathematical model includes baseline drift processing, humidity compensation processing, response function calculation and error correction processing; The specific method of processing the baseline drift in the mathematical model is as follows: First, based on the baseline resistance change pattern measured over 10 weeks, the long-term deviation pattern is calculated: y=0.3623x+2.2311 Where X represents the number of weeks of operation, and y represents the baseline resistance; After that, the microcontroller counts while running, and the count value is set to t; And the running time count in the storage module will be increased by one every running hour; The specific method of humidity compensation in the mathematical model is as follows: first, the baseline resistance of the hydrogen sensor is measured at 10%-90% humidity, and then a function of the baseline resistance changing with humidity is fitted: y=(901,237)ln(x)+7,076,279 y=(801,839)ln(x)+6,556,941 Then get the function trend as: Rz=alnH+b Finally, the most accurate baseline curve with humidity change is obtained by calibration with the least number of points; The specific method of calculating the response function in the mathematical model is: first calculate the response value X: Then list them according to the linear relationship: Y=AX+B Where Y is the hydrogen concentration, Rz is the baseline resistance, and Rs is the current sensor response resistance; Then extract A and B of the response curve and list the relationship between A and B and humidity H: A=1.3789H+21.832 B=-15.15H-17.02 Finally, the mathematical model of the real-time response resistance Rs of hydrogen concentration Y and humidity H is established based on the above data: Rz=alnH+b A=1.3789H+21.832 B = -15.15H -17.02; The hydrogen concentration results are calculated based on the established mathematical model.

2. The hydrogen detection circuit according to claim 1, characterized in that: The output module (5) comprises a CAN communication module (51), a PWM output module (52) and an analog signal output module (53), and is used to output the calibrated hydrogen detection signal output by the single chip microcomputer (1) via CAN communication, PWM signal and analog signal.

3. The hydrogen gas detection circuit according to claim 2, wherein: The signal amplifying circuit (7) comprises: An operational amplifier having a non-inverting input terminal, an inverting input terminal, and an output terminal, wherein the non-inverting input terminal is connected to a hydrogen sensor (2), the inverting input terminal is connected to a resistor R3 and then to ground, and is further connected to a resistor R1 and then to the output terminal, the output terminal is connected to a resistor R2 and then to a single-chip computer (1), and a capacitor C1 is further connected between the resistor R2 and the single-chip computer (1) and then to ground.

4. The hydrogen detection circuit according to claim 3, characterized in that: The specific method of error correction processing in the mathematical model is: take some key hydrogen concentration points at 50% humidity, 5ppm, 10ppm, and 20ppm, and the measurement results are O1, O2, and O3 respectively, as the correction errors, and calculate the correction coefficients a, b, and c: The three coefficients are applied to all humidity ranges to calibrate the correction coefficients. Specifically, take a = 1.25, and determine a correction coefficient line in the range of 0-5ppm through the two points (0,1) and (5,1.25) at two hydrogen concentrations of 0 and 5ppm: k=0.05x+1 Where x represents the hydrogen concentration before correction, k represents the correction coefficient, and the straight line represents the correction value in the range of 0-5ppm. The hydrogen concentration after correction is Y: Y=k*x The correction coefficient b when 5-10 ppm and the correction coefficient c when 10-20 ppm are also used to correct the hydrogen concentration Y in the above manner.

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