Ultrasonic flowmeter oxygen concentration and flow algorithm adapting to different air pressures and temperatures

Abstract

The invention discloses an ultrasonic flowmeter oxygen concentration and flow algorithm adapting to different air pressures and temperatures. The ultrasonic flowmeter oxygen concentration and flow algorithm comprises the following steps that the gas temperature T, the total forward propagation time tP of ultrasonic waves and the total reverse propagation time tN of the ultrasonic waves are obtained; calculating the delay durations delay15P and delay10P of the forward propagation of the ultrasonic waves and the delay durations delay15N and delay10N of the reverse propagation of the ultrasonic waves, and determining a function that the delay durations change along with the temperature; calculating an ultrasonic wave forward propagation delay time length delayTP, an ultrasonic wave reverse propagation delay time length delayTN, an ultrasonic wave forward propagation actual time length t 'P and an ultrasonic wave reverse propagation actual time length t' N; initial oxygen flow Q0 and a compensation coefficient k are calculated, and actual flow Q is calculated according to Q0 and k; and calculating an actual propagation time length mean value # imgabs0 # and a standard actual propagation time length # imgabs1 #, comparing the standard actual propagation time length # imgabs2 # with the ultrasonic propagation mean value time length tave, and calculating the current oxygen concentration # imgabs3 # according to an interpolation method. The algorithm can improve the oxygen flow and concentration calculation precision in different environments, so that the oxygen generator can better meet the oxygen uptake requirement of a user.

Description

Technical Field

[0001] The invention belongs to the technical field of ultrasonic flowmeters, and in particular relates to an ultrasonic flowmeter oxygen concentration and flow algorithm adaptable to different air pressures and temperatures. Background Art

[0002] The principle of ultrasonic flowmeter in oxygen flow and concentration measurement is to use the transducers at both ends of the airway to emit ultrasonic waves in the forward and reverse directions of oxygen flow, and collect the total time of two ultrasonic waves from the beginning of emission to the arrival at the other end to calculate the flow rate and concentration of oxygen. Due to the certain delay time of the transducer and hardware circuit, the sound speed of ultrasonic waves will inevitably be affected by the fluid when propagating in the flowing oxygen. The propagation speed of ultrasonic waves will include the flow rate of oxygen, and the total propagation time of ultrasonic waves collected must include the delay time and the actual propagation time. Generally, the delay time is calculated and fixed in still air. The actual propagation time is obtained by subtracting the delay time from the total propagation time, and then this value is substituted into the flow and concentration algorithm to calculate the flow and concentration of oxygen.

[0003] However, in actual use, the delay time is different because the performance of the transducer is different at different temperatures. The existing ultrasonic flowmeter's oxygen concentration and flow rate algorithm has the following problems: it does not take into account the impact of temperature on the delay time. If a fixed delay time is used, the measured value will deviate from the actual value after the temperature changes; it does not handle different air pressures and temperatures. In special environments (such as plateaus), the measurement results will be significantly different from the actual value; it does not make detailed processing for specific flow rates and concentrations. Summary of the invention

[0004] The purpose of the present invention is to solve at least one problem in the prior art and to provide an ultrasonic flowmeter oxygen concentration and flow algorithm that is adaptable to different air pressures and temperatures.

[0005] To achieve the above purpose, the present invention proposes an ultrasonic flowmeter oxygen concentration and flow algorithm that is adaptable to different air pressures and temperatures, comprising the following steps:

[0006] The temperature T of the gas flowing into the airway of the ultrasonic flowmeter is obtained through the thermistor, and the ultrasonic sensor obtains the total forward propagation time t of the ultrasonic wave from the first transducer through the airway to the second transducer P , the total reverse propagation time t of the ultrasonic wave from the second transducer through the airway to the first transducer N ;

[0007] According to the formula t 0 =L / V 15 Calculate the theoretical duration t of ultrasonic wave propagation 0 , where L is the length of the airway in the ultrasonic flowmeter, V15 The speed of ultrasound at 15°C is 340.11 m / s. According to the formula delay 15P =t P -t 0 Calculate the delay of ultrasonic forward propagation 15P According to the formula delay 15N =t N -t 0 Calculate the delay of ultrasonic reverse propagation delay 15N , through delay 15N 、delay 15P Determine the constant b of the delay time as a function of temperature 1 、b 3 , where the delay time varies with temperature as follows:

[0008] Using the temperature intersection point 10℃ of the delay time versus temperature function, calculate the delay 10P 、delay 10N , and according to the delay 10P 、delay 10N Calculate the constant b in the delay time function as a function of temperature variation 2 、b 4 ;

[0009] According to the delay time varying with temperature function and the current gas temperature T, calculate the ultrasonic forward propagation delay time delay TP 、Delay of ultrasonic reverse propagation TN , according to the formula t' P =t P -delay TP Calculate the actual forward propagation time t' of the ultrasonic wave P , according to the formula t' N =t N -delay TN Calculate the actual duration t' of ultrasonic reverse propagation N ;

[0010] According to the actual duration t' of ultrasonic forward propagation P and the actual duration of ultrasonic reverse propagation t' N , according to the formula Calculate the initial oxygen flow rate Q 0 , Q in the formula 0 is the initial oxygen flow rate, L is the airway length, and A is the average cross-sectional area of ​​the airway;

[0011] According to the current gas temperature T and gas pressure P, the formula

[0012] The compensation coefficient k is calculated, where c 11 =0.9367, c 12 =0.6147, c 13 =0.9546, c 14 =0.8283;

[0013] According to the compensation coefficient k, according to the formula Q = kQ 0 Calculate the actual flow rate Q;

[0014] According to the actual duration t' of ultrasonic forward propagation P , the actual duration of ultrasonic reverse propagation t' N , according to the formula Calculate the mean ultrasonic propagation time t ave ;

[0015] According to the mean ultrasonic propagation time t ave Use the table lookup method to find the two temperatures T closest to the current gas temperature T in the data table. * 、T ** And with T * The corresponding average actual propagation time of 50%, 85%, 90%, and 100% concentrations at a standard pressure of 101 kPa With T ** The corresponding standard actual propagation time average of 50%, 85%, 90%, and 100% concentration at an air pressure of 101 kPa According to the formula Calculate the average actual propagation time The superscript concentration values ​​in each parameter are 50%, 85%, 90%, or 100% respectively;

[0016] According to the average actual propagation time The current gas temperature T and gas pressure P are calculated by the formula Calculate the standard actual propagation time The superscript concentration values ​​in each parameter are 50%, 85%, 90%, or 100% respectively;

[0017] The actual propagation time of the standard and the mean ultrasonic propagation time t ave Compare and calculate the current oxygen concentration by interpolation method

[0018] Preferably, the data table is a data table of average actual propagation duration of ultrasonic waves in ultrasonic flowmeters at oxygen concentrations of 50%, 85%, 90%, and 100% at temperatures of -40°C to 60°C and standard air pressure of 101 kPa.

[0019] Preferably, when the mean ultrasonic propagation time t ave The standard actual propagation time when the concentration value is less than 50% The current oxygen concentration is 35%.

[0020] Preferably, when the mean ultrasonic propagation time t ave Standard actual propagation time between concentration values ​​of 50% The standard actual propagation time when the concentration value is 85% When Calculate the current oxygen concentration

[0021] Preferably, when the mean ultrasonic propagation time t ave Standard actual propagation time between concentration values ​​of 85% The standard actual propagation time for the concentration value to be 90% When Calculate the current oxygen concentration

[0022] Preferably, when the mean ultrasonic propagation time t ave Standard actual propagation time between concentration values ​​of 90% The standard actual propagation time when the concentration value is 100% When Calculate the current oxygen concentration

[0023] Preferably, when the mean ultrasonic propagation time t ave Not less than the standard actual propagation time when the concentration value is 100% The current oxygen concentration is 100%.

[0024] As a preferred embodiment, the gas temperature T is obtained through a thermistor temperature measurement circuit, which is composed of a 3.3V power supply, a 10kΩ resistor R1, and a thermistor RT in series. The thermistor is connected to the controller. When measuring the gas temperature T, the voltage U at both ends of the thermistor is measured. According to the formula Calculate the thermistor resistance RT according to the formula The gas temperature T is calculated.

[0025] Beneficial effects of the present invention: The present invention dynamically calculates the delay time generated when the ultrasonic flowmeter works at different temperatures by utilizing a specific delay time varying function and an algorithm formula, obtains the actual ultrasonic propagation time, calculates the compensation coefficients at different temperatures and air pressures by utilizing the algorithm formula, dynamically corrects the initial oxygen flow rate to calculate the actual flow rate, obtains the mean actual propagation time by utilizing the ultrasonic propagation mean time algorithm and the ultrasonic actual propagation time mean data table parameter lookup method, calculates the standard actual propagation time at different temperatures and air pressures by utilizing the algorithm formula, calculates the current oxygen concentration by comparing the actual propagation time mean with the standard actual propagation time, fully considers the influencing factors of temperature and air pressure in the calculation process of oxygen concentration and flow, and the algorithm greatly improves the calculation accuracy of oxygen flow and concentration under different environments, enabling the oxygen concentrator to better meet the oxygen inhalation needs of users under different air temperature and air pressure environments.

[0026] The features and advantages of the present invention will be described in detail through embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the structure of an ultrasonic flowmeter according to an embodiment of the present invention.

[0028] Figure 2 4 is a cross-sectional view of an ultrasonic flow meter according to an embodiment of the present invention.

[0029] Figure 3 1 is a thermistor temperature measurement circuit diagram of an embodiment of the present invention.

[0030] In the figure: 1. Shell; 2. Ultrasonic transducer; 3. Thermistor; 10. Airway; 11. Air inlet pipe; 12. Air outlet pipe; 13. Gas pressure detection port. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the embodiment of the present application clearer, the technical scheme in the embodiment of the present application will be clearly and completely described in conjunction with the drawings in the embodiment of the present application. Obviously, the described embodiment is a part of the embodiment of the present application, not all of the embodiments. The components of the embodiment of the present application described and shown in the drawings here can be arranged and designed in various different configurations. In the description of the present application, it should be noted that the orientation or position relationship indicated by the terms "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, or the orientation or position relationship usually placed when the application product is used, which is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0032] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "disposed" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0033] The present invention is described in detail below in conjunction with the accompanying drawings.

[0034] See also Figure 1 and Figure 2 The ultrasonic flowmeter in the present application includes a shell 1, an air duct 10 arranged inside the shell 1, ultrasonic transducers 2 are installed at both ends of the air duct 10, the shell 1 is provided with an air inlet pipe 11 and an air outlet pipe 12, the shell 1 is provided with a thermistor 3 at one end close to the air inlet pipe 11, and the shell 1 is provided with a gas pressure detection port 13 for installing a gas pressure sensor at one end close to the air outlet pipe 12. The ultrasonic transducer 2 is connected to an external ultrasonic sensor through a pin 21. When the ultrasonic flowmeter is working, the gas enters the ultrasonic flowmeter from the air inlet pipe 11 and flows out from the air outlet pipe 12 after flowing through the air duct 10. The two relative ultrasonic transducers 2 send and receive ultrasonic waves, and each ultrasonic transducer has signal transmission and signal receiving functions.

[0035] In the measurement of oxygen flow and concentration, the ultrasonic flowmeter uses the transducers at both ends of the airway to emit ultrasonic waves in the forward and reverse directions of the oxygen flow, and collects the total propagation time of the two ultrasonic waves from the beginning of emission at one end to the arrival at the other end. The total propagation time consists of two parts: delay time and actual propagation time. The delay time is inherent in the transducer and hardware. Each transducer and circuit board has a different delay time, which will change with temperature. The ultrasonic flowmeter is used in an oxygen concentrator, and through the algorithm of the present invention, it can correct the actual output values ​​of oxygen flow and oxygen concentration for the oxygen concentrator under environmental conditions of different air pressures and temperatures. The control processor in the oxygen concentrator accurately adjusts the oxygen supply according to the actual output values ​​of the corrected oxygen flow and oxygen concentration and user needs to better meet the user's oxygen inhalation needs.

[0036] The present invention provides an ultrasonic flowmeter oxygen concentration and flow rate algorithm adapted to different air pressures and temperatures, comprising the following steps:

[0037] The temperature T of the gas flowing into the airway of the ultrasonic flowmeter is obtained through the thermistor, and the ultrasonic sensor obtains the total forward propagation time t of the ultrasonic wave from the first transducer through the airway to the second transducer P, the total reverse propagation time t of the ultrasonic wave from the second transducer through the airway to the first transducer N ;

[0038] According to the formula t 0 =L / V 15 Calculate the theoretical duration t of ultrasonic wave propagation 0 , where L is the length of the airway in the ultrasonic flowmeter, V 15 The speed of ultrasound at 15°C is 340.11 m / s. According to the formula delay 15P =t P -t 0 Calculate the delay of ultrasonic forward propagation 15P According to the formula delay 15N =t N -t 0 Calculate the delay of ultrasonic reverse propagation delay 15N , through delay 15N 、delay 15P Determine the constant b that determines the delay time as a function of temperature 1 , b 3 , where the delay time varies with temperature as follows:

[0039] Using the temperature intersection point 10℃ of the delay time versus temperature function, calculate the delay 10P 、delay 10N , and according to the delay 10P 、delay 10N Calculate the constant b in the function of delay time varying with temperature 2 , b 4 ;

[0040] According to the delay time varying with temperature function and the current gas temperature T, calculate the ultrasonic forward propagation delay time delay TP 、Delay of ultrasonic reverse propagation delay TN , according to the formula t' P =t P -delay TP Calculate the actual duration t' of ultrasonic forward propagation P , according to the formula t' N =t N -delay TN Calculate the actual duration t' of ultrasonic reverse propagation N ;

[0041] According to the actual duration t' of ultrasonic forward propagation P and the actual duration of ultrasonic reverse propagation t'N , according to the formula Calculate the initial oxygen flow rate Q 0 , Q in the formula 0 is the initial oxygen flow rate, L is the airway length, and A is the average cross-sectional area of ​​the airway;

[0042] According to the current gas temperature T and gas pressure P, the formula

[0043]

[0044] The compensation coefficient k is calculated, where c 11 =0.9367, c 12 =0.6147, c 13 =0.9546, c 14 =0.8283;

[0045] According to the compensation coefficient k, the actual flow Q is calculated according to the formula Q=kQ0;

[0046] According to the actual duration t' of ultrasonic forward propagation P , the actual duration of ultrasonic reverse propagation t' N , according to the formula Calculate the mean ultrasonic propagation time t ave ;

[0047] According to the mean ultrasonic propagation time t ave Use the table lookup method to find the two temperatures T closest to the current gas temperature T in the data table. * 、T ** And with T * The corresponding average actual propagation time of 50%, 85%, 90%, and 100% concentrations at a standard pressure of 101 kPa With T ** The corresponding standard actual propagation time average of 50%, 85%, 90%, and 100% concentration at an air pressure of 101 kPa According to the formula Calculate the average actual propagation time The superscript concentration values ​​in each parameter are 50%, 85%, 90%, or 100% respectively;

[0048] According to the actual transmission time average The current gas temperature T and gas pressure P are calculated by the formula Calculate the standard actual propagation time The superscript concentration values ​​in each parameter are 50%, 85%, 90%, or 100% respectively;

[0049] The actual propagation time of the standard and the mean ultrasonic propagation time t ave Compare and calculate the current oxygen concentration by interpolation method

[0050] For actual use, refer to Figure 3 The gas temperature T is obtained through the thermistor temperature measurement circuit. The thermistor temperature measurement circuit is composed of a 3.3V power supply, a 10kΩ resistor R1, and a thermistor RT in series. When measuring the gas temperature T, the voltage U at both ends of the thermistor is measured by the controller. According to the formula Calculate the thermistor resistance RT according to the formula The gas temperature T is calculated. Assuming the voltage U across RT is 1.1V, the resistance RT of the thermistor is calculated based on the voltage: Substitute RT into the temperature measurement formula to get the current temperature T:

[0051] In actual use, the data table is a data table of the average actual propagation time of ultrasonic waves in ultrasonic flow meters at oxygen concentrations of 50%, 85%, 90%, and 100% at temperatures of -40°C to 60°C and standard air pressure of 101kPa. See Table 1 below for details.

[0052] Table 1. Average data of actual ultrasonic propagation time

[0053]

[0054]

[0055] When actually calculating the compensation coefficient k, if the gas pressure P is less than 47kPa, it is calculated as 47kPa, and if it is greater than 101kPa, it is calculated as 101kPa; if the gas temperature T is less than -40℃, it is calculated as -40℃, and if it is greater than 60℃, it is calculated as 60℃.

[0056] In actual use, when the average ultrasonic propagation time is t ave The standard actual propagation time when the concentration value is less than 50% The current oxygen concentration is 35%.

[0057] In actual use, when the average ultrasonic propagation time is t ave Standard actual propagation time between concentration values ​​of 50% The standard actual propagation time when the concentration value is 85% When Calculate the current oxygen concentration P O2 .

[0058] In actual use, when the average ultrasonic propagation time is t aveStandard actual propagation time between concentration values ​​of 85% The standard actual propagation time for the concentration value to be 90% When Calculate the current oxygen concentration

[0059] In actual use, when the average ultrasonic propagation time is t ave Standard actual propagation time between concentration values ​​of 90% The standard actual propagation time when the concentration value is 100% When Calculate the current oxygen concentration

[0060] In actual use, when the average ultrasonic propagation time t ave Not less than the standard actual propagation time when the concentration value is 100% The current oxygen concentration is 100%.

[0061] To facilitate understanding of the algorithm of the present invention, the present invention specifically provides the following embodiments. In the following embodiments, the flow meter airway length L=0.04m, the total forward propagation time t P = 250μs, the average cross-sectional area of ​​the airway is 2.83×10 -3 dm 2 , ultrasonic sound velocity V at 15℃ 15 =165.2+0.607×(T+273.15)=340.11m / s, the theoretical duration of ultrasonic propagation t 0 is 117.61μs, the delay time of ultrasonic forward propagation and ultrasonic reverse propagation is delay 15P =delay 15N =132.39μs, the constant of the delay time varying with temperature is as follows b 1 =delay 15P +0.4×15=138.39μs,b 1 =b 3 =138.39μs, the delay time varies with temperature as a piecewise function and the intersection of the two-segment function is T=10℃, so delay 10P 、delay 10N Substitute the corresponding b 1 、b 3 In functions such as delay 10P =-0.4×10+138.39=134.39μs, delay 10P =delay 10N = 134.39μs, and then use delay10P 、delay 10N Substitute the corresponding b 2 , b 4 In the function, we get b 2 =delay 10P +0.7×10=141.39μs,b 2 =b 4 =141.39μs.

[0062] In this embodiment, the temperature T of the gas currently flowing to the airway in the ultrasonic flowmeter is 20°C obtained by the thermistor, and the total forward propagation time t of the ultrasonic wave from the first transducer through the airway to the second transducer is obtained by the ultrasonic sensor. P = 250.56μs, the total reverse propagation time t of the ultrasonic wave from the second transducer through the airway to the first transducer N =251.17μs;

[0063] According to the delay time varying with temperature function and the current gas temperature T = 20 ° C, calculate the ultrasonic forward propagation delay time delay20P and the ultrasonic reverse propagation delay time delay at this temperature. 20N , delay 20P =delay 20N =-0.4T+b 2 =133.39μs, according to the formula t' P =t P -delay 20P Calculate the actual duration t' of ultrasonic forward propagation p =t P -delay 20P =117.17μs, according to the formula t N =t N -delay 20N Calculate the actual duration t' of ultrasonic reverse propagation N =t N -delay NP =117.78μs;

[0064] Initial oxygen flow

[0065] The pressure sensor obtains the current gas pressure of 80kPa, the compensation coefficient

[0066]

[0067] Actual flow rate Q = 0.8262 × 1.50 = 1.2393 L / min;

[0068] Mean ultrasonic propagation time

[0069] The current gas temperature T is 20°C. According to Table 1 above, we can find two temperatures T closest to 20°C. * =15℃, T ** =30℃, at this temperature, 50% concentration T * The corresponding standard air pressure 101kPa actual propagation time average is recorded as T ** The corresponding standard actual propagation time average of the air pressure 101kPa is recorded as Actual transmission time

[0070] At this temperature, 85% concentration T * The corresponding standard air pressure 101kPa actual propagation time average is recorded as T ** The corresponding standard actual propagation time average of the air pressure 101kPa is recorded as Actual transmission time

[0071] At this temperature, 90% concentration T * The corresponding standard air pressure 101kPa actual propagation time average is recorded as T ** The corresponding standard actual propagation time average of the air pressure 101kPa is recorded as Actual transmission time

[0072] At this temperature, 100% concentration T * The corresponding standard air pressure 101kPa actual propagation time average is recorded as T ** The corresponding standard actual propagation time average of the air pressure 101kPa is recorded as Actual transmission time

[0073] Standard actual propagation time at current gas temperature and 50% concentration

[0074] Standard actual propagation time at current gas temperature and 85% concentration

[0075] Standard actual propagation time at current gas temperature and 90% concentration

[0076] Standard actual propagation time at current gas temperature and 100% concentration

[0077] The actual propagation time of the standard and the mean ultrasonic propagation time t ave For comparison, The oxygen concentration

[0078] The above embodiments are intended to illustrate the present invention, not to limit the present invention. Any solution that is a simple transformation of the present invention belongs to the protection scope of the present invention.

Claims

1. An ultrasonic flowmeter oxygen concentration and flow algorithm adapted to different air pressures and temperatures, characterized by: It includes the following steps: The temperature T of the gas flowing into the airway of the ultrasonic flowmeter is obtained through the thermistor, and the ultrasonic sensor obtains the total forward propagation time t of the ultrasonic wave from the first transducer through the airway to the second transducer P , the total reverse propagation time t of the ultrasonic wave from the second transducer through the airway to the first transducer N ; According to the formula t0 = L / V 15 Calculate the theoretical duration of ultrasonic propagation t0, where L is the length of the airway in the ultrasonic flowmeter, V 15 The speed of ultrasound at 15°C is 340.11 m / s. According to the formula delay 15P =t P -t0 calculates the delay of ultrasonic forward propagation 15P According to the formula delay 15N =t N -t0 calculates the delay time of ultrasonic reverse propagation delay 15N , through delay 15N 、delay 15P Determine the constants b1 and b3 of the delay time varying with temperature function, where the delay time varying with temperature function is: Using the temperature intersection point 10℃ of the delay time versus temperature function, calculate the delay 10P 、delay 10N , and according to the delay 10P 、delay 10N Calculate the constants b2 and b4 in the function of delay time varying with temperature; According to the delay time varying with temperature function and the current gas temperature T, calculate the ultrasonic forward propagation delay time delay TP 、Delay of ultrasonic reverse propagation TN , according to the formula t' P =t P -delay TP Calculate the actual forward propagation time t' of the ultrasonic wave P , according to the formula t' N =t N -delay TN Calculate the actual duration t' of ultrasonic reverse propagation N ; According to the actual duration t′ of ultrasonic wave forward propagation P and the actual duration of ultrasonic reverse propagation t′ N , according to the formula Calculate the initial oxygen flow rate Q0, where Q0 is the initial oxygen flow rate, L is the airway length, and A is the average cross-sectional area of ​​the airway; According to the current gas temperature T and gas pressure P, the formula The compensation coefficient k is calculated, where c 11 =0.9367, c 12 =0.6147, c 13 =0.9546, c 14 =0.8283; According to the compensation coefficient k, the actual flow Q is calculated according to the formula Q = kQ0; According to the actual duration t′ of ultrasonic wave forward propagation P , the actual duration of ultrasonic reverse propagation t′ N , according to the formula Calculate the mean ultrasonic propagation time t ave ; According to the mean ultrasonic propagation time t ave Use the table lookup method to find the two temperatures T closest to the current gas temperature T in the data table. * , T ** And with T * The corresponding average actual propagation time of 50%, 85%, 90%, and 100% concentrations at a standard pressure of 101 kPa With T ** The corresponding standard actual propagation time average of 50%, 85%, 90%, and 100% concentration at an air pressure of 101 kPa According to the formula Calculate the average actual propagation time The superscript concentration values ​​in each parameter are 50%, 85%, 90%, or 100% respectively; According to the actual transmission time average The current gas temperature T and gas pressure P are calculated by the formula Calculate the standard actual propagation time The superscript concentration values ​​in each parameter are 50%, 85%, 90%, or 100% respectively; The actual propagation time of the standard and the mean ultrasonic propagation time t ave Compare and calculate the current oxygen concentration by interpolation method 2. The ultrasonic flowmeter oxygen concentration and flow rate algorithm adapted to different air pressures and temperatures as claimed in claim 1, characterized in that: The data table is a data table of the average values ​​of the actual propagation time of ultrasonic waves in ultrasonic flow meters at oxygen concentrations of 50%, 85%, 90%, and 100% at temperatures of -40°C to 60°C and a standard air pressure of 101 kPa.

3. The ultrasonic flowmeter oxygen concentration and flow rate algorithm adapted to different air pressures and temperatures as claimed in claim 1, characterized in that: When the mean ultrasonic propagation time t ave The standard actual propagation time when the concentration value is less than 50% The current oxygen concentration is 35%.

4. The ultrasonic flowmeter oxygen concentration and flow rate algorithm adapted to different air pressures and temperatures as claimed in claim 1, characterized in that: When the mean ultrasonic propagation time t ave Standard actual propagation time between concentration values ​​of 50% The standard actual propagation time when the concentration value is 85% When Calculate the current oxygen concentration 5. The ultrasonic flowmeter oxygen concentration and flow rate algorithm adapted to different air pressures and temperatures as claimed in claim 1, characterized in that: When the mean ultrasonic propagation time t ave Standard actual propagation time between concentration values ​​of 85% The standard actual propagation time for the concentration value to be 90% When Calculate the current oxygen concentration 6. The ultrasonic flowmeter oxygen concentration and flow rate algorithm adapted to different air pressures and temperatures as claimed in claim 1, characterized in that: When the mean ultrasonic propagation time t ave Standard actual propagation time between concentration values ​​of 90% The standard actual propagation time when the concentration value is 100% When Calculate the current oxygen concentration 7. The ultrasonic flowmeter oxygen concentration and flow rate algorithm adapted to different air pressures and temperatures as claimed in claim 1, characterized in that: When the mean ultrasonic propagation time t ave Not less than the standard actual propagation time when the concentration value is 100% The current oxygen concentration is 100%.

8. The ultrasonic flowmeter oxygen concentration and flow rate algorithm adapted to different air pressures and temperatures as claimed in claim 1, characterized in that: The gas temperature T is obtained through a thermistor temperature measurement circuit, which is composed of a 3.3V power supply, a 10kΩ resistor R1, and a thermistor RT in series. When measuring the gas temperature T, the voltage U at both ends of the thermistor is measured according to the formula Calculate the thermistor resistance RT according to the formula The gas temperature T is calculated.

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