Calibration device and calibration method for gas flow sensor in high-pressure environment

Abstract

This invention provides a calibration device and method for a gas flow sensor under high-pressure conditions. The calibration device utilizes an adjustable-speed electrode to drive a linkage mechanism, generating a stable linear velocity that pushes a piston, ejecting a volume of gas (V) from a fixed-volume gas pipe at a constant speed. This produces a stable and controllable gas flow. An impeller sensor is connected to its output terminal, and the impeller sensor's rotational speed output at different flow rates is measured to obtain its rotational speed-flow rate response curve f = K. a ·Q v +K b The entire setup is located in a pressure-controlled high-pressure test chamber. Tests are conducted under conditions of the same temperature but different pressures to obtain the variation of the two corresponding coefficients Ka and Kb in the impeller sensor response curve with pressure. This application provides a calibration device suitable for high-pressure environments, whose output can be used as the true value for sensor calibration.

Description

Technical Field

[0001] This invention relates to the field of gas flow detection applicable to high-pressure environments, including but not limited to respiratory detection of humans and animals in high-pressure environments. Background Technology

[0002] In the field of diving, divers are in an environment with atmospheric pressure several times higher than normal when underwater or in a pressurized diving chamber. To monitor their vital signs and physical condition, it is usually necessary to monitor their breathing status and oxygen uptake. Both of these monitoring methods require the use of flow sensors to record their breathing curves and obtain parameters such as respiratory rate and ventilation volume. Common flow sensors used for breathing flow transmission include differential pressure flow sensors, hot-wire mass flow sensors, ultrasonic flow sensors, and impeller / turbine flow sensors. These sensors transmit gas flow signals as changes in pressure difference, temperature, ultrasonic frequency, and rotor rotation frequency, which are then further converted into electrical signals. The transmission principle of most of these flow sensors is related to environmental pressure. When the environmental pressure changes, the output flow value will be distorted to varying degrees. Therefore, they need to be calibrated under high-pressure conditions to obtain the law of their response curve changing with environmental pressure, so that they can be used in any high-pressure environment that changes constantly.

[0003] Factory calibration or pre-use calibration of flow sensors typically involves simultaneously measuring a series of constant flow rates using another, more accurate flow metering device. The output of this metering device is then used as the true flow rate value. This yields a series of data corresponding to the output values ​​of the flow sensor being calibrated and the actual flow rates. These data values ​​are then used to fit a response curve to the flow sensor being calibrated. However, for calibration under high-pressure environments, there is currently no flow metering device suitable for respiratory flow transmitters whose output can be used as the true value for sensor calibration.

[0004] Taking a differential pressure flow sensor commonly used in ventilators and pulmonary function instruments for respiratory flow detection as an example, under stable atmospheric pressure conditions, the pressure difference across the orifice of the transmitter is proportional to the flow rate. However, the discharge coefficient C, the expansion coefficient ε of the measured compressible flow, and the density ρ of the measured gas, which affect the pressure difference value, vary with parameters such as pressure and temperature. For steady-state measurements, when the pressure varies within a small range, standard throttling devices used for flow detection in industrial pipelines can be theoretically calibrated by introducing correction coefficients. However, commercially available small gas differential pressure flow meters used for respiratory detection are non-standard throttling devices, and their expansion coefficients cannot be corrected by calculation, requiring actual flow calibration. Summary of the Invention

[0005] To overcome the above-mentioned technical defects, the first objective of this invention is to provide a calibration device for a gas flow sensor under high pressure, comprising: a power supply, a stepless speed regulation module, a high-pressure test chamber, four through-chamber electrical connectors, a reciprocating motor, a linkage mechanism, a fixed-volume gas tube, a pulse counter, and a host computer. The fixed-volume gas tube includes a front end, a piston, and a rear end. The reciprocating motor, the linkage mechanism, and the fixed-volume gas tube are located inside the high-pressure test chamber.

[0006] The power supply is used to power the stepless speed control module and the reciprocating motor;

[0007] The voltage output by the stepless speed control module is connected to the positive and negative terminals of the reciprocating motor through two through-cabin electrical connectors. The stepless speed control module is used to adjust the output speed of the reciprocating motor.

[0008] Reciprocating motors are used to drive linkage mechanisms to perform uniform linear reciprocating motion;

[0009] The moving linkage mechanism connects to the piston and is used to push and pull the piston of the constant volume gas pipe to perform uniform linear motion; in this application, the output of the flow meter is only detected during the positive stroke of the piston.

[0010] The front end of the constant volume gas tube is connected to the gas input terminal of the gas flow sensor, and the rear end is connected to the environment inside the high-pressure test chamber.

[0011] The diameter of the constant volume gas tube is the same as the diameter of the gas input end of the gas flow sensor;

[0012] The gas output of the gas flow sensor is connected to the environment inside the high-pressure test chamber;

[0013] The pulse signal output by the gas flow sensor is connected to a pulse counter located outside the high-pressure test chamber via two through-chamber electrical connectors.

[0014] The pulse counter is connected to the host computer and transmits the converted pulse counter digital signal to the host computer.

[0015] Furthermore, the ambient pressure and temperature inside the high-pressure test chamber are controllable; the ambient pressure inside the chamber can be increased by introducing high-pressure gas into the test chamber through the pressurization valve, and the ambient pressure inside the chamber can be decreased by venting the test chamber through the pressure relief valve; the current ambient pressure inside the chamber can be obtained by the pressure gauge installed on the test chamber; the high-pressure test chamber is equipped with a temperature control device (implemented by commercially available temperature control module) to ensure that the temperature inside the chamber is constant during flow calibration, and the temperature control range is 10℃~40℃.

[0016] Furthermore, the range of speeds for the piston to perform uniform linear motion is u. min =0, u max =Q max / S, where Q maxS represents the upper limit of the range of the sensor being calibrated, and S is the cross-sectional area of ​​a constant volume air tube.

[0017] Furthermore, the maximum volume V of gas in a constant-volume trachea is V = Q. max ·t, where t is the shortest time for a single calibration. Different specifications of constant volume tubes are selected according to the sensor being calibrated for different ranges. V = S·L, where S is the cross-sectional area of ​​the constant volume tube, L = vmax·t = Qmax·t / S, so V = Qmax·t, where t is the shortest time for a single calibration, and t is usually taken as 2s-5s.

[0018] Furthermore, the gas flow sensor is an impeller-type flow sensor with linear output within its range.

[0019] A second objective of this application is to provide a method for calibrating a gas flow sensor using the aforementioned calibration device, comprising:

[0020] Step S1: Connect the gas input terminal of the gas flow sensor to the output terminal of the constant volume gas tube;

[0021] Step S2: Close the test chamber door, and introduce high-pressure gas into the test chamber through the pressurization valve to raise the ambient pressure inside the chamber to P. Adjust the temperature control device to stabilize the temperature inside the chamber at T, where T is the room temperature.

[0022] Step S3: Turn on the power. The stepless speed control module adjusts the speed of the reciprocating motor. The reciprocating motor drives the linkage mechanism to push the piston linearly at a constant speed u. The piston pushes the gas in the constant volume gas tube out at a constant speed, so that the gas enters the gas input terminal of the gas flow sensor at a stable volume flow rate Qv, where Qv = u·S. Measure the gas flow at Q... v The impeller speed f at the flow rate, where S is the cross-sectional area of ​​the constant volume gas pipe;

[0023] Step S4: Change the motor speed so that the linkage mechanism pushes the piston linearly at a constant speed u', so that the gas enters the gas input end of the gas flow sensor at a flow rate of Qv', where Qv'=u'·S. Measure the impeller rotation number f' output by the gas flow sensor at a flow rate of Qv', where S is the cross-sectional area of ​​a constant volume gas pipe.

[0024] Step S5: Repeat step S3 to obtain the output revolutions of the gas flow sensor at different flow rates under pressure P, i.e., obtain its revolution-flow response curve f = K. a ·Q v +K b ;

[0025] Step S6: By introducing high-pressure gas into the test chamber through the pressurization valve, the ambient pressure inside the chamber can be increased to P'. Adjust the temperature control device to keep the temperature inside the chamber stable at T.

[0026] Step S7: Repeat steps S3-S5 to obtain the output revolutions of the gas flow sensor at different flow rates when the pressure is P', that is, obtain its revolution-flow response curve f = K'. a ·Q v +K' b ;

[0027] Step S8: Repeat steps S6-S7, changing the value of P to obtain a series of K values. a Value and K b The value is used to obtain the two corresponding coefficients K in the flow sensor revolutions-flow response curve. a and K b The relationship between pressure P and K is observed, thus allowing for the fitting of K. a and K b The formula relating pressure P to Ka(P) is: Ka(P) = f(P), K b f(P) = g(P), where both f(P) and g(P) are fitting functions, thus obtaining the rotational speed-flow response curve of the flow sensor under high pressure: f = f(P)·Q v +g(P).

[0028] Furthermore, the gas flow sensor is applicable to air and other gases besides air, requiring only that the air in the test chamber be emptied before calibration begins, and then the corresponding gas composition be introduced.

[0029] Compared with existing technologies, the above technical solution has the following advantages:

[0030] This application provides a calibration device for gas flow sensors suitable for high-pressure environments, particularly for impeller-type flow sensors. Its output can be used as the true value for sensor calibration. This application fills the gap in the existing technology for a flow metering device suitable for respiratory flow transmission. The entire device is located in a pressure-controlled high-pressure test chamber. Testing is conducted under the same temperature but different pressure conditions to obtain the variation of the two corresponding coefficients Ka and Kb in the impeller sensor response curve with pressure. Attached Figure Description

[0031] Figure 1 This is a schematic diagram illustrating the principle of a method for calibrating a gas flow sensor using the calibration device for a gas flow sensor under high pressure conditions according to this application. Detailed Implementation

[0032] The advantages of the present invention are further illustrated below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that the following detailed description is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0033] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0034] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0035] The term "comprising" and its variations as used herein signify open inclusion, i.e., "including but not limited to". It should be understood that although the terms first, second, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms. These terms are used only to distinguish information of the same type from one another and may refer to different or the same objects, and should not be construed as indicating or implying relative importance. Depending on the context, the word "if" as used herein can be interpreted as "when," "when," or "in response to a determination." In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "installed," "connected," and "linked" should be interpreted broadly, for example, as mechanical or electrical connections, or internal connections between two elements, which may be direct or indirect through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0036] like Figure 1 As shown, this embodiment provides a calibration device for calibrating a gas flow sensor under high-pressure conditions, comprising: a power supply 11, a stepless speed regulation module 12, a high-pressure test chamber 13 with a housing, two first through-chamber electrical connectors 141, two second through-chamber electrical connectors 142, a reciprocating motor 15, a linkage mechanism 16, a constant-volume gas tube (including a piston 171, a front end 172, a tube wall 173, and a rear end 174), a host computer 18, and a pulse counter 19. The gas flow sensor includes a gas input end 21, a gas output end 22, and a body 23. For example, the gas flow sensor in this embodiment is an impeller-type sensor. The impeller-type sensor, the reciprocating motor 15, the linkage mechanism 16, and the constant-volume gas tube are all located inside the high-pressure test chamber.

[0037] Power supply 11 is used to supply power to stepless speed control module 12 and reciprocating motor 15.

[0038] The voltage output by the stepless speed control module 12 is connected to the positive and negative terminals of the reciprocating motor 15 through two first through-cabin electrical connectors 141. The stepless speed control module 12 is used to adjust the output speed of the reciprocating motor 15.

[0039] The power supply 11, the stepless speed regulation module 12, the reciprocating motor 15 and the two first through-cabin electrical connectors 141 are connected in sequence.

[0040] The reciprocating motor 15 drives the linkage mechanism 16 to perform uniform linear reciprocating motion. The moving linkage mechanism 16 is connected to the piston 171 and is used to push and pull the piston 171 to perform uniform linear motion.

[0041] The front end 172 of the constant volume gas tube is connected to the gas input end 21 of the gas flow sensor, and the rear end is connected to the internal environment of the high pressure test chamber 13. The diameter of the constant volume gas tube is the same as the diameter of the gas input end of the gas flow sensor.

[0042] In this embodiment, the gas flow sensor is an impeller-type flow sensor with linear output within its measurement range. The gas output terminal 22 of the gas flow sensor is connected to the environment inside the high-pressure test chamber. The pulse signal output by the gas flow sensor is connected to a pulse counter located outside the high-pressure test chamber via two second through-chamber electrical connectors 142. The pulse counter is connected to a host computer via an I / O device, transmitting the converted pulse counter digital signal to the host computer.

[0043] The ambient pressure and temperature inside the high-pressure test chamber 13 are controllable. The ambient pressure inside the chamber can be increased by introducing high-pressure gas into the test chamber through the pressurization valve, and the ambient pressure inside the chamber can be decreased by venting the test chamber through the depressurization valve. The current ambient pressure inside the chamber can be obtained by the pressure gauge installed on the test chamber. The high-pressure test chamber is equipped with a temperature control device (using a commercially available temperature control module) to ensure that the temperature inside the chamber is constant during flow calibration, and the temperature control range is 10℃ to -40℃.

[0044] The velocity range of piston 171 in uniform linear motion is u min =0, u max =Q max / S, where Q max S represents the upper limit of the measurement range of the sensor being calibrated, and S is the cross-sectional area of ​​the constant-volume air tube. The diameter of the front end of the constant-volume air tube is equal to the diameter of the air inlet of the sensor being calibrated.

[0045] Different specifications of constant-volume tubes are selected according to the sensor being calibrated for different ranges. V = S·L, where S is the cross-sectional area of ​​the constant-volume gas tube, and L = vmax·t = Qmax·t / S. Therefore, the maximum volume V of the gas in the constant-volume gas tube is V = Qmax·t, where t is the shortest time for a single calibration, typically taken as 2s-5s. The method for calibrating impeller-type sensors using the above calibration device includes:

[0046] Step S1: Connect the gas input terminal of the gas flow sensor to the output terminal of the constant volume gas tube;

[0047] Step S2: Close the test chamber door, introduce high-pressure gas into the test chamber through the pressurization valve to raise the ambient pressure inside the chamber to P, and adjust the temperature control device to stabilize the temperature inside the chamber at T, where T is the room temperature.

[0048] Step S3: Turn on the power. The stepless speed control module adjusts the speed of the reciprocating motor. The reciprocating motor drives the linkage mechanism to push the piston linearly at a constant speed u. The piston pushes the gas in the constant volume gas tube out at a constant speed, so that the gas enters the gas input terminal of the gas flow sensor at a stable volume flow rate Qv, where Qv = u·S. Measure the gas flow at Q... v The impeller speed f at the flow rate, where S is the cross-sectional area of ​​the constant volume gas pipe;

[0049] Step S4: Change the motor speed so that the linkage mechanism pushes the piston linearly at a constant speed u', so that the gas enters the gas input end of the gas flow sensor at a flow rate of Qv', where Qv'=u'·S. Measure the impeller rotation number f' output by the gas flow sensor at a flow rate of Qv', where S is the cross-sectional area of ​​the constant volume gas pipe.

[0050] Step S5: Repeat step S3 to obtain the output revolutions of the gas flow sensor at different flow rates under pressure P, i.e., obtain its revolution-flow response curve f = K. a ·Q v +K b ;

[0051] Step S6: By introducing high-pressure gas into the test chamber through the pressurization valve, the ambient pressure inside the chamber can be increased to P'. Adjust the temperature control device to keep the temperature inside the chamber stable at T.

[0052] Step S7: Repeat steps S3-S5 to obtain the output revolutions of the gas flow sensor at different flow rates when the pressure is P', that is, obtain its revolution-flow response curve f = K'. a ·Q v +K' b ;

[0053] Step S8: Repeat steps S6-S7, changing the P value to obtain a series of K values. a Value and Kb The value is used to obtain the two corresponding coefficients K in the flow sensor revolutions-flow response curve. a and K b The relationship between pressure P and K is observed, thus allowing for the fitting of K. a and K b The formula relating pressure P to Ka(P) is: Ka(P) = f(P), K b f(P) = g(P), where both f(P) and g(P) are fitting functions, thus obtaining the rotational speed-flow response curve of the flow sensor under high pressure: f = f(P)·Q v +g(P).

[0054] It should be noted that the embodiments of the present invention have better implementability and are not intended to limit the present invention in any way. Any person skilled in the art may use the above-disclosed technical content to change or modify it into equivalent effective embodiments. However, any modifications or equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A calibration method for a calibration device for a gas flow sensor under high pressure conditions, characterized in that, The calibration method includes: Step S1: Connect the gas input terminal of the gas flow sensor to the output terminal of the constant volume gas tube; Step S2: Close the test chamber door, introduce high-pressure gas into the test chamber through the pressurization valve to raise the ambient pressure inside the chamber to P, and adjust the temperature control device to stabilize the temperature inside the chamber at T, where T is the room temperature. Step S3: Turn on the power. The stepless speed control module adjusts the speed of the reciprocating motor. The reciprocating motor drives the linkage mechanism to push the piston linearly at a constant speed (u). The piston pushes the gas in the constant volume gas tube out at a constant speed, so that the gas flows out at a stable volume flow rate (Q). v The gas enters the gas input terminal of the gas flow sensor, where Q v =u•S, The gas flow sensor measures the gas flow rate at Q. v The impeller speed f at the flow rate, where S is the cross-sectional area of ​​the constant volume gas pipe; Step S4: Change the motor speed so that the linkage mechanism pushes the piston linearly at a constant speed u', so that the gas enters the gas input end of the gas flow sensor at a flow rate of Qv', where Qv'=u'•S. Measure the impeller rotation number f' output by the gas flow sensor at a flow rate of Qv', where S is the cross-sectional area of ​​the constant volume gas pipe. Step S5: Repeat step S3 to obtain the output revolutions of the gas flow sensor at different flow rates under pressure P, i.e., obtain its revolution-flow response curve f=K. a •Q v +K b Among them, K a and K b The coefficient of the speed-flow response curve at pressure P; Step S6: High-pressure gas is introduced into the test chamber through the pressurization valve to raise the ambient pressure inside the chamber to P', and the temperature control device is adjusted to keep the temperature inside the chamber stable at T; Step S7: Repeat steps S3-S5 to obtain the output revolutions of the gas flow sensor at different flow rates when the pressure is P', that is, obtain its revolution-flow response curve f=K'. a •Q v +K' b ; where K' a and K' b The coefficient of the speed-flow response curve at pressure P' is given. Step S8: Repeat steps S6-S7, changing the pressure value to obtain a series of K values. a Value and K b The value is used to obtain the two corresponding coefficients K in the flow sensor revolutions-flow response curve. a and K b The pattern of pressure variation is used to fit K. a and K b The formula relating pressure to pressure is: Ka(P) = f(P), K b f(P) = g(P), where f(P) and g(P) are both fitting functions, thus obtaining the rotational speed-flow response curve of the flow sensor under high pressure: f = f(P)•Q v + g(P); The calibration device includes: a power supply, a stepless speed regulation module, a high-pressure test chamber, four through-chamber electrical connectors, a reciprocating motor, a linkage mechanism, a fixed-volume air tube, a pulse counter, and a host computer. The fixed-volume air tube includes a front end, a piston, and a rear end. The reciprocating motor, the linkage mechanism, and the fixed-volume air tube are located inside the high-pressure test chamber. The power supply is used to power the stepless speed control module and the reciprocating motor; The voltage output by the stepless speed control module is connected to the positive and negative terminals of the reciprocating motor through two through-cabin electrical connectors. The stepless speed control module is used to adjust the output speed of the reciprocating motor. Reciprocating motors are used to drive linkage mechanisms to perform uniform linear reciprocating motion; The moving linkage mechanism connects to the piston and is used to push and pull the piston of the constant volume gas tube to perform uniform linear motion; The front end of the constant volume gas tube is connected to the gas input terminal of the gas flow sensor, and the rear end is connected to the environment inside the high-pressure test chamber. The diameter of the constant volume gas tube is the same as the diameter of the gas input end of the gas flow sensor; The gas output of the gas flow sensor is connected to the environment inside the high-pressure test chamber; The pulse signal output by the gas flow sensor is connected to a pulse counter located outside the high-pressure test chamber via two through-chamber electrical connectors. The pulse counter is connected to the host computer and transmits the converted pulse counter digital signal to the host computer. The gas flow sensor is an impeller-type flow sensor with linear output within its range.

2. The calibration method of the calibration device for a gas flow sensor under high pressure environment as described in claim 1, characterized in that, The ambient pressure and temperature inside the high-pressure test chamber are controllable. High-pressure gas is introduced into the test chamber through a pressurizing valve to increase the ambient pressure inside the chamber, and the ambient pressure inside the chamber is reduced by venting gas through a depressurizing valve. The current ambient pressure inside the chamber is obtained by a pressure gauge installed on the test chamber. The high-pressure test chamber is equipped with a temperature control device to ensure that the temperature inside the chamber remains constant during flow calibration, and the temperature control range is 10℃ to 40℃.

3. The calibration method of the calibration device for a gas flow sensor under high pressure environment as described in claim 1, characterized in that, The range of speeds for the piston to move in uniform linear motion is u. min =0, u max =Q max / S, where Q max S represents the upper limit of the range of the sensor being calibrated, and S is the cross-sectional area of ​​a constant volume air tube.

4. The calibration method of the calibration device for a gas flow sensor under high pressure environment as described in claim 1, characterized in that, The maximum volume V of gas in a constant-volume gas tube is V = Q. max ·t, where t is the shortest time for a single calibration.

5. The calibration method of the calibration device for a gas flow sensor under high pressure environment as described in claim 1, characterized in that, Before calibration begins, the gas flow sensor purges the air from the test chamber and then fills it with gas of the appropriate composition.

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