CN116907609A - Temperature compensation method of constant temperature difference type thermal gas flowmeter and electronic equipment - Google Patents
Temperature compensation method of constant temperature difference type thermal gas flowmeter and electronic equipment Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F25/00—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume
- G01F25/10—Testing or calibration of apparatus for measuring volume, volume flow or liquid level or for metering by volume of flowmeters
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
- G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
- G01F1/688—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element
- G01F1/69—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element of resistive type
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
- G01F1/696—Circuits therefor, e.g. constant-current flow meters
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
- G01F1/696—Circuits therefor, e.g. constant-current flow meters
- G01F1/698—Feedback or rebalancing circuits, e.g. self heated constant temperature flowmeters
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/76—Devices for measuring mass flow of a fluid or a fluent solid material
- G01F1/86—Indirect mass flowmeters, e.g. measuring volume flow and density, temperature or pressure
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- General Physics & Mathematics (AREA)
- Measuring Volume Flow (AREA)
- Details Of Flowmeters (AREA)
Abstract
The application provides a temperature compensation method and electronic equipment of a constant temperature differential type thermal gas flowmeter, and relates to a flow detection area. The method comprises the following steps: determining a first equation based on the current flowing through the capacitor being equal to the current flowing through the first resistor; determining a second equation according to the voltage of the first node being equal to the voltage of the third node divided by the branch including the second resistor, the temperature compensation resistor and the thermistor; determining a third path according to the current of the second node; determining a fourth process according to a thermal equation of the heating resistor; determining a fifth equation based on the heat transfer equation; determining a sixth equation according to the thermosensitive change rule of the thermistor; obtaining a seventh equation according to the output power of the sensor driving circuit; and determining a target device from the devices according to a plurality of equations, calculating a target parameter value of the target device, and adjusting the target device according to the target parameter value. Therefore, the temperature drift can be effectively restrained, and the cost can be reduced only by adjusting the resistance parameter of the target device.
Description
Technical Field
The application relates to the field of flow detection, in particular to a temperature compensation method and electronic equipment of a constant temperature difference type thermal gas flowmeter.
Background
The flow output signal of the existing thermal type gas mass flow sensor has certain deviation along with the change of the ambient temperature, namely the temperature of different air flow media, namely obvious temperature drift. The existing temperature compensation method can solve the temperature drift problem of certain specific sensors to a certain extent, but has the defects of complex scheme principle, higher cost, complex operation and high requirements on sensor technology, and is not suitable for improving the performance and mass production of the existing thermal gas flowmeter.
Disclosure of Invention
In view of the above, the application aims to overcome the defects in the prior art, and provides a temperature compensation method and electronic equipment of a constant temperature differential type thermal gas flowmeter, which are used for solving the problems of higher cost, complex principle, complex operation and high requirements on a sensor process of the existing temperature compensation method.
The application provides the following technical scheme:
in a first aspect, the present application provides a temperature compensation method of a constant temperature differential thermal type gas flowmeter, where the constant temperature differential thermal type gas flowmeter includes a sensor driving circuit, and the sensor driving circuit includes an operational amplifier, a capacitor, a first resistor, a second resistor, a third resistor, a temperature compensation resistor, a thermistor, and a heating resistor; the first end of the second resistor, the first end of the temperature compensation resistor and the positive input end of the operational amplifier are connected to a first node, the second end of the temperature compensation resistor is connected with the first end of the thermistor, the second end of the thermistor is grounded with the first end of the heating resistor, the second end of the heating resistor, the first end of the third resistor and the first end of the first resistor are connected to a second node, the second end of the second resistor, the second end of the third resistor and the output end of the operational amplifier are connected to a third node, the second end of the first resistor, the negative input end of the operational amplifier and the first end of the capacitor are connected to a fourth node, and the second end of the capacitor is connected with the output end of the operational amplifier;
determining a first equation based on the current flowing through the capacitor being equal to the current flowing through the first resistor; determining a second equation according to the voltage of the first node being equal to the voltage of the third node divided by a branch including a second resistor, the temperature compensation resistor and the thermistor; determining a third path according to the current of the second node; determining a fourth process according to a thermal equation of the heating resistor; determining a fifth equation based on the heat transfer equation; determining a sixth equation according to the thermosensitive change rule of the thermistor; obtaining a seventh equation according to the output power of the sensor driving circuit;
determining a target device from the second resistor, the third resistor, the temperature compensation resistor, the thermistor and the heating resistor according to the first equation, the second equation, the third equation, the fourth equation, the fifth equation, the sixth equation and the seventh equation, wherein the target device has an influence on temperature difference control;
calculating a target parameter value of a target device according to a Wheatstone bridge balance equation;
and adjusting the target device according to the target parameter value.
In one embodiment, the determining the first equation based on the current flowing through the capacitor being equal to the current flowing through the first resistor includes:
the first equation is determined according to the following equation 1:
wherein V is 2 V being the voltage of the second node 3 V being the voltage of the third node 4 For the voltage of the fourth node, R 1 C is the resistance of the first resistor 1 For the resistance of the capacitor, const defines V 3 Constant is constant.
In one embodiment, the determining the second equation based on the voltage at the first node being equal to the voltage at the third node divided by a branch including the second resistor, the temperature compensation resistor, and the thermistor includes:
the second equation is determined according to the following equation 2 and equation 3:
equation 3: r is R r ＝ r0 (1+α 2 ) g ；
Wherein V is 1 For the voltage of the first node, R r Resistance value of the thermistor, R 2 R is the resistance of the second resistor 6 R is the resistance of the temperature compensation resistor r0 Alpha is the resistance value of the thermistor at 0 DEG C 2 T is the temperature coefficient of the thermistor g Is the temperature of the air flow medium.
In an embodiment, the determining a third path according to the current of the second node includes:
the third equation is determined according to the following equation 4:
wherein R is 3 R is the resistance of the third resistor h Is the resistance of the heating resistor.
In an embodiment, the determining the fourth process according to the thermal equation of the heating resistor includes:
the fourth equation is determined according to the following equation 5:
wherein T is the temperature of the heating resistor, C is the specific heat capacity of the thermistor, M is the mass of the thermistor, H is the heating power of the heating resistor, and const defines that T is constant.
In one embodiment, the determining a fifth equation according to the heat transfer equation includes:
the fifth equation is determined according to the following equation 6:
wherein L is the distance between the heating resistor and the second resistor, A is the heat transfer area, C 2 And μ is the flow rate of the air flow medium flowing through the thermistor, which is the specific heat capacity of the air flow medium.
In an embodiment, the determining the sixth equation according to the thermal change rule of the heating resistor includes:
the sixth equation is determined according to the following equation 7:
equation 7: r is R h ＝ h0 (1+ 1 )T g ；
Wherein R is h0 Alpha is the resistance value of the heating resistor at 0 DEG C 1 Is the temperature coefficient of the heating resistor.
In an embodiment, the obtaining a seventh equation according to the output rule of the sensor driving circuit includes:
the seventh equation is determined according to the following equation 8:
wherein P is the output power of the sensor driving circuit.
In an embodiment, the calculating the target parameter value of the target device according to the wheatstone bridge balance equation includes:
the target parameter value is calculated according to the following equation 9,
where Δt is the target temperature difference.
In a second aspect, the present application proposes an electronic device comprising a constant temperature differential thermal gas flow meter, a memory and a processor, the memory storing a computer program which, when executed by the processor, implements the temperature compensation method of the constant temperature differential thermal gas flow meter of the first aspect.
The application discloses a temperature compensation method and electronic equipment of a constant temperature differential type thermal type gas flowmeter, wherein a first equation is determined according to the fact that the current flowing through a capacitor is equal to the current flowing through a first resistor; determining a second equation according to the voltage of the first node being equal to the voltage of the third node divided by the branch including the second resistor, the temperature compensation resistor and the thermistor; determining a third path according to the current of the second node; determining a fourth process according to a thermal equation of the heating resistor; determining a fifth equation based on the heat transfer equation; determining a sixth equation according to the thermosensitive change rule of the thermistor; obtaining a seventh equation according to the output power of the sensor driving circuit; determining a target device from the second resistor, the third resistor, the temperature compensation resistor, the thermistor and the heating resistor according to the first equation, the second equation, the third equation, the fourth equation, the fifth equation, the sixth equation and the seventh equation, wherein the target device has influence on temperature difference control; calculating a target parameter value of a target device according to a Wheatstone bridge balance equation; and adjusting the target device according to the target parameter value. Therefore, the performance of the existing thermal type gas flowmeter under different temperature environments can be effectively improved, so that the error of the sensor can be basically kept within 1.5% under different environment temperatures, namely different air flow medium temperatures, and the temperature drift can be effectively restrained. Because the flowmeter adopts the temperature compensation method, only the resistance value of the target device is required to be adjusted, the parameter requirement of the sensor is greatly reduced, the availability of the sensor is greatly improved, and the production cost is reduced.
In order to make the above objects, features and advantages of the present application more comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a sensor driving circuit of a constant temperature differential thermal gas flowmeter according to the present application;
FIG. 2 is a schematic flow chart of a temperature compensation method of a constant temperature differential type thermal gas flowmeter according to the present application;
FIG. 3 is a graph showing the relationship between the resistance change and the temperature difference of the second resistor;
FIG. 4 is a graph showing the relationship between the resistance change and the temperature difference of a third resistor according to the present application;
FIG. 5 is a graph showing the relationship between the temperature compensation resistance change and the temperature difference;
FIG. 6 is a schematic diagram showing the relationship between the flow and the error at different temperatures before the temperature compensation provided by the application;
FIG. 7 is a schematic diagram showing the relationship between the flow and the error at different temperatures after the temperature compensation according to the present application.
Description of main reference numerals:
a-capacitance; b-a first resistor; c-a second resistor; d-a third resistor; e-a temperature compensation resistor; f-thermistor; g-a heating resistor; h is an operational amplifier; 1-a first node; 2-a second node; 3-a third node; 4-fourth node.
Detailed Description
Embodiments of the present application are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative only and are not to be construed as limiting the application.
It will be understood that when an element is referred to as being "fixed to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements present. The terms "vertical," "horizontal," "left," "right," and the like are used herein for illustrative purposes only.
In the present application, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present application, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the templates herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and/or" as used herein includes any and all combinations of one or more of the associated listed items.
Example 1
The embodiment of the disclosure provides a temperature compensation method of a constant temperature differential type thermal type gas flowmeter, which is used for reducing errors of measuring gas flow at different environment temperatures, namely different air flow medium temperatures, and can be applied to aerospace, energy sources, medical treatment, automobile industry and the like.
Specifically, referring to fig. 1, the temperature compensation method of the constant temperature differential type thermal gas flowmeter includes: the constant temperature differential type thermal gas flowmeter comprises a sensor driving circuit, wherein the sensor driving circuit comprises an operational amplifier h, a capacitor a, a first resistor b, a second resistor c, a third resistor d, a temperature compensation resistor e, a thermistor f and a heating resistor g; the first end of the second resistor c, the first end of the temperature compensation resistor e and the positive input end of the operational amplifier h are connected to the first node 1, the second end of the temperature compensation resistor e is connected to the first end of the thermistor f, the second end of the thermistor f is grounded to the first end of the heating resistor g, the second end of the heating resistor g, the first end of the third resistor d and the first end of the first resistor b are connected to the second node 2, the second end of the second resistor c, the second end of the third resistor d and the output end of the operational amplifier h are connected to the third node 3, the second end of the first resistor b, the negative input end of the operational amplifier h and the first end of the capacitor a are connected to the fourth node 4, and the second end of the capacitor a is connected to the output end of the operational amplifier h.
In this embodiment, the constant temperature difference type thermal gas mass flowmeter works on the principle that the temperature rise difference of the thermistor is kept unchanged, and the gas flow is measured by measuring the power of the thermistor. When the flow speed of the airflow medium is unchanged and the temperature of the airflow medium is changed, the resistance values of the thermistor and the heating resistor in the sensor driving circuit are changed, and if the temperature coefficients of the resistors are inconsistent, the magnitude of the output signal voltage of the sensor driving circuit is affected, so that the temperature drift problem is caused.
Referring to fig. 2, the sensor driving circuit is a wheatstone bridge. The common temperature compensation method is to add a temperature compensation resistor e on one side of a temperature measurement branch of the wheatstone bridge, so as to obtain the sensor driving circuit of the sensor in the embodiment, which is used for balancing temperature deviation generated when temperature coefficients of the thermistor and the heating resistor are inconsistent under different environment temperatures, namely different air flow medium temperatures.
Step S101, determining a first equation according to the fact that the current flowing through the capacitor a is equal to the current flowing through the first resistor b; determining a second equation based on the voltage at the first node 1 being equal to the voltage at the third node 3 divided by a branch comprising a second resistor c, the temperature compensation resistor e and the thermistor f; determining a third path according to the current of the second node 2; determining a fourth process according to the heat equation of the heating resistor g; determining a fifth equation based on the heat transfer equation; determining a sixth equation according to the thermosensitive change rule of the thermistor f; and obtaining a seventh equation according to the output power of the sensor driving circuit.
In this embodiment, seven equations are obtained for the capacitance a, the first resistor b, the second resistor c, the third resistor d, the temperature compensation resistor e, the thermistor f, and the heating resistor g by performing deep analysis on the sensor driving circuit according to kirchhoff's law.
In a specific embodiment, the determining the first equation according to the current flowing through the capacitor a being equal to the current flowing through the first resistor b includes:
the first equation is determined according to the following equation 1:
wherein V is 2 For the voltage of the second node 2, 1 3 V being the voltage of the third node 3 4 For the voltage of the fourth node 4, R 1 C is the resistance value of the first resistor b 1 For the resistance of the capacitor a, const defines V 3 Constant is constant.
In the present embodiment, it can be obtained from the fact that the current flowing through the capacitor a is equal to the current flowing through the first resistor bAnd then by->The deformation gives equation 1:
in a specific embodiment, the determining the second equation according to the voltage of the first node 1 being equal to the voltage of the third node 3 divided by the branch including the second resistor c, the temperature compensation resistor e and the thermistor f includes:
the second equation is determined according to the following equation 2 and equation 3:
equation 3: r is R r ＝ r0 (1+α 2 ) g ；
Wherein V is 1 For the voltage of the first node 1, R r Resistance value of the thermistor f, R 2 R is the resistance of the second resistor c 6 R is the resistance value of the temperature compensation resistor e r0 Alpha is the resistance value of the thermistor f at 0 DEG C 2 T is the temperature coefficient of the thermistor f g Is the temperature of the air flow medium.
In the present embodiment, since the first node 1 is located in the second resistor c and the temperature compensation circuitBetween resistances e, equation 2 is obtained:equation 3: r is R r ＝ r0 (1+α 2 ) g 。
In a specific embodiment, the determining a third path according to the current of the second node 2 includes:
the third equation is determined according to the following equation 4:
wherein R is 3 R is the resistance of the third resistor d h The resistance of the heating resistor g.
In this embodiment, the sum of the currents flowing into the node is equal to the sum of the currents flowing out of the node for any node in the circuit according to the node current law, i.e. at any timeFurther deformation yields equation 4:
in a specific embodiment, the determining the fourth process according to the thermal equation of the heating resistor g includes:
the fourth equation is determined according to the following equation 5:
wherein T is the temperature of the heating resistor g, C is the specific heat capacity of the thermistor f, M is the mass of the thermistor f, H is the heating power of the heating resistor g, and cOnst defines T as constant.
In the present embodiment, the thermal equation based on the heating resistance gThe deformation can give equation 5: />
In a specific embodiment, the determining a fifth equation according to the heat transfer formula includes:
the fifth equation is determined according to the following equation 6:
wherein L is the distance between the heating resistor g and the second resistor C, A is the heat transfer area, and C 2 Mu is the flow rate of the air flow medium flowing through the thermistor f, which is the specific heat capacity of the air flow medium.
In the present embodiment, according to the heat transfer formula, the relationship between the temperature and the heat, that is, the relationship between the temperature T of the heating resistor and the heating power H of the heating resistor can be obtained: the deformation gives equation 6: />
In a specific embodiment, the determining a sixth equation according to the change rule of the heating resistance g includes:
the sixth equation is determined according to the following equation 7:
equation 7: r is R h ＝ h0 (1+ 1 )T g ；
Wherein R is h0 Alpha is the resistance value of the heating resistor g at 0 DEG C 1 Is the temperature coefficient of the heating resistor g.
In a specific embodiment, the obtaining a seventh equation according to the output rule of the sensor driving circuit includes:
the seventh equation is determined according to the following equation 8:
wherein P is the output power of the sensor driving circuit.
In the present embodiment, the above equations 1 to 8, i.e., the first equation to the seventh equation, are coupling relationships among the parameters of the capacitor a, the first resistor b, the second resistor c, the third resistor d, the temperature compensation resistor e, the thermistor f and the heating resistor g, and the target device affecting the temperature difference control can be obtained by analysis based on the coupling relationships among the parameters.
Step S102, determining a target device from the second resistor c, the third resistor d, the temperature compensation resistor e, the thermistor f and the heating resistor g according to the first equation, the second equation, the third equation, the fourth equation, the fifth equation, the sixth equation and the seventh equation, wherein the target device has an influence on temperature difference control.
In this embodiment, in combination with the above seven equations, the influence of the resistance errors of the thermistor f, the heating resistor g, the second resistor c, the third resistor d, and the temperature compensation resistor e in the sensor driving circuit on the circuit temperature difference can be analyzed. The specific process is as follows: when analyzing the influence of the resistance error of the second resistor c, the third resistor d and the temperature compensation resistor e are ideal values obtained according to the calculation process, the second resistor c is made to fluctuate within ±1% with the ideal value as the center, the final temperature difference is observed, the same analysis method is also adopted when analyzing the third resistor d and the temperature compensation resistor e, and the analysis results are shown in fig. 3, 4 and 5.
As can be seen from the analysis result, the resistance value precision of the second resistor c and the third resistor d has a larger influence on the constant temperature difference control of the circuit, and when the resistance values of the second resistor c and the third resistor d fluctuate by 1%, the temperature deviation of 6 ℃ can be generated; the resistance value precision of the temperature compensation resistor has relatively small influence on the constant temperature difference control of the system, when the resistance value fluctuates by 6.8%, the temperature difference fluctuates by 3.5 ℃, namely when the resistance value fluctuates by 1%, the temperature deviation is about 0.58 ℃. The reason is analyzed, the second resistor c and the third resistor d directly determine the current ratio of the Wheatstone bridge, and the calculation of the temperature compensation resistor e depends on the value of the current ratio, so that the second resistor c, the third resistor d and the temperature compensation resistor e have more obvious influence on the whole system, namely the second resistor c, the third resistor d and the temperature compensation resistor e are determined as target devices. In the embodiment, a simulation model of the sensor driving circuit can be constructed by combining the seven equations, and simulation analysis is performed according to the simulation model to determine a target device affecting temperature difference control.
Step S103, calculating the target parameter value of the target device according to the Wheatstone bridge balance equation.
In a specific embodiment, calculating the target parameter value of the target device according to the wheatstone bridge balance equation includes:
the target parameter value is calculated according to the following equation 9,
where Δt is the target temperature difference.
In the present embodiment, since the second resistor c, the third resistor d, and the temperature compensation resistor e have a more pronounced influence on the entire circuit, the second resistor c, the third resistor d, and the temperature compensation resistor e are determined as target devices, and the resistance value R of the third resistor is known 3 The values of the second resistor c and the temperature compensation resistor e need to be calculated.
The wheatstone bridge is a type of bridge consisting of 4 resistors (R x1 ，R x2 ，R x3 ，R x4 ) Means are made for measuring the resistance of one of the resistances (the remaining 3 resistances are known). The 4 resistors are sequentially connected to form a square, and the products of the diagonal resistors are equal. The balance equation of the Wheatstone bridge is R x1 : x2 ＝R x4 : x3 From the balance equation of this wheatstone bridge, equation 8 can be derived:by formula 8: />Can be obtained after deformation Obtaining a fixed resistance R of a third resistor d 3 Resistance R of thermistor at 0 DEG C r0 Resistance R of heating resistor at 0 DEG C h0 Temperature coefficient alpha of thermistor 2 And temperature coefficient of heating resistance alpha 1 Setting a target temperature difference delta T, wherein the setting of the target temperature difference needs to be carried out firstly to determine a temperature difference which can meet the requirement from the minimum flow to the maximum flow of the constant temperature difference type thermal gas flowmeter, setting the temperature difference as the target temperature difference, and substituting the target temperature difference into the constant temperature difference type thermal gas flowmeter to calculate the resistance R of the second resistor 2 And temperature compensation resistance R 6 In the formula of (a), target parameter values of the second resistor c and the temperature compensation resistor e, namely a target resistance value of the second resistor and a target resistance value of the temperature compensation resistor, are obtained.
And step S104, adjusting the target device according to the target parameter value.
In this embodiment, after obtaining the target parameter values of the second resistor c and the temperature compensation resistor e, that is, the target resistance value of the second resistor and the target resistance value of the temperature compensation resistor, the target device is adjusted. If the second resistor c and the temperature compensation resistor e in the constant temperature difference type thermal type gas flowmeter are not variable resistors, replacing the actual second resistor and the temperature compensation resistor in the constant temperature difference type thermal type gas flowmeter with a second resistor with the resistance value of a second resistor target resistance value and a temperature compensation resistor with the resistance value of a temperature compensation resistor target resistance value to obtain a new constant temperature difference type thermal type gas flowmeter after temperature compensation, and then carrying out flow detection by using the new constant temperature difference type thermal type gas flowmeter; if the second resistor c and the temperature compensation resistor e in the constant temperature difference type thermal gas flowmeter are variable resistors, only the resistance value of the second resistor and the resistance value of the temperature compensation resistor are required to be adjusted to be the target resistance value of the second resistor and the target resistance value of the temperature compensation resistor. Therefore, the temperature compensation can be effectively realized by adjusting the resistance value of the second resistor and the resistance value of the temperature compensation resistor in the constant temperature difference type thermal gas flowmeter, and the temperature compensation device is simple in scheme and low in cost and only adjusts the resistor.
Referring to fig. 6 and 7, in order to verify whether the temperature compensation method according to the present embodiment is effective, experimental comparative analysis before and after temperature compensation is performed using a constant temperature differential type thermal gas flowmeter. As can be seen from fig. 6 and 7, the temperature compensation method proposed in the present embodiment has a significant effect. Before temperature compensation, the measurement error caused by temperature drift is very large, as in the case of 55 ℃ and-10 ℃ at high temperature in fig. 6, the error range is far beyond the allowable error range for normal use, and after temperature compensation, the error is reduced to below 1.5% in all the temperature environments tested in fig. 7. Experiments show that the temperature compensation method provided by the embodiment can effectively improve the performance of the traditional thermal type gas flowmeter under different temperature environments, so that the error of the sensor can be basically kept within 1.5% under different environment temperatures, namely different air flow medium temperatures, and the temperature drift can be effectively restrained.
According to the temperature compensation method of the constant temperature differential type thermal type gas flowmeter disclosed by the embodiment, a first equation is determined according to the fact that the current flowing through the capacitor is equal to the current flowing through the first resistor; determining a second equation according to the voltage of the first node being equal to the voltage of the third node divided by the branch including the second resistor, the temperature compensation resistor and the thermistor; determining a third path according to the current of the second node; determining a fourth process according to a thermal equation of the heating resistor; determining a fifth equation based on the heat transfer equation; determining a sixth equation according to the thermosensitive change rule of the thermistor; obtaining a seventh equation according to the output power of the sensor driving circuit; determining a target device from the second resistor, the third resistor, the temperature compensation resistor, the thermistor and the heating resistor according to the first equation, the second equation, the third equation, the fourth equation, the fifth equation, the sixth equation and the seventh equation, wherein the target device has an influence on temperature difference control; calculating a target parameter value of a target device according to a Wheatstone bridge balance equation; and adjusting the target device according to the target parameter value. Therefore, the performance of the existing thermal type gas flowmeter under different temperature environments can be effectively improved, so that the error of the sensor can be basically kept within 1.5% under different environment temperatures, namely different air flow medium temperatures, and the temperature drift can be effectively restrained. Because the flowmeter adopts the temperature compensation method, only the resistance value of the target device is required to be adjusted, the parameter requirement of the sensor is greatly reduced, the availability of the sensor is greatly improved, and the production cost is reduced.
Example 2
The application also provides electronic equipment, which comprises the constant temperature difference type thermal type gas flowmeter, a memory and a processor, wherein the memory stores a computer program, and the computer program realizes the temperature compensation method of the constant temperature difference type thermal type gas flowmeter when being executed by the processor.
The electronic device provided in this embodiment may implement the temperature compensation method of the constant temperature difference type thermal gas flowmeter provided in embodiment 1, and in order to avoid repetition, details are not repeated here.
Any particular values in all examples shown and described herein are to be construed as merely illustrative and not a limitation, and thus other examples of exemplary embodiments may have different values.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures.
The above examples merely represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the present application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application.
Claims (10)
1. The temperature compensation method of the constant temperature difference type thermal gas flowmeter is characterized in that the constant temperature difference type thermal gas flowmeter comprises a sensor driving circuit, wherein the sensor driving circuit comprises an operational amplifier, a capacitor, a first resistor, a second resistor, a third resistor, a temperature compensation resistor, a thermistor and a heating resistor; the first end of the second resistor, the first end of the temperature compensation resistor and the positive input end of the operational amplifier are connected to a first node, the second end of the temperature compensation resistor is connected with the first end of the thermistor, the second end of the thermistor is grounded with the first end of the heating resistor, the second end of the heating resistor, the first end of the third resistor and the first end of the first resistor are connected to a second node, the second end of the second resistor, the second end of the third resistor and the output end of the operational amplifier are connected to a third node, the second end of the first resistor, the negative input end of the operational amplifier and the first end of the capacitor are connected to a fourth node, and the second end of the capacitor is connected with the output end of the operational amplifier;
determining a first equation based on the current flowing through the capacitor being equal to the current flowing through the first resistor; determining a second equation according to the voltage of the first node being equal to the voltage of the third node divided by a branch including a second resistor, the temperature compensation resistor and the thermistor; determining a third path according to the current of the second node; determining a fourth process according to a thermal equation of the heating resistor; determining a fifth equation based on the heat transfer equation; determining a sixth equation according to the thermosensitive change rule of the thermistor; obtaining a seventh equation according to the output power of the sensor driving circuit;
determining a target device from the second resistor, the third resistor, the temperature compensation resistor, the thermistor and the heating resistor according to the first equation, the second equation, the third equation, the fourth equation, the fifth equation, the sixth equation and the seventh equation, wherein the target device has an influence on temperature difference control;
calculating a target parameter value of a target device according to a Wheatstone bridge balance equation;
and adjusting the target device according to the target parameter value.
2. The method of temperature compensation of a constant temperature differential thermal gas flow meter of claim 1, wherein determining the first equation based on the current flowing through the capacitor being equal to the current flowing through the first resistor comprises:
the first equation is determined according to the following equation 1:
equation 1:
wherein V is 2 V being the voltage of the second node 3 V being the voltage of the third node 4 For the voltage of the fourth node, R 1 C is the resistance of the first resistor 1 For the resistance of the capacitor, const defines V 3 Constant is constant.
3. The method of temperature compensation of a constant temperature differential thermal gas flow meter of claim 2, wherein said determining a second equation based on a voltage at said first node being equal to a voltage at said third node divided by a branch comprising a second resistor, said temperature compensation resistor, and said thermistor, comprises:
the second equation is determined according to the following equation 2 and equation 3:
equation 2:
equation 3: r is R r ＝R r0 (1+α 2 )T g ；
Wherein V is 1 For the voltage of the first node, R r Resistance value of the thermistor, R 2 R is the resistance of the second resistor 6 R is the resistance of the temperature compensation resistor r0 Alpha is the resistance value of the thermistor at 0 DEG C 2 T is the temperature coefficient of the thermistor g Is the temperature of the air flow medium.
4. A method of temperature compensation of a constant temperature differential thermal gas flow meter according to claim 3, wherein said determining a third path based on the current at the second node comprises:
the third equation is determined according to the following equation 4:
equation 4:
wherein R is 3 R is the resistance of the third resistor h Is the resistance of the heating resistor.
5. The method of temperature compensation of a constant temperature differential thermal gas flow meter according to claim 4, wherein said determining a fourth equation from a thermal equation of said heating resistance comprises:
the fourth equation is determined according to the following equation 5:
equation 5:
wherein T is the temperature of the heating resistor, C is the specific heat capacity of the thermistor, M is the mass of the thermistor, H is the heating power of the heating resistor, and const defines that T is constant.
6. The method of temperature compensation of a constant temperature differential thermal gas flow meter of claim 5, wherein said determining a fifth equation based on a heat transfer equation comprises:
the fifth equation is determined according to the following equation 6:
equation 6:
wherein L is the distance between the heating resistor and the second resistor, A is the heat transfer area, C 2 And μ is the flow rate of the air flow medium flowing through the thermistor, which is the specific heat capacity of the air flow medium.
7. The method of temperature compensation of a constant temperature differential thermal gas flow meter according to claim 6, wherein determining a sixth equation based on a law of thermal change of the heating resistor comprises:
the sixth equation is determined according to the following equation 6:
equation 7: r is R h ＝R h0 (1+α 1 )T g ；
Wherein R is h0 Alpha is the resistance value of the heating resistor at 0 DEG C 1 Is the temperature coefficient of the heating resistor.
8. The method for temperature compensation of a constant temperature differential thermal gas flow meter according to claim 7, wherein the obtaining a seventh equation according to the output rule of the sensor driving circuit comprises:
the seventh equation is determined according to the following equation 8:
equation 8:
wherein P is the output power of the sensor driving circuit.
9. The method of temperature compensation of a constant temperature differential thermal gas flow meter of claim 1, wherein said calculating the target parameter value of the target device according to the wheatstone bridge balance equation comprises:
the target parameter value is calculated according to the following equation 8,
equation 9:
where Δt is the target temperature difference.
10. An electronic device comprising a constant temperature differential thermal gas flow meter, a memory and a processor, the memory storing a computer program which, when executed by the processor, performs the steps of the method of temperature compensation of a constant temperature differential thermal gas flow meter as claimed in any one of claims 1 to 9.
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