CN114440998A - Fluid mass flow measuring circuit and fluid mass flow meter - Google Patents
Fluid mass flow measuring circuit and fluid mass flow meter Download PDFInfo
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- CN114440998A CN114440998A CN202111565885.6A CN202111565885A CN114440998A CN 114440998 A CN114440998 A CN 114440998A CN 202111565885 A CN202111565885 A CN 202111565885A CN 114440998 A CN114440998 A CN 114440998A
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- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 18
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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
Abstract
The invention relates to the technical field of fluid measurement, and discloses a fluid mass flow measuring circuit and a fluid mass flow measuring meter, wherein the fluid mass flow measuring circuit connects a speed measuring module for measuring the flow velocity of a fluid to be measured in a pipe wall with a working power supply, connects a temperature measuring module for measuring the temperature of the fluid to be measured with a constant current source, respectively connects the speed measuring module and the temperature measuring module through a voltage control module, controls the temperature difference between the speed measuring module and the temperature measuring module to be kept within a preset threshold range to realize constant temperature difference, connects the speed measuring module through a mass flow determining module, determines the mass flow of the fluid to be measured according to the heating power of the speed measuring module and the temperature difference between the speed measuring module and the temperature measuring module, and measures the mass flow of the fluid to be measured through a pure hardware mode compared with the adoption of a microprocessor for obtaining the mass flow of the fluid to be measured, the response speed for obtaining the measurement result is improved.
Description
Technical Field
The invention relates to the technical field of fluid measurement, in particular to a fluid mass flow measuring circuit and a fluid mass flow meter.
Background
The thermal gas mass flowmeter originated in the 60 s, and through the technological accumulation of more than 20 s, the thermal gas mass flowmeter is a meter for measuring the gas flow in the early 90 s, and the thermal gas mass flowmeter measures the heat exchange relationship between flowing gas and a gas internal heat source or a measuring pipe external heat source and is essentially based on the King's law of measurement by adopting double platinum resistors. The device has the characteristics of high reliability, strong stability, small pressure loss, convenience in installation, high range ratio and the like.
At present, the thermal gas mass flow meter adopts a microprocessor to realize the measurement of mass flow, and the response speed for obtaining the measurement result is slower because the microprocessor is required to receive and calculate data.
Disclosure of Invention
The following presents a simplified summary in order to provide a basic understanding of some aspects of the disclosed embodiments. This summary is not an extensive overview nor is intended to identify key/critical elements or to delineate the scope of such embodiments but rather as a prelude to the more detailed description that is presented later.
In view of the above-mentioned drawbacks of the prior art, the present invention provides a fluid mass flow measurement circuit and a fluid mass flow meter to improve the response speed for obtaining the measurement result.
The invention discloses a fluid mass flow measuring circuit, comprising: the speed measuring module is connected with the working power supply and used for measuring the flow speed of the fluid to be measured in the pipe wall; the temperature measuring module is connected with the constant current source and used for measuring the temperature of the fluid to be measured; the voltage control module is respectively connected with the speed measuring module and the temperature measuring module and is used for converting the temperature of the temperature measuring module and the flow velocity of the speed measuring module into corresponding voltages, determining the temperature difference between the speed measuring module and the temperature measuring module according to the voltage difference between the speed measuring module and the temperature measuring module and controlling the temperature difference to be kept within a preset threshold range to realize constant temperature difference; and the mass flow determining module is connected with the speed measuring module and used for determining the mass flow of the fluid to be measured according to the heating power of the speed measuring module and the temperature difference between the speed measuring module and the temperature measuring module.
Optionally, the fluid mass flow measurement circuit further includes an overcurrent protection module, and the speed measurement module is connected to the working power supply through the overcurrent protection module.
Optionally, the overcurrent protection module includes a protection MOS transistor, a protection triode, a load resistor, a pull-down resistor, a protection resistor, and a filtering unit, the working power supply is respectively connected to one end of the load resistor and an emitter of the protection triode, and the other end of the load resistor is respectively connected to a base of the protection triode and a source of the protection MOS transistor; the collector of the protection triode is respectively connected with one end of the pull-down resistor and the grid of the protection MOS tube; the other end of the pull-down resistor is grounded; a protection resistor is connected between the source electrode and the drain electrode of the protection MOS tube; the drain electrode of the protection MOS tube is connected with the output current of the filtering unit in parallel; when the protection MOS is in a conducting state, outputting a filtered current signal; when the emitter and the base of the protection triode are conducted, the pull-down resistor is connected with a working power supply, the grid voltage of the protection MOS tube is increased, the protection MOS tube is in a cut-off state, and the working power supply is enabled to carry out overcurrent protection through the current output by the protection resistor.
Optionally, the fluid mass flow measurement circuit further includes a current detection module, and the current detection module is connected to the speed measurement module and is configured to measure a current of the current detection module.
Optionally, the voltage control module includes a temperature difference setting unit, a voltage operation unit, an amplifier unit, and an adjustment pipe, and the fluid mass flow measurement circuit further includes: the temperature difference setting unit is used for outputting a set voltage according to the preset temperature difference threshold value; the input end of the voltage operation unit is respectively connected with the speed measurement module, the temperature measurement module and the current detection module, and the calculation unit is used for outputting operation voltage according to the voltage of the speed measurement module, the voltage of the temperature measurement module and the voltage of the current detection module; the input end of the amplifier unit is respectively connected with the output end of the voltage operation unit and the output end of the temperature difference setting unit, the output end of the amplifier unit is connected with the base electrode of the adjusting tube, the working power supply is connected with the speed measuring module after passing through the collector electrode and the emitter electrode of the adjusting tube, the amplifier unit is used for determining the output amplification factor to control the output current of the adjusting tube after comparing with the temperature difference between the speed measuring module and the temperature measuring module according to the set voltage serving as a reference, and further reversely controlling the operation voltage to be kept in the set voltage.
Optionally, the voltage operation unit includes a first amplification sub-unit, a second amplification sub-unit, a third amplification sub-unit, a division sub-unit, and a subtraction sub-unit, and the fluid mass flow measurement circuit further includes: the input end of the first amplification subunit is connected with the speed measuring module, the second amplification subunit is connected with the current detecting module, and the input end of the third amplification subunit is connected with the temperature measuring module; the input end of the dividing subunit is respectively connected with the output end of the first amplifying subunit and the output end of the second amplifying subunit; the input end of the subtraction subunit is connected to the output end of the third amplification subunit and the output end of the division subunit respectively, and the output end of the subtraction subunit is connected to the second input end of the amplifier unit.
Optionally, the calculating unit further includes a voltage follower subunit, an output end of the division subunit is connected to an input end of the subtraction subunit through the voltage follower subunit, and the voltage follower subunit is configured to isolate signal interference between the division subunit and the subtraction subunit.
Optionally, the set voltage is determined by:
wherein, V7For the set voltage, K is the coefficient of operation, TsIs the preset temperature difference threshold value, k1Is the gain, k, of the first amplification subunit2Is the gain, k, of the second amplification subunit3Is the gain of the division subunit, k5Is the gain of the third amplification subunit, A1Is the temperature coefficient between the tachometer resistance and the tachometer module temperature, A2Is the temperature coefficient, R, between the temperature measuring resistor and the temperature measuring module1Is the resistance of the current sensing module, IPT2Is the current of the constant current power supply.
Optionally, the mass flow rate of the fluid to be measured is determined by:
wherein Q ismFor the mass flow of the fluid to be measured, S is the cross-sectional area of the fluid to be measured, V is the flow velocity of the fluid to be measured, P isPT1Is the speed measurement power of the speed measurement module, delta T is the temperature difference between the speed measurement module and the temperature measurement module, n1、n2、n3Is a preset calibration parameter.
The invention discloses a fluid mass flow measuring meter which is characterized in that a current conversion device comprises the fluid mass flow measuring circuit.
The invention has the beneficial effects that: a speed measuring module for measuring the flow speed of the fluid to be measured in the pipe wall is connected with a working power supply, a temperature measuring module for measuring the temperature of the fluid to be measured is connected with a constant current source, the voltage control module is respectively connected with the speed measuring module and the temperature measuring module so as to convert the temperature of the temperature measuring module and the flow velocity of the speed measuring module into corresponding voltage and determine the temperature difference between the speed measuring module and the temperature measuring module according to the voltage difference between the speed measuring module and the temperature measuring module, further controlling the temperature difference to be kept within the preset threshold range to realize constant temperature difference, connecting the mass flow rate determining module with the speed measuring module, compared with the method that the mass flow of the fluid to be measured is obtained by adopting a microprocessor, the mass flow of the fluid to be measured is measured in a pure hardware mode, and the response speed of obtaining the measurement result is improved.
Drawings
FIG. 1 is a schematic diagram of a typical model of King's Law in an embodiment of the present invention;
FIG. 2 is a schematic diagram of a fluid mass flow measurement circuit in accordance with an embodiment of the present invention;
fig. 3 is a schematic structural diagram of an overcurrent protection module according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of another fluid mass flow measurement circuit in an embodiment of the invention;
FIG. 5 is a schematic diagram of a signal power extraction unit according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a constant current source circuit according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of a preset amplifying subunit according to an embodiment of the present invention;
FIG. 8 is a diagram illustrating a structure of a division subunit according to an embodiment of the present invention;
FIG. 9 is a schematic structural diagram of a temperature difference setting unit according to an embodiment of the present invention;
fig. 10 is a schematic diagram of the structure of an amplifier unit in the embodiment of the present invention.
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that, in the following embodiments and examples, subsamples may be combined with each other without conflict.
It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.
In the following description, numerous details are set forth to provide a more thorough explanation of embodiments of the present invention, however, it will be apparent to one skilled in the art that embodiments of the present invention may be practiced without these specific details, and in other embodiments, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring embodiments of the present invention.
The terms "first," "second," and the like in the description and in the claims, and the above-described drawings of embodiments of the present disclosure, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It should be understood that the data so used may be interchanged under appropriate circumstances such that embodiments of the present disclosure described herein may be made. Furthermore, the terms "comprising" and "having," as well as any variations thereof, are intended to cover non-exclusive inclusions.
The term "plurality" means two or more unless otherwise specified.
In the embodiment of the present disclosure, the character "/" indicates that the preceding and following objects are in an or relationship. For example, A/B represents: a or B.
The term "and/or" is an associative relationship that describes objects, meaning that three relationships may exist. For example, a and/or B, represents: a or B, or A and B.
Referring to FIG. 1, a typical King's law model includes a velocity measurement module 101 and a temperature measurement module 102, qTo be measuredFor the flow direction of the fluid to be measured, the flow speed of the fluid to be measured is determined by the following method:
wherein, IPT1Drive current for speed measuring module, RPT1Resistance of the tachometer module, n1、n2、n3For presetting calibration parameters, V is the flow rate of the fluid to be measured, TPT1For measuring the temperature of the module, TPT2Is the temperature of the temperature measuring module.
OptionallyEarth, n1、n2The temperature measuring device is determined by at least one of the parameters such as the size of the metal probe, the fluid property of the fluid to be measured, the environmental flow condition and the like, wherein the metal probe is used for measuring the temperature of the speed measuring module or the temperature measuring module.
Optionally, the speed measuring module or the temperature measuring module includes an electric heating element, and a platinum resistor may be specifically used.
Optionally, the resistance value of the platinum resistor is determined by:
R＝β+A·T，
wherein, R is the resistance value of the platinum resistor, beta is the reference resistance of the platinum resistor, A is the temperature coefficient of the platinum resistor, and T is the surface temperature of the platinum resistor.
In some embodiments, the tachometer module and the thermometry module are both PT100 platinum resistors, wherein the PT100 platinum resistors have a temperature coefficient of 0.39 Ω/deg.c.
Referring to fig. 2, an embodiment of the present disclosure provides a fluid mass flow measurement circuit, which includes a velocity measurement module 201, a temperature measurement module 202, a voltage control module 203, and a mass flow determination module 204. The speed measuring module 201 is connected to the working power supply a and is used for measuring the flow speed of the fluid to be measured in the pipe wall. The temperature measuring module 202 is connected to the constant current source B and is used for measuring the temperature of the fluid to be measured. The voltage control module 203 is respectively connected with the speed measuring module and the temperature measuring module, and is used for converting the temperature of the temperature measuring module and the flow velocity of the speed measuring module into corresponding voltage, determining the temperature difference between the speed measuring module and the temperature measuring module according to the voltage difference between the speed measuring module and the temperature measuring module, and controlling the temperature difference to be kept within a preset threshold range to realize constant temperature difference. The mass flow rate determination module 204 is connected to the speed measurement module, and is configured to determine the mass flow rate of the fluid to be measured according to the heating power of the speed measurement module and the temperature difference between the speed measurement module and the temperature measurement module.
By adopting the fluid mass flow measuring circuit provided by the embodiment of the disclosure, the speed measuring module for measuring the flow velocity of the fluid to be measured in the pipe wall is connected with the working power supply, the temperature measuring module for measuring the temperature of the fluid to be measured is connected with the constant current source, the speed measuring module and the temperature measuring module are respectively connected through the voltage control module so as to convert the temperature of the temperature measuring module and the flow velocity of the speed measuring module into corresponding voltages, the temperature difference between the speed measuring module and the temperature measuring module is determined according to the voltage difference between the speed measuring module and the temperature measuring module, the temperature difference is further controlled to be kept within the preset threshold range to realize constant temperature difference, the speed measuring module is connected through the mass flow determining module so as to determine the mass flow of the fluid to be measured according to the heating power of the speed measuring module and the temperature difference between the speed measuring module and the temperature measuring module, compared with the method that a microprocessor is adopted to obtain the mass flow of the fluid to be measured, the mass flow of the fluid to be measured is measured in a pure hardware mode, the response speed for obtaining the measurement result is improved.
Optionally, the fluid mass flow measurement circuit further includes an overcurrent protection module, and the speed measurement module is connected to the working power supply through the overcurrent protection module. Therefore, the overcurrent protection module prevents overlarge current from passing through, so that the circuit is prevented from being damaged, and the safety and the reliability of the circuit are improved.
Referring to fig. 3, an embodiment of the present disclosure provides an overcurrent protection module, which includes a protection MOS transistor 301, a protection transistor 302, a load resistor 303, a pull-down resistor 304, a protection resistor 305, and a filtering unit 306. The working power supply A is respectively connected with one end of a load resistor 303 and an emitting electrode of a protection triode 302, and the other end of the load resistor is respectively connected with a base electrode of the protection triode and a source electrode of a protection MOS tube 301; the collector of the protection triode is respectively connected with one end of the pull-down resistor 304 and the grid of the protection MOS tube; the other end of the pull-down resistor is grounded; a protection resistor 305 is connected between the source and the drain of the protection MOS tube; the drain electrode of the protection MOS tube is connected in parallel with a filtering unit 306 to output current, wherein when the protection MOS tube is in a conducting state, a filtered current signal is output; when the emitter and the base of the protection triode are conducted, the pull-down resistor is connected with the working power supply, the grid voltage of the protection MOS tube is increased, the protection MOS tube is in a cut-off state, and the working power supply is enabled to carry out overcurrent protection through the current output by the protection resistor.
As shown in fig. 3, the load resistor 303 includes a first load sub-resistor 3031, a second load sub-resistor 3032, and a third load sub-resistor 3033; the filtering unit 306 includes a first filtering capacitance 3061, a second filtering capacitance 3062, and a third filtering capacitance 3063.
Optionally, the fluid mass flow measurement circuit further includes a current detection module, and the current detection module is connected to the speed measurement module and is configured to measure a current of the current detection module.
Optionally, the current detection module includes a current detection resistor, wherein a resistance value of the current detection resistor includes 1 Ω to 10 Ω.
Optionally, the voltage control module includes a temperature difference setting unit, a voltage operation unit, an amplifier unit, and an adjusting tube, and the fluid mass flow measurement circuit further includes: the temperature difference setting unit is used for outputting a set voltage according to a preset temperature difference threshold value; the input end of the voltage operation unit is respectively connected with the speed measurement module, the temperature measurement module and the current detection module, and the calculation unit is used for outputting operation voltage according to the voltage of the speed measurement module, the voltage of the temperature measurement module and the voltage of the current detection module; the input end of the amplifier unit is respectively connected with the output end of the voltage operation unit and the output end of the temperature difference setting unit, the output end of the amplifier unit is connected with the base electrode of the adjusting tube, the working power supply is connected with the speed measuring module after passing through the collector electrode and the emitter electrode of the adjusting tube, the amplifier unit is used for determining the output amplification factor to control the output current of the adjusting tube after comparing with the temperature difference between the speed measuring module and the temperature measuring module according to the set voltage as the reference, and further reversely controlling the operation voltage to be kept in the set voltage.
Optionally, the voltage operation unit includes a first amplification subunit, a second amplification subunit, a third amplification subunit, a division subunit, and a subtraction subunit, and the fluid mass flow measurement circuit further includes: the input end of the first amplification subunit is connected with the speed measurement module, the second amplification subunit is connected with the current detection module, and the input end of the third amplification subunit is connected with the temperature measurement module; the input end of the division subunit is respectively connected with the output end of the first amplification subunit and the output end of the second amplification subunit; the input end of the subtraction subunit is respectively connected with the output end of the third amplification subunit and the output end of the division subunit, and the output end of the subtraction subunit is connected with the second input end of the amplifier unit.
Optionally, the calculating unit further includes a voltage follower subunit, an output end of the division subunit is connected to an input end of the subtraction subunit through the voltage follower subunit, and the voltage follower subunit is configured to isolate signal interference between the division subunit and the subtraction subunit.
Referring to fig. 4, an embodiment of the present disclosure provides a fluid mass flow measurement circuit, which includes a velocity measurement module 201, a temperature measurement module 202, a voltage control module 203, a mass flow determination module 204, an overcurrent protection module 205, and a current detection module 206. The speed measuring module 201 is connected with a working power supply. The temperature measurement module 202 is connected with a constant current source. The current detection module 206 is connected to the speed measurement module. The voltage control module 203 includes a temperature difference setting unit 2031, a voltage operation unit 2032, an amplifier unit 2033, and an adjustment pipe 2034. The voltage operation unit 2032 includes a first amplification sub-unit 20321, a second amplification sub-unit 20322, a third amplification sub-unit 20323, a division sub-unit 20324, a subtraction sub-unit 20325, and a voltage follower sub-unit 20326. The input end of the first amplification subunit 20321 is connected to the speed measurement module. The second amplification subunit 20322 is connected to the current detection module. The input end of the third amplification subunit 20323 is connected to the temperature measurement module. The input end of the division subunit 20324 is connected to the output end of the first amplification subunit and the output end of the second amplification subunit, respectively, and the output end of the division subunit is connected to the input end of the subtraction subunit through the voltage follower subunit 20326. An input terminal of the subtracting sub-unit 20325 is connected to an output terminal of the third amplifying sub-unit, and an output terminal of the subtracting sub-unit is connected to a second input terminal of the amplifier unit 2033. A first input end of the amplifier unit 2033 is connected to an output end of the temperature difference setting unit 2031, and an output end of the amplifier unit is connected to a base of the adjusting tube 2034. The working power supply is connected with the speed measuring module after passing through the overcurrent protection module 205 and the collector and emitter of the adjusting tube 2034 in sequence,
by adopting the fluid mass flow measuring circuit provided by the embodiment of the disclosure, the speed measuring module for measuring the flow velocity of the fluid to be measured in the pipe wall is connected with the working power supply, the temperature measuring module for measuring the temperature of the fluid to be measured is connected with the constant current source, the speed measuring module and the temperature measuring module are respectively connected through the voltage control module so as to convert the temperature of the temperature measuring module and the flow velocity of the speed measuring module into corresponding voltages, the temperature difference between the speed measuring module and the temperature measuring module is determined according to the voltage difference between the speed measuring module and the temperature measuring module, the temperature difference is further controlled to be kept within the preset threshold range to realize constant temperature difference, the speed measuring module is connected through the mass flow determining module so as to determine the mass flow of the fluid to be measured according to the heating power of the speed measuring module and the temperature difference between the speed measuring module and the temperature measuring module, compared with the method that a microprocessor is adopted to obtain the mass flow of the fluid to be measured, the mass flow of the fluid to be measured is measured in a pure hardware mode, the response speed for obtaining the measurement result is improved.
Alternatively, the set voltage is determined by:
wherein, V7To set the voltage, K is the coefficient of operation, TsIs a preset temperature difference threshold value, k1Is the gain, k, of the first amplification subunit2Is the gain, k, of the second amplification subunit3Is the gain of the division subunit, k5Is the gain of the third amplification subunit, A1Is the temperature coefficient between the speed measuring resistor and the temperature of the speed measuring module, A2Is the temperature coefficient between the temperature measuring resistor and the temperature measuring module, R1To the resistance of the current-sensing module, IPT2Is the current of a constant current power supply.
Referring to fig. 4, in some embodiments, the resistance of the tachometer module is RPT1The current value of the speed measuring module is IPT1The resistance value of the temperature measuring module is RPT2The resistance value of the current detection module is 1 Ω, the current of the constant current source is 1mA, the gain of the first amplification subunit is 0.25, the gain of the second amplification subunit is 5, the gain of the third amplification subunit is 50, and the gain of the division subunit is 1, so that the voltage at the output end of the first amplification subunit is obtained
Voltage V at output terminal of second amplifier subunit2＝5·IPT1Voltage V at the output of the third amplifier subunit3＝0.05·RPT2Voltage V at the output of the divider subunit4＝0.05·RPT1Voltage V at the output of the subtraction subunit5＝0.05·(RPT1-RPT2)＝0.05×A×(TPT1-TPT2) If A is 0.39 omega/DEG C, the voltage difference between the speed measuring module and the temperature measuring module is 30 ℃, the voltage of the output end of the temperature difference setting unit is 0.585V.
Optionally, the mass flow determination module includes a signal power extraction unit and a mass flow calculation unit, and the mass flow calculation unit is configured to calculate the power obtained by the signal power extraction unit to determine the mass flow.
With reference to fig. 5, the present disclosure provides a signal power extraction unit, which includes a first power signal extraction chip U51, a second power signal extraction chip U52, a power extraction unit amplifier U53, a first power extraction unit capacitor C51, a second power extraction unit capacitor C52, a third power extraction unit capacitor C53, a fourth power extraction unit capacitor C54, a fifth power extraction unit capacitor C55, a first power extraction unit resistor R51, a second power extraction unit resistor R52, a third power extraction unit resistor R53, a fourth power extraction unit resistor R54, and a fifth power extraction unit resistor R55, where the first power signal extraction chip is respectively connected to the first power extraction unit capacitor C51, the second power extraction unit capacitor C52, the third power extraction unit capacitor C53, the first power extraction unit resistor R51, and an input end of the power extraction unit amplifier U53 is respectively connected to the first power extraction unit resistor R51, A second power extraction unit resistor R52, the inverting input terminal of the power extraction unit amplifier U53 is connected with a second power extraction unit resistor R52 and a third power extraction unit resistor R53 respectively, the homodromous input terminal of the power extraction unit amplifier U53 is connected with a fourth power extraction unit capacitor C54 and a fourth power extraction unit resistor R54 respectively, the second power signal extraction chip U52 is connected with a fourth power extraction unit resistor R54, a fifth power extraction unit resistor R55 and a fifth power extraction unit capacitor C55 respectively, the first power extraction unit port P51 is connected to the output end of the first amplification subunit and the first power signal extraction chip, the second power extraction unit port P52 is connected to the same-direction input end of the power extraction unit amplifier U53 and the output end of the second amplification subunit, and the third power extraction unit port is connected to the mass flow calculation unit.
With reference to fig. 6, the present disclosure provides a constant current source circuit, including a first constant current source amplifier U61, a second constant current source amplifier U62, a first constant current source capacitor C61, a second constant current source capacitor C62, a first constant current source resistor R61, a second constant current source resistor R62, a third constant current source resistor R63, a fourth constant current source resistor R64, a fifth constant current source resistor R65, a constant current source MOS transistor Q61, a constant current source diode D61, and a constant current source inductor L61, wherein a same-direction input end of the first constant current source amplifier U61 is respectively connected to a 10V voltage and the first constant current source capacitor C61, an opposite-direction input end of the first constant current source capacitor C61 is sequentially connected to the first constant current source resistor R61 and the second constant current source resistor R62, a power input end of the first constant current source capacitor C61 is respectively connected to a 12V voltage and the second constant current source capacitor C62, an output end of the first capacitor C61 is connected to the third constant current source resistor R63, the reverse input end of the second constant current source amplifier U62 is connected to the gate of the third constant current source resistor R63 and the constant current source MOS transistor Q61, the same-direction input end of the second constant current source amplifier U62 is connected to the first constant current source resistor R61 and the second constant current source resistor R62, the output end of the second constant current source amplifier U62 outputs a constant current through the fourth constant current source resistor R64, the source and drain of the constant current source MOS transistor Q61, the constant current source diode D61, and the constant current source inductor L61, and the fifth constant current source resistor R65 is connected to the fourth constant current source resistor R64.
Optionally, at least one of the first amplification subunit or the second amplification subunit is a preset amplification subunit.
With reference to fig. 7, an embodiment of the present disclosure provides a preset amplification subunit, which includes an amplification chip U71, a first amplification unit capacitor C71, a second amplification unit capacitor C72, a third amplification unit capacitor C73, a fourth amplification unit capacitor C74, a fifth amplification unit capacitor C75, a sixth amplification unit capacitor C76, a first amplification unit resistor R71, a second amplification unit resistor R72, and a third amplification unit resistor R73, where the first amplification unit port P71 is connected to the first amplification unit resistor R71 and the first amplification unit capacitor C71, the amplification chip U71 is connected to the first amplification unit resistor R71, the second amplification unit resistor R72, the third amplification unit resistor R73, +12V voltage, -12V voltage, the second amplification unit capacitor C72, the third amplification unit capacitor C73, the fourth amplification unit capacitor C74, the fifth amplification unit capacitor C75, and the sixth amplification unit capacitor 76, the amplification chip U71 outputs the amplified signal through the second amplification unit port P72 and the third amplification unit port P73.
Referring to fig. 8, an embodiment of the present disclosure provides a division subunit, which includes a divider chip U81, a first division unit amplifier U82, a second division unit amplifier U83, a third division unit amplifier U84, a first division unit capacitor C81, a second division unit capacitor C82, a third division unit capacitor C83, a fourth division unit capacitor C84, a fifth division unit capacitor C85, a first division unit resistor R81, a second division unit resistor R82, a third division unit resistor R83, a fourth division unit resistor R84, a fifth division unit resistor R85, a sixth division unit resistor R86, a seventh division unit resistor R87, an eighth division unit resistor R88, a ninth division unit resistor R89, and a tenth division unit resistor R810, where the divider chip is connected to a working power supply VCC, -12V power supply, a first division unit capacitor C81, and a fifth division unit resistor R85, the homodromous input end of a first division unit amplifier U82 is connected with a first division unit resistor R81, the inverting input end of a first division unit amplifier U82 is respectively connected with a second division unit resistor R82 and a third division unit resistor R83, the output end of a first division unit amplifier U82 is connected with a second division unit resistor R82, a third division unit resistor R83 is connected with a fourth division unit resistor R84, the power supply input end of the first division unit amplifier U82 is respectively connected with a +12V power supply and a second division unit capacitor C82, the power supply output end of a first division unit amplifier U82 is respectively connected with a-12V power supply and a third division unit capacitor C83, the homodromous input end of the second division unit amplifier U83 is connected with a seventh division unit resistor R87, the inverting input end of the second division unit amplifier U83 is respectively connected with a fifth division unit resistor R85 and a sixth division unit resistor R86, the output end of the second division unit amplifier U83 is connected to the first division unit resistor R81, the output end of the third division unit amplifier U84 is connected to the sixth division unit resistor R86 and the eighth division unit resistor R88, the power input end of the third division unit amplifier U83 is connected to the +12V power supply and the fourth division unit capacitor C84, the power output end of the third division unit amplifier U83 is connected to the-12V power supply and the fifth division unit capacitor C85, the same-direction input end of the third division unit amplifier U83 is connected to the tenth division unit resistor R810, and the reverse input end of the third division unit amplifier U83 is connected to the eighth division unit resistor R88 and the ninth division unit resistor R89.
With reference to fig. 9, an embodiment of the present disclosure provides a temperature difference setting unit, which includes a temperature difference setting unit output end P91, a temperature difference setting unit input end P92, a first temperature difference setting unit amplifier U91, a second temperature difference setting unit amplifier U92, a first temperature difference setting unit resistor R91, a second temperature difference setting unit resistor R92, a third temperature difference setting unit resistor R93, a fourth temperature difference setting unit resistor R94, a fifth temperature difference setting unit resistor R95, a sixth temperature difference setting unit resistor R96, a seventh temperature difference setting unit resistor R97, a first temperature difference setting unit capacitor C91, a second temperature difference setting unit capacitor C92, a third temperature difference setting unit capacitor C93, and a fourth temperature difference setting unit capacitor C94, where the output end of the first temperature difference setting unit amplifier U91 is respectively connected to the second temperature difference setting unit capacitor C92 and the third temperature difference setting unit resistor R93, and the third temperature difference setting unit resistor R93 is respectively connected to the first temperature difference setting unit resistor R91 and the second temperature difference setting unit resistor R8252 A resistor R92, a first temperature difference setting unit resistor R91 is connected with a first temperature difference setting unit capacitor C91, the reverse input end of a first temperature difference setting unit amplifier U91 is respectively connected with a second temperature difference setting unit capacitor C92 and a fourth temperature difference setting unit resistor R94, the output end of a second temperature difference setting unit amplifier U92 is respectively connected with the same-direction input end of the first temperature difference setting unit amplifier U91 and the reverse input end of the second temperature difference setting unit amplifier U92, the forward input end of the second temperature difference setting unit amplifier U92 is respectively connected with a fifth temperature difference setting unit resistor R95 and a sixth temperature difference setting unit resistor R96, a seventh temperature difference setting unit resistor R97 is respectively connected with a sixth temperature difference setting unit resistor R96 and a fourth temperature difference setting unit capacitor C94, a fourth temperature difference setting unit capacitor C94 is connected with a fifth temperature difference setting unit resistor R95, the power supply input end of the second temperature difference setting unit amplifier U92 is connected with a +24V voltage and a third temperature difference setting unit capacitor C93, the output end P91 of the temperature difference setting unit is respectively connected with a first temperature difference setting unit resistor R91, a second temperature difference setting unit resistor R92 and a third temperature difference setting unit resistor R93, and the input end P92 of the temperature difference setting unit is connected with a fourth temperature difference setting unit resistor R94.
With reference to fig. 10, an embodiment of the present disclosure provides an amplifier unit, which includes an amplifier unit input end P101, an amplifier unit output end P102, an amplifier unit transistor Q101, a first amplifier unit resistor R101, a second amplifier unit resistor R102, a third amplifier unit resistor R103, and a first amplifier unit capacitor C101, where a base of the amplifier unit transistor Q101 is connected to the amplifier unit input end P101, a collector of the amplifier unit transistor Q101 is connected to the amplifier unit output end P102 through the third amplifier unit resistor R103, an emitter of the amplifier unit transistor Q101 is connected to a 24V power supply through the second amplifier unit resistor R102, the first amplifier unit resistor R101 is respectively connected to a collector and an emitter of the amplifier unit transistor Q101, and the first amplifier unit capacitor C101 is connected to the emitter of the amplifier unit transistor Q101.
Optionally, the mass flow rate of the fluid to be measured is determined by:
wherein Q ismIs the mass flow of the fluid to be measured, S is the cross-sectional area of the fluid to be measured, V is the flow velocity of the fluid to be measured, PPT1Is the speed measurement power of the speed measurement module, delta T is the temperature difference between the speed measurement module and the temperature measurement module, n1、n2、n3Is a preset calibration parameter.
The embodiment of the disclosure provides a fluid mass flow meter, and a current conversion device comprises the fluid mass flow measurement circuit.
By adopting the fluid mass flow meter provided by the embodiment of the disclosure, the speed measuring module for measuring the flow speed of the fluid to be measured in the pipe wall is connected with the working power supply, the temperature measuring module for measuring the temperature of the fluid to be measured is connected with the constant current source, the speed measuring module and the temperature measuring module are respectively connected through the voltage control module so as to convert the temperature of the temperature measuring module and the flow speed of the speed measuring module into corresponding voltages, the temperature difference between the speed measuring module and the temperature measuring module is determined according to the voltage difference between the speed measuring module and the temperature measuring module, the temperature difference is further controlled to be kept within the preset threshold range to realize constant temperature difference, the speed measuring module is connected through the mass flow determining module so as to determine the mass flow of the fluid to be measured according to the heating power of the speed measuring module and the temperature difference between the speed measuring module and the temperature measuring module, compared with the method that a microprocessor is adopted to obtain the mass flow of the fluid to be measured, the mass flow of the fluid to be measured is measured in a pure hardware mode, the response speed for obtaining the measurement result is improved.
The above description and drawings sufficiently illustrate embodiments of the disclosure to enable those skilled in the art to practice them. Other embodiments may incorporate structural, logical, electrical, process, and other changes. The examples merely typify possible variations. Individual components and functions are optional unless explicitly required, and the sequence of operations may vary. Portions and subsamples of some embodiments may be included in or substituted for portions and subsamples of other embodiments. Furthermore, the words used in the specification are words of description only and are not intended to limit the claims. As used in the description of the embodiments and the claims, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Similarly, the term "and/or" as used in this application is meant to encompass any and all possible combinations of one or more of the associated listed. Furthermore, the terms "comprises," "comprising," and variations thereof, when used in this application, specify the presence of stated sub-samples, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other sub-samples, integers, steps, operations, elements, components, and/or groups thereof. Without further limitation, an element defined by the phrase "comprising an …" does not exclude the presence of other like elements in a process, method or apparatus that comprises the element. In this document, each embodiment may be described with emphasis on differences from other embodiments, and the same and similar parts between the respective embodiments may be referred to each other. For methods, products, etc. of the embodiment disclosures, reference may be made to the description of the method section for relevance if it corresponds to the method section of the embodiment disclosure.
In the embodiments disclosed herein, the disclosed methods, products (including but not limited to devices, apparatuses, etc.) may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units may be only one logical division, and there may be other divisions in actual implementation, for example, a plurality of units or components may be combined or may be integrated into another system, or some subsamples may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form. The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to implement the present embodiment. In addition, functional units in the embodiments of the present disclosure may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit.
The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods and computer program products according to embodiments of the present disclosure. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. In the description corresponding to the flowcharts and block diagrams in the figures, operations or steps corresponding to different blocks may also occur in different orders than disclosed in the description, and sometimes there is no specific order between the different operations or steps. For example, two sequential operations or steps may in fact be executed substantially concurrently, or they may sometimes be executed in the reverse order, depending upon the functionality involved. Each block of the block diagrams and/or flowchart illustrations, and combinations of blocks in the block diagrams and/or flowchart illustrations, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.
Claims (10)
1. A fluid mass flow measurement circuit, comprising:
the speed measuring module is connected with the working power supply and used for measuring the flow speed of the fluid to be measured in the pipe wall;
the temperature measuring module is connected with the constant current source and used for measuring the temperature of the fluid to be measured;
the voltage control module is respectively connected with the speed measuring module and the temperature measuring module and is used for converting the temperature of the temperature measuring module and the flow velocity of the speed measuring module into corresponding voltages, determining the temperature difference between the speed measuring module and the temperature measuring module according to the voltage difference between the speed measuring module and the temperature measuring module and controlling the temperature difference to be kept within a preset threshold range to realize constant temperature difference;
and the mass flow determining module is connected with the speed measuring module and used for determining the mass flow of the fluid to be measured according to the heating power of the speed measuring module and the temperature difference between the speed measuring module and the temperature measuring module.
2. The fluid mass flow measurement circuit of claim 1, further comprising an over-current protection module, the speed measurement module being connected to the operating power supply through the over-current protection module.
3. The fluid mass flow measurement circuit of claim 2, wherein the over-current protection module comprises a protection MOS transistor, a protection triode, a load resistor, a pull-down resistor, a protection resistor and a filtering unit,
the working power supply is respectively connected with one end of a load resistor and an emitting electrode of the protection triode, and the other end of the load resistor is respectively connected with a base electrode of the protection triode and a source electrode of the protection MOS tube; the collector of the protection triode is respectively connected with one end of the pull-down resistor and the grid of the protection MOS tube; the other end of the pull-down resistor is grounded; a protection resistor is connected between the source electrode and the drain electrode of the protection MOS tube; the drain electrode of the protection MOS tube is connected with the output current of the filtering unit in parallel;
when the protection MOS is in a conducting state, outputting a filtered current signal; when the emitter and the base of the protection triode are conducted, the pull-down resistor is connected with a working power supply, the grid voltage of the protection MOS tube is increased, the protection MOS tube is in a cut-off state, and the working power supply is enabled to carry out overcurrent protection through the current output by the protection resistor.
4. The fluid mass flow measurement circuit of claim 1, further comprising a current sensing module coupled to the current sensing module for measuring a current of the current sensing module.
5. The fluid mass flow measurement circuit of claim 4, wherein the voltage control module comprises a temperature difference setting unit, a voltage operation unit, an amplifier unit, an adjustment tube, the fluid mass flow measurement circuit further comprising:
the temperature difference setting unit is used for outputting a set voltage according to the preset temperature difference threshold value;
the input end of the voltage operation unit is respectively connected with the speed measurement module, the temperature measurement module and the current detection module, and the calculation unit is used for outputting operation voltage according to the voltage of the speed measurement module, the voltage of the temperature measurement module and the voltage of the current detection module;
the input end of the amplifier unit is respectively connected with the output end of the voltage operation unit and the output end of the temperature difference setting unit, the output end of the amplifier unit is connected with the base electrode of the adjusting tube, the working power supply is connected with the speed measuring module after passing through the collector electrode and the emitter electrode of the adjusting tube, the amplifier unit is used for determining the output amplification factor to control the output current of the adjusting tube after comparing with the temperature difference between the speed measuring module and the temperature measuring module according to the set voltage serving as a reference, and further reversely controlling the operation voltage to be kept in the set voltage.
6. The fluid mass flow measurement circuit of claim 5, wherein the voltage arithmetic unit comprises a first amplification sub-unit, a second amplification sub-unit, a third amplification sub-unit, a division sub-unit, a subtraction sub-unit, the fluid mass flow measurement circuit further comprising:
the input end of the first amplification subunit is connected with the speed measuring module, the second amplification subunit is connected with the current detecting module, and the input end of the third amplification subunit is connected with the temperature measuring module;
the input end of the dividing subunit is respectively connected with the output end of the first amplifying subunit and the output end of the second amplifying subunit;
the input end of the subtraction subunit is connected to the output end of the third amplification subunit and the output end of the division subunit, respectively, and the output end of the subtraction subunit is connected to the second input end of the amplifier unit.
7. The fluid mass flow measurement circuit of claim 6, wherein the calculation unit further comprises a voltage follower sub-unit, an output of the division sub-unit being connected to an input of the subtraction sub-unit via the voltage follower sub-unit, the voltage follower sub-unit being configured to isolate signal interference between the division sub-unit and the subtraction sub-unit.
8. The fluid mass flow measurement circuit of claim 7, wherein the set voltage is determined by:
wherein, V7For the set voltage, K is the coefficient of operation, TsIs the preset temperature difference threshold value, k1Is the gain, k, of the first amplification subunit2Is the gain, k, of the second amplification subunit3Is the gain of the division subunit, k5Is the gain of the third amplification subunit, A1Is the temperature coefficient between the tachometer resistance and the tachometer module temperature, A2Is the temperature coefficient, R, between the temperature measuring resistor and the temperature measuring module1Is the resistance of the current sensing module, IPT2Is the current of the constant current power supply.
9. A fluid mass flow measurement circuit according to any one of claims 1 to 8, wherein the mass flow of the fluid under test is determined by:
wherein Q ismFor the mass flow of the fluid to be measured, S is the cross-sectional area of the fluid to be measured, V is the flow velocity of the fluid to be measured, P isPT1Is the speed measurement power of the speed measurement module, delta T is the temperature difference between the speed measurement module and the temperature measurement module, n1、n2、n3Is a preset calibration parameter.
10. A fluid mass flow meter, characterized in that the current transformation means comprises a fluid mass flow measurement circuit according to any one of claims 1 to 9.
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| CN115452080A (en) * | 2022-08-08 | 2022-12-09 | 重庆川仪自动化股份有限公司 | Signal linearization circuit and method for thermal gas mass flowmeter |
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