CN112393777A - Constant-power thermal type gas mass flow meter - Google Patents
Constant-power thermal type gas mass flow meter Download PDFInfo
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- CN112393777A CN112393777A CN202011120727.5A CN202011120727A CN112393777A CN 112393777 A CN112393777 A CN 112393777A CN 202011120727 A CN202011120727 A CN 202011120727A CN 112393777 A CN112393777 A CN 112393777A
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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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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
- G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
- G05F1/66—Regulating electric power
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- Automation & Control Theory (AREA)
- Measuring Volume Flow (AREA)
Abstract
The invention provides a constant-power thermal gas mass flowmeter, which comprises a speed measuring unit and a temperature measuring unit, wherein the mass flow is obtained according to the voltage difference value of the speed measuring unit and the temperature measuring unit, and the flowmeter comprises a constant-power circuit; the speed measuring unit is provided with constant heating power by the constant power circuit, and the temperature measuring unit is heated by an external power supply. The invention adopts the constant power circuit to realize constant power measurement, simultaneously needs no independent heating wire, and the tachometer resistor is a heating element, thereby reducing the complexity of the circuit and saving the cost.
Description
Technical Field
The invention relates to the field of metering measurement, in particular to a constant-power thermal type gas mass flowmeter.
Background
At present, differential pressure, turbine and positive displacement flow meters are generally adopted for industrial gas measurement, and the gas flow meters based on the measurement principles have certain defects: first, differential pressure and volumetric flow meters have large pressure losses. Secondly, the measuring range is smaller; thirdly, the accuracy is poor.
The constant-power thermal type gas mass flowmeter has the advantages of small pressure loss, wide measurement range, capability of directly measuring mass flow and the like, and is more and more widely concerned and applied in the field of gas measurement.
The constant-power thermal type gas mass flowmeter is divided into two measurement principles of constant temperature difference and constant power, and essentially the two measurement principles are both based on the King's law, and a typical model of the King's law is shown in figure 1.
Wherein, K1,K2,K3For design and calibration parameters, Δ T is the temperature difference, which is equal to (T)2-T1),T1For measuring temperature of thermal resistance, T2For measuring the speed of the thermal resistor, P is the input heating power, qmIs the mass flow rate.
In the above formula, if the input heating power P is kept constant, the temperature difference between the two probes and the mass flow qmChanges occur and the mass flow can be calculated by measuring Δ T.
The traditional constant power heating generally needs an additional heating wire to provide constant heating power for the speed measuring thermal resistor, and the two thermal resistors are driven by constant current sources with the same current.
Disclosure of Invention
In view of the above-mentioned drawbacks of the prior art, it is an object of the present invention to provide a constant power thermal gas mass flow meter that solves at least one of the drawbacks of the prior art.
In order to achieve the above and other related objects, the present invention provides a constant power thermal gas mass flowmeter, comprising a speed measuring unit and a temperature measuring unit, wherein a mass flow is obtained according to a voltage difference between the speed measuring unit and the temperature measuring unit, and the flowmeter comprises a constant power circuit; the speed measuring unit is provided with constant heating power by the constant power circuit, and the temperature measuring unit is heated by an external power supply.
Optionally, the constant power circuit comprises:
a current detection unit for detecting a current value of the speed measurement unit;
a voltage detection unit for detecting a voltage value of the speed measurement unit;
the multiplication unit is used for obtaining an actual power value according to the current value and the voltage value of the speed measurement unit;
and the power adjusting unit is used for providing constant heating power for the speed measuring unit according to the actual power value and the power set value.
Optionally, the power adjusting unit includes:
the power amplifier comprises an operational amplifier and a triode, wherein the operational amplifier adjusts the triode according to an actual power value and a power set value so as to output constant power.
Optionally, the current detection unit comprises a current detection element and a gain amplifier;
the gain amplifier is used for amplifying the voltage of the current detection element, so that the output value of the gain amplifier is consistent with the current value of the speed measurement unit.
Optionally, the current detection element is a resistor with a resistance of 0.1 ohm, and the gain of the gain amplifier is 10.
Optionally, the voltage detection unit includes a first differential amplifier connected in parallel to both ends of the speed measurement unit.
Optionally, the gain of the first differential amplifier is 1.
Optionally, the speed measuring unit and the temperature measuring unit are both electric heating elements.
Optionally, the electric heating element is a platinum resistor.
Optionally, the voltage values of the speed measurement unit and the temperature measurement unit are amplified by a second differential amplifier and then go through a linearization circuit to obtain the mass flow.
As described above, the constant-power thermal gas mass flowmeter of the present invention has the following beneficial effects:
the invention adopts the constant power circuit to realize constant power measurement, simultaneously needs no independent heating wire, and the tachometer resistor is a heating element, thereby reducing the complexity of the circuit and saving the cost.
Drawings
FIG. 1 is a typical model of King's Law;
fig. 2 is a schematic diagram of a constant power thermal gas mass flowmeter according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will become apparent to those skilled in the art from the present disclosure.
It should be understood that the structures, ratios, sizes, and the like shown in the drawings and described in the specification are only used for matching with the disclosure of the specification, so as to be understood and read by those skilled in the art, and are not used to limit the conditions under which the present invention can be implemented, so that the present invention has no technical significance, and any structural modification, ratio relationship change, or size adjustment should still fall within the scope of the present invention without affecting the efficacy and the achievable purpose of the present invention. In addition, the terms "upper", "lower", "left", "right", "middle" and "one" used in the present specification are for clarity of description, and are not intended to limit the scope of the present invention, and the relative relationship between the terms and the terms is not to be construed as a scope of the present invention.
As shown in fig. 2, the present invention provides a constant power thermal type gas mass flowmeter, which includes a speed measuring unit and a temperature measuring unit, wherein a mass flow is obtained according to a voltage difference between the speed measuring unit and the temperature measuring unit, and the flowmeter includes a constant power circuit; the speed measuring unit is provided with constant heating power by the constant power circuit, and the temperature measuring unit is heated by an external power supply.
In the present embodiment, the flow meter includes a speed measuring unit and a temperature measuring unit, and the two measuring units may be resistors. One of the resistors is a temperature measuring resistor RT1 for measuring the temperature of the measured fluid, and the other resistor is a speed measuring resistor RT2 for measuring the speed of the measured fluid. Wherein, temperature measurement resistance RT1 and test the speed resistance RT2 all can be the electro-heat element, specifically can adopt platinum resistance, provide a invariable power through constant power circuit and heat the platinum resistance that tests the speed, the fluid tests speed resistance RT2 and temperature measurement resistance RT1 surface temperature difference DeltaT ═ T when staticRT2-TRT1At the maximum, the temperature difference between the surfaces of the two platinum resistors is reduced along with the flowing of the medium, and the temperature difference between the two platinum resistors is smaller when the flow rate of the fluid is larger. The platinum resistor has different resistance values due to different temperatures, and the fluid flow is reflected by detecting the voltage difference between the tachometer resistor RT2 and the temperature measurement resistor RT 1.
In one embodiment, the constant power circuit includes:
a current detection unit for detecting a current value of the speed measurement unit;
a voltage detection unit for detecting a voltage value of the speed measurement unit;
the multiplication unit is used for obtaining an actual power value according to the current value and the voltage value of the speed measurement unit;
and the power adjusting unit is used for providing constant heating power for the speed measuring unit according to the actual power value and the power set value.
As shown in fig. 2, the power adjusting unit includes:
the power amplifier comprises an operational amplifier and a triode, wherein the operational amplifier adjusts the triode according to an actual power value and a power set value so as to output constant power.
As shown in fig. 2, the current detection unit includes a current detection element and a gain amplifier;
the gain amplifier is used for amplifying the voltage of the current detection element, so that the output value of the gain amplifier is consistent with the current value of the speed measurement unit. The current detection element is a resistor, the resistance value of the current detection element is 0.1 ohm, and the gain of the gain amplifier is 10.
As shown in fig. 2, the voltage detection unit includes a first differential amplifier connected in parallel to both ends of the speed measurement unit. Wherein the gain of the first differential amplifier is 1.
In one embodiment, the speed measuring unit and the temperature measuring unit are both electric heating elements. Wherein, the electric heating element is a platinum resistor.
In one embodiment, the voltage values of the speed measurement unit and the temperature measurement unit are amplified by a second differential amplifier and then go through a linearization circuit to obtain the mass flow.
As shown in fig. 2, RT1 and RT2 are temperature measurement and tachometer resistor, respectively, in the present invention, the tachometer resistor RT2 is also a heating element of constant power principle, and in order to ensure the heating power on the tachometer resistor to be constant, the constant power circuit shown in fig. 2 is adopted.
The power P of the tachometer resistor RT2 is I0I 0 RT 2I 0U.
I0 is RT2 flowing current, U is RT2 two-end voltage, RT2 is about 50 ohm generally; r3 is a current detection element, has a resistance of 0.1 ohm, has a voltage of 0.1 × I0 at both ends, and has a voltage of 0.1 × I0 × 10 ═ I0 after 10-time gain amplification; meanwhile, the voltage of the speed measuring resistor RT2 is differentially amplified by the gain of 1 to output a voltage U, the voltage U and the current I0 are multiplied by a multiplier to output a power signal, and after negative feedback stabilization is formed by an operational amplifier and a triode Q1, constant power conforming to a power set value is output on the speed measuring resistor RT 2; along with different flow rates, the voltage difference values of the tachometer resistor RT2 and the thermometric resistor RT1 are also different, and the mass flow is obtained by the operation of a linear circuit after passing through the differential amplifier.
The adjustment process of the operational amplifier and the triode Q1 is as follows: when the power value output by the multiplier changes, the difference value between the power value and the power set value is amplified by the operational amplifier so as to control and adjust the base current of the transistor Q1 and change the voltage drop between the emitter and the collector, thereby keeping the output power stable.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (10)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN202011120727.5A CN112393777A (en) | 2020-10-19 | 2020-10-19 | Constant-power thermal type gas mass flow meter |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202011120727.5A CN112393777A (en) | 2020-10-19 | 2020-10-19 | Constant-power thermal type gas mass flow meter |
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| CN112393777A true CN112393777A (en) | 2021-02-23 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113108856A (en) * | 2021-04-14 | 2021-07-13 | 合肥工业大学 | Constant-power thermal mass flowmeter with pure hardware circuit and calibration method thereof |
| CN114440998A (en) * | 2021-12-20 | 2022-05-06 | 重庆川仪自动化股份有限公司 | Fluid mass flow measuring circuit and fluid mass flow meter |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0443919A (en) * | 1990-06-11 | 1992-02-13 | Yamatake Honeywell Co Ltd | Heater temperature control circuit |
| CN101221060A (en) * | 2007-12-28 | 2008-07-16 | 当代天启技术（北京）有限公司 | Thermal dissipation type mass flowmeter and method for measuring mass flux |
| CN107689833A (en) * | 2017-09-29 | 2018-02-13 | 武汉光迅科技股份有限公司 | A kind of apparatus and method of VOA power limitation controls |
-
2020
- 2020-10-19 CN CN202011120727.5A patent/CN112393777A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0443919A (en) * | 1990-06-11 | 1992-02-13 | Yamatake Honeywell Co Ltd | Heater temperature control circuit |
| CN101221060A (en) * | 2007-12-28 | 2008-07-16 | 当代天启技术（北京）有限公司 | Thermal dissipation type mass flowmeter and method for measuring mass flux |
| CN107689833A (en) * | 2017-09-29 | 2018-02-13 | 武汉光迅科技股份有限公司 | A kind of apparatus and method of VOA power limitation controls |
Non-Patent Citations (1)
| Title |
|---|
| 汪栋良: "井下恒功率热式流量计设计与实现", 石油管材与仪器, vol. 4, no. 2 * |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113108856A (en) * | 2021-04-14 | 2021-07-13 | 合肥工业大学 | Constant-power thermal mass flowmeter with pure hardware circuit and calibration method thereof |
| CN113108856B (en) * | 2021-04-14 | 2022-05-27 | 合肥工业大学 | Constant-power thermal mass flowmeter with pure hardware circuit and calibration method thereof |
| CN114440998A (en) * | 2021-12-20 | 2022-05-06 | 重庆川仪自动化股份有限公司 | Fluid mass flow measuring circuit and fluid mass flow meter |
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Application publication date: 20210223 |