JPH0646324U - Mass flow meter - Google Patents

Abstract

(57) [Summary] [Purpose] An object is to provide an improved mass flowmeter having a simple structure. [Structure] A sensor in which a pressure detecting element and a temperature detecting element are integrally mounted, a vortex generator that incorporates the sensor and generates a vortex corresponding to the flow rate of the measured fluid, and a vortex generator provided in the vortex generator. Pressure detection hole that introduces the fluid pressure in the vicinity of the vortex generator to the previous sensor and the detection signal detected by the previous pressure detection element through the low-pass filter and the previous detection Microprocessor means for obtaining a mass flow rate by executing a predetermined calculation using the flow velocity signal obtained through the high-pass filter and the temperature signal detected by the temperature detecting element It is a thing.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a mass flow meter that calculates a mass flow rate by using a vortex flow meter that measures a volume flow rate by a Karman vortex generated by a vortex generator placed in a measurement fluid, and particularly has a simple configuration. The present invention relates to a mass flowmeter improved as described above.

[0002]

[Prior art]

FIG. 4 is a configuration diagram showing a configuration of a conventional mass flow meter. A flow meter 11 for measuring a volumetric flow rate is attached to the pipe 10 through which the measurement fluid flows, and the flow rate is detected here and is output to the mass flow meter 12 as a flow rate signal Q ₁ .

Further, a pressure gauge 13 for measuring the pressure of the measurement fluid in the pipe is attached to the pipe 10, and the pressure is detected here and is output to the mass flow meter 12 as a pressure signal P ₁ .

A temperature measuring resistor 14 for measuring the temperature of the fluid to be measured in the pipe is attached to the pipe 10, and the temperature is detected here and output to the mass flow meter 12 as a temperature signal T ₁ .

The mass flow meter 12 has a microprocessor incorporated therein, and has a flow rate signal Q ₁ from the flow meter 11, a pressure signal P ₁ from the pressure gauge 13, and a temperature signal T ₁ from the resistance temperature detector 14. Are input respectively, and the calculation according to the following equations (1) and (2) is executed to obtain a mass flow rate M ₁ , for example, as a unified current of 4 to 20 mA, or as a pulse signal to a load (not shown). It is transmitted by two transmission lines.

Taking the case of gas as an example, the specific weight γ is P _f , T _f is the pressure and temperature in the operating state, P _N and T _N are the pressure in the standard state, temperature, and K is the type of gas. The coefficient is calculated as follows: γ = (P _f · T _N ) / (P _N · T _f · K) (1)

Therefore, the mass flow rate M ₁ is calculated as M ₁ = Q ₁ · γ (2) using the flow rate signal Q ₁ as the volume flow rate.

[0008]

[Problems to be solved by the device]

 However, in order to measure the mass flow rate with the above system, in addition to the flowmeter main body, the pressure gauge 13, the resistance temperature detector 14, etc. are required, which makes the device large and the cost also high. There is.

[0009]

[Means for Solving the Problems]

 The present invention has, as a configuration for solving the above problems, a sensor in which a pressure detection element and a temperature detection element are integrally mounted, and a vortex is generated in accordance with the flow rate of the measured fluid in which the sensor is built. The vortex generator to be generated, a pressure introduction hole provided in the vortex generator for introducing the fluid pressure in the vicinity of the previous vortex generator to the previous sensor, and the detection signal detected by the previous pressure detection element is low-pass filtered. The pressure signal obtained through the temperature detector and the previous detection signal are used as the flow velocity signal obtained through the high-pass filter and the temperature signal detected by the previous temperature detection element to execute a predetermined calculation to determine the mass. And a microprocessor means for obtaining a flow rate.

[0010]

[Work]

 The sensor has a pressure detection element and a temperature detection element integrally mounted, and the vortex generator has this sensor built-in and generates a vortex corresponding to the flow rate of the measured fluid. The pressure introducing hole is provided in this vortex generator to introduce the fluid pressure near the former vortex generator to the previous sensor.

The microprocessor means includes the pressure signal obtained by the low-pass filter of the detection signal detected by the pressure detection element, and the flow velocity signal obtained by the high-pass filter of the previous detection signal, and the pressure signal obtained by the high-pass filter. A predetermined calculation is executed using the temperature signal detected by the temperature detecting element to obtain the mass flow rate.

[0012]

【Example】

 Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing a main configuration of an embodiment of the present invention. FIG. 1A is a vertical sectional view, and FIG. 1B is a horizontal sectional view. Reference numeral 20 denotes a conduit through which a measurement fluid flows, and a quadrangular pyramid-shaped vortex generator 21 penetrates through the guide tube 20 and is fixed therein.

A sensor 22 is fixed in the vortex generator 21. A lead wire 23 for leading out a signal or the like from the sensor 22 is drawn out to a signal processing unit 24 having a built-in microprocessor or the like fixed to the outer peripheral surface of the conduit 20.

FIG. 2 is a sectional view taken along line AA ′ showing the details of the vortex generator 21 shown in FIG. An internal chamber 25 is formed inside the vortex generator 21, and a sensor 22 is stored in the internal chamber 25. A pressure guiding hole 26 for detecting a fluid pressure or a fluid temperature around the vortex generator 21 is formed in the inner chamber 25 so as to penetrate into the conduit 20.

The sensor 22 is composed of, for example, a diaphragm 27 made of silicon single crystal and having a rectangular outer shape, and a support portion 28 made of Pyrex glass or the like for fixing the diaphragm 27. The diaphragm 27 and the support portion 28 are joined by, for example, anodic joining.

The diaphragm 27 has a circular recess 29 in the center thereof. By forming the concave portion 29, a circular strain generating portion 30 in which the thickness of the single crystal is thin and a fixing portion 31 around the strain generating portion 30 are formed.

A strain gauge 32 for detecting the fluid pressure is formed near the boundary between the strain-flexing portion 30 and the fixed portion 31, and a temperature gauge 33 for detecting the fluid temperature is formed on the fixed portion 31. . A circuit for converting the outputs of the strain gauge 32 and the temperature gauge 33 into an electric signal is mounted on the diaphragm 27, but it is omitted.

Further, a through hole 34 that connects the recess 29 and the internal chamber 25 is formed in the center of the support portion 28. A vacuum is maintained between the recess 29 and the internal chamber 25.

FIG. 3 is a configuration diagram showing a configuration of a signal processing unit that processes a signal detected by the sensor 22. The temperature signal T ₂ is derived from the temperature gauge 33 and output to the microprocessor 35, and the pressure signal P ₂ is derived from the strain gauge 32 and output to the low pass filter 36.

The low-pass filter 36 removes the fluctuation component of the pressure signal P ₂ and outputs the pressure signal P ₃ to the micro processor 35. Further, the pressure signal P ₂ is also output to the high-pass filter 37, where the fluctuation of the pressure signal P ₂ is detected.

This variation is output to the Schmitt circuit 38, where it is converted into a pulse signal P ₄ with a predetermined threshold as a reference and output to the microprocessor 35.

The temperature signal T ₂ , the pressure signal P ₃ , and the pulse signal P ₄ are input to the microprocessor 35, and a predetermined calculation is executed using these to calculate the mass flow rate M _2. Output to the output terminal 39.

[0023] In the above configuration, the measuring fluid Q _f flows from the left side of the conduit 20, around this measurement fluid Q _f is the vortex generator 21, Karman vortices are made form behind the vortex generator 21 . Due to the formation of this vortex, a pressure fluctuation is generated around the vortex generator 21 in proportion to the number of vortices generated.

Since this pressure fluctuation occurs in proportion to the flow velocity of the measurement fluid Q _f , the strain gauge 32 of the sensor 22 changes in strain corresponding to this pressure fluctuation, which is output as the pressure signal P _2. To be done.

The pressure signal P ₂ is output as a pressure signal P ₃ which is the static pressure of the measurement fluid by removing the fluctuation of the pressure due to the Karman vortex by passing through the low pass filter 36.

The high-pass filter 37 detects a variation of the pressure signal P ₂ corresponding to the number of Karman vortices, and the Schmitt circuit 38 makes a pulse. The number of pulses of the pulse signal P ₄ is proportional to the flow velocity V of the measuring fluid.

The pressure P in the use state in the equation (1)_fAnd temperature T_fIs the pressure signal P in FIG. ₃ And temperature signal T₂And the pressure P in the standard state_N, Temperature T_NThe coefficient K depending on the type of gas is stored in advance in the memory in the microprocessor 35.

Therefore, the microprocessor 35 can calculate the specific weight γ by using the arithmetic program corresponding to the formula (1) incorporated therein. Further, the volume flow rate Q _V is calculated by a calculation program for multiplying the flow velocity V obtained from the pulse signal P ₄ by the cross-sectional area S of the conduit 20. Next, the mass flow rate M ₂ is calculated by multiplying the volume flow rate Q _V by the specific weight γ according to the equation (2).

[0029]

[Effect of device]

 As described above in detail with reference to the embodiments, according to the present invention, the mass flow rate can be measured only by the vortex flowmeter without using a device such as a resistance temperature detector or a pressure converter as in the conventional case. As a result, not only can the equipment configuration be simplified and cost can be reduced, but also the labor of instrumentation can be greatly reduced and space can be saved.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a main part of an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a detailed configuration of the sensor shown in FIG.

3 is a configuration diagram showing a configuration of a signal processing unit that processes a signal of the sensor shown in FIG.

FIG. 4 is a configuration diagram showing a configuration of a conventional mass flow meter.

[Explanation of symbols]

 10, 20 Conduit 11 Flowmeter 12 Mass flow computer 13 Pressure gauge 14 Resistance thermometer 21 Vortex generator 22 Sensor 24 Signal processing unit 25 Internal chamber 26 Pressure guide hole 27 Diaphragm 32 Strain gauge 33 Temperature gauge 35 Microprocessor 36 Low-pass filtering Vessel 37 High-pass filter

Claims (1)

[Scope of utility model registration request] 1. A sensor in which a pressure detection element and a temperature detection element are integrally mounted, a vortex generator which incorporates the sensor and generates a vortex corresponding to the flow rate of the fluid to be measured, and the vortex generator. A pressure introducing hole provided for introducing the fluid pressure in the vicinity of the vortex generator to the sensor, a pressure signal obtained by a low-pass filter for a detection signal detected by the pressure detection element, and a high detection signal. A mass flow rate, comprising: microprocessor means for performing a predetermined calculation by using a flow velocity signal obtained through a bandpass filter and a temperature signal detected by the temperature detection element to obtain a mass flow rate. Total.