JPS62119412A - Vortex flowmeter - Google Patents

Abstract

PURPOSE:To achieve a higher measuring accuracy, by detecting a displacement of a metal diaphragm due to a difference in a Karman's vortex generated according to the flow rate as changes in the electric resistance. CONSTITUTION:When a differential vortex pressure due to a Karman's vortex generated according to the flow rate of a fluid to be measured is introduced into lead chambers 12a and 12b through a different vortex pressure introduction holes 5a and 5b, metal diaphragms 9a and 9b are displaced differentially accompanied by the movement of a sealing liquid 16 as conducting liquid. As a result, the interval changes between the metal diaphragm 9a and 9b and fixed electrodes 11a and 11b to vary electric resistance value through the sealing liquid 16 therebetween. So to speak, the displacement of the metal diaphragm 9a and 9b due to differential vortex of the Karman's vortex is detected as change in the electric resistance between the metal diaphragms 9a and 9b and fixed electrodes 11a and 11b and a flow rate measurement signal is outputted from a flow rate detecting section 1.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an eddy flow meter, and more particularly to an eddy current submeter that detects the vortex differential pressure of a Karman vortex generated by a vortex generator as a displacement of a diaphragm.

Conventional technology In general, a vortex flow meter has a vortex generator installed in a fluid flow path, and a pair of diaphragms are displaced by the vortex differential pressure of Karman vortices that are alternately generated downstream of the vortex generator, and the displacement of the diaphragm is measured. It is configured to measure the flow rate and flow velocity of the fluid to be measured by detecting the . Conventionally, as a means for detecting the displacement of a diaphragm, an electrostatic capacitance type detection means has been used. In other words, a fixed electrode is provided at a position facing and separated from the diaphragm, and an insulating fluid (such as silicone oil) is placed in the space between the diaphragm and the fixed electrode.
The diaphragm and fixed electrode form a parallel plate type capacitor, and the change in capacitance of the capacitor due to displacement of the diaphragm is extracted as a flow signal.

Problems to be Solved by the Invention As mentioned above, conventional vortex flowmeters are configured to detect displacement of a diaphragm as a change in capacitance of a capacitor formed by a diaphragm and a fixed electrode. The pair of capacitors formed by the above are configured to generate the above-mentioned flow rate signal by being incorporated into a bridge circuit. However, in electrostatic marine vortex flowmeters, the change in capacitance of the capacitor due to diaphragm displacement is small, so in order to generate a good flow signal, the frequency of the power supply applied to the bridge circuit must be increased. Due to this, in order to prevent disturbances, each of the above capacitors and a preamplifier that detects and amplifies the flow rate signal must be placed close to each other.
bridge circuit.

There was a problem in that the stray capacitance of the lead wire connecting the preamplifier etc. had to be selected to be small and stable.

Therefore, an object of the present invention is to provide a vortex flowmeter that solves the above problems by detecting the displacement of the diaphragm as a change in electrical resistance.

Means for Solving the Problems In order to solve the above problems, in the present invention, the vortex current meter is provided with a vortex generator disposed in the flow path of the piping, which is displaced in accordance with the pressure difference between the vortices generated on both sides of the vortex generator. A diaphragm, a fixed electrode disposed facing away from the diaphragm, and a conductive liquid filled in a space between the diaphragm and the fixed electrode are provided, and the diaphragm and the fixed electrode are separated by displacement of the diaphragm. The flow rate is detected based on the change in electrical resistance of the conductive liquid according to the change in the distance between the conductive liquid and the conductive liquid.

Embodiment FIG. 2 shows a flow a detection section of an embodiment of the vortex flowmeter according to the present invention. The flow rate detection section 1 shown in FIG. 2 is attached to the upper surface 2a of the pipe 2 as shown in FIG. 3. Figures 4 and 5
As shown in the figure, a vortex generator 4 is provided in the flow path 3 in the pipe 2. The vortex generator 4 has a differential pressure introduction hole 5a communicating with the flow path 3 from both sides.

5b. Further, above the flow rate detection section 1, a circuit case 6 is provided which includes an electric circuit that outputs a pulse signal according to the signal detected by the flow rate detection section 1.

A pair of sensor parts 7a and 7b are provided inside the mounting member 1a of the flow rate detection part 1 shown in FIG. Sensor section 7
a is a mounting member 1a provided below the diaphragm chamber 8a;
It consists of a metal diaphragm 9a as a movable electrode connected to the metal diaphragm 9a, and a fixing member 111a facing the metal diaphragm 9a at a predetermined distance wi and placed on the surface of the insulator 10a above the diaphragm chamber 8a. Further, the sensor section 7b has the same configuration as the sensor section 7a described above, and includes a metal diaphragm 9b and a fixed electrode 11b. Below the metal diaphragms 9a and 9b are conductive pressures v12a and 12, respectively.
b are formed to face each other.

These pressure guiding chambers 12a, 12t) communicate with differential pressure introduction holes 5a, 5b of the vortex generator 4. Therefore, the metal diaphragms 9a and 9b are the differential pressure introduction holes 5a.

It is displaced in response to the high differential pressure introduced into the pressure chambers 12a and 12b via the pressure chambers 12a and 12b. 13 is an O-ring, the pressure chamber 12a,
12b and the mounting member 1a are sealed.

Reference numeral 14 denotes a communication hole, which is a recess provided in the intermediate mounting member 1a between the pair of sensor parts 7a and 7b.

A pair of sensor portions 7a are provided at the bottoms of the communication holes 14, respectively.

Conduction holes 14a and 14b communicating with 7b are provided.

The communication hole 14 and the communication holes 14a and 14b constitute a communication path 15 that communicates between the diaphragm chambers 8a and 8b of the pair of sensor sections 7a and 7b.

The communication passage 15 and the diaphragm chambers 8a, 8b are filled with a conductive liquid having a predetermined electrical resistance as an incompressible liquid 16. 17 is a stopcock,
The opening of the communication hole 14 for filling the communication path 15 with the sealed liquid 16 is closed.

Here, a case in which fluid is supplied into the flow path 3 of the piping 2 and the flow rate is measured will be explained. The pressure difference due to the Karman vortex generated on the downstream side of the vortex generator 4 according to the flow rate of the 1fI fluid flowing in the flow path 3 is caused by the high differential pressure introduction holes 5a and 5b of the vortex generator 4.
When introduced into the pressure chambers 12a, 12b, the metal diaphragms 9a, 9b are differentially displaced as the sealed liquid 16 moves. With this differential displacement of the metal diaphragms 9a, 9b, each metal diaphragm 9a, 9b and the fixed electrode 11a
.

11b is subject to change. As described above, the metal diaphragms 9a, 9b and the fixed electrode 11a.

A sealed liquid 16 having a predetermined resistance value is interposed between the metal diaphragms 9a and 9b, and the volume of the sealed liquid 16 in the diaphragm chambers 3a and 8b changes as the metal diaphragms 9a and 9b are displaced. As a result, the electrical resistance value between each metal diaphragm 9a, 9b and the fixed electrodes 11a, 11b corresponds to the displacement of the metal diaphragm 9a, 9b, in other words, corresponds to the generation cycle of the alternating vortex differential pressure of the Karman vortex. and change. That is, in the vortex flow meter according to the present invention, the displacement of the metal diaphragms 9a, 9b due to the vortex differential pressure of the Karman vortex is detected as a change in electrical resistance between the metal diaphragms 9a, 9b and the fixed electrodes 11a, 11b, and the flow rate detection section 1 outputs a flow rate measurement signal.

Sensor section 7a detected by flow rate detection section 1.

The electrical resistance change of 7b is caused by the lead wires 18a, 18b connected to the fixed electrodes 11a, 11b and the lead wires 1 connected to the metal diaphragms 9a, 9b via the mounting member 1a.
It is supplied to the circuit in the circuit case 6 by 8c. At this time, the metal diaphragm 9a.

Since the displacement of 9b is detected as a change in electrical resistance,
The influence of the stray capacity of each lead wire 18a to 18G is small and need not be taken into consideration.For example, even if the flow rate detection unit 1 and the circuit case 6 are arranged relatively apart, noise may be generated in the flow rate measurement signal due to disturbance. Nothing happens. Therefore, for example, when measuring the flow rate of a high-temperature fluid to be measured, the flow rate detection unit 1 becomes high temperature, but it becomes possible to arrange the flow rate detection unit 1 apart from the circuit case 6, and the electronics inside the circuit case 6 It is possible to prevent equipment etc. from being damaged by heat.

As shown in FIG. 1, the circuit inside the circuit case 6 includes a bridge circuit 19. Amplification circuit 20. The demodulation circuit 21 is roughly composed of a Schmitt circuit 22.

In addition, in the figure, 25a and 25b are metal diaphragms 9a,
Filled liquid 1 interposed between 9b and fixed electrodes 11a and 11b
It shows a resistance of 6 and also 26a.

26b is a variable resistor that performs zero point adjustment to balance the bridge circuit 19 before starting measurement.

Lead wire 18a drawn into circuit case 6.

18b is a coil 23a forming one bridge circuit.

23b. Further, the lead wire 18C is connected to the amplifier circuit 20. 24 is an AC power supply that supplies AC to the bridge circuit 19. Therefore, the Karman vortex is generated by the vortex generator 4 in proportion to the outflow of the fluid.
occurs alternately on both sides of the , resulting in antiphase pressure changes. This opposite phase pressure change is introduced into the pressure chambers 12a, 12b via the differential pressure introduction holes 5a, 5b. For this reason, the metal diaphragm 9a of the pair of sensors gA7a, 7b.

9b is differentially displaced by pressure changes in opposite phases, and metal diaphragms 9a, 9b and fixed type Fi11a.

11b increases and decreases in opposite phases.

The frequency of the change in electrical resistance of the sensor sections 7a, 7b is proportional to the flow of fluid in the flow path 3. According to the flow measurement signals detected by the pair of sensor sections 7a and 7b in this manner, the bridge circuit 19 outputs a signal that is amplitude-modulated from the AC signal from the AC power source 24 at a frequency proportional to the flow rate/flow rate of the fluid. . At this time, the bridge circuit 19 has a resistor 25a,
Consisting of 25 b s variable resistors 26a and 26b,
Since it is a so-called resistance bridge, the frequency of the applied alternating current voltage can be lowered compared to a capacitive bridge. Further, the signal output from the bridge circuit 19 is amplified by an amplifier circuit 20 and demodulated by a demodulation circuit 21. The output from the demodulation circuit 21 is output from the Schmitt circuit 22 as a pulse signal 27 with a frequency proportional to the fluid flow rate/flow rate.

It should be noted that the present invention is not limited to the above-mentioned embodiment, but includes, for example, a diaphragm chamber 29a formed in a vortex generating body 29 provided in a flow path 28 as shown in FIG.

Metal diaphragms 30a, 30b and fixed electrode 3 are attached to 29b.
1a, 31b and each diaphragm chamber 29a.
, 29b and a communication passage 32 that communicates both chambers may be filled with a conductive liquid 33.

Effects of the Invention As described above, according to the vortex flowmeter of the present invention, the vortex flowmeter includes a diaphragm that is displaced in accordance with the differential pressure caused by the vortex generated on both sides of the vortex generator provided in the flow path of the piping; A fixed electrode is arranged facing away from the diaphragm, and a conductive liquid is filled in the space between the diaphragm and the fixed electrode. Since the displacement of the diaphragm is detected as a change in electrical resistance, the frequency of the AC voltage applied to the bridge circuit is It is possible to reduce the negative effects of the stray volume ω of the components of the flow rate detection section including the lead wires and the electronic circuits in the circuit case, and the flow rate signal is not contaminated with noise, improving measurement accuracy. In addition to this, it is also possible to separate the flow rate detection section and the circuit case, which is particularly useful when measuring the flow rate of high-temperature fluids.
It has features such as being able to protect the electronic equipment and circuits inside the circuit case from the heat of the fluid being measured.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a flow rate measuring circuit of an embodiment of the vortex flowmeter according to the present invention, FIG. 2 is a sectional view of the flow rate detection section of the vortex flowmeter according to the present invention, and FIG. FIG. 4 is a side view of FIG. 3, FIG. 5 is a sectional view taken along line A-A in FIG. 4, and FIG. 6 is a vortex flow meter according to the present invention. FIG. 3 is a sectional view showing another embodiment of the invention. DESCRIPTION OF SYMBOLS 1... Flow rate detection part, 3, 28... Flow path, 4, 29...
...Vortex generator, 6...Circuit case, 7a, 7b...
Sen 9 parts, 8a, 8b, 2'9a, 29b...Diaphragm chamber, 9a, 9b, 30a, 30b...Metal diaphragm, 10a, 10b-Insulator, 118.11b.
...Fixed electrode, 14...Communication hole, 14a, 14b...
・Communication hole, 15, 32...Communication path, 16.33...
Filled liquid, 19...Bridge circuit, 26a, 26b...
・Variable resistor. Figure 3 Figure 5 Figure 6

Claims (1)

[Claims] A diaphragm that is displaced in response to a pressure difference caused by a vortex generated on both sides of a vortex generator provided in a flow path of piping, a fixed electrode disposed at a distance from and facing the diaphragm, and the diaphragm and the fixed electrode. and a conductive liquid filled in the space between the diaphragm and the fixed electrode, and the flow rate is detected by a change in electrical resistance of the conductive liquid in response to a change in the distance between the diaphragm and the fixed electrode due to displacement of the diaphragm. A vortex flow meter characterized by: