JP3144146B2 - Vortex flow meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vortex flowmeter for detecting an alternating force generated in a vortex generator by a Karman vortex corresponding to a flow of a measurement fluid and extracting the signal as a vortex flow signal. The present invention relates to a vortex flowmeter improved so as not to be affected by vibration noise generated when it is present.

[0002]

2. Description of the Related Art FIG. 3 is a structural view showing a cross section of a detecting section of a conventional vortex flowmeter. Reference numeral 10 denotes a pipe through which a fluid flows, and reference numeral 11 denotes a cylindrical nozzle provided at right angles to the pipe 10. 12
Is a column-shaped vortex generator having a trapezoidal cross-section inserted into the conduit 10 at a distance from the nozzle 11.

[0003] One end is supported by a pipe 13 by a screw 13 and the other end is fixed to the nozzle 11 by a screw or welding by a flange portion 14. Reference numeral 15 denotes a concave portion provided on the flange portion 14 side of the vortex generator 12.

In the recess 15, a metal pedestal 16, a piezoelectric element 17, an electrode plate 18, and an insulating plate 1 are sequentially arranged from the bottom thereof.
9, an electrode plate 20, and a piezoelectric element 21 are arranged in a sandwich shape, and these are pressed and fixed by a metal pressing rod 22.

Further, lead wires 23 from the electrode plate 18,
Lead wires 24 are led out from the electrode plate 20 to terminals A and B, respectively. Each of the piezoelectric elements 17 and 21 is
The left and right sides of the papers 7 and 21 are polarized in opposite directions, respectively, and generate opposite-polarized charges on the upper and lower electrodes with respect to the stress in the same direction.

The electric charge generated in the piezoelectric element 17 is applied to the electrode plate 1
The charge generated between the terminal A connected to the electrode plate 8 and the conduit 10 connected through the base 16 and generated in the piezoelectric element 21 is connected to the terminal B connected to the electrode plate 20 and the pressing rod 20. Between the pipes 10 and 10.

The charges generated on the electrode plates 18 and 20 are as follows:
As shown in FIG. 4, it is input to the charge amplifiers 25 and 26.
The output of the charge amplifier 25 and the output of the charge amplifier 26 via the volume 27 are added by an adder 28 to obtain an eddy flow signal.

A charge converter 29 is constituted by the charge amplifiers 25 and 26 and the adder 28.
The vortex flow signal appearing at the output of the adder 28 is
Are filtered to remove high-frequency noise and output to the Schmitt circuit 31.

Here, the Schmidt circuit 31 uses this vortex flow rate.
Frequency signal f proportional to the flow rate ₁Convert to frequency
/ DC eddy flow to output terminal 33 via voltage conversion circuit 32
Signal V₁Output as

Next, the operation of the vortex flowmeter configured as described above will be described. When the measurement fluid flows through the pipe 10, vibrations due to the Karman vortex are generated in the vortex generator 12 in the direction indicated by the arrow F.

Due to this vibration, stress is alternately generated in the vortex generator 12. As a result, each piezoelectric element 17, 2
1, the charges are generated alternately on the left and right sides of the paper surface, and appear at terminals A and B.

Actually, in addition to the vortex flow signal based on the Karman vortex, a pipe vibration which becomes noise also occurs. With respect to this noise, the fixed position of the piezoelectric elements 17 and 21 is made different in the longitudinal direction of the vortex generator 12 to change the ratio affected by the pipeline vibration with respect to the vortex flow signal. The minute is canceled and only the component of the vortex flow signal is output.

[0013]

However, in the vortex flowmeter described above, consideration is given to noise due to piping vibrations and the like. The vortex flow signals appearing in A and B may be locked in synchronization with the fluid pulsation, causing the entire fluid to vibrate and the vortex flow signals to disappear.

[0014]

According to the present invention, an eddy flow signal is detected by detecting an alternating signal caused by a Karman vortex generated from a vortex generator in accordance with a flow rate of a measurement fluid. Vortex detection means for detecting the drag generated by the previous measurement fluid on the previous vortex generator, and outputting it as a drag signal, the frequency of the previous vortex flow rate signal and the frequency of the previous drag signal And a switch for stopping the output of the vortex flow signal based on the output of the comparator.

[0015]

[Operation] The vortex detecting means detects an alternating signal due to Karman vortex generated from the vortex generator in accordance with the flow rate of the measurement fluid and outputs the signal as a vortex flow rate signal. The drag detecting means detects the drag generated by the measurement fluid in the previous vortex generator and outputs it as a drag signal.

When the fluid vibration is generated, the vortex flow signal is also synchronized with the fluid vibration. Therefore, the comparing means determines whether or not the frequency of the previous vortex flow signal and the frequency of the previous drag signal have the same value. When the output of the vortex flow rate signal is stopped by the switch means at the time of, the influence of noise output based on fluid vibration can be avoided.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration showing one embodiment of the present invention, and FIG. 2 is a longitudinal sectional view showing a specific configuration of the detection unit shown in FIG. Parts having the same functions as those of the conventional vortex flowmeter shown in FIGS. 3 and 4 are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

A vortex flow rate signal corresponding to the flow rate of the measurement fluid is generated in the piezoelectric elements 17 and 21 in the same manner as in the prior art, and the charge converter 29, the low-pass filter 30, and the Schmitt circuit 3 are generated.
1, and outputs it as the vortex flow signal V ₁ of the direct current to the output terminal 33 via a frequency / voltage converter circuit 32.

On the other hand, as shown in FIG. 2, at a position corresponding to the center of the pipe 10 of the vortex generator 34 and facing the flow of the measurement fluid, the vortex generator 34 is
A drag detection element 35 composed of a gauge or the like for measuring a drag generated in the sensor is fixed.

The drag detection element 35 outputs a drag signal V ₂
Is output to the amplifier 36 and amplified. After that, the high-frequency noise is removed by the low-pass filter 37 and output to the Schmitt circuit 38.

The Schmitt circuit 38 converts the alternating signal output from the low-pass filter 37 into a frequency signal f ₂ and outputs it to a frequency / voltage conversion circuit 39. Here, the frequency signal f ₂ is converted into a DC drag signal V ₂ and output to the comparison circuit 40.

The comparison circuit 40 compares the eddy flow signal V ₁ with the drag signal V _2, and when these values become equal,
When the switch 41 is turned on, the vortex flow signal V ₁ is output from the output terminal 33.
Output to

In the above configuration, in the normal state where there is no fluid vibration, a drag with a small value does not fluctuate in the drag detecting element 35 due to the measurement fluid. Accordingly, the drag signal V ₂ has a small value.

On the other hand, the vortex generator 3 is
4, an alternatingly varying electric charge is generated due to the Karman vortex, which generates an eddy flow signal V ₁ at the output end 33 with a required magnitude. Therefore, the comparison circuit 40 holds the switch 41 in the off state, and permits the generation of the eddy flow signal V ₁ at the output end 33.

However, if fluid vibration occurs in the measurement fluid flowing inside the pipe 10 for some reason, the entire measurement fluid inside the pipe 10 starts to vibrate in synchronization with the vibration. Therefore, signals of the same frequency are generated in the piezoelectric elements 17 and 21 and the drag detecting element 35 by the alternating vibration of the same frequency.

Therefore, the vortex flow signal V ₁ and the drag signal V ₂
Since bets are the same size, the comparison circuit 40 detects this and stops the output of the vortex flow signal V ₁ the switch 41 as an on. For this reason, a signal based on the fluid vibration does not appear at the output end and no erroneous signal is output.

[0027]

According to the present invention, as described above in detail with the embodiment, a drag detecting means for detecting a drag is provided, and when these signals are compared with the eddy flow signal, when these signals have the same value. Since the output of the vortex flow rate signal is cut off, an alternating signal caused by fluid vibration can be identified, and no erroneous signal is output.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of one embodiment of the present invention.

FIG. 2 is a longitudinal sectional view showing a configuration of a detection unit shown in FIG.

FIG. 3 is a longitudinal sectional view showing a configuration of a detection unit of a conventional vortex flowmeter.

FIG. 4 is a configuration diagram showing a configuration of a vortex flowmeter shown in FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Pipeline 12, 34 Vortex generator 17, 21 Piezoelectric element 18, 20 Electrode plate 29 Charge converter 30, 37 Low-pass filter 31, 38 Schmitt circuit 32, 39 Frequency / voltage conversion circuit 35 Drag detection element 40 Comparison circuit 41 switch

Claims (1)

(57) [Claims] 1. A vortex detecting means for detecting an alternating signal due to Karman vortices generated from a vortex generator in accordance with a flow rate of a measurement fluid and outputting the signal as a vortex flow rate signal, the vortex generator being generated by the measurement fluid. Drag detecting means for detecting a drag and outputting it as a drag signal; comparing means for judging whether the frequency of the eddy flow signal and the frequency of the drag signal have the same value; and outputting the vortex flow signal by the output of the comparing means. And a switch means for stopping the output of the vortex flowmeter.