JP3021781B2 - 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, and more particularly to a vortex flowmeter capable of obtaining good measurement data.

[0002]

2. Description of the Related Art Conventionally, there is a vortex flow meter as a flow meter for measuring a flow rate. This vortex flowmeter generates a so-called Karman vortex street downstream of a vortex generating column provided in a pipe, and measures the flow rate of a fluid flowing in the pipe based on the generation cycle of the vortex. . Some vortex flowmeters of this type are configured as shown in FIG. 4 in order to prevent a decrease in flow rate detection sensitivity due to changes in external conditions such as temperature.

[0003] In the drawings, reference numeral 1 denotes a pipe through which a fluid flows. A vortex generator 2 having a triangular cross section (may be a trapezoidal cross section or the like) is provided in the pipeline 1 so as to be substantially perpendicular to the cross section. Then, the Karman vortex streets 3, 3,... Are generated on the downstream side of the vortex generator 2 by the fluid flowing in the pipe line 1. On the downstream side of the vortex generator 2, an ultrasonic transmission element (ultrasonic sensor) for transmitting ultrasonic waves to a fluid flowing in the pipe 1 on a side of the pipe 1.
4, 4 are provided, and these ultrasonic transmitting elements 4, 4 are provided.
Is connected to a transmission circuit 6 via a selection circuit 5. In addition, an ultrasonic receiving element (ultrasonic wave) that receives ultrasonic waves transmitted from the ultrasonic wave transmitting elements 4 and 4 and propagated in the fluid at a position facing the ultrasonic wave transmitting elements 4 and 4 is provided in the pipe 1. Sensors 7) and 7) are provided. A phase comparison circuit 8 compares the phase of the received ultrasonic wave with a previously input phase, detects a change in the phase, and outputs detected data.
Is connected to the phase comparison circuit 8, and a flow rate calculator 9 for calculating the flow rate of the fluid from the detection data is connected.

Here, the structure of the ultrasonic transmitting element 4 and the ultrasonic receiving element 7 is, as shown in FIG. 5, a structure in which an element 13 is placed inside a holder main body 12 having a diaphragm 11 at a tip end. The element 13 is supported in a state where the element 13 is pressed against the diaphragm 11 by the urging force of the compression spring 14. That is, when used as the ultrasonic wave transmitting element 4, by supplying a drive signal to the element 13 via the lead wire 15, the element 13 vibrates and vibrates the diaphragm 11 to transmit ultrasonic waves. It has become. When used as the ultrasonic receiving element 7, the ultrasonic wave is transmitted to the diaphragm 11 so that the diaphragm 11
Vibrates to cause the element 13 to vibrate, and this vibration is output as a signal via the lead wire 15. Further, a temperature sensor 16 is provided further downstream of the pipeline 1, and the temperature sensor 16 has a temperature monitor circuit 1.
7 is connected. The detection signal output from the temperature sensor 16 is output to the selection circuit 5 via the temperature monitor circuit 17.

[0005] Based on the detection signal, the selecting circuit 5 selects the ultrasonic wave transmitting elements 4 and 4 and the ultrasonic wave receiving elements 4 from among the driving signals a, b and c output from the transmitting circuit 6 and having different transmitting frequencies. The element having the highest transmission / reception gain of the elements 7, 7 is selected and supplied to the ultrasonic transmission elements 4, 4. Here, for example, when the temperature of the fluid changes from A ° C. to B ° C., the transmission / reception gain characteristics of the ultrasonic transmitting elements 4 and 4 and the ultrasonic receiving elements 7 and 7 are the temperature characteristics (the element 13 or the diaphragm 11). As shown in FIG. 6, the transmission / reception gain Ga at the transmission frequency fa changes to the temperature B ° C. at the temperature A ° C. by changing from A to B as shown in FIG. Gc, so at temperature B ° C.
The selection circuit 5 outputs the driving signals a,
The one closest to the transmission frequency fb is selected from b and c, and the transmission / reception gain is corrected so as to approach the best state Gb.

[0006]

In the prior art, since the transmission frequency is corrected in accordance with the temperature, the ultrasonic transmitting elements 4, 4 and the ultrasonic receiving elements 7, 4 corresponding to the temperature change. 7, a change in transmission / reception gain, that is, the temperature characteristics of each of the ultrasonic transmitting elements 4 and 4 and the ultrasonic receiving elements 7 and 7 had to be checked in advance. In addition, each time the ultrasonic transmitting elements 4 and 4 and the ultrasonic receiving elements 7 and 7 are replaced with other ones, the temperature characteristics of the ultrasonic transmitting element and the ultrasonic receiving element to be newly installed and
That is, unless the thickness of the diaphragm 11, the characteristics of the element 13 itself, and the like are checked and the correction reference of the selection circuit 5 is changed in accordance with the temperature characteristics, it is impossible to select a drive signal having an optimum transmission frequency. There were drawbacks.

The present invention has been made in view of the above circumstances, and provides an eddy flow meter capable of correcting a transmission frequency of an ultrasonic wave very easily and accurately to prevent a reduction in transmission / reception gain. It is intended to provide.

[0008]

A vortex flowmeter according to the present invention comprises:
In a vortex flowmeter for providing a vortex generator in a conduit and measuring a flow rate based on a Karman vortex street generated in the fluid by the vortex generator, the vortex flowmeter is provided downstream of the vortex generator and is superimposed into the fluid. An ultrasonic sensor for transmitting a sound wave and detecting the modulation of the ultrasonic wave by the Karman vortex street to determine the generation cycle of the vortex of the Karman vortex street and measuring the flow rate, and provided in the conduit, into the fluid And correcting means for transmitting a ultrasonic wave, detecting a change in transmission / reception gain of the ultrasonic wave, and correcting the transmission frequency of the ultrasonic sensor based on the change in the transmission / reception gain.

[0009]

According to the vortex flowmeter of the present invention, the correction means constantly monitors the change of the transmission / reception gain due to the temperature change of the fluid,
Since the frequency of the ultrasonic wave transmitted from the ultrasonic sensor is corrected, it is possible to prevent the transmission / reception gain from being reduced even if the temperature changes.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a vortex flow meter according to the present invention will be described below with reference to FIGS. Note that the same reference numerals are given to the same structural parts as in the related art, and description thereof will be omitted. As shown in the figure, a correcting ultrasonic transmitting element 21 and a correcting ultrasonic receiving element 22 are provided at opposing positions on the side of the pipeline 1 on the upstream side of the vortex generator 2. The correction ultrasonic transmission element 21 and the correction ultrasonic reception element 22 are the same as the ultrasonic transmission elements 4 and 4 and the ultrasonic reception elements 7 and 7, respectively, that is, those having the same temperature characteristics. ing. The correction ultrasonic transmission element 21 is connected to a correction transmission circuit 23, which outputs a drive signal to the correction ultrasonic transmission element 21 to transmit ultrasonic waves.

A receiving circuit 24 is connected to the correcting ultrasonic receiving element 22, and the correcting ultrasonic receiving element 2
The ultrasonic wave received at 2 is converted into a received signal by the receiving circuit 24 and output. A signal level detection circuit 25 is connected to the reception circuit 24. The signal level detection circuit 25 monitors the signal level of the reception signal, and outputs a reception level detection signal when the signal level decreases. . The controller (correction means) 26 is connected to the signal level detection circuit 25. The controller 26 controls the transmission circuit 6 and the correction transmission circuit 23 by outputting a frequency setting signal based on the reception level detection signal output from the signal level detection circuit 25 so that the transmission circuit 6 and the correction It corrects the frequency of the drive signal output from the transmission circuit 23.

Next, the operation of measuring the flow rate by the vortex flowmeter configured as described above will be described. When the fluid flows through the pipe 1, a so-called Karman vortex street 3, downstream of the vortex generator 2,
3 ... occur. The Karman vortex streets 3, 3,... Modulate the phase of the ultrasonic waves transmitted from the ultrasonic transmitting elements 4, 4 and propagated into the fluid. Then, the ultrasonic waves whose phases have been modulated are received by the ultrasonic receiving elements 7 and 7, the phases of the ultrasonic waves received by the phase comparison circuit 8 are compared, and the comparison data is output to the flow rate calculator 9. You. Then, the flow rate calculator 9 calculates the flow rate of the fluid flowing in the pipeline 1 based on the comparison data, and outputs the calculation result.

Next, the operation of correcting the frequency of the ultrasonic waves transmitted from the ultrasonic transmitting elements 4 and 4 for preventing the transmission / reception gain from being reduced will be described with reference to the flowchart shown in FIG. Step SP1 The ultrasonic wave transmitted into the fluid from the correction ultrasonic transmission element 21 is received by the correction ultrasonic reception element 22. Step SP2 The ultrasonic wave received by the correcting ultrasonic receiving element 22 is converted into a received signal by the receiving circuit 24. Step SP3: The signal level detection circuit 25 monitors the signal level of the received signal. Here, when the signal level has decreased, the process proceeds to step SP4. Step SP4: The signal level detection circuit 25 outputs a reception level detection signal.

Step SP5 The controller 26 outputs a frequency setting signal to the transmission circuit 6 and the correction transmission circuit 23 based on the reception level detection signal. Step SP6 Control is performed by inputting the frequency setting signal to the transmission circuit 6 and the correction transmission circuit 23, and the frequency of the drive signal output from the transmission circuit 6 and the correction transmission circuit 23 is corrected. Step SP7 By correcting the frequency of the drive signal, the frequency of the ultrasonic waves transmitted from the ultrasonic transmitting elements 4 and 4 and the correcting ultrasonic transmitting element 21 is corrected, and the process proceeds to step SP1.

That is, when the temperature of the fluid changes, as described above, the ultrasonic transmitting elements 4, 4 and the ultrasonic receiving elements 7, 4
7, the transmission / reception gain of the ultrasonic wave changes. At this time,
The correcting ultrasonic transmitting element 21 and the correcting ultrasonic receiving element 22 provided on the upstream side of the vortex generator 2 also have the same temperature characteristics as the ultrasonic transmitting elements 4, 4 and the ultrasonic receiving elements 7, 7. As a result, the transmission / reception gain similarly changes.

Here, for example, when the temperature of the fluid changes from A ° C. to B
° C, when the transmission circuit 6 is controlled by the frequency setting signal from the controller 26, the frequency of the ultrasonic waves transmitted from the ultrasonic transmission elements 4 and 4 changes from fa to fb.
It is corrected and transmitted. Thereby, the highest transmission / reception gain Gb at the temperature B can be obtained without reducing the transmission / reception gain from Ga to Gc (see FIG. 6).
That is, even if the temperature changes, the reduction of the transmission / reception gain can be eliminated, and the measurement data obtained by the flow rate calculator 9 can be made extremely reliable.

According to the vortex flow meter of the above embodiment, the ultrasonic transmitting elements 4 and 4 and the ultrasonic receiving elements 7 and 7 for measurement are used.
In order to correct the transmission / reception gain, the correction ultrasonic transmission elements 21 and 22 having the same temperature characteristics as those of the measurement ultrasonic transmission elements 4 and 4 and the ultrasonic reception elements 7 and 7 are used. For example, the ultrasonic transmitters 4 and 4 and the ultrasonic receivers 7 and 7 for measuring fluids are used.
Can be replaced with another one, the replacement of the correction ultrasonic transmission element 21 and the correction ultrasonic reception element 22 with another, that is, the same one used for the flow rate measurement is very easy. Thus, the transmission / reception gains of the other ultrasonic transmitting elements and the ultrasonic receiving elements can be corrected. Further, since the controller 26 constantly monitors the change of the transmission / reception gain, and automatically corrects the drive signal output from the transmission circuit as needed to obtain the best transmission / reception gain, the controller 26 can operate in a wide temperature range. A very effective and accurate flow measurement can be carried out over a wide range. In addition,
The specific structure and configuration of the vortex flowmeter of the above embodiment are not limited to the embodiment.

[0018]

As described above, according to the vortex flowmeter of the present invention, the following effects can be obtained. The correction means constantly monitors the change of the transmission / reception gain due to the temperature change of the fluid, and eliminates the reduction of the transmission / reception gain even if the temperature changes to correct the frequency of the ultrasonic wave transmitted from the ultrasonic emission sensor. And the measurement data can be extremely reliable. Also, the flow rate can be measured very effectively and accurately over a wide temperature range.

In order to correct the transmission and reception of the ultrasonic transmitting and receiving elements provided on the ultrasonic sensor side, a transmitting element and a receiving element having the same characteristics as the transmitting and receiving elements on the ultrasonic sensor side are used. By using, for example, when changing the transmitting element and the receiving element on the ultrasonic sensor side, only by replacing the transmitting element and the receiving element on the correcting means side with the same one used on the ultrasonic sensor side,
The transmission and reception gains of the other transmitting and receiving elements can be very easily corrected. That is, it is possible to eliminate the hassle of changing the correction reference by checking the characteristics of each of the transmitting element and the receiving element as in the related art.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view illustrating a configuration of a vortex flowmeter according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view illustrating a configuration of a vortex flowmeter according to an embodiment of the present invention.

FIG. 3 is a flowchart illustrating an operation of correcting a transmission / reception gain of the vortex flowmeter according to the embodiment of the present invention.

FIG. 4 is a schematic longitudinal sectional view illustrating the configuration of a conventional vortex flowmeter.

FIG. 5 is a cross-sectional view illustrating a structure of an ultrasonic transmitting element and an ultrasonic receiving element.

FIG. 6 is a diagram illustrating a change in transmission / reception gain due to a temperature change.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pipeline 2 Vortex generator 3 Karman vortex street 4 Ultrasonic transmitting element (ultrasonic sensor) 7 Ultrasonic receiving element (ultrasonic sensor) 26 Controller (correction means)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-134213 (JP, A) JP-A-63-201528 (JP, A) JP-B 1-331573 (JP, B2) (58) Field (Int.Cl. ⁷ , DB name) G01F 1/32 G01F 15/02

Claims (1)

(57) [Claims] 1. A vortex flowmeter for measuring a flow rate based on a Karman vortex street generated in a fluid by a vortex generator provided in a pipe line, wherein the vortex generator is provided downstream of the vortex generator. An ultrasonic sensor that transmits an ultrasonic wave into a fluid and detects the modulation of the ultrasonic wave by the Karman vortex street to determine the generation period of the vortex of the Karman vortex street and measures the flow rate, and is provided in the conduit. Correction means for transmitting an ultrasonic wave into the fluid, detecting a change in transmission / reception gain of the ultrasonic wave, and correcting the transmission frequency of the ultrasonic sensor based on the change in the transmission / reception gain. And vortex flowmeter.