JP2002296084A - Ultrasonic vortex flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flowmeter capable of measuring highly accurately in a wide temperature range without changing largely the constitution of a conventional ultrasonic sensor and a flowmeter. SOLUTION: In this ultrasonic vortex flowmeter 20, a drive signal to an ultrasonic transmitter 26 is changed to a wideband signal by a wideband transmission circuit 30, and thereby a stable ultrasonic transmission/reception characteristic not influenced by resonance point temperature drift of the ultrasonic transmitter 26 is acquired, and the using temperature range can be widened regardless of the kind of fluid (liquid, gas) to be measured. Therefore, an ultrasonic wave can be transmitted efficiently without being influenced by shift of the resonance point of the ultrasonic transmitter 26 caused by a temperature change, by driving the ultrasonic transmitter 26 beforehand by a wideband signal without switching a driving frequency to the ultrasonic transmitter 26, to thereby cope with a wide temperature range without changing the structure of a conventional ultrasonic sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic vortex flowmeter, and more particularly to an ultrasonic vortex flowmeter for measuring the flow rate of a fluid to be measured using ultrasonic waves.

[0002]

2. Description of the Related Art In an ultrasonic vortex flowmeter for measuring the flow rate of a fluid to be measured using ultrasonic waves, ultrasonic waves are transmitted and received at the resonance frequency of an ultrasonic transmitter and an ultrasonic receiver comprising an ultrasonic sensor. Thus, the optimum sound wave propagation efficiency is obtained. However, in the ultrasonic sensor, the resonance point drifts with a change in the temperature of the fluid, and as a result, the frequency band showing the optimal sound wave transmission moves. When the ultrasonic sensor is driven at a fixed frequency, the temperature range of the flow meter is determined by the temperature characteristics of the ultrasonic sensor.

In an ultrasonic sensor for liquid, since the acoustic impedance (ρc) difference between the diaphragm and the liquid is small and the propagation efficiency to the liquid is good, a wide ultrasonic transmission bandwidth can be secured. On the other hand, when measuring a gas such as a gas, the difference in acoustic impedance between the diaphragm and the gas is large and the propagation efficiency is poor, so that the ultrasonic transmission bandwidth becomes narrow. Therefore, when the ultrasonic sensor is driven at a fixed frequency, the measurable temperature range tends to be narrower with a gas flowmeter than with a liquid flowmeter.

For example, as shown in FIG. 6, in an ultrasonic type vortex flowmeter using an ultrasonic sensor as a vortex detection sensor for detecting Karman vortices generated in a fluid to be measured, a flowmeter main body 1 is provided. The vortex generator 2 is assembled inside by welding or integral molding. On the inner wall of the flow path 1a downstream of the vortex generator 2, an ultrasonic transmitter 3a composed of a set of ultrasonic sensors and an ultrasonic receiver 3b are attached so as to face each other. Also, the ultrasonic transmitter 3a
Are connected to an oscillating circuit 4 that outputs a drive signal for generating ultrasonic waves. The ultrasonic transmitter 3a and the ultrasonic receiver 3b are connected to the phase comparison circuit 7 via the amplifier circuits 5a and 5b, respectively.

The phase comparison circuit 7 compares the phase of the drive signal generated by the oscillation circuit 4 with the phase of the signal received from the ultrasonic receiver 3b, and outputs a signal corresponding to the frequency of occurrence of Karman vortices. Then, the signal output from the phase comparison circuit 7 is subjected to waveform shaping by the waveform shaping circuit 8 and then converted into a flow rate value by the flow rate calculation circuit 9.

When the fluid to be measured flows in the flow path 1a, Karman vortices proportional to the flow velocity of the fluid to be measured are alternately generated on the left and right sides downstream of the vortex generator 2. The ultrasonic wave transmitted from the ultrasonic transmitter 3a is subjected to Doppler modulation and received by the ultrasonic receiver 3b due to a change in flow caused by the generation of the Karman vortex. The Doppler modulation of the ultrasonic signal due to the Karman vortex is phase-demodulated by the amplifier circuit 5a,
Detects the occurrence frequency of the Karman vortex, and the flow rate calculation circuit 9 calculates the flow rate of the fluid to be measured.

As described above, in the method of detecting the Karman vortex by the phase modulation of the ultrasonic waves, it is necessary to cancel the influence (noise) of the change in the sound speed of the fluid to be measured through which the ultrasonic waves propagate. Therefore, in the ultrasonic vortex flowmeter, it is necessary to control so that the phase difference generated by the change in the sound velocity of the fluid to be measured through which the ultrasonic wave propagates does not exceed the range of the demodulator.

As a solution to this, as shown in FIG. 7, reception of ultrasonic waves propagating in the same fluid using ultrasonic transmitters 3a and 3c and ultrasonic receivers 3b and 3d comprising two sets of ultrasonic sensors. There is also a method of canceling the influence (noise) of the change in sound speed by comparing the phases of the signals.

The ultrasonic waves transmitted from the ultrasonic transmitters 3a and 3c propagate through the fluid to be measured and are received by the ultrasonic receivers 3b and 3d. The signals received from the ultrasonic receivers 3b and 3d are connected to the phase comparison circuit 7 via the amplifier circuits 5a and 5b.

In the phase comparison circuit 7, the ultrasonic receiver 3b,
The phase of the received signal from 3d is compared to cancel the influence (noise) of the change in sound speed and to output a signal corresponding to the frequency of occurrence of Karman vortices. Then, the signal output from the phase comparison circuit 7 is subjected to waveform shaping by the waveform shaping circuit 8 and then converted into a flow rate value by the flow rate calculation circuit 9.

The ultrasonic transmitters 3a and 3c and the ultrasonic receivers 3b and 3d have the same structure. For example, as shown in FIG.
An ultrasonic element 11 composed of a piezoelectric element is housed in the inside, and is pressed and fixed via an adhesive or a bonding agent. here,
Inside the bottom of the holder that joins the holder 10 and the piezoelectric element 11
(Plate portion) is a diaphragm 12 for transmitting and receiving ultrasonic waves.

When the piezoelectric element 11 in contact with the vibration plate 12 is vibrated in a vibration mode (longitudinal vibration) in the thickness direction, the vibration plate 1
It is generally said that the thickness of 2 is the optimum value when it is an integral multiple of 1 / 2λ with respect to the transmission frequency.

Therefore, the thickness of the diaphragm 12 is set so that the transmission and reception gain of the ultrasonic transmitters 3a and 3c becomes maximum at a temperature near the center value of the measurement temperature range.

[0014]

However, the above-mentioned conventional ultrasonic vortex flowmeter has the following problems. For example, in the conventional method of measuring the flow rate by ultrasonic waves, when the operating temperature range of the fluid to be measured is widened, the sound speed C of the ultrasonic waves changes, and the wavelength λ changes (λ = c / f). As a result, the matching between the oscillation frequency (in the case of a fixed frequency) and the diaphragm 12 (set so as to be optimal at the center temperature within the temperature range) is deteriorated, and the propagation characteristics of the ultrasonic sensor are reduced. I will.

Therefore, conventionally, as shown in FIG.
Since the temperature range Ta (shown by hatching in the figure) of the fluid to be measured spreads to the high-temperature side Tmax and the low-temperature side Tmin, the transmission / reception propagation characteristics deteriorate, and the S / N required for the circuit cannot be obtained.
Flow measurement cannot be continued at high and low temperatures.

Particularly, in the case of gas, the acoustic impedance (ρC) between the ultrasonic sensor diaphragm and the fluid to be measured is significantly different from that of the liquid, the ultrasonic wave propagation characteristics are reduced, and the ultrasonic wave transmission characteristics with respect to the frequency are: Q (quality fact indicating the sharpness of the vibration system)
It is difficult to widen the temperature range because it has a high or) and a narrow bandwidth. (1) In order to solve the above-mentioned problem, there is a method of changing the drive frequency by sweeping the frequency (changing the frequency every predetermined time) to detect the optimum frequency with respect to the temperature change. This causes a problem that the flow rate cannot be measured at the moment when the driving frequency is switched, and the circuit configuration becomes complicated. (2) There is also a method of switching to the optimum driving frequency according to the temperature, but there is a problem that the circuit configuration becomes complicated or expensive because a switching device and a temperature sensor are required. (3) There is also a method in which the drive frequency follows the movement of the resonance point by a self-excited oscillation circuit that feedbacks the resonance frequency to the transmission circuit. However, under high pressure in gas fluid measurement, etc., a sub-resonance point appears near the resonance point of the ultrasonic sensor, making it impossible to follow the movement of the resonance point, causing a jump in the oscillation frequency, etc., and stable flow measurement There is a problem that can not be performed. (4) Also, there is a method in which a plurality of sets of ultrasonic sensors are provided and switched for each temperature. This requires a plurality of sets of ultrasonic sensors, and has problems such as an increase in mounting space and an increase in cost.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a flow meter that can measure with high accuracy over a wide temperature range without greatly changing the configuration of a conventional ultrasonic sensor and flow meter.

[0018]

The present invention has the following features to solve the above-mentioned problems. According to the first aspect of the present invention, the ultrasonic transmitter includes a drive signal generating unit that outputs a drive signal having a widened frequency. Stable ultrasonic transmission / reception characteristics not affected by the temperature drift of the resonance point of the acoustic wave transmitter can be obtained, and the operating temperature range can be widened regardless of the type of fluid to be measured (liquid or gas). Therefore, by driving the ultrasonic transmitter in advance with a wideband signal without switching the driving frequency to the ultrasonic transmitter, it is possible to efficiently operate without being affected by the shift of the resonance point of the ultrasonic transmitter due to a temperature change. Ultrasonic waves can be transmitted, and a wide temperature range can be accommodated without changing the structure of a conventional ultrasonic sensor.

Further, the invention according to claim 2 is provided with temperature detecting means for obtaining the temperature of the fluid to be measured based on the frequency of the ultrasonic wave received by the ultrasonic receiver, without providing a temperature sensor or the like. The temperature of the fluid to be measured can be detected.

[0020]

Embodiments of the present invention will be described below. Here, the configuration of an ultrasonic vortex flowmeter will be described as an example of the present invention.

FIG. 1 shows an ultrasonic vortex flowmeter according to the present invention.
FIG. 1 is a block diagram illustrating a schematic configuration of one embodiment. As shown in FIG. 1, the ultrasonic vortex flowmeter 20 includes a flowmeter main body 22 formed in a cylindrical shape, and a vortex generator fixed so as to cross a flow path 22 a formed inside the flowmeter main body 22. Body 24
Having. Both ends of the vortex generator 24 are sealed by an O-ring (not shown) or the like, and are fixed to the inner wall of the flow channel 22a by screwing, welding, or the like. In addition, the vortex generator 24
May be integrally formed with the flow meter body 22 by casting.

Downstream in the flow direction of the vortex generator 24, an ultrasonic transmitter 26 and an ultrasonic receiver 28 for detecting the occurrence of Karman vortices are mounted at positions facing each other in a direction of 180 degrees. In addition, the ultrasonic transmitter 26 and the ultrasonic receiver 28
A sealing material (not shown) such as a packing or an O-ring is sandwiched between the flow meter main bodies 22 and fastened with screws or the like.

The ultrasonic transmitter 26 includes a broadband oscillation circuit 30
When a drive signal is input from the controller, the diaphragm is vibrated to generate ultrasonic waves. The ultrasonic receiver 28 that has received the ultrasonic wave transmitted from the ultrasonic transmitter 26 is an amplifier circuit 3
4 is connected to the phase comparison circuit 36.

In the phase comparison circuit 36, the transmission signal output from the vibration frequency detector 44a described later and the ultrasonic receiver 3
b) and outputs a signal corresponding to the frequency of occurrence of the Karman vortex by comparing the phase with the received signal. Then, the signal output from the phase comparison circuit 36 is subjected to waveform shaping by the waveform shaping circuit 38 and then converted into a flow rate value by the flow rate calculation circuit 40.

FIGS. 2A and 2B are diagrams showing a configuration of an ultrasonic sensor used in the ultrasonic transmitter 26. FIG. 2A is a longitudinal sectional view of the ultrasonic sensor used in the ultrasonic transmitter 26, and FIG. FIG. 4 is a plan view of a vibrator used for the sound wave transmitter 26. As shown in FIGS. 2A and 2B, the ultrasonic transmitter 26 and the ultrasonic receiver 28 include a bottomed cylindrical sensor holder 42 made of a metal member such as stainless steel or a resin member. A vibrator 44 made of a piezoelectric material is fixed using an acoustic bonding agent 46 such as a silicone adhesive or an epoxy resin.

The vibrator 44 includes a piezoelectric element 44c, a vibration frequency detector 44a that outputs vibration of the piezoelectric element 44c as an electric signal (transmission signal), a piezoelectric element 44c, and a vibration frequency detector 44a made of the same material. And are integrally joined by an electrical insulating material 44b. Further, the vibration frequency detector 44a converts a vibration frequency at which the piezoelectric element 44c vibrates upon receiving a signal from the broadband oscillation circuit 30 into an electric signal (transmission signal).

The thickness t of the vibration plate 42a of the sensor holder 42 is set to be equal to the oscillation frequency 1 in consideration of the radiation efficiency of ultrasonic waves.
/ 2λ is set to be an integral multiple n, and in the calculation, the transmission efficiency is set to be the maximum near the center temperature of the operating temperature range.

At the upper opening of the sensor holder 42, a lid 48 is provided.
Are hermetically inserted by bonding, projection welding, screwing, or the like. A lead wire extraction pipe 50 is inserted into the center hole 48 a of the lid 48. Lead wires 52 and 53 made of a PTFE wire, a urethane wire, or the like are inserted into the lead wire extracting pipe 50.

The piezoelectric element 44c is connected to the broadband oscillating circuit 30 via a lead wire 52 inserted through a lead wire extracting pipe 50. The vibration frequency detector 44a is connected to the amplifier circuit 32 via a lead wire 53 inserted through the lead wire extraction pipe 50. Further, the ultrasonic receiver 28 is connected to the amplifier circuit 34 via the lead wire 51. The transmission signal output from the vibration frequency detector 44a is input to the above-described phase comparison circuit 36.

In this embodiment, a vibrator 44 in which a piezoelectric element 44c and a vibration frequency detector 44a are integrally formed.
However, the present invention is not limited to this, and the piezoelectric element 44c and the vibration frequency detector 44a may be formed separately and mounted on the vibration plate 42a of the sensor holder 42.

Further, the ultrasonic receiver 28 only receives the ultrasonic waves transmitted from the ultrasonic transmitter 26, and does not need to provide the vibration frequency detector 44a like the ultrasonic transmitter 26. The configuration is the same as that shown in FIG.

Here, the flow measurement operation by the ultrasonic vortex flowmeter 20 configured as described above will be described.
The ultrasonic vortex flowmeter 20 is provided with a flow path 22 a of the flowmeter main body 22.
When the fluid to be measured flows into the fluid, Karman vortices are generated in the fluid to be measured by the vortex generator 24, and a pressure difference alternately occurs on the left and right sides downstream of the vortex generator 24. The ultrasonic wave transmitted from the ultrasonic transmitter 26 undergoes phase modulation due to the flow change of the alternating Karman vortex generated by the vortex generator 24.

The modulated ultrasonic wave is converted by the ultrasonic receiver 28 into an electric ultrasonic received signal. The ultrasonic reception signal converted by the ultrasonic receiver 28 is supplied to the amplifier circuit 3
4 and input to the phase comparison circuit 36. The phase comparison circuit 36 compares the phase of the reception signal output from the ultrasonic receiver 28 with the phase of the transmission signal output from the vibration frequency detector 44a, and forms a sine wave synchronized with the alternating phase lead / lag. . When this sine wave is input to the waveform shaping circuit 38, a vortex pulse is obtained. The flow rate calculation circuit 40 calculates the flow rate and thus the flow rate based on the vortex pulse,
Output the measured flow value to the outside.

The broadband oscillation circuit 30 transmits a signal having a certain bandwidth to the ultrasonic transmitter 26 and transmits the signal to the ultrasonic transmitter 2.
The sixth piezoelectric element 44 is driven. The ultrasonic transmitter 26 receives the broadband drive signal, but the piezoelectric element 44c
Vibrates at a frequency that easily vibrates near the resonance point, so that the ultrasonic transmitter 26 transmits ultrasonic waves of the above-described frequency into the fluid.

As shown in FIG. 3, the frequency of the resonance point of the ultrasonic transmitter 26 changes depending on the temperature. However,
By setting the bandwidth of the broadband transmission circuit 30 as the drift range of the resonance point that has been checked in advance, the ultrasonic frequency emitted into the fluid to be measured follows the resonance point drift of the ultrasonic transmitter 26. Therefore, unlike the conventional case, the ultrasonic emission is not disabled due to the temperature change. However, a high temperature exceeding the Curie point of the piezoelectric element 44, a bonding agent,
Naturally, it cannot cope with a temperature change exceeding the limit of the adhesive.

Similarly, as shown in FIG. 3, the frequency-reception voltage characteristics (hereinafter, ultrasonic transmission characteristics) of the ultrasonic transmitter 26 and the ultrasonic receiver 28 change with the temperature drift of the resonance point. The frequency at the maximum reception voltage of the ultrasonic receiver 28 moves substantially in the same manner as the resonance point of the ultrasonic transmitter 26.

As described above, the ultrasonic transmitter 26 and the ultrasonic receiver 28 transmit and receive ultrasonic waves at a frequency optimum for the temperature during the flow rate measurement contained in the broadband drive signal transmitted from the broadband transmission circuit 30. And maximum efficiency can be obtained.

Here, the operation and configuration of the broadband transmission circuit 30 will be described. For example, when the direct spread spectrum is used, the broadband oscillation circuit 30 uses +1 as shown in FIG.
-1, a carrier code generator 56 for determining a center frequency which is a driving frequency of the ultrasonic sensor at room temperature, and the spread code generator 54
And a spread modulator 58 for performing spread modulation with the spread code of the above and the carrier signal of the carrier generator.

In the spread modulator 58, the carrier generator 56
Is spread at the chip rate determined by the spreading code. As a result, the output of the spread modulator 58 becomes a broadband spectrum signal having a frequency band determined by the chip rate with respect to the center frequency.

As described above, by broadening the drive signal to the ultrasonic transmitter 26 by the broadband transmission circuit 30, a stable ultrasonic transmission / reception characteristic which is not affected by the resonance point temperature drift of the ultrasonic transmitter 26 can be obtained. The operating temperature range can be widened irrespective of the type (fluid, gas) of the fluid to be measured. Therefore, by driving the ultrasonic transmitter 26 in advance with a broadband signal without switching the driving frequency to the ultrasonic transmitter 26, the ultrasonic transmitter 26 is not affected by the shift of the resonance point due to the temperature change. Can transmit ultrasonic waves efficiently without changing the structure of conventional ultrasonic sensors.
Compatible with a wide temperature range.

Next, a second embodiment of the present invention will be described. FIG. 5 is a block diagram showing the configuration of the second embodiment. As shown in FIG. 5, the ultrasonic vortex flowmeter 60 of the second embodiment
The ultrasonic waves transmitted from the ultrasonic transmitters 63a and 63c propagate through the fluid to be measured and are received by the ultrasonic receivers 63b and 63d. The signals received from the ultrasonic receivers 63b and 63d are connected to the phase comparison circuit 67 via the amplifier circuits 65a and 65b.

It should be noted that the ultrasonic transmitters 63a and 63 of the second embodiment
3c and the ultrasonic receivers 63b and 63d are provided with the vibration frequency detector 4 like the ultrasonic transmitter 26 described in the first embodiment.
Since there is no need to provide 4a, the configuration is the same as that shown in FIG. 9 described above.

In the phase comparison circuit 67, the ultrasonic receiver 63
b, 63d to cancel the influence (noise) of the change in sound speed by comparing the phases of the received signals, and output a signal corresponding to the frequency of occurrence of Karman vortices. Then, the signal output from the phase comparison circuit 67 is subjected to waveform shaping by the waveform shaping circuit 68 and then converted into a flow rate value by the flow rate calculation circuit 69.

As described above, the ultrasonic eddy flow meter 60 according to the second embodiment has an ultrasonic transmitter 6 composed of two sets of ultrasonic sensors.
The effects of the change in sound speed are canceled by comparing the phases of a pair of ultrasonic reception signals transmitted through the fluid to be measured using the ultrasonic receivers 3a and 63c and the ultrasonic receivers 63b and 63d.

In the cross sensing method of the second embodiment,
In order to compare the phases of the ultrasonic waves received by the ultrasonic receivers 63b and 63d, the ultrasonic transmitters 63a and 63c need to transmit ultrasonic waves of the same frequency.

Further, the ultrasonic vortex flowmeter 6 of the second embodiment
0 indicates that the ultrasonic transmitter 63a transmits an ultrasonic wave based on the drive signal transmitted from the broadband oscillation circuit 30, and the ultrasonic frequency is extracted from the piezoelectric element 44 and amplified by the amplifier circuit 70. The signal is transmitted to the ultrasonic transmitter 63c.
To drive the ultrasonic transmitter 63c.

As described above, the ultrasonic transmitters 63a, 63
c, the ultrasonic eddy flow meter 60 configured to cancel the effect of the change in sound speed using the ultrasonic receivers 63b and 63d.
In the same manner as in the first embodiment, the broadband oscillation circuit 30 widens the drive signals to the ultrasonic transmitters 63a and 63c, so that the resonance point temperature drift of the ultrasonic transmitter 26 does not affect the stability. The obtained ultrasonic transmission / reception characteristics can be obtained, and the operating temperature range can be widened regardless of the type of fluid to be measured (liquid or gas).

Next, a third embodiment of the present invention will be described. FIG. 6 is a block diagram showing the configuration of the third embodiment.
As shown in FIG. 6, in the ultrasonic vortex flow meter 80 of the third embodiment, the ultrasonic vortex flow meter 20 of the first embodiment described above is used.
In, the ultrasonic wave is converted to an electric signal by the ultrasonic wave receiver, and the frequency of the ultrasonic wave transmitted and received at a certain temperature is detected by the frequency detector in the signal amplified by the amplifier circuit. The frequency detected by the frequency detector 82 is at the peak voltage of the ultrasonic transmission band of the ultrasonic transceiver 28 as described in the first embodiment, and is determined by the temperature.

Therefore, if the oscillation frequency table for the temperature of the ultrasonic transmitter 26 and the ultrasonic receiver 28 to be used is given to the flow rate calculation circuit 40 by the initial setting, the temperature information of the fluid to be measured can be obtained.

That is, in the ultrasonic vortex flowmeter 80 of the third embodiment, the temperature of the fluid to be measured can be detected without providing a temperature sensor. , Temperature correction can be performed.

[0051]

As described above, according to the first aspect of the present invention, since the transmission and reception of ultrasonic waves can be performed without switching the optimum frequency for the temperature at the time of measurement from the broadband drive signal, the temperature range of the flow meter can be transmitted through the ultrasonic wave. The operating temperature range of the flowmeter can be extended to the structural limit of the ultrasonic transmitter without being affected by the temperature drift of the characteristics. Therefore, by driving the ultrasonic transmitter in advance with a wideband signal without switching the driving frequency to the ultrasonic transmitter, it is possible to efficiently operate without being affected by the shift of the resonance point of the ultrasonic transmitter due to a temperature change. Ultrasonic waves can be transmitted, and a wide temperature range can be accommodated without changing the structure of a conventional ultrasonic sensor.

According to the second aspect of the present invention, there is provided temperature detecting means for obtaining the temperature of the fluid to be measured based on the frequency of the ultrasonic wave received by the ultrasonic receiver, and a temperature sensor and the like are provided. The temperature of the fluid to be measured can be detected without measuring the temperature of the fluid to be measured, and the temperature of the fluid to be measured can be known by measuring the transmission / reception frequency of the ultrasonic wave.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a first embodiment of the present invention.

FIGS. 2A and 2B are diagrams showing a configuration of an ultrasonic sensor used in the ultrasonic transmitter 26, wherein FIG. 2A is a longitudinal sectional view of the ultrasonic sensor used in the ultrasonic transmitter 26, and FIG. FIG. 4 is a plan view of a vibrator used for the vessel 26.

FIG. 3 is a graph showing frequency-received voltage characteristics of the first embodiment.

FIG. 4 is a block diagram showing a configuration of a broadband oscillation circuit 30.

FIG. 5 is a block diagram showing a configuration of a second embodiment.

FIG. 6 is a block diagram showing a configuration of a third embodiment.

FIG. 7 is a block diagram showing an example of a conventional ultrasonic vortex flowmeter.

FIG. 8 is a block diagram showing another example of a conventional ultrasonic vortex flowmeter.

FIG. 9 is a longitudinal sectional view showing a configuration of a conventional ultrasonic transmitter.

FIG. 10 is a graph showing a conventional frequency-reception voltage characteristic.

[Explanation of symbols]

 20, 60, 80 Ultrasonic vortex flowmeter 22 Flowmeter main body 24 Vortex generator 26, 63a, 63c Ultrasonic transmitter 28, 63b, 63d Ultrasonic receiver 30 Broadband oscillation circuit 36 Phase comparison circuit 38 Waveform shaping circuit 40 Flow rate Arithmetic circuit 42 Sensor holder 42a Vibrating plate 44 Vibrator 44a Vibration frequency detector 44c Piezoelectric element 48 Cover 52 Lead wire 54 Spread code generator 56 Carrier generator 58 Spread modulator 82 Frequency detector

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Hirofumi Yoshikura 1-6-3 Fujimi, Kawasaki-ku, Kawasaki-shi, Kanagawa Tokiko Corporation

Claims (2)

[Claims] An ultrasonic transmitter for transmitting an ultrasonic wave into a fluid to be measured flowing through a flow path, an oscillation circuit for outputting a drive signal to the ultrasonic transmitter, and an ultrasonic wave transmitted through the fluid to be measured An ultrasonic vortex flowmeter comprising: an ultrasonic receiver that receives a signal; and an arithmetic unit that obtains a flow rate from a phase difference between a signal received by the ultrasonic receiver and a signal transmitted from the ultrasonic transmitter. The ultrasonic eddy flow meter according to claim 1, wherein the oscillation circuit includes a drive signal generating unit that outputs a drive signal having a widened frequency to the ultrasonic transmitter. 2. The ultrasonic eddy flow according to claim 1, further comprising temperature detecting means for obtaining the temperature of the fluid to be measured based on the frequency of the ultrasonic wave received by said ultrasonic receiver. Total.