JPH0989616A - Ultrasonic flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flowmeter for properly measuring flow rate by generating an ultrasonic vibration with the maximum amplitude. SOLUTION: A flow-rate meter has a filter 13 for inputting the ultrasonic vibration of a piezoelectric ceramic body 6 of an ultrasonic converter 3 for transmitting signal, an amplifier 14 for amplifying a signal from the filter 13, and a phase control circuit 15 for outputting a drive signal A for driving the piezoelectric ceramic body 6 by setting a phase based on the phase difference between the phase of a signal from the amplifier 14 and that of ultrasonic vibration to the piezoelectric ceramic body 6. A phase control circuit 15 can set the phase of the drive signal A based on the phase difference between the phase of a signal from the amplifier 14 and that of ultrasonic vibration and can output the drive signal A with the same phase as that of ultrasonic vibration, thus maximizing the amplitude of the ultrasonic vibration and stably measuring flow rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flowmeter for measuring a flow rate of a fluid.

[0002]

2. Description of the Related Art As an example of a conventional ultrasonic flowmeter, a pair of ultrasonic transducers each having a function of transmitting and receiving an ultrasonic wave are provided, and an ultrasonic wave transmitted from one of the pair of ultrasonic transducers to the other is provided. There is a method in which the flow rate of a fluid is measured based on a change in sound waves caused by the flow of the fluid.

[0003]

By the way, in the above-mentioned ultrasonic flowmeter, it is desirable to generate the ultrasonic wave of the maximum amplitude because proper measurement can be achieved if the ultrasonic wave of the maximum amplitude is generated. In response to such a demand, there is a configuration in which the temperature of the ultrasonic transducer is measured and the ultrasonic frequency is adjusted based on the measured value. As a result, a deviation from the resonance frequency is likely to occur, and the above-mentioned demand has not always been met.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an ultrasonic flowmeter capable of generating ultrasonic vibration of maximum amplitude and performing proper flow rate measurement.

[0005]

According to the first aspect of the present invention,
A pair of ultrasonic transducers having a function of transmitting and receiving ultrasonic waves is provided, and the flow rate of the fluid is changed based on the change in the ultrasonic waves transmitted from one of the pair of ultrasonic transducers to the other due to the flow of the fluid. In an ultrasonic flow meter for measurement, a vibration detecting means for detecting ultrasonic vibration of the transmitting portion of the one ultrasonic transducer, an amplifying means for amplifying a signal from the vibration detecting means, and a signal from the amplifying means. And a phase controller that sets the phase of the drive signal that drives the transmitter based on the phase difference between the phase of the ultrasonic vibration of the transmitter and outputs the drive signal to the transmitter. Is characterized by.

With such a configuration, the phase control section can set the phase of the drive signal based on the phase difference between the phase of the signal from the amplifying means and the phase of the ultrasonic vibration. The amplitude of the ultrasonic vibration reaches the maximum value by outputting the drive signal having the same phase as the vibration phase.

According to a second aspect of the present invention, in the structure according to the first aspect, a transmission side temperature detecting means for detecting the temperature of the transmission section of one ultrasonic transducer is provided, and the phase control section is provided for the transmission side. The phase of the drive signal is adjusted based on the detection data of the temperature detecting means.

With such a configuration, the phase control unit
The phase of the drive signal is adjusted based on the detection data of the transmission side temperature detecting means.

According to a third aspect of the present invention, in the structure according to the first aspect, a transmitting side temperature detecting means for detecting the temperature of the transmitting section of one ultrasonic transducer, and a receiving section of the other ultrasonic transducer. And a receiving side temperature detecting means for detecting the temperature of
The phase control unit adjusts the phase of the drive signal based on the detection data of the temperature detecting means on the sending and receiving sides.

With this structure, the phase control section
The phase of the drive signal is adjusted based on the detection data of the temperature detecting means on the sending and receiving sides.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An ultrasonic flowmeter according to a first embodiment of the present invention will be described below with reference to FIGS. 1 and 2. In the figure, a vortex generating column 2 for generating a Karman vortex is provided in a pipe 1 through which a fluid flows. The tube 1 is provided with a pair of ultrasonic transducers 3 and 4 each having a function of transmitting and receiving ultrasonic waves with the vortex generation region in the tube 1 in between.

A drive circuit 5 is connected to one of the pair of ultrasonic transducers 3 and 4 (hereinafter referred to as transmitting ultrasonic transducer) 3 and a driving signal A is transmitted to the transmitting ultrasonic transducer 3. The ultrasonic wave is output to the acoustic wave transducer 3 to vibrate the piezoelectric ceramic body 6 of the transmitting ultrasonic wave transducer 3 to generate ultrasonic waves B. The ultrasonic wave B from the transmitting ultrasonic wave transducer 3 passes through the vortex generation region and is modulated by the Karman vortex so that the other ultrasonic wave transducer (hereinafter,
It is called a receiving ultrasonic transducer. ) 4 is received. A vortex signal detector 7 is connected to the reception-side ultrasonic transducer 4, and signals received by the reception-side ultrasonic transducer 4 and the drive circuit 5 are connected.
Is compared with the drive signal A output by the pulse generator to extract the modulation component, and the pulsed vortex signal D indicating the vortex generation frequency is output. Then, based on the vortex signal D, a measuring unit (not shown) determines the flow rate of the fluid.

The transmitting ultrasonic transducer 3 is provided with a substantially rectangular piezoelectric ceramic body 6 (transmitting portion), which vibrates in response to a drive signal A to generate an ultrasonic wave B. The piezoelectric ceramic body 6 is provided with a common electrode 8 on one surface side (lower side in FIG. 2), the one surface side is arranged close to the tube 1, and the other surface side (upper side in FIG. 2) facing the one surface side is arranged. A drive electrode 9 and a vibration detection electrode (vibration detection means) 10 are provided. In this case, the drive electrode 9 and the vibration detection electrode 10 are formed separately. In FIG. 2, reference numeral 11 denotes a housing, which supports the piezoelectric ceramic body 6, the drive electrode 9, and the vibration detection electrode 10.

The driving circuit 5 is a filter 1 connected in series.
3, the amplifier 14, and the phase control circuit 15, and together with the drive electrode 9 and the vibration detection electrode 10, constitute the vibration feedback oscillation circuit 12. The ultrasonic flowmeter is equipped with a power supply 16, and the power supply 16 includes the filter 13 and the amplifier 1.
4, the phase control circuit 15 is connected in parallel.

When the piezoelectric ceramic body 6 vibrates under pressure, a voltage having a magnitude corresponding to the vibration is generated, and in response to this, the vibration detection electrode 10 receives the voltage and vibrates the piezoelectric ceramic body 6. The detected vibration signal E is output to the filter 13. The filter 13 has a vibration signal E
The unnecessary ultrasonic wave component is removed from the
The frequency component in the vicinity of the operating frequency is extracted and output to the amplifier 14.

The amplifier 14 amplifies the signal from the filter 13 to a desired size (a size sufficient to vibrate the piezoelectric ceramic body 6) and outputs the amplified signal to the phase control circuit 15.

The phase control circuit 15 shifts the phase of the amplified signal so that the phase of the drive signal A becomes equal to the phase of the vibration of the piezoelectric ceramic body 6 (vibration signal E). The amount of phase shift (shift amount) of the phase control circuit 15 is determined by the amount of phase rotation of the filter 13 and the amplifier 14, and the amount of phase difference between the vibration of the piezoelectric ceramic body 6 and the vibration signal E. It is preset. Here, the amount of phase rotation of the filter 13 and the amplifier 14 and the amount of phase difference between the vibration of the piezoelectric ceramic body 6 and the vibration signal E do not change significantly due to external factors such as temperature and pressure.

In the ultrasonic flowmeter constructed as described above, the phase control circuit 15 shifts the phase of the signal from the amplifier 14 by a preset phase shift amount, and a phase equivalent to the phase of vibration of the piezoelectric ceramic body 6. Is generated and the drive signal A is output to the piezoelectric ceramic body 6. Then, since the phase of the drive signal A is the same as the phase of the vibration of the piezoelectric ceramic body 6, the amplitude of the vibration (vibration signal E) of the piezoelectric ceramic body 6 becomes maximum, and stable and favorable flow rate measurement is performed. be able to.

Further, the phase shift amount is set based on the amount of phase rotation and the amount of phase difference that hardly change due to temperature and pressure changes, and the phase of the drive signal A is shifted by the amount of this phase shift and the vibration signal of maximum amplitude is set. Since E is generated, a large ultrasonic wave B can be obtained even if the temperature or pressure fluctuates, and thus stable flow rate measurement can be achieved.

FIG. 3 shows an ultrasonic flowmeter according to a second embodiment of the present invention for performing more stable ultrasonic wave transmission / reception.

The phase difference between the ultrasonic vibration of the piezoelectric ceramics body 6 and the vibration signal E is caused by the transfer characteristic from the drive electrode 9 to the vibration detection electrode 10 inside the piezoelectric ceramics body 6, and this is due to the temperature change. Changes slightly depending on. Therefore, if the amount of phase shift in the phase control circuit 15 is constant as in the ultrasonic flowmeters of FIGS. 1 and 2, the ultrasonic transmission / reception state changes due to temperature changes. On the other hand, the temperature change rate of the transfer characteristic of the piezoelectric ceramic body 6 can be confirmed in advance. Therefore, as shown in FIG. 3, a temperature detector (hereinafter, referred to as a transmission side temperature detector) 20 that measures the temperature of the transmitting ultrasonic transducer 3 and outputs the temperature signal F is provided, and the phase control circuit 15A is provided. , Temperature signal F
The amount of phase shift set in advance is corrected on the basis of the above to match the frequency of the drive signal A with the resonance frequency of the piezoelectric ceramic body 6 to minimize the change in ultrasonic transmission / reception due to temperature change.

Next, a third embodiment of the present invention will be described with reference to FIG. Compared with the ultrasonic flowmeter shown in FIG. 3, this ultrasonic flowmeter has a temperature detector for detecting the temperature of the ultrasonic transducer 4 on the receiving side (hereinafter referred to as temperature detector on the receiving side).
21 is provided, a temperature difference determiner 22 that obtains a difference between the detection value of the transmission side temperature detector 20 and the detection value of the reception side temperature detector 21 is provided, and the phase control circuit 15A of FIG.
Instead, the phase control circuit 15B is provided.

The phase control circuit 15B corrects a preset phase shift amount when the difference between the detection signals of the transmitting side and receiving side temperature detectors 20 and 21 is equal to or more than a certain value, and the frequency of the drive signal A is set to the transmitting side. It is set to an intermediate value between the resonance frequencies of the piezoelectric ceramic bodies 6 and 6 on the receiving side.

In this ultrasonic flowmeter, even if there is a difference in the transmission / reception characteristics between the transmission and reception ultrasonic transducers 3 and 4 due to the temperature difference, the deterioration of the transmission / reception characteristics should be minimized. As a result, stable ultrasonic wave transmission / reception can be achieved and stable flow rate measurement can be performed.

In the above embodiment, the so-called ultrasonic vortex flowmeter, which measures the flow rate by utilizing the modulation of the ultrasonic waves by the Karman vortex, has been taken as an example.
The present invention is not limited to this, and may be an ultrasonic flowmeter of a type that does not utilize Karman vortex.

[0026]

According to the present invention, the phase control section can set the phase of the drive signal based on the phase difference between the phase of the signal from the amplifying means and the phase of the ultrasonic vibration. By outputting the drive signal having the same phase as the phase, the amplitude of ultrasonic vibration reaches the maximum value, and stable flow rate measurement can be achieved.

Further, a transmission side temperature detecting means for detecting the temperature of the transmitting section of one ultrasonic transducer is provided, and the phase control section is
By adjusting the phase of the drive signal based on the detection data of the transmitting side temperature detecting means, it is possible to minimize the change in ultrasonic transmission / reception due to the temperature change.

Further, a transmitting side temperature detecting means for detecting the temperature of the transmitting section of one ultrasonic transducer and a receiving side temperature detecting means for detecting the temperature of the receiving section of the other ultrasonic transducer are provided, and the phase is set. When the control unit adjusts the phase of the drive signal based on the detection data of the sending and receiving side temperature detecting means, in the case where a difference in transmission and reception characteristics occurs between the pair of ultrasonic transducers due to the temperature difference. Also, the deterioration of the transmission / reception characteristics can be suppressed to a minimum, and by extension, proper ultrasonic transmission / reception can be achieved and stable flow rate measurement can be performed.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing an ultrasonic flowmeter according to a first embodiment of the present invention.

FIG. 2 is a diagram schematically showing a transmitting side of the ultrasonic flow meter.

FIG. 3 is a diagram schematically showing an ultrasonic flowmeter according to a second embodiment of the present invention.

FIG. 4 is a diagram schematically showing an ultrasonic flowmeter according to a third embodiment of the present invention.

[Explanation of symbols]

 3 Ultrasonic Transducer for Transmission 4 Ultrasonic Transducer for Reception 5 Drive Circuit 6 Piezoelectric Ceramics Body 10 Vibration Detection Electrode 13 Filter 14 Amplifier 15 Phase Control Circuit

Claims (3)

[Claims] 1. A pair of ultrasonic transducers having a function of transmitting and receiving ultrasonic waves, the ultrasonic wave being transmitted from one of the pair of ultrasonic transducers to the other based on a change caused by a fluid flow. In an ultrasonic flowmeter for measuring the flow rate of a fluid, a vibration detecting means for detecting ultrasonic vibration of the transmitting portion of the one ultrasonic transducer, an amplifying means for amplifying a signal from the vibration detecting means, Phase control for setting the phase of the drive signal for driving the transmitter based on the phase difference between the phase of the signal from the amplifier and the phase of the ultrasonic vibration of the transmitter and outputting the drive signal to the transmitter. And an ultrasonic flowmeter. 2. A transmission side temperature detecting means for detecting a temperature of a transmitting section of the one ultrasonic transducer is provided, and the phase control section controls the phase of the drive signal based on the detection data of the transmitting side temperature detecting means. The ultrasonic flowmeter according to claim 1, wherein the ultrasonic flowmeter is adjusted. 3. A transmitting side temperature detecting means for detecting a temperature of a transmitting section of the one ultrasonic transducer, and a receiving side temperature detecting means for detecting a temperature of a receiving section of the other ultrasonic transducer. The ultrasonic flowmeter according to claim 1, wherein the phase controller adjusts the phase of the drive signal based on the detection data of the temperature detecting means on the sending and receiving sides.