JPH09236475A - Water level measurement device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device which measures water level stably without affected by environment change in gas phase or liquid phase. SOLUTION: A water level measurement device 10, together with a super sonic wave vibratar 11 and a wave guide rod 12 connected to the vibrator 11, constitutes a transducer. To the vibrator 11, a resonance characteristics measurement device 14 is connected through a signal cable 17, and, to the lower stream side of the resonance characteristics measurement device 14, a signal processor 15 and a water level display 16 are connected. A part of wave guide rod 12 is submerged in a liquid phase 7, and at the vibrator 11 fixed to a water vessel 1 with a support fix device 13, longitudinal wave, distortional wave, transverse wave or flex vibration is generated, and the wave motion from the vibrator is propagated to the wave guide rod 12. The transducer resonates when a.c. signal of specific frequency zone is applied. Since resonance characteristics changes when a part of the wave guide rod 12 is submerged, water level is decided by measuring the resonance change.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water level measuring device for measuring the water level in a water tank such as a pressure vessel or a tank.

[0002]

2. Description of the Related Art As a water level measuring device for measuring the water level in a water tank, an ultrasonic water level meter, a differential pressure type water level meter, etc. have been widely used. The ultrasonic level gauge uses a method called the pulse echo method, and the measurement principle is shown in Fig. 13.
Will be described with reference to (a) and (b). That is, FIG.
As shown in (a), the ultrasonic transducer 2 is provided at the upper end of the water tank 1, and the ultrasonic wave is radiated from the ultrasonic transducer 2 onto the water surface 3 to determine the intensity and time of the incident pulse 4 and the reflected pulse 5. Upon measurement, the water level can be measured from these relationships as shown in FIG. 13 (b). That is, the incident pulse 4 is emitted from the ultrasonic transducer 2 from the gas phase 6 to the liquid phase 7, the round trip time of the reflected pulse 5 from the water surface 3 is measured, and the height to the water surface 3 is measured.

On the other hand, the differential pressure type water level gauge is used for measuring the water level in a nuclear power plant. The principle of this water level gauge will be explained with reference to FIG. That is, as shown in FIG. 14, a guide pipe 8 for connecting the gas phase 6 and the liquid phase 7 is provided outside the water tank 1 with the water surface 3 in the water tank 1 as a boundary.
Is attached, and the pressure difference between the gas phase 6 and the liquid phase 7 is measured with a differential pressure gauge 9 and converted into a water level.

[0004]

However, in the conventional differential pressure type water level gauge used in a nuclear reactor or the like, the guide pipe 8 is drawn out from the bottom, hot leg or top of the reactor vessel and led to the differential pressure gauge 9. Therefore, during a transient reactor, there is a problem that an error occurs in the measured water level due to the influence of the complicated flow inside the core and the temperature difference inside and outside the core.

On the other hand, an ultrasonic water level meter using the pulse echo method is susceptible to measurement fluctuations due to the temperature fluctuations in the gas phase 6, and the reflected pulse does not return due to ripples or bubbles on the liquid surface, making measurement impossible. There is a problem that becomes.

The present invention has been made to solve the above problems, and can stably measure the water level even if the environment such as temperature distribution and flow distribution changes in the gas phase or the liquid phase, and the S / N ratio is improved.
It is to provide a water level measuring device having excellent characteristics.

[0007]

According to a first aspect of the present invention, a vibrator that generates a wave such as a longitudinal wave, a torsion wave, a transverse wave, a surface wave or a bending vibration is joined to the vibrator, and the wave is generated. Resonance characteristic measurement connected by a waveguide rod to be propagated, a supporting and fixing device for supporting or fixing the waveguide rod, the oscillator, or the waveguide rod and the oscillator in an aquarium, and a signal cable that gives an electrical signal to the oscillator It is characterized by including a device, a signal processing device, and a water level display device.

According to the first aspect of the present invention, a transducer is constituted by a vibrator that generates a longitudinal wave, a torsional wave, a transverse wave, or a bending vibration, and a waveguide rod that propagates the wave from the vibrator. When an AC electric signal in a frequency band peculiar to the transducer is applied to the transducer from the signal cable, the transducer resonates.

When the waveguide rod portion of the resonating transducer is submerged, the resonance characteristic changes. Further, the resonance characteristic changes depending on the size of the water immersion part. The water level can be identified by measuring the change.

When a longitudinal wave oscillator is used, the mechanical impedance or admittance at the resonance point or antiresonance point can be used as a measurement parameter. Further, not only the water level measurement but also the limit switch function relating to the presence or absence of the water level is provided, so that there is an advantage that the limit switch can be used.

On the other hand, when a torsional wave or transverse wave oscillator is used, the vibration is damped not only by the water level of the measurement object but also by the viscous resistance of the measurement object, and this principle can be used to measure the viscosity. When the bending vibration is used, the sensitivity and S / N are improved.

Further, when the waveguide rod or the vibrator is supported or fixed by the supporting and fixing device, a specific vibration mode can be strongly excited and unnecessary modes can be suppressed. For example, when flexural vibration is strongly excited, it is possible to suppress vibration modes other than the measurement target, such as longitudinal waves generated in the same frequency band, and improve S / N in resonance characteristics.

According to a second aspect of the present invention, the waveguide rod has a uniform cross-sectional shape and is a round rod, a cylindrical rod, a hollow elliptic rod,
It is characterized by comprising a rod-shaped body selected from a square rod or a hollow square rod.

According to the second aspect of the present invention, by using a round rod or a cylindrical rod as the waveguide rod, it is possible to uniformly and efficiently generate a longitudinal wave and a torsional wave. Furthermore, bending vibration can be efficiently generated by using square rods or hollow rods.

According to a third aspect of the present invention, a piezoelectric element having a vibrator structure of (2n-1) sheets is sandwiched alternately with 2n electrode plates in a sandwich shape, and an insulator is provided on one end side thereof. It is characterized by a Langevin type structure in which both ends are sandwiched by fixing devices.

According to the present invention, only the specific vibration mode can be strongly excited due to the structure of the vibrator, and the vibration mode can be selected. For example, the structure of the vibrator is a Langevin type structure in which (2n + 1) piezoelectric bodies are sandwiched between 2n electrode plates, an insulator is provided on one end side, and both ends are sandwiched by a fixing device. This makes it possible to strongly excite longitudinal vibration or torsional waves.

According to a fourth aspect of the invention, the structure of the vibrator is a Langevin type structure in which 2n piezoelectric bodies are sandwiched between (2n + 1) electrode plates and both ends are sandwiched by a fixing device. It is characterized by that. According to the invention described in claim 4, longitudinal vibration or torsional wave can be excited more strongly, and the sensitivity and S / N are improved.

The invention according to claim 5 is characterized in that a torsional coupler is interposed between the vibrator and the waveguide rod. According to this invention, the torsional wave can be more strongly excited by interposing the torsion coupler between the vibrator and the waveguide rod.

According to a sixth aspect of the present invention, as an alternative to the vibrator, a vibrating device that vibrates horizontally or vertically with respect to the axial direction of the rod is used at one end of the rod. According to the invention of claim 6, as an alternative to the vibrator, by using a vibrating device which vibrates at one end of the rod horizontally or vertically with respect to the axial direction of the rod, longitudinal vibration and bending vibration are strongly excited. can do.

According to the invention of claim 7, the ultrasonic transducer consisting of the vibrator and the waveguide rod is bonded by adhesive bonding, welding or bolt connection, or the waveguide rod and the vibrator are integrally molded. Is characterized by.

According to the invention described in claim 7, the propagation of vibration is different due to the difference in the joining method between the waveguide rod and the vibrator. In the case of adhesive bonding, the vibration of the vibrator is efficiently transmitted due to the close connection. On the other hand, welded joints have excellent workability. In addition, the bolted connection allows easy removal during maintenance of the vibrator or the waveguide rod, has excellent maintainability, and has good reproducibility during mounting. When the waveguide rod and the vibrator are integrally molded, the vibration can be propagated most efficiently.

The invention according to claim 8 is characterized in that both ends of the transducer, one end, the waveguide rod portion, or the end portion of the transducer and the waveguide rod portion are supported or fixed.
According to the invention described in claim 8, by supporting or fixing one end of the transducer, the waveguide rod portion, or the end portion of the transducer and the waveguide rod portion, the unnecessary vibration mode can be suppressed, and the standing wave The sensitivity can be made uniform by making the wavelength uniform.

The invention according to claim 9 is characterized in that the supporting or fixing position of the waveguide rod portion is a node portion of a standing wave generated in the waveguide rod. According to the invention described in claim 9, since the supporting or fixing position of the waveguide rod portion is the node portion of the standing wave generated in the waveguide rod, the standing of the propagating ultrasonic wave Support without affecting the waves.

According to a tenth aspect of the present invention, the resonance characteristic measuring device is characterized in that the transducer is frequency-swept with a sine wave signal to measure the frequency response characteristic, and the resonance point or anti-resonance point is obtained by performing a peak search. There is. According to the invention described in claim 10, a high-speed response can be realized by performing a peak search to find a resonance point or an anti-resonance point.

According to the eleventh aspect of the present invention, the signal processing device has a function of integrally calculating each measurement data from the resonance characteristic measuring device. According to the invention described in claim 11, the resonance characteristic or the frequency response characteristic at a plurality of resonance points or anti-resonance points of the transducer is simultaneously measured, and the water level is obtained by performing an integrated calculation from the relationship between the plurality of water levels and the resonance characteristic. This improves the reliability of water level information.

The invention according to claim 12 is characterized in that the water level display device has a function of measuring, calculating and displaying the viscosity of the object to be measured. According to the twelfth aspect of the present invention, the viscosity or density and the water level of the measurement target can be displayed by receiving signals from the resonance characteristic measuring device that measures the resonance characteristic or the frequency response characteristic and the signal processing device.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a water level measuring device according to the present invention will be described with reference to FIGS. In FIG.
The water level measuring device 10 according to the present embodiment first forms a transducer by the ultrasonic transducer 11 and the waveguide rod 12 connected to the transducer 11. The waveguide bar 12 is immersed in the liquid phase 7 in the water tank 1 from the center to the lower end. Waveguide rod 12 is waveguide rod 12
It is fixed to the water tank 1 by the supporting and fixing device 13 of. The oscillator 11 is connected to the resonance characteristic measuring device 14 by a signal cable 17, and a signal processing device is provided on the downstream side of the resonance characteristic measuring device 14.
15 and the water level indicator 16 are connected.

In this water level measuring device 10, an oscillator 11 for generating an ultrasonic wave is integrally connected to the waveguide rod 12 by contacting them without a gap by an adhesive, welding, bolting or the like. The waveguide rod has a uniform cross-sectional shape and is composed of a rod-shaped body selected from a round rod, a cylindrical rod, an elliptic rod, a hollow elliptic rod, a square rod, or a hollow square rod.

The resonance characteristic measuring device 14 can receive the electric signal from the vibrator 11 to measure the resonance characteristic, the signal processing device 15 can convert the water level, and the water level display device 16 can display the water level.

First, the measurement principle will be described. Oscillator 11
Then, longitudinal wave, torsional wave, transverse wave or bending vibration is generated,
Waves from the oscillator 11 are propagated to the waveguide rod 12. Oscillator 11
The transducer constituted by the waveguide rod 12 and the waveguide rod 12 resonates when an AC electric signal in a specific frequency band is applied.

When a part of the waveguide rod 12 of the resonating transducer is submerged, the resonance characteristic changes, and the resonance characteristic also changes depending on the size of the submerged portion. The water level can be identified by measuring the change.

FIG. 2 shows an example of the resonance waveform in the relationship between the signal strength and the frequency. Resonance waveform when the water level is low 18, high water level
If it is 19, the resonance waveform changes, and the frequency or signal strength at the resonance point 20 and the anti-resonance point 21 changes greatly.

Here, the measurement point is the resonance point.
The mechanical impedance, admittance, or frequency at 19 or anti-resonance point 21 is available. The relationship between the frequency at the resonance point 20 and the anti-resonance point 21 and the water level is shown in FIG.

Regarding the measurement of the resonance characteristic, an electric signal of a sine wave signal whose frequency changes with time is generated and transmitted to the vibrator 11 via the signal cable 17, and the electric signal is converted into ultrasonic waves. , Propagated to the waveguide rod 12. At this time, the waveguide rod 12 has an inherent resonance frequency determined by the material, length and diameter of the waveguide rod 12.

The waveguide rod 12 resonates at a frequency of a predetermined value, and when the waveguide rod 12 is in a resonance state, the waveguide rod 12 causes the oscillator 11 to move.
As a reaction to the stress, the stress is propagated, and when the voltage of the vibrator 11 is measured, the resonance waveform as shown in FIG. 2 is observed.

The resonance characteristic measuring device 14 measures the impedance or admittance of the transducer of the water level measuring device 10 on the basis of the electric circuit shown in FIG. The value and the voltage value are measured by the voltage / current measuring device 23.

In FIG. 4, reference numeral 24 is a high resistance, which is connected between the variable frequency power source 22 and the current sensor 25, and is connected to the voltage signal line 26.
The current signal line 27 and the current signal line 27 are connected to the voltage / current measuring device 23, respectively.

FIGS. 5 (a) and 5 (b) show the vibrator shown in FIG.
The 1st example of 11 is shown, (a) is a top view, (b) is a longitudinal cross-sectional view of (a). As shown in FIG. 5, (2n−
1) A piezoelectric body 28 is sandwiched between 2n electrode plates 29 in a sandwich shape, an insulator is provided on one end side thereof, and both ends thereof are sandwiched by a fixing device 30. The negative potential line 25 and the positive potential line 26 are connected to the electrode plate 29. Reference numeral 27 indicates the polarization direction.

In addition, 2n piezoelectric bodies 28 are sandwiched between (2n + 1) electrode plates 29 in a sandwich shape, and ultrasonic waves are generated by using a Langevin type oscillator in which both ends thereof are sandwiched by a fixing device 30. You can

6 (a) and 6 (b) are the same as in FIG.
11 shows a second example of the vibrator 11, in which the vibrator 11 is a piezoelectric body 28.
The electrode 29 is tightened with the bolt 34. Piezoelectric body 28
When the alternating voltage is loaded on the negative potential line 31 and the positive potential line 32 as shown in FIG. 5, the polarization direction 33 is opposite to the polarization direction 33, and it can be made parallel by adjusting the electrode lines.

In FIG. 1, the vibration condition when the vibrator 11 is a general Langevin type vibrator (standing wave 41)
Is shown in FIG. 7 (a), and its structure is shown in FIG. 7 (b). That is, in FIG. 7B, three electrode plates 29 are sandwiched between a pair of ultrasonic waveguide rods 12 and 12, and these electrode plates 29 are connected to the variable frequency power source 22. In a), the vertical axis represents the amplitude, and the horizontal axis represents the wavelength λ / 2 corresponding to the ultrasonic waveguide rod 12.

FIG. 8 is an ultrasonic transducer shown in FIGS. 5 to 7.
An example of arrangement of 11 parts is shown as an exploded view. That is, the bolt 34 is connected to the fixing device 30, and the piezoelectric body 28, the electrode plate 29 with the lead wire 35, the piezoelectric body 28,
The electrode plate 29 with the lead wire 35 and the taper disk 36 are sequentially inserted, and the internal thread 38 of the torsion connector 37 is screwed into the bolt 34 to be integrated to assemble the ultrasonic transducer 11. As shown in FIG. 8, a torsional coupler 37 can be sandwiched between the vibrator 11 and the tapered disk 36 serving as a waveguide rod to efficiently generate a torsional wave.

FIG. 9 shows a second embodiment of the water level measuring device according to the present invention. In this embodiment, a vibrating device 39 is used in place of the vibrator 11 of the first embodiment, and the upper end of the waveguide rod 12 is attached to the fixed wall 40 via the fixing device 30 and guided. The vibration is propagated to the corrugated rod 12 via the transmission portion 41.

As the material of the waveguide rod 12, an elastic body such as metal and alloy such as stainless steel, aluminum and duralumin, or a synthetic resin such as acrylic rod can be used. The shape of the waveguide rod 12 may be a round rod, a square rod, a hollow, or the like, and the transmission part 41 and the waveguide rod 12 may be connected by bolting, welding, or an adhesive.

Next, the oscillator 11 and the waveguide rod 12 shown in FIG.
A method of supporting or fixing the above will be described with reference to FIGS. 10 to 12. FIG. 10A shows an example in which the connecting portion between the oscillator 11 and the waveguide rod 12 and the lower end portion of the waveguide rod 12 are supported at two points by the support fixing device 13, and FIG. 10B is the upper end of the oscillator 11. And the lower end of the waveguide rod 12 is also supported at two points.

FIG. 11A shows an example in which only the connecting portion between the vibrator 11 and the waveguide rod 12 is supported by the supporting and fixing device 13 at one point.
11 (b) is an example in which only the upper end of the vibrator 11 is also supported at one point. FIG. 12 shows a case of a long waveguide rod 12 and an example in which a supporting point is provided also in an intermediate portion and three-point supporting is performed. This intermediate support point supports a point corresponding to a node portion of the standing wave 41 of the ultrasonic wave generated in the conductive rod 12 and three upper and lower ends by the support fixing device 13.

As a result, the transducer constituted by the oscillator 11 and the waveguide rod 12 has a plurality of resonance points such as primary, secondary, tertiary ... and these resonance points or anti-resonance points. The measurement accuracy is improved by utilizing and complementing the characteristics of.

[0048]

According to the present invention, since the standing wave ultrasonic wave in the conductive rod is utilized, the water level can be accurately measured without being affected by the environment such as the temperature distribution and the flow distribution of the surrounding water. Further, in the conventional pulse echo method, in measuring the time between ultrasonic pulses, it is necessary to determine the threshold value of the crest value of the pulse, and a measurement error occurs depending on the threshold setting method. According to this, since the resonance frequency and the anti-resonance frequency are used as the measured value of the water level, there is no need to set a threshold value, and there is an effect that the S / N characteristic is superior to that in pulse measurement.

[Brief description of drawings]

FIG. 1 is a system diagram for explaining a first embodiment of a water level measuring device according to the present invention.

FIG. 2 is a characteristic diagram showing a relationship between signal strength and frequency in FIG.

FIG. 3 is a characteristic diagram showing the relationship between the water level and the resonance or anti-resonance frequency in FIG.

FIG. 4 is an electric circuit diagram for explaining the principle of measuring the resonance characteristic in FIG.

5A is a top view showing a first example of the vibrator in FIG. 1, and FIG. 5B is a vertical sectional view of FIG.

6A is a top view showing a second example of the vibrator in FIG. 1, and FIG. 6B is a vertical sectional view of FIG.

7A is a characteristic diagram showing the relationship between the amplitude and wavelength of the oscillator in FIG. 1, and FIG. 7B is a perspective view schematically showing a state in which the oscillator of FIG.

8 is an exploded view showing an example of components of the vibrator shown in FIG.

FIG. 9 is a schematic diagram showing a second embodiment of a water level measuring device according to the present invention.

10A is a schematic diagram showing a first example in which a transducer according to the present invention is supported at both ends, and FIG. 10B is a schematic diagram showing a second example in FIG. 10A.

11A is a schematic view showing a first example in which the transducer of the present invention is supported at one end, and FIG. 11B is a schematic view showing a second example in FIG. 11A.

FIG. 12 is a schematic view showing an example in which the transducer of the present invention is intermediately supported.

13A is a vertical cross-sectional view schematically showing a first example of a conventional water level gauge, and FIG. 13B is a waveform diagram showing a relationship between pulse intensity and time in FIG. 13A.

FIG. 14 is a vertical sectional view schematically showing a second example of a conventional water level gauge.

[Explanation of symbols]

1 ... Water tank, 2 ... Ultrasonic transducer, 3 ... Water surface, 4
... incident pulse, 5 ... reflected pulse, 6 ... gas phase, 7 ... liquid phase,
8 ... Guide tube, 9 ... Differential pressure gauge, 10 ... Water level measuring device, 11 ... Oscillator, 12 ... Waveguide rod, 13 ... Support fixing device, 14 ... Resonance characteristic measuring device, 15 ... Signal processing device, 16 ... Water level display Equipment, 17 ... Signal cable, 18 ... Low water level, 19 ... High water level, 20 ... Resonance point, 21 ...
Anti-resonance point, 22 ... Variable frequency power supply, 23 ... Voltage / current measuring device, 24 ... High resistance, 25 ... Current sensor, 26 ... Voltage signal line, 27 ... Current signal line, 28 ... Piezoelectric body, 29 ... Electrode plate, 30
… Fixing device, 31… Negative potential line, 32… Positive potential line, 33
... Polarization direction, 34 ... Bolt, 35 ... Lead wire, 36 ... Taper disk, 37 ... Torsion connector, 38 ... Female thread, 39 ... Vibration device, 40 ... Fixed wall, 41 ... Standing wave.

Claims (12)

[Claims] 1. A vibrator that generates a wave such as a longitudinal wave, a torsional wave, a transverse wave, a surface wave, or a bending vibration, a waveguide rod that is joined to the vibrator and propagates the wave, the waveguide rod, and the waveguide bar. A water level measuring device comprising: a supporting and fixing device that supports at least one of the vibrators; a resonance characteristic measuring device connected to the vibrator via a signal cable; a signal processing device; and a water level display device. 2. The waveguide rod has a uniform cross-sectional shape,
2. A rod-shaped body selected from a cylindrical rod, an elliptic rod, a hollow elliptic rod, a rectangular rod, or a hollow rectangular rod.
The described water level measuring device. 3. The vibrator comprises (2n-1) piezoelectric bodies alternately sandwiched by 2n electrode plates, an insulator provided on one end side, and both ends sandwiched by a fixing device. The water level measuring device according to claim 1, which is characterized in that. 4. The vibrator comprises 2n piezoelectric bodies (2n +
1) The water level measuring device according to claim 1, wherein the electrode is sandwiched between the electrode plates, and both ends thereof are sandwiched by fixing devices. 5. The water level measuring device according to claim 1, wherein a torsional connector is interposed between the vibrator and the waveguide rod. 6. The water level measuring device according to claim 1, wherein a vibrating device that vibrates horizontally or vertically with respect to the axial direction of the rod is used at one end of the rod instead of the vibrator. apparatus. 7. The water level measuring device according to claim 1, wherein the transducer and the waveguide rod are integrally connected by an adhesive, welding, or bolting to form a transducer. 8. The transducer according to claim 1, wherein both ends, one end, the waveguide rod portion, or the end portion of the vibrator and the waveguide rod portion are supported by a supporting and fixing device. Water level measuring device. 9. The water level measuring device according to claim 1, wherein the supporting portion of the waveguide rod portion is a node portion of a standing wave generated in the waveguide rod. 10. The resonance characteristic measuring device has a function of obtaining a resonance point or an anti-resonance point by performing frequency sweep of a sine wave on the transducer to measure a frequency response characteristic and performing a peak search. Item 1. A water level measuring device according to item 1. 11. The water level measuring device according to claim 1, wherein the signal processing device has a function of integrally calculating each measurement data from the resonance characteristic measuring device. 12. The water level measuring device according to claim 1, wherein the water level display device has a function of measuring, calculating and displaying the viscosity of a measurement target.