JP2020038119A - Ultrasonic wave measuring apparatus and ultrasonic wave measuring method - Google Patents

Abstract

To determine whether there is a liquid even when a reception signal has a small difference in amplitude according to whether there is the liquid.SOLUTION: An ultrasonic wave measuring apparatus comprises: a transmitting probe 11 which transmits an ultrasonic wave to a plate-like part; a receiving probe 12 which receives an ultrasonic wave from the plate-like part and converts the same into an electric signal; a reception unit 14 which receives as a reception signal the electric signal obtained by the receiving probe 12; and a liquid presence/absence determination unit 154 which determines whether there is a liquid in contact with the plate-like part based upon the number of reception signals received by the reception unit 14 and duration of the reception signals.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ultrasonic measurement device and an ultrasonic measurement method for determining the presence or absence of a liquid in contact with a plate-shaped portion using ultrasonic waves.

In recent years, appropriate maintenance has been required for various aging devices. For example, a pole switch, which is one type of power distribution equipment, is installed above a power pole and is a sealed metal box as a structure. If this pole-mounted switch is used for a long period of time, rainwater will enter inside due to corrosion of the packing or the outer frame or the like. Then, if the water retention of the pole switch exceeds the limit, an accident such as a power failure may be caused. Therefore, there is a need for a technology that can easily determine the presence or absence of flooding from outside.
Here, a method using an electromagnetic wave may be used as the above-described determination for a device for which the presence or absence of inundation cannot be measured visually or by tapping sound. However, since the above determination for the pole switch is for the inside of the metal box, it is difficult to use electromagnetic waves, and a technique using ultrasonic waves is expected.

  A technique for determining the presence or absence of water in a metal box using ultrasonic waves is disclosed in, for example, Patent Document 1. In the technology disclosed in Patent Document 1, transmission and reception of ultrasonic waves are performed by a transmission ultrasonic probe and a reception ultrasonic probe, and the presence or absence of water intrusion is determined using the amplitude of a reception signal at that time. Is determined.

International Publication No. 2017/149658

  On the other hand, the difference between the amplitudes of the received signals may be small when water is present and when water is not present. Therefore, in the presence / absence determination of the inundation using only the amplitude of the received signal, the presence / absence of the inundation may not be determined.

  The present invention has been made in order to solve the above-described problem, and has an ultrasonic measurement apparatus capable of determining the presence or absence of a liquid even when the difference in amplitude of a received signal is small between the presence and absence of a liquid. It is intended to provide.

  An ultrasonic measurement device according to the present invention includes a transmission probe that transmits an ultrasonic wave to a plate-shaped portion, a reception probe that receives an ultrasonic wave from the plate-shaped portion and converts the ultrasonic wave into an electric signal, and a reception probe. A receiving unit that receives the electric signal obtained by the receiving unit as a received signal, and the presence or absence of a liquid that determines the presence or absence of a liquid in contact with the plate-shaped portion based on the number of received signals received by the receiving unit and the duration of the received signal A determination unit.

  According to the present invention, since the configuration is as described above, it is possible to determine the presence / absence of liquid even when the difference between the amplitudes of the received signals is small when liquid is present and when liquid is not present.

FIG. 2 is a diagram illustrating a configuration example of an ultrasonic measurement device according to Embodiment 1 of the present invention. FIG. 3 is a diagram illustrating a configuration example of a signal processing unit according to the first embodiment of the present invention. FIG. 3 is a diagram illustrating an example of a hardware configuration of a signal processing unit according to Embodiment 1 of the present invention. 4A to 4C are conceptual diagrams illustrating an example of a relationship between a reception signal received by the ultrasonic measurement device according to Embodiment 1 of the present invention, presence / absence of water, and water depth. 5A and 5B are diagrams illustrating an example of response characteristics of the transmission probe according to Embodiment 1 of the present invention. FIG. 3 is a diagram illustrating an example of dispersion characteristics of ultrasonic waves transmitted by the transmission probe according to Embodiment 1 of the present invention. FIG. 3 is a diagram illustrating simulation conditions of the ultrasonic measurement device according to the first embodiment of the present invention. 8A to 8G are diagrams showing received signals obtained by simulation of the ultrasonic measurement device according to Embodiment 1 of the present invention. FIG. 9 is a diagram showing a relationship between the amplitude of the received signal shown in FIG. 8 and the water depth. 5 is a flowchart illustrating an operation example of a signal processing unit according to Embodiment 1 of the present invention. 11A and 11B are diagrams illustrating an example of a method of counting a reception signal by the liquid presence / absence determination unit according to Embodiment 1 of the present invention. FIG. 12A and FIG. 12B are diagrams illustrating an example of a case where the duration of a received signal received by the ultrasonic measurement device according to Embodiment 1 of the present invention is shorter and longer than a reference value. FIGS. 13A to 13H are diagrams illustrating an example of a relationship between a reception signal received by the ultrasonic measurement apparatus according to the first embodiment of the present invention, a frequency spectrum at a tail portion, and water depth. FIG. 14 is a diagram illustrating a relationship between a peak frequency of a reception signal illustrated in FIG. 13 and a water depth. FIG. 3 is a diagram illustrating an example of a case where there is water but a reflected wave from the water surface is not received in the ultrasonic measurement device according to Embodiment 1 of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration example of an ultrasonic measurement device 1 according to Embodiment 1 of the present invention.
The ultrasonic measurement device 1 determines the presence or absence of the water 10 inside the metal box 2 using ultrasonic waves. The ultrasonic measuring device 1 shown in FIG. 1 also estimates the water depth in addition to the determination of the presence or absence of the water 10. In FIG. 1, the inside of the metal box 2 is illustrated, where the metal box 2 is submerged, and d indicates the water depth. Hereinafter, the case where the liquid is water 10 is shown, but other liquids may be used. Also, in the following, a case where the measurement target of the ultrasonic measurement device 1 is the metal box 2 is shown. However, the present invention is not limited to this. In addition, any object may be used as long as the object has a plate-shaped portion in a portion where the liquid contacts.
As shown in FIG. 1, the ultrasonic measurement device 1 includes a transmission probe 11, a reception probe 12, a transmission unit 13, a reception unit 14, and a signal processing unit 15. Further, in the ultrasonic measurement device 1 shown in FIG. 1, the transmission unit 13, the reception unit 14, and the signal processing unit 15 are included in the transceiver 16.

The transmission probe 11 is an ultrasonic probe which is attached to the bottom surface (plate portion) of the metal box 2 and transmits ultrasonic waves to the inside of the bottom surface of the metal box 2. The ultrasonic wave transmitted by the transmission probe 11 is a pulse wave having a finite duration.
The receiving probe 12 is an ultrasonic probe which is attached to the bottom surface of the metal box 2 with a gap provided with the transmitting probe 11 and receives ultrasonic waves from the bottom surface of the metal box 2 and converts them into electric signals. .

The transmission unit 13 generates an excitation signal (electric signal) according to the control signal from the signal processing unit 15 and outputs the excitation signal (electric signal) to the transmission probe 11 to excite the transmission probe 11.
The receiving unit 14 receives an electric signal obtained by the reception probe 12 as a reception signal. At this time, the receiving unit 14 may amplify the received signal as needed.

  The signal processing unit 15 controls the transmission unit 13, and determines the presence / absence of the water 10 inside the metal box 2 and estimates the water depth based on the reception signal received by the reception unit 14. As shown in FIG. 2, the signal processing unit 15 includes a control unit 151, a storage unit 152, a reading unit 153, a liquid presence / absence determining unit 154, a liquid depth estimating unit 155, and a display unit 156.

The control unit 151 generates a control signal and outputs the control signal to the transmission unit 13.
Storage section 152 stores the received signal received by receiving section 14. The storage unit 152 also appropriately stores information indicating the determination result by the liquid presence / absence determination unit 154 and information indicating the estimation result by the liquid depth estimation unit 155.
Reading section 153 reads the received signal stored in storage section 152.

  The liquid presence / absence determining unit 154 determines the presence / absence of water 10 inside the metal box 2 based on the reception signal read by the reading unit 153. The liquid presence determination unit 154 determines that there is water 10 when determining that the number of the reception signals is plural. In addition, the liquid presence / absence determination unit 154 determines that there is water 10 when it is determined that the number of the received signals is not plural and when it is determined that the duration of the received signal is longer than the reference value. . In addition, the liquid presence / absence determining unit 154 determines that the duration of the received signal is not longer than the reference value, and determines that the water 10 is present when it determines that the amplitude of the received signal is smaller than the threshold value. judge. On the other hand, when determining that the amplitude of the received signal is not smaller than the threshold, the liquid presence determination unit 154 determines that there is no water 10.

  The liquid depth estimating unit 155 estimates the water depth inside the metal box 2 based on the reception signal read by the reading unit 153. The liquid depth estimating unit 155 estimates the water depth from the time difference between the received signals when the liquid presence / absence determining unit 154 determines that the number of the received signals is plural and determines that there is water 10. In addition, the liquid depth estimating unit 155 estimates the water depth from the frequency spectrum of the received signal when the liquid presence / absence determining unit 154 determines that the number of the received signals is not plural and determines that there is water 10. I do.

  The liquid depth estimating unit 155 estimates the water depth inside the metal box 2 as described above. On the other hand, if the shape inside the metal box 2 is known, the amount of water inside the metal box 2 can be estimated from the water depth inside the metal box 2. Therefore, the signal processing unit 15 may have a function of estimating the amount of water inside the metal box 2 based on the water depth estimated by the liquid depth estimating unit 155 (liquid amount estimating unit).

Display unit 156 displays the received signal read by reading unit 153, information indicating the result of determination by liquid presence / absence determining unit 154, and information indicating the result of estimation by liquid depth estimating unit 155.
Here, the case where the display unit 156 is provided inside the ultrasonic measurement device 1 is shown. However, the invention is not limited thereto, and the display unit 156 may be provided outside the ultrasonic measurement device 1.

  FIG. 2 illustrates a case where the ultrasonic measurement device 1 includes the liquid depth estimating unit 155. However, the present invention is not limited to this, and the ultrasonic measurement device 1 may not include the liquid depth estimating unit 155. Hereinafter, the description will be given on the assumption that the ultrasonic measurement device 1 includes the liquid depth estimation unit 155.

Next, an example of a hardware configuration of the signal processing unit 15 will be described with reference to FIG.
The signal processing unit 15 can be realized using, for example, a computer with a built-in CPU (Central Processing Unit) such as a personal computer or a workstation. In addition, the signal processing unit 15 may be an LSI (Large-Scale) that uses an LSI such as a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), or an LSI (Field-Programmable Gate Array) such as an FPGA (Field-Programmable Gate Array).

  In the example of FIG. 3, a processor 501 including a CPU, a ROM (Read Only Memory) 502, a RAM (Random Access Memory) 503, a recording medium 504, a transmission / reception interface circuit 505, a display interface circuit 506 are implemented as means for realizing the signal processing unit 15. And a display 507 are provided. In addition, the processor 501, the ROM 502, the RAM 503, the recording medium 504, the transmission / reception interface circuit 505, the display interface circuit 506, and the display 507 are mutually connected via a signal path 508 such as a bus circuit.

  The processor 501 implements a control unit 151, a reading unit 153, a liquid presence / absence determining unit 154, and a liquid depth estimating unit 155, and uses the RAM 503 as a working memory for ultrasonic measurement read from the ROM 502. Run a computer program. The recording medium 504 realizes the storage unit 152 and is configured using, for example, a volatile memory such as an SDRAM (Synchronous DRAM), an HDD (Hard Disk Drive), or an SSD (Solid State Drive). The transmission / reception interface circuit 505 is a circuit used for signal transmission with the transmission unit 13 and signal transmission with the reception unit 14. The display interface circuit 506 is a circuit used for signal transmission with the display 507.

  The display 507 realizes the display unit 156. Note that the display method on the display 507 is not particularly limited, and a numerical value may be displayed by a number or by the brightness of an LED lamp.

Next, the operation principle of the ultrasonic measurement device 1 according to the first embodiment will be described.
In the ultrasonic measurement device 1 according to the first embodiment, as shown in FIG. 1, the transmission probe 11 transmits ultrasonic waves to the inside of the bottom surface of the metal box 2. Thereby, an ultrasonic wave (plate wave) propagates inside the bottom surface of the metal box 2. This ultrasonic wave is a pulse wave having a finite duration. Thereafter, the ultrasonic waves are received by the receiving probe 12. Here, a path through which the ultrasonic wave propagates only inside the bottom surface of the metal box 2 is referred to as a first path (path indicated by reference numeral 101 in FIG. 1).

  On the other hand, when the water 10 is present inside the metal box 2, part of the ultrasonic waves propagating inside the bottom surface of the metal box 2 also propagates into the water 10. Thereafter, the ultrasonic waves are reflected on the water surface, return to the bottom surface of the metal box 2, and propagate inside the bottom surface of the metal box 2 again. In this manner, the path through which the ultrasonic wave propagates not only inside the bottom surface of the metal box 2 but also into the water 10 is referred to as a second path (path indicated by reference numeral 102 in FIG. 1).

  As described above, when the metal box 2 is flooded, there are two paths of the ultrasonic wave, the first path and the second path. Here, since the second path has time to propagate in the water 10, the receiving probe 12 receives the ultrasonic wave that has propagated through the second path later than the ultrasonic wave that has propagated through the first path. . The delay time at this time varies depending on the water depth, and becomes, for example, as shown in FIG.

  FIG. 4 schematically shows a reception signal received by the ultrasonic measurement device 1. FIG. 4A shows a reception signal in a case where there is no water 10 inside the metal box 2. FIG. 4B shows a reception signal when the water 10 is small in the metal box 2 and the water depth is equal to or less than the wavelength of the ultrasonic wave in the water (when the water depth is shallow). FIG. 4C shows a reception signal when a large amount of water 10 is present inside the metal box 2 and the water depth is sufficiently larger than the wavelength of ultrasonic waves in the water (when the water depth is sufficiently deep). I have. In FIG. 4, λ represents the wavelength of ultrasonic waves in water, and the wavelength of ultrasonic waves in water is determined by the speed of sound in water and the frequency of ultrasonic waves.

  When there is no water 10 inside the metal box 2, the second path does not exist, so that only the ultrasonic wave transmitted through the first path is received by the receiving probe 12. Therefore, as shown in FIG. 4A, the number of received signals is one, and the received signal has a very simple waveform.

  On the other hand, when the water 10 is inside the metal box 2 and the water depth is shallow, the ultrasonic wave transmitted through the first path and the ultrasonic wave transmitted through the second path are in a state of being overlapped. Therefore, as shown in FIG. 4B, the received signal has a complicated received waveform.

When the water 10 is inside the metal box 2 and the water depth is sufficiently deep, the ultrasonic waves transmitted through the first path and the ultrasonic waves transmitted through the second path are clearly separated. Therefore, as shown in FIG. 4C, the receiving unit 14 receives a plurality of received signals.
In addition, as shown in FIG. 4C, the number of ultrasonic waves propagated along the second path is not limited to one, and a plurality of ultrasonic waves may be propagated. This is because the ultrasonic wave is repeatedly reflected and propagated between the water surface and the bottom surface of the metal box 2. In FIG. 4C, as indicated by reference numeral 401, there are three ultrasonic waves that have propagated through the second path.

Next, how the reception signal received by the ultrasonic measurement device 1 changes with respect to the water depth will be examined by simulation.
FIG. 5 is a diagram illustrating response characteristics of the transmission probe 11 used in the simulation. As shown in FIG. 5, the center frequency of the transmission probe 11 is 0.5 MHz, which is a relatively wide band. The reason why the center frequency is set to 0.5 MHz is to make it possible to cope with a case where a coating film having a thickness of about 400 μm exists outside the metal box 2. Since the center frequency of the transmission probe 11 is 0.5 MHz, the wavelength of the ultrasonic wave in water is about 3 mm.

FIG. 6 shows a dispersion characteristic (phase velocity) when the ultrasonic wave transmitted by the transmission probe 11 shown in FIG. 5 propagates on the bottom surface of the metal box 2. 6, the material of the bottom surface of the metal box 2 is steel and the thickness of the bottom surface is 2.3 mm. Further, although a large number of higher-order mode plate waves actually propagate, FIG. 6 shows only the second-order mode.
As shown in FIG. 6, the phase speed of the ultrasonic wave changes depending on the frequency. Since the center frequency is set to 0.5 MHz in the simulation, the phase speed of the A0 mode is about 2450 m / s in this case. Therefore, hereinafter, a case where a plate wave having a phase velocity of 2450 m / s is used will be considered.

Then, a received signal in the case of transmitting and receiving an A0 mode plate wave having a phase velocity of 2450 m / s was obtained by simulation.
FIG. 7 shows the simulation conditions. As shown in FIG. 7, the transmission probe 11 and the reception probe 12 are installed on the bottom surface of the metal box 2 so as to face each other, and the distance between the transmission probe 11 and the reception probe 12 is 100 mm. And Further, it is assumed that coating films 701 and 702 exist on the inside and outside of the bottom surface of the metal box 2. The thickness of the coating 701 was 50 μm, and the thickness of the coating 702 was 400 μm.

FIG. 8 shows the result of obtaining a received signal by performing a simulation while changing the water depth.
As shown in FIG. 8A, when there is no water 10 (d = 0 mm), the number of received signals is one, and a simple received waveform is obtained. Although FIG. 4A simulates a received signal whose amplitude is only on the positive side, the AC signal actually has an AC waveform as shown in FIG. 8A.

Further, for example, as shown in FIG. 8B, when the water depth is shallow (d = 0.8 mm in FIG. 8B), the amplitude of the received signal is significantly reduced. This is because the condition is such that the ultrasonic wave transmitted through the first path and the ultrasonic wave transmitted through the second path cancel each other out due to phase interference.
For example, in the case of FIG. 8C (d = 1.6 mm), the received signal has the same amplitude as that in the case where there is no water 10. This is because the condition is such that the ultrasonic wave propagating on the first path and the ultrasonic wave propagating on the second path are strengthened by phase interference.
8D and 8E (d = 2.4 mm, d = 3.0 mm), the received signal has a complicated received waveform.
That is, when the water depth is equal to or less than the wavelength of the ultrasonic wave in water (about 3 mm), the waveform of the received signal becomes complicated.

On the other hand, in the case of FIG. 8F (d = 5.0 mm), the ultrasonic wave propagated on the first path and the ultrasonic wave propagated on the second path are separated.
Further, in the case of FIG. 8G (d = 7.0 mm), the ultrasonic wave transmitted through the first path and the ultrasonic wave transmitted through the second path are clearly separated. Also, in FIG. 8G, it can be seen that there is not only one ultrasonic wave propagating in the second path, but a plurality of ultrasonic waves. In FIG. 8G, reference numeral 801 indicates an ultrasonic wave that has propagated along the first path, and reference numeral 802 indicates an ultrasonic wave that has propagated along the second path.

Next, FIG. 9 shows the relationship between the amplitude (relative echo height) of the received signal shown in FIG. 8 and the water depth. In FIG. 9, each amplitude is normalized by the amplitude when there is no water 10 (d = 0 mm).
As shown in FIG. 9, when the water depth is shallow, the amplitude shows a complicated characteristic. This is because, as described above, the ultrasonic waves propagated on the first path and the ultrasonic waves propagated on the second path cause phase interference. On the other hand, when the water depth becomes deep and becomes 4 mm or more, the amplitude of the received signal hardly changes.
As described above, it is difficult to determine the presence or absence of the water 10 before estimating the water depth using only the amplitude of the received signal. For example, the amplitudes of the received signals are almost the same between d = 0 mm and d = 1.6 mm, and it is very difficult to distinguish between the two only by the amplitude.

On the other hand, if information such as the number of received signals, the duration of the received signal, and the amplitude of the received signal is effectively used, the presence or absence of the water 10 can be determined. In addition, if the frequency spectrum of the trailing portion of the received signal is used, the depth can be estimated when the water 10 is shallow.
Hereinafter, an operation example of the signal processing unit 15 according to the first embodiment will be described with reference to FIG. The transmitting probe 11 transmits ultrasonic waves to the bottom of the metal box 2, the receiving probe 12 receives the ultrasonic waves from the bottom of the metal box 2, converts the ultrasonic waves into electric signals, and The electric signal is received as a reception signal, and the storage unit 152 stores the reception signal.

  In the operation example of signal processing section 15 in the first embodiment, first, reading section 153 reads a received signal stored in storage section 152 (step ST1001).

  Next, liquid presence / absence determining section 154 counts the number of received signals read by reading section 153, and determines whether the number of received signals is plural (steps ST1002 and ST1003).

  Here, an example of a method of counting the reception signal by the liquid presence / absence determination unit 154 is shown in FIG. In FIG. 11, only the positive side of the received signal is schematically shown, and the number of received signals is counted by the liquid presence / absence determining unit 154 counting the number of peaks (arrows shown in FIG. 11) of the amplitude of the received signal. Shows how to do it. FIG. 11A shows a case where there is one amplitude peak, and FIG. 11B shows a case where there are four amplitude peaks. Note that the method of counting the reception signal by the liquid presence / absence determination unit 154 is not limited to the method using the number of amplitude peaks shown in FIG. You may. Here, it is assumed that the response characteristics of the transmission probe 11 are simple as shown in FIG. 5 and can be regarded as a single signal. On the other hand, the response characteristic itself of the transmission probe 11 is complicated and is out of the applicable range when it is regarded as a plurality of signals.

  When determining in step ST1003 that the number of received signals is plural, liquid presence / absence determining section 154 determines that water 10 is present inside metal box 2 (step ST1004). For example, as shown in FIG. 8G (d = 7.0 mm), if there are a plurality of received signals, the ultrasonic wave propagating through the second path is present, so the liquid presence / absence determination unit 154 has the water 10. Can be determined.

  Next, liquid depth estimating section 155 estimates the water depth inside metal box 2 from the time difference between the received signals read by reading section 153 (step ST1005). The depth estimation using the time difference of the received signal by the liquid depth estimating unit 155 can apply a conventionally known technique, and a detailed description thereof will be omitted. Thereafter, the sequence ends.

  On the other hand, when determining in step ST1003 that the number of received signals is not plural, liquid presence / absence determining section 154 calculates the duration of the received signal (step ST1006).

  Next, liquid presence / absence determining section 154 determines whether or not the duration of the received signal is longer than the reference value (step ST1007). The reference value is set based on the response characteristics of the transmission probe 11. For example, when the response characteristic of the transmission probe 11 is the characteristic shown in FIG. 5, the duration of the received signal is about 6 μs from the time waveform, and the reference value is set based on this value.

In this step ST1007, when determining that the duration of the received signal is longer than the reference value, liquid presence / absence determining section 154 determines that water 10 is present inside metal box 2 (step ST1008).
FIG. 12 shows an example in which there is one received signal and the duration of the received signal is shorter and longer than the reference value. In FIG. 12, reference numeral 1201 represents a reference value. FIG. 12B shows the reception signal at d = 2.0 mm obtained by the simulation, and the duration of the reception signal is longer than the reference value. In such a case, since the reflected wave from the water surface affects the received signal, the liquid presence / absence determination unit 154 can determine that the water 10 is present. The start position of the reference value is a rising portion of the received signal, which is determined based on the group velocity of the ultrasonic wave and the distance between the transmission probe 11 and the reception probe 12.

  Next, liquid depth estimating section 155 calculates the frequency spectrum in the gate of the received signal read by reading section 153 (step ST1009). The gate is set to start at a point of the received signal read by the reading unit 153 exceeding a reference value and end at a point set as appropriate.

  Next, liquid depth estimating section 155 calculates a peak frequency from the frequency spectrum (step ST1010).

  Next, liquid depth estimation section 155 estimates the water depth inside metal box 2 from the peak frequency (step ST1011). At this time, the liquid depth estimating unit 155 estimates the water depth from the relationship between the peak frequency and the water depth obtained in advance. Thereafter, the sequence ends.

  In this case, the received waveform becomes complicated due to the interference between the ultrasonic waves transmitted through the first path and the ultrasonic waves transmitted through the second path. Therefore, it is difficult to estimate the water depth only by the amplitude of the received signal. Therefore, the frequency spectrum of the tail portion is used. Here, the trailing portion is a portion of the received signal that exceeds a reference value. FIG. 13 shows an example of the received signal and the frequency spectrum of the trailing portion. In FIG. 13, the tailing portion is shown with a gate. In FIG. 13, reference numeral 1301 represents a reference value, and reference numeral 1302 represents a gate.

  As shown in FIG. 13, the frequency spectrum of the trailing portion differs depending on the water depth. As a remarkable feature, the peak frequency changes with the water depth. FIG. 13 shows the received signal and the frequency spectrum from d = 1.0 mm to d = 1.6 mm, and it can be seen that the peak frequency decreases as the water depth increases.

FIG. 14 shows the relationship between the peak frequency and the water depth shown in FIG.
As shown in FIG. 14, the peak frequency decreases as the water depth increases up to about d = 1.6 mm. On the other hand, when d = 1.8 mm, it increases sharply because the phase has periodicity. Further, from d = 1.8 mm to d = 2.6 mm, the peak frequency decreases as the water depth increases.
The liquid depth estimation unit 155 can estimate the water depth by using this characteristic. For example, the liquid depth estimating unit 155 obtains the frequency spectrum of the tailing portion, and when the peak frequency is 0.4 MHz, can obtain “1.3 mm in water” from FIG.

  The characteristic shown in FIG. 14 is a characteristic when the acoustic velocity in water is 1480 m / s, and the A0 mode ultrasonic wave having a phase velocity of about 2450 m / s is transmitted to a 2.3 mm thick steel plate. is there. This characteristic changes depending on various factors. For example, when the speed of sound in water changes depending on temperature, when the thickness of the bottom surface of the metal box 2 is slightly thinner or thicker than 2.3 mm, or when the material of the metal box 2 is not steel but other metal. In some cases, this characteristic changes. As described above, the relationship between the water depth and the peak frequency changes depending on various factors, and the characteristics shown in FIG. 14 are only examples.

On the other hand, when determining in step ST1007 that the duration of the received signal is not longer than the reference value, liquid presence determining section 154 calculates the amplitude of the received signal (step ST1012).
If the number of received signals is one and the duration of the received signal is shorter than the reference value, two cases can be considered. One is a case where there is no water 10 as shown in FIG. 12A. The other is a case where there is water 10 but the ultrasonic wave transmitted through the second path is not received by the receiving probe 12. An example of the latter is shown in FIG. As shown in FIG. 15, when a large amount of water 10 has entered, a reflected wave from the water surface may return farther than the position of the reception probe 12 depending on the position of the reception probe 12. In this case, the ultrasonic wave that has propagated through the second path cannot be received by the receiving probe 12. In FIG. 15, reference numeral 1501 represents a first path, and reference numeral 1502 represents a second path. Further, even when the metal box 2 is inclined and the water surface is inclined when viewed from the transmission probe 11 and the reception probe 12, the reflected wave from the water surface does not return to the desired direction, In some cases, the ultrasonic wave that has propagated through the two paths is not received by the receiving probe 12. This is also included in the case where “there is the water 10 but the ultrasonic wave transmitted through the second path is not received by the receiving probe 12”.

  Next, liquid presence / absence determining section 154 determines whether the calculated amplitude of the received signal is smaller than a threshold (step ST1013). That is, the liquid presence / absence determining unit 154 compares the amplitude of the received signal with the threshold value in order to identify the above two cases. Here, if the water 10 is present, the energy of the plate wave propagates into the water 10, so that the amplitude of the received signal based on the ultrasonic wave that has propagated through the first path is smaller than when there is no water 10. Therefore, when the amplitude of the received signal is smaller than the threshold value, liquid presence determination section 154 determines that water 10 is present. Note that the threshold is determined based on the amplitude of the received signal when there is no water 10. This determination may be made using a test body or using a value obtained by calculation.

  In this step ST1013, when determining that the amplitude of the received signal is smaller than the threshold value, liquid presence / absence determining section 154 determines that water 10 is present inside metal box 2 (step ST1014). Thereafter, the sequence ends.

  On the other hand, in step ST1013, when determining that the amplitude of the received signal is not smaller than the threshold value, liquid presence / absence determining section 154 determines that water 10 does not exist inside metal box 2 (step ST1015). That is, the liquid presence / absence determination unit 154 determines that there is no water 10 when three conditions are satisfied that the number of received signals is one, the duration of the received signal is short, and the amplitude of the received signal is large. . Thereafter, the sequence ends.

  The display unit 156 displays the received signal read by the reading unit 153, information indicating the determination result by the liquid presence / absence determination unit 154, and information indicating the estimation result by the liquid depth estimation unit 155. The storage unit 152 appropriately stores information indicating the determination result by the liquid presence / absence determination unit 154 and information indicating the estimation result by the liquid depth estimation unit 155.

  As described above, according to the first embodiment, the ultrasonic measuring device 1 transmits the ultrasonic wave to the plate-like portion, and receives the ultrasonic wave from the plate-like portion to convert the ultrasonic signal into an electric signal. The receiving probe 12 to be converted, the receiving unit 14 for receiving the electric signal obtained by the receiving probe 12 as a received signal, the number of received signals received by the receiving unit 14 and the duration of the received signal. A liquid presence / absence determination unit 154 for determining the presence / absence of a liquid in contact with the plate-shaped portion based on the presence / absence of the liquid. Thereby, the ultrasonic measurement device 1 according to the first embodiment can determine the presence or absence of the liquid even when the difference in the amplitude of the received signal is small between the case where the liquid is present and the case where the liquid is not present.

  In the present invention, it is possible to modify any components of the embodiment or omit any components of the embodiment within the scope of the invention.

  Reference Signs List 1 ultrasonic measuring device, 2 metal box, 10 water, 11 transmitting probe, 12 receiving probe, 13 transmitting unit, 14 receiving unit, 15 signal processing unit, 16 transceiver, 151 control unit, 152 storage unit, 153 readout unit, 154 liquid presence / absence determination unit, 155 liquid depth estimation unit, 156 display unit, 501 processor, 502 ROM, 503 RAM, 504 recording medium, 505 transmission / reception interface circuit, 506 display interface circuit, 507 display, 508 signal Road.

Claims (8)

A transmission probe for transmitting ultrasonic waves to the plate portion,
A receiving probe that receives an ultrasonic wave from the plate-like portion and converts the ultrasonic signal into an electric signal,
A reception unit that receives an electric signal obtained by the reception probe as a reception signal,
An ultrasonic measurement device comprising: a liquid presence / absence determination unit configured to determine presence / absence of a liquid in contact with the plate-shaped portion based on a number of reception signals received by the reception unit and a duration of the reception signal. The liquid presence / absence determination unit, when determining that the number of reception signals received by the reception unit is plural, determines that there is a liquid in contact with the plate-shaped portion. Ultrasonic measuring device. The liquid presence determination unit, when it is determined that the number of received signals is not a plurality, when the duration of the received signal is longer than a reference value, it is determined that there is a liquid in contact with the plate-shaped portion. The ultrasonic measuring device according to claim 2. The liquid presence / absence determination unit determines that the number of received signals is not plural and determines that the duration of the received signal is not longer than a reference value.If the amplitude of the received signal is smaller than a threshold value, The ultrasonic measurement device according to claim 3, wherein it is determined that there is a liquid in contact with the plate-shaped portion. A liquid depth estimating unit for estimating a depth of a liquid in contact with the plate-shaped portion based on a frequency spectrum of a received signal received by the receiving unit. The ultrasonic measurement device according to any one of the preceding claims. The liquid depth estimating unit, when it is determined by the liquid presence / absence determining unit that the number of received signals is not plural and when it is determined that there is liquid, calculates a peak frequency from the frequency spectrum of the received signal, The ultrasonic measurement device according to claim 5, wherein a depth of the liquid is estimated from a peak frequency. The display device according to any one of claims 1 to 6, further comprising: a display unit that displays a reception signal received by the reception unit and information indicating a determination result by the liquid presence / absence determination unit. Ultrasonic measuring device. A transmission probe that transmits ultrasonic waves to the plate-shaped portion, a reception probe that receives ultrasonic waves from the plate-shaped portion and converts the ultrasonic waves into an electric signal, and receives an electric signal obtained by the reception probe. An ultrasonic measurement method by an ultrasonic measurement device including a receiving unit that receives a signal,
A step of determining whether liquid is in contact with the plate-shaped portion based on the number of received signals received by the receiving unit and the duration of the received signals, Measuring method.

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