JP7480390B2 - Sensor device, sensor system, and method for using the sensor device - Google Patents

Description

The present invention relates to a sensor device equipped with an ultrasonic sensor and a method for arranging the ultrasonic sensor.

Conventionally, technology has been proposed that uses ultrasonic sensors to identify when a river has reached a dangerous water level. As an example of this type of technology, Patent Document 1 discloses a technology in which an ultrasonic sensor is attached to an arm that extends from the riverbank, thereby installing the ultrasonic sensor at a predetermined height above the water surface. In Patent Document 1, the ultrasonic sensor detects the distance between the sensor and the water surface (hereinafter referred to as the sensor-to-water surface distance) based on the time between transmitting ultrasonic waves toward the water surface and receiving the reflected waves (ultrasonic reflection waves) reflected by the water surface. Then, by rotating the arm horizontally, the horizontal position of the ultrasonic sensor can be changed (i.e., the detection position of the sensor-to-water surface distance by the ultrasonic sensor can be changed horizontally).

JP 2002-174516 A

However, in Patent Document 1, although the horizontal position of the ultrasonic sensor can be changed by rotating the arm as described above, the vertical position of the ultrasonic sensor is fixed. For this reason, when a general-purpose ultrasonic sensor is used, the output of the ultrasonic sensor is low, so the sensor-to-water surface distance can only be detected when the sensor-to-water surface distance is short (for example, when the sensor-to-water surface distance is 4 m or less). When there is a possibility that the sensor-to-water surface distance will increase due to a drop in the water level, it is necessary to use an ultrasonic sensor with high output, which requires high costs.

In addition, in Patent Document 1, the vertical position of the ultrasonic sensor is fixed, so even if the ultrasonic sensor fails to detect the sensor-to-water surface distance due to a malfunction, the manager may assume that the reason for not detecting the sensor-to-water surface distance is that the water level has dropped and the sensor-to-water surface distance has increased. As a result, if the malfunction in the ultrasonic sensor is left unattended, the ultrasonic sensor may not operate when the water level reaches a dangerous level, and it may not be possible to identify when the water level has reached a dangerous level.

The present invention has been made in consideration of the above, and its purpose is to provide a sensor device and ultrasonic sensor placement method that can obtain information that can reliably identify when a river or ocean reaches a dangerous water level while keeping costs low.

To achieve the above objectives, the present invention includes the following subject matter:

Item 1. An ultrasonic sensor capable of measuring the time from when an ultrasonic wave is emitted until when the reflected wave of the ultrasonic wave reflected by a measurement object is received, and transmitting information based on the time to the outside, and a support body supporting the ultrasonic sensor so that the ultrasonic sensor is positioned above the water surface of a river or sea,
The ultrasonic sensor is attached to the support so that the ultrasonic waves are directed toward the water surface of the river or sea.
The support is capable of moving the ultrasonic sensor up and down.

Item 2. The ultrasonic sensor further includes a housing that houses the ultrasonic sensor.
the housing is attached to the support so that the ultrasonic waves emitted from the opening of the housing are directed toward the water surface of a river or an ocean;
2. The sensor device according to item 1, wherein the support is capable of moving the housing up and down.

Item 3. A sensor device according to item 2, in which the material forming the housing contains a repellent material to prevent insects from approaching.

Item 4. A sensor device according to item 2 or 3, in which a repellent material is applied to at least a portion of the surface of the housing to prevent insects from approaching.

Item 5. A sensor device according to any one of items 1 to 4, in which a water repellent agent is applied to the surface of the housing.

Item 6. A sensor device according to any one of items 1 to 5, in which the opening of the housing is covered with a sheet to prevent insects from entering.

Item 7. The support includes a pole extending in the vertical direction,
7. The sensor device according to any one of items 2 to 6, wherein the housing can be moved up and down by sliding the pole in the up and down direction.

Item 8. The support includes an arm extending horizontally,
8. The sensor device according to item 7, wherein the pole is attached to one end of the arm, and the housing is attached to the other end of the arm.

Item 9. An antenna connected to the ultrasonic sensor,
the antenna is attached to the arm so as to extend in a longitudinal direction of the arm, or the antenna is constituted by the arm,
9. The sensor device according to item 8, wherein the ultrasonic sensor transmits the information based on the time from the antenna to an outside.

Item 10. Further comprising a support,
the support body includes an arm to which the housing is attached;
The arm extends horizontally, and one end of the arm is fastened to a support column extending vertically.
the support is detachably attached to the support column near and below the arm, and by loosening the fastening of one end of the arm to the support column, the arm can be rotated around the support column with the one end of the arm supported by the support,
A sensor device as described in any one of items 2 to 6, wherein the arm can be slid vertically along the support by loosening the fastening of one end of the arm to the support and removing the support from the support, thereby moving the housing up and down.

Item 11. The arm further includes a stopper that is detachably attached to the support column near the upper side of the arm,
When the fastening of the one end side of the arm to the support is loosened, the one end side of the arm supported by the support tool can be pressed downward by the pressing tool,
The sensor device described in item 10, wherein the arm can be slid vertically along the support by loosening the fastening of one end of the arm to the support and removing the support and the fastening device from the support, thereby moving the housing up and down.

Item 12. A sensor device according to any one of items 8 to 11, in which the housing is attached to the arm so as to be slidable in the horizontal direction.

Item 13. A sensor system including the sensor device according to any one of items 1 to 12,
A sensor system comprising a distance acquisition means for acquiring information indicating the distance from the ultrasonic sensor to the measurement object based on the time measured by the ultrasonic sensor and the speed of sound calculated using the air temperature near the ultrasonic sensor at the time the ultrasonic wave is transmitted or the reflected wave is received.

Item 14. A method for arranging an ultrasonic sensor, comprising:
The ultrasonic sensor measures the time from when an ultrasonic wave is emitted until when the reflected wave of the ultrasonic wave reflected by a measurement object is received, and is capable of transmitting information based on the time to the outside, and the ultrasonic sensor is disposed so that the ultrasonic wave is directed toward a solid part located below a dangerous water level of a river or the sea,
A method for arranging an ultrasonic sensor, wherein the distance between the solid portion and the ultrasonic sensor is shorter than the maximum distance at which the ultrasonic sensor can detect the reflected wave.

Item 15. The ultrasonic sensor arrangement method according to Item 14, wherein the solid body is a river bank.

Item 16. An ultrasonic sensor disposed above the water surface of a river or sea;
A reflector is disposed between the ultrasonic sensor and the water surface,
The ultrasonic sensor radially transmits ultrasonic waves downward, and is capable of outputting a signal related to the ultrasonic waves as the ultrasonic waves are transmitted, and outputting a signal related to the reflected waves as the ultrasonic waves are received and reflected by an object to be measured,
the distance between the reflector and the ultrasonic sensor is shorter than the maximum distance at which the ultrasonic sensor can detect the reflected wave;
A sensor device in which a portion of the ultrasonic waves emitted from the ultrasonic sensor are directed toward the reflector, and the remaining ultrasonic waves are directed below the reflector.

Item 17. The sensor device according to item 16, wherein the distance between the ultrasonic sensor and a dangerous water level of a river or sea is equal to or less than the maximum distance at which the ultrasonic sensor can detect the reflected wave.

According to the sensor device of the present invention, the support can move the ultrasonic sensor up and down, so that the distance between the water surface of the river or sea and the ultrasonic sensor can be made shorter than the maximum distance that can be detected by the ultrasonic sensor (hereinafter referred to as the maximum detection distance). Therefore, unless a malfunction occurs, the ultrasonic sensor constantly detects reflected waves, measures the time from when the ultrasonic sensor transmits an ultrasonic wave to when it receives the reflected wave of the ultrasonic wave reflected by the measurement object, and transmits information based on that time. Therefore, if a malfunction occurs in the ultrasonic sensor, the above information will no longer be transmitted from the ultrasonic sensor, and the manager will recognize that the ultrasonic sensor has malfunctioned (this can avoid the manager from assuming that the ultrasonic sensor does not detect the distance because the distance is large, as in the past). Therefore, measures to repair the ultrasonic sensor can be taken quickly, so that the ultrasonic sensor can be reliably operated normally when the river or sea reaches a dangerous water level. As a result, it is possible to reliably identify that the river or sea has reached a dangerous water level based on the distance detected by the ultrasonic sensor.

In addition, according to the sensor device of the present invention, since the support can move the ultrasonic sensor up and down, even if a commonly used low-output ultrasonic sensor is used and the maximum detection distance is shortened, the distance between the water surface of the river or sea and the ultrasonic sensor can be made shorter than the maximum detection distance. Therefore, even if a low-output ultrasonic sensor is used, the ultrasonic sensor can be made to be in a state where it can always detect reflected waves, so there is no need to use a high-output ultrasonic sensor. Therefore, costs can be kept low. In addition, the ultrasonic sensor can be attached to an arm at a location where it is easy to install, such as inside a bridge, and then adjusted to the height to be placed for measurement using a pole. This allows the ultrasonic sensor to be placed safely without incurring costs such as scaffolding. Similarly, maintenance such as updating the power supply unit (device) of the ultrasonic sensor when the battery or other power supply unit (device) has reached the end of its life or replacing it due to a malfunction can be done safely and inexpensively. Furthermore, the same effect can be obtained when the water level measurement is stopped and the ultrasonic sensor is raised to a higher height or the ultrasonic sensor is retrieved to prevent damage to the ultrasonic sensor due to collision with driftwood when the river rises above the dangerous water level.

According to the ultrasonic sensor arrangement method of the present invention, the height of the solid part is constant, and the distance between the solid part and the ultrasonic sensor is shorter than the maximum detection distance. As a result, when the water level of the river or sea is below the dangerous water level, the ultrasonic sensor always detects the reflected wave, measures the time from when the ultrasonic wave is emitted to when the reflected wave reflected by the measurement object is received, and transmits information based on that time, unless the ultrasonic sensor malfunctions. Therefore, if the ultrasonic sensor malfunctions, the ultrasonic sensor will no longer transmit the above information, and the administrator will recognize that the ultrasonic sensor malfunctions. Therefore, measures to repair the ultrasonic sensor can be taken quickly. As a result, the ultrasonic sensor can be reliably operated normally when the river or sea reaches a dangerous water level, and it is possible to reliably identify that the river or sea has reached a dangerous water level based on the distance detected by the ultrasonic sensor.

Even when a commonly used low-output ultrasonic sensor is used, the ultrasonic sensor can always detect reflected waves by making the distance between the solid part and the ultrasonic sensor shorter than the maximum detection distance. This eliminates the need to use a high-output ultrasonic sensor, and allows costs to be kept low.

In addition, according to the sensor device of the present invention, the distance between the reflector and the ultrasonic sensor is made shorter than the maximum detection distance, so that the ultrasonic sensor always outputs a signal related to the reflected wave from the reflector unless a malfunction occurs in the ultrasonic sensor. Therefore, if a malfunction occurs in the ultrasonic sensor, the ultrasonic sensor will no longer output the signal, and the manager will recognize that a malfunction has occurred in the ultrasonic sensor. Therefore, measures can be taken quickly to repair the ultrasonic sensor. This ensures that the ultrasonic sensor can operate normally when the river or sea reaches a dangerous water level, making it possible to reliably identify that the river or sea has reached a dangerous water level.

Even if a commonly used low-output ultrasonic sensor is used, by making the distance between the reflector and the ultrasonic sensor shorter than the maximum detection distance, the ultrasonic sensor will output a signal related to the reflected waves from the reflector. This means that there is no need to use a high-output ultrasonic sensor, and costs can be kept low.

1 is a perspective view showing a sensor device according to a first embodiment of the present invention; 1 is a schematic diagram showing a state in which a sensor device according to a first embodiment is placed above a river. 1 is a schematic diagram showing a state in which a sensor device according to a first embodiment is placed above a river. FIG. 2 is a side view showing the pole attached to the post by the fastener. FIG. 13 is a plan view showing the fasteners used to attach the pole to the post. 1 is a schematic diagram showing a sensor system in which a sensor device according to a first embodiment is incorporated; FIG. 2 is a plan view showing a housing that houses an ultrasonic sensor. FIG. 11 is a schematic diagram showing a state in which a sensor device according to a second embodiment of the present invention is placed above a river. FIG. 11 is a schematic diagram showing a state in which a sensor device according to a second embodiment of the present invention is placed above a river. FIG. 11 is a perspective view showing a sensor device according to a third embodiment of the present invention. FIG. 13 is a perspective view showing a modified example of the sensor device according to the third embodiment of the present invention. FIG. 11 is a schematic diagram showing a sensor system in which a sensor device according to a third embodiment is incorporated. This is a graph showing the time trends of temperature announced by the Meteorological Agency and the time trends of the temperature inside the casing. 11 is a graph showing the time progression of the distance between the ultrasonic sensor and the water surface of the river, which is determined using the transmission and reception time measured by the ultrasonic sensor. FIG. 11 is a perspective view showing a sensor device according to a fourth embodiment of the present invention. FIG. 13 is a schematic side view showing a sensor device according to a fourth embodiment. FIG. 13 is a schematic plan view showing a sensor device according to a fourth embodiment. FIG. 13 is a perspective view showing an instrument that can be used as a support or a retainer. 13A and 13B are diagrams showing a modified example of the sensor device according to the fourth embodiment, in which (A) is a schematic side view and (B) is a schematic plan view. FIG. 11 is a schematic diagram showing a state in which a sensor device according to a modified example of the present invention is placed above a river or the sea. FIG. 11 is a schematic diagram showing a state in which a sensor device according to a modified example of the present invention is placed above a river or the sea. 4 is a graph showing the relationship between wave intensity and time as indicated by an output signal of an ultrasonic sensor. 4 is a graph showing the relationship between wave intensity and time as indicated by an output signal of an ultrasonic sensor. 11 is a flowchart illustrating an example of a process executed by a management server. 11A and 11B are diagrams showing a sensor device according to a modified example of the present invention, in which (A) is a perspective view and (B) is a side view.

The first embodiment of the present invention will be described below with reference to the accompanying drawings. Fig. 1 is a perspective view showing a sensor device 1 according to the first embodiment of the present invention. Figs. 2 and 3 are schematic diagrams showing a state in which the sensor device 1 according to the first embodiment is placed above a river K. Fig. 2 shows the state when the river K is at a normal water level, and Fig. 3 shows the state when the river K has reached a dangerous water level. The dangerous water level is, for example, any of the flood danger water level, evacuation decision water level, flood caution water level, and flood defense corps standby water level designated by the Japan Meteorological Agency.

The sensor device 1 of the first embodiment is used to identify when the river K reaches a dangerous water level. In the example shown in Figures 2 and 3, the sensor device 1 is suspended from a guardrail R of a bridge girder B that crosses above the river K, so that the sensor device 1 is located above the river K.

As shown in Figures 1 to 3, the sensor device 1 includes an ultrasonic sensor 2, a housing 3, a support 4, and an antenna 5.

The support 4 comprises a pole 7 extending in the vertical direction and an arm 8 extending in the horizontal direction. The pole 7 is made of metal with excellent rust resistance such as resin, FRP, carbon, or aluminum, or metal that has been treated with rust prevention treatment such as painting or resin coating. The pole 7 is attached to the support 6 of the guardrail R so that it can slide freely in the vertical direction (Figs. 2 and 3). This attachment is performed, for example, using a fastener 50 shown in Figs. 4 and 5. The fastener 50 is called a parent-child band, and has traditionally been used to attach poles to safety fences and signs.

The fastener 50 comprises semicircular bands 51, 51 arranged on one side and semicircular bands 52, 52 arranged on the other side. Each of the semicircular bands 51, 51 has a fastening piece 53 extending outward from one end, and a fastening piece 54 extending outward from the other end. Each of the semicircular bands 52, 52 has a fastening piece 55 extending outward from one end, and a fastening piece 56 extending outward from the other end.

When the fastener 50 is in use, the semicircular bands 51, 51 face each other, the semicircular bands 52, 52 face each other, and the fastening pieces 54, 54 of the semicircular bands 51, 51 are positioned between the fastening pieces 55, 55 of the semicircular bands 52, 52.

When attaching the pole 7 to the support 6, the pole 6 is passed through the inside of the ring formed by the semicircular bands 51, 51, and the pole 7 is passed through the inside of the ring formed by the semicircular bands 52, 52. Then, a nut 58 is screwed onto the bolt 57 that passes through the fastening pieces 53, 53, a nut 60 is screwed onto the bolt 59 that passes through the fastening pieces 54, 54, 55, 55, and a nut 62 is screwed onto the bolt 61 that passes through the fastening pieces 56, 56. Through the above operations, the pole 6 is fastened to the semicircular bands 51, 51, and the pole 7 is fastened to the semicircular bands 52, 52, so that the pole 7 is attached to the support 6 via the fastener 50. With the fastener 50, the fastening of the fastening pieces 53, 53 by the bolt 61 and nut 62 can be loosened, and if necessary, the fastening of the fastening pieces 54, 54, 55, 55 by the bolt 59 and nut 60 can also be loosened, thereby loosening the clamping of the pole 7 by the semicircular bands 52, 52. This allows the pole 7 to slide up and down. Note that the fastener that can be used to attach the pole 7 to the support 6 is not limited to the fastener 50 described above, and any known fastener that can attach the pole 7 to the support 6 so that it can slide up and down can be used.

The arm 8 (Figs. 1 to 3) is made of metal with excellent rust resistance such as resin, FRP, carbon, or aluminum, or metal that has been subjected to rust prevention treatment such as painting or resin coating. One end of the arm 8 is fixed to the pole 7. In the example shown in Fig. 1, the pole 7 is passed through the inside of a metal U-shaped clamp 9, and both ends of the U-shaped clamp 9 are fastened to one end of the arm 8 using bolts 10, thereby fixing one end of the arm 8 to the pole 7. Note that one end of the arm 8 may be fixed to the pole 7 by a known means other than the U-shaped clamp 9. In the illustrated example, the arm 8 is fixed to the lower end of the pole 7, but the arm 8 can be fixed to any height position of the pole 7. Note that it is preferable to fix the arm 8 to the lower side of the pole 7 so that the ultrasonic sensor 2 can be placed at a position close to the water surface S of the river K.

The arm 8 has a cavity extending in the longitudinal direction. The antenna 5 is disposed in the cavity of the arm 8 and extends in the longitudinal direction of the arm 8.

The housing 3 is box-shaped and is attached to the other end of the arm 8. The housing 3 is made of resin, FRP, or a metal with excellent rust resistance, such as aluminum, which has a structure that allows radio waves for communication to pass through. In order to prevent insects from approaching the housing 3, the material of the housing 3 contains an insect repellent. The repellent material may contain, for example, one or more of pyrethroid compounds, organophosphorus compounds, organochlorine compounds, organosilicon compounds, carbamate compounds, oxadiazole compounds, nereistoxin compounds, amidinohydrazone compounds, phenylpyrazole compounds, isoxazoline compounds, macrolide compounds, IGR agents, neonicotinoids, sodium oleate, fatty acid glycerides, sorbitan fatty acid esters, polysulfide lime, boric acid, flubendiamide, diafenthiloun, pymetrozine, benzyl alcohol, lithium sulfonate, machine oil, diatomaceous earth, rotenone, nicotine sulfate, naphthalene, camphor, DEET, icaridin, farnesyl acetone, isoprothiolane, thiuram, ziram, ethyl butylacetylaminopropionate, p-menthane-3,8-diol, cinnamon, cinnamyl acetate, and terpineol.

The ultrasonic sensor 2 includes a transmitter that transmits ultrasonic waves P, a receiver that receives reflected waves H, and a control device that controls the operation of the transmitter and receiver.

The control device is disposed inside the housing 3. The control device is connected to the antenna 5 via a cable 12, and this connection enables the control device to transmit information from the antenna 5 (one end of the cable 12 passes through the housing 3 and is connected to the control device, and the other end of the cable 12 passes through the arm 8 and is connected to the antenna 5). Note that the cable 12 does not necessarily have to be disposed outside the housing 3, and the cable 12 may be disposed inside the housing 3.

An opening 17 (Fig. 1) is formed in the wall surface 3a of the housing 3, and the transmitter and receiver are arranged in the opening 17 so that ultrasonic waves P emitted from the transmitter are emitted from the opening 17 and reflected waves H passing through the opening 17 are received by the receiver.

As shown in Figures 2 and 3, the sensor device 1 is placed above the river K so that the wall surface 3a of the housing 3 on which the opening 17 is formed faces the river K (downward). As a result, the ultrasonic waves P emitted from the opening 17 are directed toward the water surface S of the river K, and the reflected waves H reflected by the water surface S that enter the opening 17 are received by the receiver.

The control device of the ultrasonic sensor 2 measures the time from when the ultrasonic wave P is transmitted until when the reflected wave H is received by the receiver (hereinafter, the transmission/reception time) each time the receiver receives the reflected wave H. The control device then transmits information based on the transmission/reception time to the outside from the antenna 5.

For example, the above-mentioned "information based on the transmission and reception time" is "information indicating the measurement value of the transmission and reception time." In this case, for example, each time a predetermined time elapses, the control device transmits information indicating the measurement value of the transmission and reception time measured within the predetermined time from the antenna 5 to the outside.

Alternatively, the above-mentioned "information based on transmission and reception time" is information indicating the maximum value, minimum value, mode value, or final value (the last detected value of the transmission and reception time) of the measurement values of the transmission and reception time measured within a specified time. In this case, the control device 23 transmits information indicating the above-mentioned maximum value, minimum value, mode value, or final value to the outside from the antenna 5 every time the specified time elapses.

Alternatively, the above-mentioned "information based on transmission/reception times" is "information indicating the average value of multiple transmission/reception times measured within a specified time period." In this case, the control device 23 calculates the average value of the transmission/reception times measured within the specified time period each time the specified time period elapses, and transmits information indicating the average value from the antenna 5 to the outside.

Alternatively, the above-mentioned "information based on the transmission/reception time" is "information indicating the fluctuation value of the transmission/reception time." In this case, each time the control device measures the transmission/reception time, it calculates the "fluctuation value of the transmission/reception time" by dividing the "difference between the currently measured transmission/reception time and the previously measured transmission/reception time" by the "time from when the previously measured transmission/reception time is measured to when the current transmission/reception time is measured," and transmits information indicating the fluctuation value from antenna 5 to the outside.

The calculation for determining the "variation value of the transmission and reception time" may be performed by the management server 22 (FIG. 6) described below. In this case, the control device of the ultrasonic sensor 2 transmits "information indicating the measured value of the transmission and reception time" to the management server 22 each time it measures the transmission and reception time. The management server 22 uses the information received from the ultrasonic sensor 2 to determine the "variation value of the transmission and reception time".

The above-mentioned "information based on the transmission and reception time" is, for example, information indicating the value of the distance L between the ultrasonic sensor 2 and the water surface. In this case, each time the control device measures the transmission and reception time, it determines the value of the distance L between the ultrasonic sensor 2 and the water surface from the value of the transmission and reception time and the speed of sound. Then, each time a predetermined time elapses, the control device 23 transmits information indicating the value of the distance L determined within that predetermined time from the antenna 5 to the outside.

Alternatively, the above-mentioned "information based on transmission and reception time" is information indicating the maximum, minimum, most frequent, or final value (the absolute value of the last detected distance L) of the values of distance L found within a specified time. In this case, each time a specified time elapses, the control device 23 transmits information indicating the maximum, minimum, most frequent, or final value of the multiple values of distance L found within that specified time to the outside from the antenna 5.

Alternatively, the "information based on the transmission and reception time" is "information indicating the average value of multiple distances L." In this case, the control device 23 calculates the average value of the distances L calculated within a predetermined time each time the predetermined time elapses, and transmits information indicating the average value of the distances L from the antenna 5 to the outside.

Alternatively, the above-mentioned "information based on the transmission/reception time" is the "variation value of distance L." In this case, each time the control device measures the transmission/reception time, it calculates the value of distance L from the value of that transmission/reception time and the speed of sound, and calculates the "variation value of distance L" by calculating "the difference between the currently calculated value of distance L and the previously calculated value of distance L" / "the time from the previous calculation of the value of distance L to the current calculation of the value of distance L." The control device then transmits information indicating the variation value to the outside from antenna 5.

The process of determining the "value of distance L," "maximum, minimum, mode and final values of distance L," "average value of distance L," or "variation value of distance L" may be performed by the management server 22 (FIG. 6) described below. In this case, the control device of the ultrasonic sensor 2 transmits "information indicating the measured value of the transmission and reception time" to the management server 22 each time it measures the transmission and reception time. The management server 22 uses the information received from the ultrasonic sensor 2 to determine the "value of distance L," "maximum, minimum, mode and final values of distance L," "average value of distance L," or "variation value of distance L."

The ultrasonic waves P traveling from the ultrasonic sensor 2 to the water surface S, and the reflected waves H traveling from the water surface S to the ultrasonic sensor 2, attenuate in intensity as they propagate through space. For this reason, there is a limit to the distance L at which the ultrasonic sensor 2 can detect the reflected waves H (hereinafter, the maximum "distance L between the ultrasonic sensor 2 and the water surface S" at which the ultrasonic sensor 2 can detect the reflected waves H reflected by the water surface S will be referred to as the "maximum detection distance Lmax").

In the first embodiment, the ultrasonic sensor 2 is moved up and down by sliding the pole 7 in the vertical direction (specifically, the arm 8 is moved up and down by sliding the pole 7, and the housing 3 in which the ultrasonic sensor 2 is housed is moved up and down accordingly), so that the distance L between the ultrasonic sensor 2 and the water surface S is made shorter than the maximum detection distance Lmax. For example, in normal times when the river K is at a normal water level, the distance L between the ultrasonic sensor 2 and the normal water level is made shorter than the maximum detection distance Lmax by sliding the pole 7, so that the ultrasonic sensor 2 can detect the reflected wave H (Figure 2). In addition, during a period when the river K is likely to rise to a dangerous water level due to the arrival of heavy rain or a typhoon, the distance L between the ultrasonic sensor 2 and the dangerous water level is made shorter than the maximum detection distance Lmax by sliding the pole 7, so that the ultrasonic sensor 2 can detect the reflected wave H (Figure 3).

Figure 6 shows an example of a sensor system 20 into which the sensor device 1 of the first embodiment is incorporated (note that the sensor systems into which the sensor device 1 of the present invention can be incorporated are not limited to those shown in Figure 6).

The sensor system 20 shown in FIG. 6 includes the sensor device 1, the base station 21, and the management server 22. In this sensor system 20, communication between the base station 21 and the management server 22 is possible via a wireless or wired network N. In addition, communication between the ultrasonic sensor 2 and the base station 21 is possible by a communication method such as LPWA (Low Power Wide Area), Wi-Fi (registered trademark), 3G, or 4G. From the viewpoint of realizing long-distance communication while suppressing power consumption, it is preferable that the communication method is LPWA. In the first embodiment, by extending the antenna 5 (FIG. 1) along the arm 8, communication between the ultrasonic sensor 2 and the base station 21 is possible even if the sensor device 1 is far away from the base station 21. The arm 8 may be configured as an antenna. Even in this case, the length of the antenna can be increased, so that communication between the ultrasonic sensor 2 and the base station 21 is possible even if the sensor device 1 is far away from the base station 21. The antenna may be provided inside the housing 3.

In the above sensor system 20, the "information based on the transmission and reception time" transmitted from the ultrasonic sensor 2 is received by the base station 21. Then, the "information based on the transmission and reception time" transmitted from the base station 21 is received by the management server 22 via the network N. The management server 22 compares the value indicated in the "information based on the transmission and reception time" with a threshold value, and outputs information based on the comparison result. For example, if the "information based on the transmission and reception time" is the above-mentioned "information indicating the measured value, average value, maximum value, minimum value, mode value, and final value of the transmission and reception time" or "information indicating the value, average value, maximum value, minimum value, mode value, and final value of the distance L", the management server 22 outputs information indicating that the river K has reached a dangerous water level when the value indicated in the information becomes smaller than the threshold value. Also, if the "information based on the transmission and reception time" is the above-mentioned "information indicating the fluctuation value of the transmission and reception time" or "information indicating the fluctuation value of the distance L", the management server 22 outputs information indicating that the river K is likely to reach a dangerous water level when the fluctuation value indicated in the information becomes larger than the threshold value.

Furthermore, if a failure occurs in the ultrasonic sensor 2, the ultrasonic sensor 2 will not measure the transmission and reception time by not emitting ultrasonic waves P or detecting reflected waves H. As a result, "information based on the transmission and reception time" will no longer be transmitted from the ultrasonic sensor 2. Then, if the management server 22 does not receive "information based on the transmission and reception time" for a specified period of time, it outputs information indicating that a failure has occurred in the ultrasonic sensor 2.

According to the first embodiment described above, the ultrasonic sensor 2 can be moved up and down by sliding the pole 7 to make the distance L between the ultrasonic sensor 2 and the water surface S shorter than the maximum detection distance Lmax (FIGS. 2 and 3). Therefore, the ultrasonic sensor 2 always detects the reflected wave H, measures the transmission and reception time, and transmits "information based on the transmission and reception time" unless a malfunction occurs. As a result, if a malfunction occurs in the ultrasonic sensor 2, the "information based on the transmission and reception time" is not transmitted from the ultrasonic sensor 2, so that the manager can recognize that the ultrasonic sensor 2 has malfunctioned (this can prevent the manager from assuming that the reason the ultrasonic sensor does not transmit information is because the distance L between the ultrasonic sensor and the water surface is large, as in the conventional case). Therefore, measures to repair the ultrasonic sensor 2 can be taken quickly, so that the ultrasonic sensor 2 can be reliably operated normally when the river K reaches a dangerous water level. Therefore, the "information based on the transmission and reception time" transmitted by the ultrasonic sensor 2 can reliably identify that the river K has reached a dangerous water level.

Furthermore, according to the first embodiment, as described above, the ultrasonic sensor 2 can be moved up and down by sliding the pole 7, so even when a commonly used low-output ultrasonic sensor 2 is used, the distance L between the sensor 2 and the water surface S can be made shorter than the maximum detection distance Lmax. Therefore, even when a low-output ultrasonic sensor 2 is used, the ultrasonic sensor 2 can be set to a state in which it constantly detects reflected waves and measures the transmission and reception time, so there is no need to use a high-output ultrasonic sensor 2. This allows costs to be kept low.

The object on which the pole 7 is slidably attached (the object on which the sensor device 1 is hung) is not limited to the support pillar 6 of the guardrail R provided on the bridge girder B, but may be a part of the bridge girder B other than the support pillar 6, or a support erected on the bank or bottom of a river. Also, instead of or in addition to making the pole 7 slidable in the vertical direction, the arm 8 may be attached to the pole 7 so as to be slidable in the vertical direction. Even in this case, the sliding of the arm 8 can make the distance L between the ultrasonic sensor 2 and the water surface S shorter than the maximum detection distance Lmax, so that it is possible to identify when the river K has reached a dangerous water level.

Furthermore, according to the first embodiment, the material of the housing 3 contains an insect repellent, which can prevent insects from approaching the housing 3. This prevents the opening 17 from being blocked by an insect, preventing the ultrasonic wave P from being emitted from the opening 17 and preventing the reflected wave H from passing through the opening 17. Therefore, the ultrasonic sensor 2 can stably detect the distance L.

In addition to or instead of incorporating the repellent material into the material of the housing 3, the repellent material may be applied to at least a portion of the surface (inner and outer surfaces) of the housing 3. This also prevents insects from approaching the opening 17. In this case, it is preferable to apply the repellent material to at least the inner surface of the opening 17. This can reliably prevent insects from approaching the opening 17.

A water repellent may also be applied to the surface of the housing 3. Examples of water repellent include fluorine-based paint and silicon-based paint. Applying a water repellent to the surface of the housing 3 makes the surface of the housing 3 smooth, which makes it possible to prevent insects from attaching to the housing 3. This also makes it possible to prevent insects from laying their eggs on the surface of the housing 3. This makes it possible to prevent the insects themselves or their eggs from preventing the ultrasonic waves P from being emitted from the opening 17 and the reflected waves H from passing through the opening 17.

7, the opening 17 of the housing 3 may be covered with a sheet 63 to prevent insects from entering. For example, a mesh-like film or cloth may be used as the sheet 63. Alternatively, a nonwoven fabric or a sheet with multiple holes formed by punching may be used as the sheet 63. For example, resin, metal, or metal oxide may be used as the material of the sheet 63. If the opening 17 of the housing 3 is covered with the sheet 63 as described above, it is possible to prevent insects from entering the opening 17. This prevents the ultrasonic wave P from being emitted from the opening 17 and the reflected wave H from passing through the opening 17 due to the insect entering the opening 17. Note that the material constituting the sheet 63 may contain an insect repellent material, or the surface of the sheet 63 may be coated with an insect repellent material. In this way, it is possible to prevent insects from attaching to the sheet 63, and therefore it is possible to more reliably prevent the ultrasonic wave P from being emitted from the opening 17 and the reflected wave H from passing through the opening 17.

Next, another embodiment of the present invention will be described. Below, differences from the first embodiment will be described, and points in common with the first embodiment will be denoted by the same reference numerals in the drawings and detailed description will be omitted.

Figures 8 and 9 are schematic diagrams showing the state in which the sensor device 1 according to the second embodiment is installed above a river K. Figure 8 shows the state when the river K is at a normal water level, and Figure 9 shows the state when the river K has reached a dangerous water level.

In the second embodiment, as in the first embodiment, a sensor device 1 equipped with an ultrasonic sensor 2 is used to identify when the river K reaches a dangerous water level, and the sensor device 1 constitutes the sensor system 20 shown in FIG. 6, but the position of the ultrasonic sensor 2 differs from that of the first embodiment.

That is, in the second embodiment, the ultrasonic sensor 2 is positioned so that the ultrasonic wave P is directed toward "a portion Ta (solid portion) of the embankment T that is located below the dangerous water level of the river K and has a constant height." This positioning can be achieved by adjusting the hanging position of the pole 7 on the guardrail R, etc. (for example, by selecting the support 6 of the guardrail R from which the pole 7 is hung).

Then, by adjusting the height position of the pole 7 fixed to the guardrail R, the distance L between the portion Ta of the embankment T and the ultrasonic sensor 2 is made shorter than the maximum detection distance Lmax of the ultrasonic sensor 2.

According to the second embodiment, the distance L between the portion Ta of the embankment T and the ultrasonic sensor 2 is made shorter than the maximum detection distance Lmax. Therefore, as shown in FIG. 8, during the period when the water level of the river K is below the dangerous water level and the portion Ta of the embankment T is exposed above the water surface S, the ultrasonic sensor 2 always detects the reflected wave H unless a malfunction occurs, measures the time (transmission/reception time) from when the ultrasonic wave P is transmitted to when the reflected wave H reflected by the water surface S (measurement object) is received, and transmits information based on the transmission/reception time. Therefore, if a malfunction occurs in the ultrasonic sensor 2, the ultrasonic sensor 2 will no longer transmit the above information, and the manager will recognize that a malfunction has occurred in the ultrasonic sensor 2. Therefore, measures to repair the ultrasonic sensor 2 can be taken quickly. As a result, the ultrasonic sensor 2 can be reliably operated normally when the river K reaches a dangerous water level as shown in FIG. 9, so that it is possible to reliably identify that the river K has reached a dangerous water level based on the transmission/reception time or distance L detected by the ultrasonic sensor 2.

Even when a commonly used low-output ultrasonic sensor 2 is used, the ultrasonic sensor 2 can be kept in a state where it can always detect the reflected wave H by making the distance L between the portion Ta of the embankment T and the ultrasonic sensor 2 shorter than the maximum detection distance Lmax. This means that there is no need to use a high-output ultrasonic sensor 2, and costs can be kept low.

In the second embodiment, the object to which the pole 7 is slidably attached (the object from which the sensor device 1 is hung) is not limited to the support pillar 6 of the guardrail R provided on the bridge girder B, but may be a part of the bridge girder B other than the support pillar 6, or a support pillar erected on the bank or bottom of a river, etc.

In the second embodiment, the pole 7 does not necessarily need to be slidable, and a predetermined position of the pole 7 may be fixed to the bridge girder B, a pillar, or the like. Furthermore, the pole 7 may be omitted, and the support body 4 may consist only of an arm 8 extending horizontally. Even in this case, by attaching the arm 8 to the bridge girder B, a pillar, or the like so that the distance L between the portion Ta of the embankment T and the ultrasonic sensor 2 is shorter than the maximum detection distance Lmax, it is possible to reliably identify when the river K has reached a dangerous water level while keeping costs low.

Furthermore, the solid part to which the ultrasonic waves P are directed is not limited to the part Ta of the embankment T described above. For example, the ultrasonic sensor 2 may be positioned so that the ultrasonic waves are directed to "bridge piers, abutments, rocks, and riverbed parts (solid parts) that are located below the dangerous water level of the river K and have a constant height." Even in this case, if the distance L between the solid part and the ultrasonic sensor 2 is made shorter than the maximum detection distance Lmax, it is possible to reliably identify that the river K has reached a dangerous water level while keeping costs low.

Next, a third embodiment of the present invention will be described. Figure 10 is a perspective view showing a sensor device 65 according to the third embodiment of the present invention.

The sensor device 65 of the third embodiment further includes a temperature sensor 66 in addition to the configuration shown in the first embodiment (the configuration shown in FIG. 1).

The temperature sensor 66 is disposed inside the housing 3 and measures the air temperature T inside the housing 3. The air temperature T measured by the temperature sensor 66 is input to the control device of the ultrasonic sensor 2 via wired or wireless communication.

The control device of the ultrasonic sensor 2 measures the time (transmission/reception time) from when the ultrasonic wave P is transmitted until the reflected wave H is received by the receiver each time the receiver receives the reflected wave H, and obtains the air temperature T at the time when the ultrasonic wave P is transmitted or when the reflected wave H is received from the temperature sensor 66, and calculates the speed of sound c (the speed of ultrasonic waves P and H) using the air temperature T. The control device of the ultrasonic sensor 2 then calculates the value of the distance L (see Figures 2 and 3) between the ultrasonic sensor 2 and the water surface S based on the transmission/reception time and the speed of sound c, and transmits information indicating the value of the distance L to the management server 22 (Figure 6).

For example, the control device of the ultrasonic sensor 2 determines the value of the distance L from the following formula 1, which uses the sound speed c (m/s) and the transmission/reception time t (s).

<Formula 1>
L = ct/2
Speed of sound: c (m/s)
Transmission/reception time: t (s)

For example, the control device of the ultrasonic sensor 2 can obtain the sound speed c (m/s) used in equation 1 from the following equation 2, which uses the air temperature T (°C) measured by the temperature sensor 66.

<Formula 2>
c = 331.5 + 0.61T
Temperature measured by the temperature sensor 66: T (°C)

According to the sensor device 65 of the third embodiment, the speed of sound c is calculated using the air temperature T measured by the temperature sensor 66, and the speed of sound c becomes close to the actual speed of the ultrasonic waves P and H. The value of the distance L is calculated using the speed of sound c, and the calculated value of the distance L becomes close to the actual value of the distance L. Therefore, the water level of the river K can be determined more accurately based on the "information indicating the value of the distance L" transmitted from the ultrasonic sensor 2.

In addition, in the third embodiment, a temperature sensor 66 is provided inside the housing 3, which makes it possible to waterproof the temperature sensor 66 and reduces the effort and cost required to install the temperature sensor 66.

Note that it is not necessary to provide the temperature sensor 66 inside the housing 3. As shown in FIG. 11, the temperature sensor 66 may be disposed outside the housing 3 to measure the temperature T outside the housing 3. In this case, the "temperature T outside the housing 3" measured by the temperature sensor 66 is input to the control device of the ultrasonic sensor 2 via wired or wireless communication (in the illustrated example, the temperature T measured by the temperature sensor 66 is input to the control device of the ultrasonic sensor 2 via cable 13 (wired)). In the above case, the sound speed c is calculated using the temperature T of the space outside the housing 3 through which the ultrasonic waves P and H travel, so that the sound speed c is closer to the actual speed of the ultrasonic waves P and H. Therefore, the value of the distance L calculated using the sound speed c is closer to the actual value.

In the above example, the control device of the ultrasonic sensor 2 functions as information acquisition means that calculates the speed of sound using the air temperature T near the ultrasonic sensor 2 when the ultrasonic wave P is emitted or when the reflected wave H is received, and acquires information indicating the distance L based on the sound speed c and the transmission/reception time measured by the ultrasonic sensor 2, but the information acquisition means may be configured in the management server 22. In this case, the control device of the ultrasonic sensor 2 measures the transmission/reception time each time the receiver receives the reflected wave H, acquires the air temperature T at the time the reflected wave H is received from the temperature sensor 66, and transmits information indicating the transmission/reception time and the air temperature T to the management server 22.

Then, each time the management server 22 receives the above information, it calculates the sound speed c (the speed of ultrasonic waves P and H) using the temperature T indicated in the information, and calculates the value of the distance L (Figures 2 and 3) between the ultrasonic sensor 2 and the water surface S based on the calculated sound speed c and the transmission and reception time indicated in the information.

The sound speed c (the speed of ultrasonic waves P and H) may also be calculated using the temperature T stored in the database server. In this case, the sensor system in which the sensor device is incorporated is modified as shown in FIG. 12.

The sensor system 67 shown in FIG. 12 has a sensor device 68 equipped with an ultrasonic sensor 2, a base station 21, a management server 22, and a database server 69. In this sensor system 67, communication between the ultrasonic sensor 2 and the base station 21 is possible using a communication method such as LPWA (Low Power Wide Area), Wi-Fi (registered trademark), 3G, or 4G. In addition, communication between the base station 21 and the management server 22, and communication between the management server and the database server 69 are possible via a wireless or wired network N.

The database server 69 acquires the temperature T measured by a temperature sensor (not shown) installed near the ultrasonic sensor 2 at a predetermined time interval and stores the temperature in a database. For example, a server that stores the outside temperatures announced by the Japan Weather Association can be used as the database server 69.

The control device of the ultrasonic sensor 2 measures the time (transmission/reception time) from when the ultrasonic wave P is transmitted to when the reflected wave H is received by the receiver each time the receiver receives the reflected wave H, and transmits information indicating the value of the transmission/reception time and the time when the reflected wave H was received to the management server 22.

Each time the management server 22 receives the above information, it obtains from the database server 69 the air temperature T near the ultrasonic sensor 2 at the "time of reception of the reflected wave" indicated in the information, and uses that air temperature T to calculate the speed of sound c (the speed of ultrasonic waves P and H).

Here, the above "air temperature T near ultrasonic sensor 2" refers to the above "air temperature T measured by a temperature sensor installed near ultrasonic sensor 2." The "temperature sensor installed near ultrasonic sensor 2" refers to, for example, a "temperature sensor installed in the city, town, or village in which ultrasonic sensor 2 is located." If multiple temperature sensors are installed in the city, town, or village in which ultrasonic sensor 2 is located, and the temperatures measured by these multiple temperature sensors are stored in database server 69, management server 22 obtains from database server 69 the air temperature T measured by the temperature sensor closest to ultrasonic sensor 2.

The "temperature T at the time the reflected wave H is received" is, for example, the temperature T stored in the database server 69 immediately before or immediately after the reflected wave H is received by the ultrasonic sensor 2. For example, if the temperatures T are stored in the database server 69 at 12:00, 13:00, and 14:00, and the reflected wave H is received by the ultrasonic sensor 2 at 13:12:20, the management server 22 obtains from the database server 69 the temperature T at 13:00, immediately before 13:12:20, or the temperature T at 14:00, immediately after 13:12:20.

Then, the management server 22 calculates the speed of sound c using the temperature T obtained from the database server 69, and calculates the value of the distance L (see Figures 1 and 2) between the ultrasonic sensor 2 and the water surface S based on the speed of sound c and the transmission and reception time indicated in the information transmitted from the ultrasonic sensor 2.

When the temperature T stored in the database server 69 immediately after the reception of the reflected wave H described above (hereinafter, the immediately following temperature T) is used to calculate the speed of sound c, the management server 22 cannot calculate the speed of sound c and distance L from the reception of the reflected wave H until the immediately following temperature T is stored in the database server 69 (in the above example, the speed of sound c and distance L cannot be calculated from 13:12:20 to 14:00:47:40). Therefore, when the time interval at which the temperature T is stored in the database server 69 is long, it is preferable to calculate the speed of sound c using the temperature T stored in the database server 69 immediately before the reception of the reflected wave H.

The management server 22 may also obtain the temperature stored in the database server at the time closest to the reception time of the reflected wave H, and use that temperature to calculate the sound speed c. In this way, the temperature used to calculate the sound speed c will be close to the temperature at the reception time of the reflected wave H. This makes it possible to make the value of the distance L calculated from the sound speed c closer to the actual value.

Also, instead of the above-mentioned "air temperature T near the ultrasonic sensor 2 at the time of receiving the reflected wave H," "air temperature T near the ultrasonic sensor 2 at the time of transmitting the ultrasonic wave P" may be used. In this case, from the time when the current ultrasonic wave P is transmitted until the next ultrasonic wave P is transmitted, the control device of the ultrasonic sensor 2 measures the time (transmission reception time) from the time when the current ultrasonic wave P is transmitted until the reflected wave H is received by the receiver every time the receiver receives the reflected wave H, and transmits information indicating the value of the transmission reception time and the time of transmission of the current ultrasonic wave P to the management server 22. Each time the management server 22 receives the above-mentioned information, it obtains the air temperature T near the ultrasonic sensor 2 at the "time when the current ultrasonic wave P is transmitted" indicated in the information from the database server 69, and uses the air temperature T to obtain the sound speed c (the speed of the ultrasonic waves P and H). Furthermore, the management server 22 obtains the value of the distance L (see Figures 1 and 2) between the ultrasonic sensor 2 and the water surface S based on the sound speed c and the transmission reception time indicated in the information transmitted from the ultrasonic sensor 2. As mentioned above, the "temperature T near the ultrasonic sensor 2" is the "temperature T measured by a temperature sensor installed near the ultrasonic sensor 2." The temperature T at the "time of transmission of the current ultrasonic wave P" is, for example, the temperature T stored in the database server 69 immediately before or immediately after the time when the current ultrasonic wave P is transmitted to the ultrasonic sensor 2. If the time interval at which the temperature T is stored in the database server 69 is long, it is preferable to calculate the speed of sound c using the temperature T stored in the database server 69 immediately before the transmission of the ultrasonic wave P. The management server 22 may also obtain the temperature stored in the database server at the time closest to the reception time of the reflected wave H, from among the temperatures stored in the database server, and use that temperature to calculate the speed of sound c.

In order to confirm the effect of calculating the speed of sound using the air temperature near the ultrasonic sensor 2, the inventors conducted a test comparing Case 1, in which the speed of sound is calculated using the air temperature near the ultrasonic sensor 2 measured by the temperature sensor 66, Case 2, in which the speed of sound is calculated using the air temperature near the ultrasonic sensor 2 announced by the Japan Weather Association, and Case 3, in which the speed of sound is calculated with the air temperature held constant.

In the above test, a sensor device with a temperature sensor 66 disposed inside the housing 3 was placed above the river K. Then, between 0:00 AM on October 19, 2018 and 0:00 AM on October 20, 2018, the ultrasonic sensor 2 and temperature sensor 66 provided in the sensor device were operated to confirm the transmission and reception time measured by the ultrasonic sensor 2 and the temperature measured by the temperature sensor 66 disposed inside the housing 3 (hereinafter abbreviated as the temperature inside the housing 3). Then, among the temperatures announced by the Japan Weather Association, the temperature near the ultrasonic sensor 2 between 0:00 AM on October 19, 2018 and 0:00 AM on October 20, 2018 (hereinafter abbreviated as the temperature announced by the Japan Weather Association) was confirmed.

The following Table 1 shows the temperatures announced by the Meteorological Association and the temperature inside the housing 3 during the time period when the test was conducted (from midnight on October 19, 2018 to midnight on October 20, 2018). Line A in FIG. 13 shows the time progression of the temperature announced by the Meteorological Association, and line B in FIG. 13 shows the time progression of the temperature inside the housing 3.

The temperature values published by the Meteorological Association shown in Table 1 confirmed that during time period T1 (FIG. 13) from 1:00 to 6:00 on October 19th, the temperature outside the housing 3 (the temperature published by the Meteorological Association shown by line A in FIG. 13) was in the range of 12°C to 13°C. During time period T2 from 7:00 to 19:00 on October 19th, it was confirmed that the temperature outside the housing 3 (the temperature published by the Meteorological Association) rose from 13°C due to sunlight irradiation to a range of 13°C to 23°C. Furthermore, during time period T3 from 20:00 on October 19th to midnight on October 20th, it was confirmed that the temperature outside the housing 3 (the temperature published by the Meteorological Association) dropped from 17°C to a range of 14°C to 17°C.

In addition, by comparing the temperatures published by the Meteorological Association shown in Table 1 with the temperature inside the housing 3, it was confirmed that during time periods T1 and T3 (T1: 1:00-6:00 on October 19th, T3: 20:00-0:00 on October 20th), the temperature inside the housing 3 shown by line B in FIG. 13 was approximately the same (13°C-17°C) as the temperature outside the housing 3 (temperature published by the Meteorological Association shown by line A in FIG. 13). However, during the daytime period T2 (7:00-19:00 on October 19th), it was confirmed that the temperature inside the housing 3 was higher than the temperature outside the housing 3 (temperature published by the Meteorological Association).

In this test, the distance L between the water surface S of the river K and the ultrasonic sensor 2 was determined for each of cases 1 to 3 using the method described below.

Case 1: In the above equation 2, the temperature T is set to a constant value (14°C) and the sound speed c (340 m/s (= 331.5 + 0.61 × 14)) is calculated. The calculated sound speed c (340 m/s) and the transmission and reception time t measured by the ultrasonic sensor 2 are used in the above equation 1 to calculate the distance L.
Case 2: The speed of sound c is calculated using the temperature published by the Meteorological Agency as the temperature T in the above equation 2, and the calculated speed of sound c and the transmission and reception time t measured by the ultrasonic sensor 2 are used in the above equation 1 to calculate the distance L.
Case 3: The speed of sound c is calculated using the air temperature inside the housing 3 as the air temperature T in the above equation 2, and the calculated speed of sound c and the transmission and reception time t measured by the ultrasonic sensor 2 are used in the above equation 1 to calculate the distance L.

The temperature value (14°C) used in Case 1 is the average temperature (temperature outside the housing 3) announced by the Meteorological Agency for time periods T1 and T2 (T1: 1:00-6:00 on October 19th, T2: 20:00 on October 19th-0:00 on October 20th), and is calculated as (13°C+13°C+13°C+13°C+12°C+12°C+17°C+16°C+16°C+15°C+14°C)/11. Case 1 is a case in which the speed of sound c is calculated using the "average temperature (14°C) for time periods T1 and T2" described above, and the speed of sound c and distance L are calculated without taking into account the rise in temperature due to exposure to sunlight.

Furthermore, in this test, a scale was erected on the bottom of river K to measure the distance L between the water surface S of river K and the sensor device using a scale. After passing underwater in river K, this scale extended from the water surface S into the air and passed to the side (directly beside) of the sensor device. In this test, the average value of distance L obtained by steps 1 to 4 below, 272 cm, was taken as the true value of distance L.

Task 1: The scale is photographed with a fixed camera so that position A of the scale where the water surface S of the river K crosses and position B of the scale to the side (directly beside) the sensor device are captured.
Task 2: Extract multiple still images at 10-minute intervals from the video captured by the fixed camera. Task 3: By checking the scale marks at positions A and B shown in each still image extracted in Task 2, identify the distance L between positions A and B at the time each still image was captured.
Task 4: The average value of the distance L identified for each still image in Task 3 is calculated (the above-mentioned 272 cm, which was taken as the true value of the distance L in this test, is the average value of the distance L calculated in Task 4).

Figure 14 is a graph showing the change over time in distance L found in cases 1 to 3. Line C in Figure 14 shows distance L obtained in case 1, where the speed of sound c is found at a constant air temperature (14°C). Line D in Figure 14 shows distance L obtained in case 2, where the speed of sound c is found using the air temperature published by the Meteorological Association (the air temperature outside the housing 3). Line E in Figure 14 shows distance L obtained in case 3, where the speed of sound c is found using the air temperature inside the housing 3.

In case 1, where the speed of sound c was calculated with the temperature held constant (14°C), the value of distance L calculated from the speed of sound c (340 m/s) tended to be smaller than the true value of distance L (272 cm) during time period T2 (7:00-19:00 on October 19th), when the temperature rose due to exposure to sunlight (line C in Figure 14). However, the difference from the true value of distance L (272 cm) (hereafter referred to as distance difference) was kept within 5 cm. Furthermore, during time period T1 (1:00-6:00 on October 19th) and time period T3 (20:00 on October 19th-0:00 on October 20th), the value of distance L calculated from the speed of sound c (340 m/s) was almost the same as the true value of distance L (272 cm).

In Case 2, where the speed of sound c was calculated using the temperature published by the Meteorological Agency, the value of distance L calculated from the speed of sound c tended to be nearly equal to the true value of distance L (272 cm) throughout the entire test period (12:00 AM, October 19th to 12:00 AM, October 20th) (line D in Figure 14), and the difference in distance was kept within 2 cm.

In case 3, where the speed of sound c was calculated using the air temperature inside the housing 3, the value of distance L calculated from the speed of sound c tended to be larger than the true value of distance L (272 cm) during time period T2 (7:00-19:00 on October 19th) when the air temperature rose due to exposure to sunlight (line E in Figure 14), but the difference in distance was kept within 4 cm. Also, during time period T1 (1:00-6:00 on October 19th) and time period T2 (20:00 on October 19th-0:00 on October 20th), the value of distance L calculated from the speed of sound (340 m/S) was almost the same as the true value of distance L (272 cm).

From the above results, it was confirmed that in all of Case 1, where the speed of sound c is calculated at a constant temperature (14°C), Case 2, where the speed of sound c is calculated using the temperature published by the Meteorological Agency, and Case 3, where the speed of sound c is calculated using the temperature inside the housing 3, the difference between the value of distance L calculated from the speed of sound c and the true value of distance L can be kept to the order of centimeters. Furthermore, it was confirmed that in Case 2, where the temperature published by the Meteorological Agency is used, and Case 3, where the temperature inside the housing 3 is used, the value of distance L during time period T2 when the temperature rises due to exposure to sunlight can be calculated with greater accuracy than in Case 1, where the temperature is kept constant (14°C).

It was also confirmed that when the temperature sensor 66 is placed inside the housing 3, the air temperature inside the housing 3 (line B in FIG. 13) becomes higher than the air temperature outside the housing 3 (line A in FIG. 13) during daytime time period T2, and the value of the distance L calculated from the speed of sound c (line C in FIG. 14) becomes greater than the true value of the distance L (272 cm). Therefore, when the temperature sensor 66 is placed inside the housing 3, it is preferable to take one or more of the following measures 1 to 13 in order to make the air temperature inside the housing 3 equivalent to the air temperature outside the housing 3.

Countermeasure 1: Attach a reflective material (such as aluminum foil) that reflects infrared rays to the outer surface of the housing 3.
Countermeasure 2: Apply paint that reflects infrared rays (for example, paint containing aluminum powder) to the outer surface of the housing 3.
Countermeasure 3: Attach a sheet or plate with high heat dissipation properties to the outer surface of the housing 3.
Countermeasure 4: Apply paint with high heat dissipation properties to the outer surface of the housing 3.
Countermeasure 5: The housing 3 is formed using a material that contains a filler with high heat dissipation properties.
Countermeasure 6: Increasing the outer surface area of the housing 3 by providing protrusions on the outer surface of the housing 3 (for example, providing a plurality of spaced-apart ridges as the above-mentioned protrusions on the outer surface of the housing 3).
Countermeasure 7: Attach a reflective material (e.g., aluminum foil) that reflects infrared rays to the outer surface of the support body 4 (it is particularly preferable to attach the above-mentioned reflective material to the outer surface of the arm 8).
Countermeasure 8: Applying paint that reflects infrared rays (for example, paint containing aluminum powder) to the outer surface of the support 4 (it is particularly preferable to apply the above-mentioned paint to the outer surface of the arm 8).
Countermeasure 9: Attaching a sheet or plate with high heat dissipation properties to the outer surface of the support 4 (it is particularly preferable to apply the above-mentioned sheet or plate with high heat dissipation properties to the outer surface of the arm 8).
Countermeasure 10: Apply a highly heat-dissipating paint to the outer surface of the support 4 (it is particularly preferable to apply the above-mentioned paint to the outer surface of the arm 8).
Countermeasure 11: Form the support 4 using a material that contains a filler with high heat dissipation properties (it is particularly preferable to form the arm 8 using the above material).
Countermeasure 12: Increasing the outer surface area of the support 4 by providing protrusions on the outer surface of the support 4 (for example, providing a plurality of spaced-apart ridges as the above-mentioned protrusions on the outer surface of the arm 8).
Countermeasure 13: Place a heat insulating material (foam, etc.) between the support body 4 and the housing 3 (between the arm 8 and the housing 3 in the illustrated example).

Measures 1 and 2 prevent the temperature inside the housing 3 from becoming too high by reflecting the infrared rays of sunlight irradiating the housing 3.

Measures 3 to 6 allow heat applied to the housing 3 by infrared irradiation, etc., and heat inside the housing 3 to be dissipated to the outside of the housing 3, preventing the temperature inside the housing 3 from becoming too high.

Measures 7 and 8 prevent the temperature of the support 4 from rising due to the reflection of infrared rays from sunlight irradiating the support 4. This reduces the amount of heat transferred from the support 4 to the housing 3, preventing the temperature inside the housing 3 from rising.

Measures 9 to 12 allow the heat applied to the support 4 by infrared irradiation, etc., to be dissipated, preventing the temperature of the support 4 from becoming too high. This in turn reduces the amount of heat transferred from the support 4 to the housing 3, preventing the temperature inside the housing 3 from becoming too high.

According to measure 13, by disposing a heat insulating material between the support 4 and the housing 3, it is possible to reduce the heat transferred from the support 4 to the housing 3. This makes it possible to prevent the temperature inside the housing 3 from becoming too high.

When measures 1 to 13 above are taken, it is possible to prevent the temperature inside the housing 3 from rising as described above, and therefore the air temperature inside the housing 3 measured by the temperature sensor 66 can be made equivalent to the air temperature outside the housing 3 through which the ultrasonic waves P and H travel. This allows the sound speed c found using the air temperature measured by the temperature sensor 66 to approach the actual speed of the ultrasonic waves P and H. This allows the value of distance L found using the sound speed c to approach the actual value of distance L between the ultrasonic sensor 2 and the water surface S, so that the water level of the river K can be accurately identified based on the "information indicating distance L" transmitted from the ultrasonic sensor 2.

Next, a fourth embodiment of the present invention will be described. FIG. 15 is a perspective view showing a sensor device 70 according to the fourth embodiment. FIG. 16 is a schematic side view showing a sensor device 70 according to the fourth embodiment. FIG. 17 is a schematic plan view showing a sensor device 70 according to the fourth embodiment.

The sensor device 70 according to the fourth embodiment has an arm 72 extending horizontally as a support for supporting the housing 3.

The arm 72 has a structure similar to that of the arm 8 shown in FIG. 1. One end of the arm 72 is fastened to a vertically extending support 6 (support 6 of a guardrail R provided on a bridge girder B) using a fastener 9, and the housing 3 is attached to the other end of the arm 72.

In the illustrated example, a U-clamp is used as the fastener 9, and with the post 6 of the guardrail R passing through the inside of the U-clamp 9, both ends of the U-clamp 9 are fastened to one end of the arm 72 using bolts 10, so that the U-clamp 9 tightly clamps the post 6, and one end of the arm 72 is fixed to the post 6. Then, by loosening the fastening of the bolt 10 and loosening the fastening of the U-clamp 9 to the post 6, the arm 72 can be rotated around the post 6. Then, by rotating the arm 72, the housing 3 that houses the ultrasonic sensor 2 can be moved near the bridge girder B, as shown in FIG. 17. This allows the manager P standing on the bridge girder B to perform maintenance and replacement of the ultrasonic sensor 2.

The fastener 9 is not limited to the U-clamp described above. Any known fastener that can fasten the arm 72 to the support 6 and can rotate the arm 72 around the support 6 by loosening the fastening can be used as the fastener 9.

Furthermore, in the sensor device 70 according to the fourth embodiment, a support 73 is provided as shown in FIG. 17 to prevent the arm 72 from falling when the fastening of the arm 72 to the support 6 by the fastener 9 is loosened.

The support 73 is detachably attached to the support 6 near the underside of the arm 72. When the fastening of one end of the arm 72 by the fastener 9 is loosened, the arm 72 can be rotated around the support 6 with one end of the arm 72 supported by the support 73. This allows the arm 72 to rotate smoothly without dropping (i.e., while maintaining the arm 72 at a constant height). Therefore, by rotating the arm 72, it is easy to bring the housing 3 closer to the administrator. In the above-mentioned "state in which the fastening of one end of the arm 72 by the fastener 9 is loosened," the fastener 9 extending around the outer periphery of the support 6 is connected to one end of the arm 72 by the bolt 10. The support 73 may directly support one end of the arm 72 by contacting one end of the arm 72, or may indirectly support one end of the arm 72 via the fastener 9 by contacting the fastener 9.

In the example shown in FIG. 15, a device (FIG. 18) having a pair of semicircular bodies 74, 74 is used as the support 73. In this device, one ends of the semicircular bodies 74, 74 are connected to each other by a hinge 75, so that the semicircular bodies 74, 74 can be opened and closed around the hinge 75 as an axis, and the other ends of the semicircular bodies 74, 74 are provided with fastening pieces 76, 76 extending outward.

When attaching the above-mentioned tool (support 73) to the support 6, the semicircular bodies 74, 74 are opened to create a gap between the fastening pieces 76, 76, and then the support 6 is passed between the semicircular bodies 74, 74 through the gap while the semicircular bodies 74, 74 are closed to butt the fastening pieces 76, 76 together. The fastening pieces 76, 76 are then fastened with bolts and nuts, so that the tool (support 73) is attached to the support 6. The tool (support 73) can be removed from the support 6 by releasing the fastening of the fastening pieces 76, 76 with the bolts and nuts.

Furthermore, in the sensor device 70 according to the fourth embodiment, a retainer 77 is provided to prevent the arm 72 from tilting due to the weight of the housing 3, etc., when the fastening of the arm 72 to the support 6 by the fastener 9 is loosened.

The restraining device 77 is removably attached to the support 6 near and above the arm 72. When the fastening device 9 is loosened from the one end of the arm 72 to the support 6, the restraining device 77 can press down the one end of the arm 72 supported by the support 73. This can prevent the arm 72 from tilting due to the weight of the housing 3, allowing the arm 72 to rotate more smoothly. For example, the device shown in FIG. 18 can be used as the restraining device 77.

In addition, in the sensor device 70 according to the fourth embodiment, by loosening the fastening of one end of the arm 72 to the support 6 and removing the support 73 and the retainer 77 from the support 6, the arm 72 can be slid vertically along the support 6, thereby moving the housing 3 housing the ultrasonic sensor 2 up and down. When the device shown in FIG. 18 is used as the support 73 and the retainer 77, removing the support 73 and the retainer 77 from the support 6 corresponds to releasing the fastening pieces 76, 76 fastened by the bolt and nut, and by performing this operation, the arm 72 can be slid vertically along the support 6.

Furthermore, in the sensor device 70 according to the fourth embodiment, even if the length of the arm 72 is increased, the arm 72 can be extended straight horizontally by clamping the fastener 9 or the arm 72 with the support 73 and the restraining device 77. Therefore, the position of the housing 3 in which the ultrasonic sensor 2 is housed can be moved away from the structure B (bridge girder) that supports the support pillar 6. This makes it possible to prevent the structure B that supports the support pillar 6 from interfering with the progress of the ultrasonic waves P (i.e., the structure B that supports the support pillar 6 can be prevented from entering the radiation range Z of the ultrasonic waves P). Note that it is not necessary to provide the restraining device 77 in the sensor device 70, and the restraining device 77 can be omitted when the length of the arm 72 is short, etc.

The devices that can be used as the support 73 and the holding down device 77 are not limited to those shown in FIG. 18. The support 73 can be any known device that can be detachably attached to the support 6 and can support one end of the arm 72. The holding down device 77 can be any known device that can be detachably attached to the support 6 and can hold one end of the arm 72 downward.

The support pillars to which the arm 72 is attached and the pole 7 shown in FIG. 19 is attached are not limited to the support pillars 6 of the guardrail R provided on the bridge girder B, but may be support pillars erected on the bank or bottom of the river K.

The sensor device of the fourth embodiment can also be modified as shown in FIG. 19.

The sensor device 80 shown in Figure 19 is obtained by adding the support device 73 and the stopper device 77 to the sensor device 1 shown in Figures 1 to 3.

In the sensor device 80 shown in FIG. 19, a support 73 is removably attached to the support 6 below and near the fastener 50. A retainer 77 is removably attached to the support 6 above and near the fastener 50.

According to the sensor device 80 shown in FIG. 19, when the fastener 50 is loosened from the support 6 (when the bolt 57 and nut 58 shown in FIG. 5 are loosened, and when the bolt 59 and nut 60 are also loosened if necessary), the fastener 50 can be rotated around the support 6 while supported by the support 73. As the fastener 50 rotates, the support 4 (pole 7 and arm 8) supporting the housing 3 can be rotated horizontally. Therefore, the housing 3 housing the ultrasonic sensor can be brought closer to the administrator.

In addition, with the sensor device 80 shown in FIG. 19, when the fastener 50 is loosened from the support 6, the retainer 77 can press the fastener 50 supported by the support 73 downward. This prevents the support 4 (pole 7 and arm 8) from tilting due to the weight of the housing 3, etc., and allows the fastener 50 to rotate smoothly.

Furthermore, with the sensor device 80, when the fastener 50 on the pole 7 is loosened (when the bolt 61 and nut 62 shown in FIG. 5 are loosened, and when necessary, the bolt 59 and nut 60 are also loosened), the pole 7 can be slid up and down. As the pole 7 slides, the arm 8 can be moved up and down, and accordingly, the housing 3 housing the ultrasonic sensor 2 can be moved up and down.

In the fourth embodiment, the support pillars to which the arm 72 (FIGS. 15 to 17) is attached and the support pillars to which the pole 7 (FIG. 19) is attached are not limited to the support pillars 6 of the guardrail R provided on the bridge girder B, but may be parts of the bridge girder B other than the support pillars 6, or support pillars erected on the bank or bottom of a river, etc.

The present invention is not limited to the above embodiment and can be modified in various ways.

For example, in the first to fourth embodiments, the housing 3 that houses the ultrasonic sensor 2 is attached to the support 4, 72, but the housing 3 may be omitted and the ultrasonic sensor 2 may be attached to the support 4, 72.

In the first to fourth embodiments, an ultrasonic sensor 2 is used to identify the time when the river K reaches a dangerous water level, but the ultrasonic sensor 2 may also be used to identify the time when the sea reaches a dangerous water level.

In the above case, the sensor device 1 of the present invention is provided with supports 4, 72 that support the ultrasonic sensor 2 so that the ultrasonic sensor 2 is positioned above the sea surface. The ultrasonic sensor 2 is attached to the supports 4, 72 so that the ultrasonic waves are directed toward the sea surface, and the supports 4, 72 are capable of moving the ultrasonic sensor 2 up and down.

Alternatively, the ultrasonic sensor 2 is positioned so that ultrasonic waves are directed toward a solid part located below the danger level of the sea, and the distance between the solid part and the ultrasonic sensor 2 is made smaller than the maximum distance that the ultrasonic sensor 2 can detect.

By doing this, for the same reasons as in the above embodiment, it is possible to reliably identify when the sea reaches a dangerous water level while keeping costs low.

The means for confirming that the ultrasonic sensor 2 is operating normally is not limited to the solid parts (bridges, piers, abutments, riverbeds, rocks, etc.) shown in the second embodiment, but can be a reflector capable of reflecting ultrasonic waves P. Below, a sensor device 30 equipped with such a reflector will be described with reference to Figures 20 and 21.

The sensor device 30 shown in Figures 20 and 21 includes an ultrasonic sensor 2 placed above the water surface S of a river or ocean, and a reflector 31 placed between the ultrasonic sensor 2 and the water surface S. In the illustrated example, the ultrasonic sensor 2 and the reflector 31 are supported by an arm 32.

The arm 32 comprises a main body 33 and a branch 34. The main body 33 extends horizontally, and one end of the main body 33 is attached to a support 40 erected in a river or the sea. The branch 34 extends downward from the main body 33 and then extends horizontally. The arm 32 may be attached to the pole 7 shown in the above embodiment.

The ultrasonic sensor 2, like that shown in FIG. 1, includes a transmitter, a receiver, and a control device, with the control device disposed inside the housing 3 and the transmitter and receiver disposed in the opening 17 of the housing 3.

The housing 3 is attached to the tip of the main body 33 of the arm 32, so that the ultrasonic sensor 2 is positioned above the water surface S of the river or sea. By adjusting the height of the arm 32, the distance L1 between the ultrasonic sensor 2 and the danger water level is set to be equal to or less than the maximum distance Lmax at which the ultrasonic sensor 2 can detect the reflected wave H. Although the distance L1 may be equal to the maximum detection distance Lmax, it is more preferable to position the ultrasonic sensor 2 so that the distance L1 is shorter than the maximum detection distance Lmax, as shown in Figures 20 and 21 (Figure 20 shows a case where the water surface S is higher than the danger water level and the distance L between the ultrasonic sensor 2 and the water surface S is smaller than the maximum detection distance Lmax. Figure 21 shows a case where the water surface S is lower than the danger water level and the distance L between the ultrasonic sensor 2 and the water surface S is greater than the maximum detection distance Lmax).

In the sensor device 30 shown in Figs. 20 and 21, the inner surface of the opening 17 of the housing 3 is tapered so that the inner diameter increases toward the bottom, and the ultrasonic sensor 2 transmits ultrasonic waves P radially downward. The control device of the ultrasonic sensor 2 outputs a signal indicating the intensity of the ultrasonic waves P as the ultrasonic waves P are transmitted, and transmits the signal to the outside via the antenna. The control device also outputs a signal indicating the intensity of the reflected waves H of the ultrasonic waves P reflected by the object to be measured as the receiver receives the reflected waves H, and transmits the signal to the outside via the antenna. The above antenna is attached to the arm 32 so as to extend along the arm 32, or is constituted by the arm 32. The antenna may be provided inside the housing 3.

The reflector 31 is in the form of a film, sheet, or plate. The material of the reflector 31 is resin, FRP, a molded body containing carbon fiber, metal, metal oxide, or a mixture of these.

In the example shown in Figures 20 and 21, the reflector 31 is attached to the tip of the branch 34 of the arm 32, so that the reflector 31 is positioned between the ultrasonic sensor 2 and the water surface S. In addition, by adjusting the height of the tip of the branch 34, etc., the distance L2 between the reflector 31 and the ultrasonic sensor 2 is made shorter than the maximum detection distance Lmax.

In the sensor device 30, the reflector 31 attached to the tip of the branch 34 is positioned within the ultrasonic radiation range H, but not directly below the ultrasonic sensor 2, so that of the ultrasonic waves P emitted from the ultrasonic sensor 2, some of the ultrasonic waves P1 are directed toward the reflector 31, and the remaining ultrasonic waves P2 are directed below the reflector 31.

The sensor device 30 described above, together with a base station and a server, constitutes a sensor system. In this sensor system, the signal output by the ultrasonic sensor is transmitted to the base station using a communication method such as LPWA (Low Power Wide Area), Wi-Fi (registered trademark), 3G, or 4G. Furthermore, the signal received by the base station is transmitted to a management server via a wireless or wired network.

Figure 22 is a graph showing the relationship between time and the "intensity of waves P, H" indicated by the signal output from the ultrasonic sensor when the distance L2 between the ultrasonic sensor 2 and the water surface S is smaller than the maximum detection distance Lmax, as shown in Figure 20. Figure 23 is a graph showing the relationship between time and the "intensity of waves P, H" indicated by the signal output from the ultrasonic sensor when the distance L2 between the ultrasonic sensor 2 and the water surface S is larger than the maximum detection distance Lmax, as shown in Figure 21.

According to the sensor device 30 described above, ultrasonic waves P1 traveling in the direction of the reflector 31 and ultrasonic waves P2 traveling in the direction of the water surface S are simultaneously emitted from the ultrasonic sensor 2. When this is emitted, the ultrasonic sensor 2 outputs a high-intensity output signal A (Figures 22 and 23), and this output signal A is sent to the management server.

Then, as the reflected wave H1 from the reflector 31, which is close by, is received by the ultrasonic sensor 2, the ultrasonic sensor 2 outputs a signal B (Figures 22 and 23) derived from the reflected wave H1 from the reflector 31, and the signal B is sent to the management server.

As shown in FIG. 20, when the water surface S is higher than the danger level, the distance L between the ultrasonic sensor 2 and the water surface S is smaller than the maximum detection distance Lmax, and the reflected wave H2 from the water surface S is received by the ultrasonic sensor 2 with a delay. This causes the ultrasonic sensor 2 to output a signal C (FIG. 22) derived from the reflected wave H2 from the water surface S, and the signal C is sent to the management server.

On the other hand, as shown in FIG. 21, when the water surface S is lower than the danger level and the distance L between the ultrasonic sensor 2 and the water surface S is greater than the maximum detection distance Lmax, the reflected wave H2 from the water surface S is significantly attenuated in intensity when it reaches the ultrasonic sensor 2. As a result, the ultrasonic sensor 2 does not output a signal C derived from the reflected wave H2 from the water surface S (FIG. 23), and the signal C is not sent to the management server.

Figure 24 is a flowchart showing an example of processing executed by the management server. The processing shown in Figure 24 is described below.

In the process of FIG. 24, it is determined whether or not "signal B derived from reflected wave H1 from reflector 31" has been received by the management server within a predetermined time after "output signal A" has been received by the management server in step S1 (step S2). Then, in step S3 or step S4 following step S2, it is determined whether or not "signal C derived from reflected wave H2 from the water surface S" has been received by the management server within a predetermined time after output signal A has been received in step S1.

If the answer is NO in step S2 and NO in step S3, the management server outputs information indicating that "the sensor device 30 is malfunctioning" (step S5).

If step S2 is NO and step S3 is YES, the management server outputs information suggesting that "sensor 2 is operating normally, but there may be foreign matter or water attached to reflector 31 or around sensor 2" (step S6).

If step S2 is YES and step S4 is NO, the management server outputs information indicating that "the device 30 is operating normally and the water surface S is below the danger level" (step S7).

If step S2 is YES and step S4 is YES, the management server outputs information indicating that "the device 30 is operating normally and the water surface S has risen above the dangerous water level" (step S8).

The information output in steps S5, S6, S7, and S8 may be changed as appropriate depending on the manager's capabilities, etc. If the manager is familiar with the sensor device 30, information simply indicating whether signals B and C have been received may be output in steps S5, S6, S7, and S8 (an administrator familiar with the sensor device can understand, for example, that "information indicating that signals B and C have not been received" output in step S5 suggests "the device is malfunctioning." Also, for example, that "information indicating that signal B has not been received and signal C has been received" output in step S6 suggests "sensor 2 is operating normally, but there may be a foreign object or water attached to reflector 31 or the periphery of sensor 2.")

According to the sensor device 30 described above, the distance L2 between the reflector 31 and the ultrasonic sensor 2 is made shorter than the maximum detection distance Lmax, so that the ultrasonic sensor 2 always outputs the signal B (FIGS. 22 and 23) derived from the reflected wave H1 from the reflector 31 unless a malfunction occurs in the ultrasonic sensor 2. Therefore, if a malfunction occurs in the ultrasonic sensor 2, the ultrasonic sensor 2 will no longer output the signal B (corresponding to NO in steps S2 and S3 in FIG. 19), and the administrator will recognize that a malfunction has occurred in the ultrasonic sensor 2. Therefore, measures to repair the ultrasonic sensor 2 can be taken quickly. This ensures that the ultrasonic sensor 2 can operate normally when the river or sea reaches a dangerous water level, so that it is possible to reliably identify that the river or sea has reached a dangerous water level.

The processing executed by the management server may be performed by a control device or the like included in the sensor device 30.

Even when a commonly used low-output ultrasonic sensor 2 is used, by making the distance L2 between the reflector 31 and the ultrasonic sensor 2 shorter than the maximum detection distance Lmax, the ultrasonic sensor 2 outputs a "signal B derived from the reflected wave H1 from the reflector 31 (Figures 22 and 23)." Therefore, there is no need to use a high-output ultrasonic sensor 2, and costs can be kept low.

In addition, the sensor device 30 uses a reflector 31 as a means for checking that the ultrasonic sensor 2 is operating normally, so that the operation of the sensor 2 can be checked even in a river or ocean without embankments, where the distance L between the sensor 2 and the water surface S is large. In addition, the peak of the reflector can be used to grasp deviations in the accuracy of the measured distance.

Furthermore, if the distance L1 between the ultrasonic sensor 2 and the dangerous water level S is set equal to the maximum detection distance Lmax, it is possible to determine whether the water surface S of the river or ocean has risen above the dangerous water level based on whether the ultrasonic sensor 2 outputs a "signal C derived from the reflected wave H2 from the water surface S." Furthermore, if the distance L1 is set to be equal to or less than the maximum detection distance Lmax, the management server or a control device of the sensor device 30 may determine whether the water surface S of the river or ocean has risen above the dangerous water level based on the intensity of the reflected wave H2 indicated by the signal C, for example, and if it is determined that the water surface S has risen above the dangerous water level, output information indicating that fact.

The means for supporting the ultrasonic sensor 2 and the reflector 31 is not limited to the arm 32 shown in Figures 20 and 21, and various means can be used that can position the ultrasonic sensor 2 above the water surface S and position the reflector 31 between the ultrasonic sensor 2 and the water surface S. The ultrasonic sensor 2 and the reflector 31 may also be supported by separate means.

The signal output from the ultrasonic sensor 2 is not limited to a signal indicating the intensity of the waves P and H, but can be a signal related to the waves P and H other than the intensity. For example, the ultrasonic sensor 2 may output a signal indicating the time when the ultrasonic wave P was emitted, or a signal indicating the time when the reflected wave H was received. Even in this case, if the distance L2 between the reflector 31 and the ultrasonic sensor 2 is made shorter than the maximum detection distance Lmax, for the same reasons as above, it is possible to reliably identify when the river or sea has reached a dangerous water level while keeping costs low.

In addition, in the first to fourth embodiments, the arm 90 shown in FIG. 25 can be used instead of the arm 8 (FIGS. 1 to 3, 6, 8 to 12, and 19) or the arm 72 (FIGS. 15 to 17). (FIG. 25(A) is a perspective view of the arm 90, and FIG. 25(B) is a cross-sectional view of the arm 90.)

The arm 90 extends horizontally. One end of the arm 90 is fastened to a vertically extending support 6 or pole 7 using a fastener 9. In the illustrated example, the fastener 9 is the U-clamp shown in the first embodiment.

A groove 91 is formed in the arm 90. The groove 91 extends in the longitudinal direction (horizontal direction) of the arm 90 and opens to the side surface 90a of the arm 90.

A slide member 92 that can slide along the groove 91 is attached to the arm 90, and a housing 3 that houses an ultrasonic sensor is attached to the slide member 92.

The groove 91 is composed of a narrow portion 91a whose one end opens to the side surface 90a of the arm 90, and a wide portion 91b that is connected to the other end of the narrow portion 91a.

The slide member 92 has an L-shaped cross section and includes a plate 92a extending vertically and a plate 92b extending horizontally from the lower end of the plate 92a. The plate 92a is arranged along the side surface 90a of the arm 90 so as to cover the narrow portion 91a of the groove 91. The housing 3 is fastened to the plate 92b so that the wall surface 3a of the housing 3 where the opening 17 is formed faces the river side (lower side) (in the illustrated example, the housing 3 is fastened to the plate 92b using a bolt 100 and a nut 101). As a result, the ultrasonic waves P emitted from the opening 17 are directed toward the water surface of the river, and the reflected waves H reflected by the water surface that enter the opening 17 are received by the receiver.

As shown in FIG. 25(B), the head 93a of the bolt 93 is placed in the wide portion 91b of the groove 91, and the column portion 93b of the bolt 93 passes through the narrow portion 91a of the groove 91 (the column portion 93b extends from the head 93a, and the diameter of the column portion 93b is smaller than the diameter of the head 93a). The tip side of the column portion 93b penetrates the plate 92a and extends from the plate 92a to the opposite side of the arm 90 (the left side in FIG. 25(B)).

In the above-mentioned arm 90, the sliding member 92 supporting the housing 3 can be fixed to the arm 90 by fastening a nut 98 to the tip side of the column portion 93b extending from the plate 92a, and the sliding member 92 can be slid along the groove 91 by loosening the nut 98. The sliding of the sliding member 92 can move the housing 3 housing the ultrasonic sensor 2 in the longitudinal direction (horizontal direction) of the arm 90, so that the irradiation position of the ultrasonic wave P can be adjusted. When the sliding member 92 is slid, the head 93a of the bolt 93 slides within the groove 91 to guide the sliding of the sliding member 92.

When the arm 90 is used, for example, an antenna is provided on the arm 90, and the ultrasonic sensor can transmit information based on the transmission and reception time to the outside via the antenna. For example, the antenna is disposed in the groove 91, so that the antenna extends in the longitudinal direction of the arm 8. Alternatively, the antenna is disposed in a cavity in the arm 90 formed separately from the groove 91, so that the antenna extends in the longitudinal direction of the arm 8. The antenna may be formed by the arm 90, or may be provided inside the housing 3.

The means for moving the housing 3 in the longitudinal direction (horizontal direction) of the arm 90 is not limited to the groove 91 and slide member 92 described above. As a means for moving the housing 3, known means other than the groove 91 and slide member 92 may be provided on the arm 90.

1, 30, 65, 68, 70, 80 Sensor device 2 Ultrasonic sensor 3 Housing 4 Support 5 Antenna 7 Pole 8, 32, 72, 90 Arm 17 Opening of housing 20, 67 Sensor system,
K River S Water surface T Levee (solid)
Ta: Part of the embankment (solid part)

Claims (6)

an ultrasonic sensor capable of measuring a time from transmitting an ultrasonic wave to receiving a reflected wave of the ultrasonic wave reflected by a measurement object, and transmitting information based on the measured time to an external device;
A housing that houses the ultrasonic sensor;
a support and a support tool for supporting the ultrasonic sensor so that the ultrasonic sensor is located above the water surface of the river or sea;
The support includes a horizontally extending arm;
One end of the arm is fastened to a support extending in a vertical direction, and the housing is attached to the other end of the arm so that the ultrasonic waves emitted from an opening of the housing are directed toward the water surface of a river or an ocean,
the support is detachably attached to the support column near and below the arm, and by loosening the fastening of one end of the arm to the support column, the arm can be rotated around the support column with the one end of the arm supported by the support,
A sensor device in which the housing can be moved up and down by loosening the fastening of one end of the arm to the support and removing the support from the support, thereby sliding the arm vertically along the support. a stopper detachably attached to the support column near the upper side of the arm,
When the fastening of the one end side of the arm to the support is loosened, the one end side of the arm supported by the support tool can be pressed downward by the pressing tool,
The sensor device of claim 1, wherein the arm can be slid vertically along the support by loosening the fastening of one end of the arm to the support and removing the support and the fastening device from the support, thereby moving the housing up and down. The sensor device according to claim 1 or 2, wherein the housing is attached to the arm so as to be freely slidable in the horizontal direction. A sensor system comprising the sensor device according to any one of claims 1 to 3,
A sensor system comprising a distance acquisition means for acquiring information indicating the distance from the ultrasonic sensor to the measurement object based on the time measured by the ultrasonic sensor and the speed of sound calculated using the air temperature near the ultrasonic sensor at the time the ultrasonic wave is transmitted or the reflected wave is received. A method for using the sensor device according to any one of claims 1 to 3, comprising:
The ultrasonic sensor measures the time from when an ultrasonic wave is emitted until when the reflected wave of the ultrasonic wave reflected by a measurement object is received, and can transmit information based on the time to the outside. The ultrasonic sensor is disposed so that the ultrasonic wave is directed toward a solid part located below a dangerous water level of a river or sea.
A method for using a sensor device, wherein the distance between the solid part and the ultrasonic sensor is shorter than the maximum distance at which the ultrasonic sensor can detect the reflected wave. The method for using the sensor device according to claim 5, wherein the solid body is a river bank.