JP7742338B2 - Water level gauge, water level gauge storage component, and water level gauge installation structure - Google Patents

Description

This invention relates to a water level gauge, a water level gauge storage member, and a water level gauge installation structure, and in particular to a water level gauge, a water level gauge storage member, and a water level gauge installation structure for detecting the water level in a farm field, for example.

An example of a conventional water level meter of this type is disclosed in Patent Document 1. With the technology in Patent Document 1, a single-tube pipe (a rod-shaped fixture) is inserted into the field, and the housing of the water level meter (sensor terminal) is connected and fixed to the single-tube pipe using a flexible clamp or similar, thereby erecting the water level meter in the field.

Japanese Patent Application Laid-Open No. 2020-103099

Field water contains many impurities such as mud, straw, and fallen leaves. With the technology of Patent Document 1, the field water comes into direct contact with the sensor part of the water level gauge, which can lead to measurement errors due to impurities adhering to the sensor part. Furthermore, because the sensor part is easily soiled, frequent maintenance is required, and this maintenance is also time-consuming.

Therefore, the primary object of this invention is to provide a novel water level gauge, water level gauge storage member, and water level gauge installation structure.

Another object of the present invention is to provide a water level gauge, a water level gauge storage member, and a water level gauge installation structure that allows the sensor unit to be less susceptible to contamination and to accurately and stably measure the water level in a field.

The first invention is a water level meter that detects the water level in a field. It comprises a sensor body with a sensor unit that detects the water level, a vertical cylindrical sensor case that has an air vent formed at the top and a first water port formed at the bottom and that houses the sensor unit, and a sealing membrane that is formed in the shape of an expandable bag with an opening and is arranged so that its interior communicates with the first water port. Fresh water is stored inside the sealing membrane, and the sealing membrane is arranged so that its outer surface comes into contact with the field water.

In a first aspect of the invention, the water level meter comprises a sensor body having a sensor unit, a vertically tubular sensor case that houses the sensor unit, and a sealing membrane formed in the shape of an expandable bag. The sensor case has an air vent at its top and a first water inlet at its bottom. The sealing membrane has an opening and is arranged so that its interior communicates with the first water inlet of the sensor case. Furthermore, the sealing membrane stores fresh water inside and is arranged so that its outer surface comes into contact with field water.

In this type of water level gauge, the sealing membrane expands and contracts in response to fluctuations in the water level in the field, causing the clear water level to fluctuate up and down. The expansion and contraction of the sealing membrane stops when the internal and external pressures acting on the sealing membrane reach equilibrium, i.e., when the clear water level matches the water level in the field. In other words, the clear water level and the water level in the field remain consistent, so the water level in the field can be detected by detecting the clear water level with the sensor unit.

According to the first invention, a barrier membrane with fresh water stored inside is used, and the fresh water, rather than field water, is brought into contact with the sensor unit to detect the water level in the field. This makes it possible to prevent the sensor unit from becoming dirty, allowing for accurate and stable measurement of the water level in the field. Furthermore, because the sensor unit is less likely to become dirty, the frequency of maintenance of the water level gauge can be significantly reduced.

The second invention is dependent on the first invention, and the opening of the shielding membrane is watertightly connected to the sensor case.

A third invention is dependent on the first or second invention, and the air vent is formed at a position above the upper measurement limit of the sensor unit, and the first water passage is formed at a position below the lower measurement limit of the sensor unit.

The fourth invention is dependent on the first or second invention and includes a second water passage opening that opens at a position below the lower measurement limit position of the sensor unit, and a cylindrical protective member with a bottom that is arranged to surround the blocking membrane.

According to the fourth aspect of the present invention, a protective member is provided that surrounds the shielding membrane, thereby properly protecting the shielding membrane and allowing it to operate (expand and contract) appropriately.

The fifth invention is dependent on the fourth invention, and the protective member is arranged to surround the entire shielding film.

The sixth invention is dependent on the fifth invention, and the protective member has an air vent formed in the upper part.

According to the sixth aspect of the invention, air can be appropriately supplied and exhausted from within the protective member.

The seventh invention is dependent on the fourth invention, and the protective member has a bottom-raised portion provided at the bottom of the side wall and a mud drain port formed in the bottom wall.

According to the seventh invention, even if mud gets inside the protective member, it is discharged below the bottom wall through the mud drainage port, preventing accumulated mud from adversely affecting the operation of the shielding membrane.

The eighth invention is dependent on the first or second invention, and the opening of the shielding film is connected to the lower end of the sensor case.

According to the eighth invention, the shielding film (and protective member) can be made as small as possible.

The ninth invention is dependent on the eighth invention, and the lower end of the sensor case is tapered, increasing in diameter as it extends downward.

According to the ninth invention, when the water level inside the shielding membrane rises, fresh water flows smoothly into the sensor case.

The tenth invention is dependent on the fourth invention, and the lower end of the shielding film is connected to the bottom wall of the protective member.

According to the tenth aspect of the invention, deformation that causes the lower end of the shielding membrane to float from the bottom wall is eliminated, making it difficult for mud to accumulate between the lower end of the shielding membrane and the bottom wall, and air accumulation can also be prevented. This prevents accumulated mud and trapped air from adversely affecting the operation of the shielding membrane.

The eleventh invention is dependent on the fifth invention, and the protective member has a horizontal pipe portion that protrudes laterally, and the second water passage port is formed at the tip of the horizontal pipe portion.

According to the eleventh invention, field water can be drawn from a location away from the sensor body (and thus the water tap), meaning that a stable water level can be detected at a location that is less affected by water level fluctuations during water supply, thereby further improving the detection accuracy of the water level meter.

A twelfth invention is dependent on the first or second invention, and the sensor case has a horizontally tubular extension at its lower part, and the first water passage is formed at the tip of the extension.

According to the twelfth invention, field water is drawn from a location away from the sensor body (and thus the water tap), meaning that a stable water level is detected at a location that is less susceptible to water level fluctuations during water supply, thereby further improving the detection accuracy of the water level meter.

A thirteenth invention is dependent on the first or second invention, and the sensor main body is detachably attached to the sensor case.

The thirteenth invention enables flexible operation, such as removing only the sensor body from the field and storing it in a storage facility during agricultural off-seasons such as winter.

A fourteenth invention is dependent on the first or second invention, and the sensor body includes an inner cover that protects the sensor unit.

According to the fourteenth aspect, the sensor unit can be more appropriately protected.

A fifteenth invention is dependent on the first or second invention, and the amount of fresh water is greater than the volume of space within the sensor case below the upper measurement limit position of the sensor unit.

A sixteenth invention is dependent on the second invention, in which the shielding membrane is arranged to cover the lower part of the sensor case, and the sensor case has a second ventilation hole formed directly below the connection position with the shielding membrane.

According to the sixteenth invention, the air inside the shielding membrane can be maintained at an appropriate atmospheric pressure.

A seventeenth invention is dependent on the second invention and includes a second shielding membrane formed in an expandable and contractible bag shape and airtightly connected to the ventilation hole, and a second protective member having a third ventilation hole and arranged to surround the second shielding membrane.

According to the seventeenth aspect of the invention, the air inside the sensor case and the shielding membrane is not discharged to the outside, preventing the fresh water from decreasing due to evaporation (a decrease in the amount of fresh water), and eliminating the need to replenish the fresh water.

The eighteenth invention is dependent on the fourth invention, and the protective member restricts the shape of the shielding membrane to a fixed shape when expanded.

A nineteenth invention is dependent on the first or second invention, and the sensor unit is formed in a rectangular plate shape, and the sensor case is formed in a rectangular tube shape that fits along the outer surface of the sensor unit with a predetermined gap between them.

A twentieth invention is dependent on the first or second invention, and the sensor unit is a pressure-type sensor housed in the lower end of the sensor case.

The 21st invention is a water level gauge storage member that, together with a sensor main body having a sensor unit, constitutes a water level gauge that detects the water level in a farm field. The water level gauge storage member includes a vertical cylindrical sensor case that has an air vent formed at the top and a first water passage formed at the bottom and that houses the sensor unit, and an inflatable, bag-shaped sealing membrane with an opening, the interior of which is in communication with the first water passage.

In a 21st invention, a water level gauge housing member is used together with a sensor main body having a sensor unit to form a water level gauge that detects the water level in a farm field. This water level gauge housing member includes a vertically tubular sensor case that houses the sensor unit, and a sealing membrane formed in the shape of an expandable bag. An air vent is formed in the upper part of the sensor case, and a first water passage port is formed in the lower part. The sealing membrane has an opening, and is arranged so that its interior communicates with the first water passage port of the sensor case.

According to the 21st invention, the sensor portion of the sensor body can be made less susceptible to contamination, making it possible to construct a water level meter that can accurately and stably measure the water level in a field. Furthermore, it is possible to construct a water level meter that significantly reduces the frequency of maintenance, and the sensor body can be removed and stored when not in use.

The 22nd invention is an installation structure for a water level meter that detects the water level in a farm field, comprising a water level meter according to any one of the first to eighteenth inventions, and a cylindrical or bottomed cylindrical manhole that has multiple holes penetrating in its thickness direction and is installed in the farm field to surround the water level meter.

According to the 22nd invention, as with the first invention, the sensor unit can be made less susceptible to contamination, allowing for accurate and stable measurement of the water level in the field. Furthermore, because the sensor unit is less susceptible to contamination, the frequency of water level meter maintenance can be significantly reduced. Furthermore, because the water level meter is installed within a manhole, the water level meter itself is properly protected, and the manhole prevents large debris and mud from entering the area around the water level meter, making it even more difficult for the sensor unit to become dirty.

This invention makes it possible to make the sensor unit less susceptible to contamination, allowing for accurate and stable measurement of the water level in the field. Furthermore, because the sensor unit is less susceptible to contamination, the frequency of maintenance of the water level gauge can be significantly reduced.

The above and other objects, features, and advantages of the present invention will become more apparent from the detailed description of the embodiments below, which proceeds with reference to the drawings.

1 is a diagram showing a field water management system equipped with a water level meter according to an embodiment of the present invention; FIG. 2 is a cross-sectional view showing the internal structure of the electric actuator. FIG. A cross-sectional view showing the internal structure of the water level gauge FIG. FIG. FIG. 4 is a cross-sectional view showing a water level gauge housing member. FIG. 2 is an illustrative view for explaining the operation of the water level meter. FIG. 2 is an illustrative view for explaining the operation of the water level meter. FIG. 2 is an illustrative view for explaining the operation of the water level meter. FIG. 10 is a schematic diagram showing a water level meter according to another embodiment of the present invention. FIG. 10 is a schematic diagram showing a water level meter according to still another embodiment of the present invention. FIG. 10 is a schematic diagram showing a water level meter according to still another embodiment of the present invention. FIG. 10 is a schematic diagram showing a water level meter according to still another embodiment of the present invention. FIG. 10 is a schematic diagram showing a water level meter according to still another embodiment of the present invention. FIG. 10 is a schematic diagram showing a water level meter according to still another embodiment of the present invention. FIG. 17 is a schematic diagram showing a cross section of the water level meter of FIG. 16; FIG. 10 is a schematic diagram showing a water level meter according to still another embodiment of the present invention. FIG. 19 is a schematic diagram showing a cross section of the water level meter of FIG. 18 .

Referring to Figure 1, a water level meter 50 according to one embodiment of the present invention is used in a field water management system 10 (hereinafter simply referred to as "system 10") to detect the water level in a field 100. As will be described in detail below, the water level meter 50 comprises a sensor body 52 and a water level meter housing member 54, and is installed in a manhole 56 provided for the water level meter 50.

First, before providing a detailed description of the water level indicator 50, we will briefly explain an example of the configuration of the system 10. However, the configuration of the system 10 (such as the specific configuration of the water tap 12, water outlet 14, and electric actuator 16) is not limited to this example and can be modified as appropriate.

As shown in FIG. 1, system 10 is a field facility that manages water in field 100 by remote control or automatic control based on a pre-stored program. In this embodiment, system 10 includes a water supply faucet 12 and a water outlet 14, and an electric actuator 16 is attached to each of water supply faucet 12 and water outlet 14. In other words, electric actuators 16 with the same structure are used to drive the displacement mechanisms of water supply faucet 12 and water outlet 14.

In this embodiment, the system 10 includes multiple cultivated areas separated by ridges 102. A water tap 12 and a water outlet 14 are installed in each cultivated area, and each electric actuator 16 attached to each tap is wirelessly connected to a repeater (parent unit) using a wireless communication method conforming to the specified low-power wireless standard (920 MHz band). Each electric actuator 16 is then wirelessly connected to a remote control terminal such as a user's smartphone, tablet, PDA, or PC via the repeater and a management server or the like installed on the network. However, the electric actuator 16 may also communicate wirelessly with external devices such as the management server or remote control terminal without using a repeater.

It is recommended that this wireless communication utilize cloud computing. For example, information acquired by each electric actuator 16 (information regarding the status of the water faucet 12 and the water outlet 14, such as the valve opening degree of the water faucet 12 and the outlet height of the water outlet 14, as well as sensor information such as the water level in the field 100 received from the water level gauge 50) is transmitted as needed to and stored in a cloud server, which is an example of a management server. By accessing the cloud server from a remote control terminal, a user can check the information acquired by each electric actuator 16 and remotely operate each electric actuator 16 using the remote control terminal to manage the water in the field 100.

The water hydrant 12 is a water supply device for controlling the water supply from the irrigation pipeline 106 to the cultivated area (field 100), and has a displacement mechanism including a valve stem and valve element. This embodiment uses a commonly used water hydrant 12 in which the valve stem and valve element move up and down as the valve stem rotates. This type of water hydrant 12 is placed in a water supply pit 104 installed on the levee 102, and is attached to the downstream end of a branch pipe 108 that branches off from the irrigation pipeline 106 laid under the levee 102 and extends into the field 100. An electric actuator 16 is attached to the water hydrant 12, and the displacement mechanism (valve stem and valve element) of the water hydrant 12 is operated by the electric actuator 16.

On the other hand, the water outlet 14 is a drainage device for controlling drainage from the field 100 and has a displacement mechanism including a partition. In this embodiment, a water outlet 14 with a water level setting function is used. Briefly, the water outlet 14 has a cylindrical partition 18 whose upper opening functions as a drainage outlet. The partition 18 moves up and down, allowing the drainage outlet to be adjusted to any height. This water outlet 14 is placed in a drainage basin 110 provided on the levee 102 and attached to the upstream end of a drainage pipe 114 extending to a drainage channel 112. An electric actuator 16 is attached to the water outlet 14, and the displacement mechanism (partition) of the water outlet 14 is moved up and down by the electric actuator 16. When attaching the electric actuator 16 to the water outlet 14, an adapter 20 is used, which converts the rotational force of the electric actuator's rotation shaft 46 (see Figure 2) into a vertical (axial) force and transmits it to the partition.

Referring to Figures 1 and 2, the electric actuator 16 includes a cylindrical main body case 30. A solar cell panel 32 is detachably attached to the top of the main body case 30. The solar cell panel 32 is supported at a predetermined angle by a bent metal plate-shaped holder 34.

The main body case 30 also houses an electronic board 36, a storage battery 38, and a drive mechanism including a motor 40 and a main gear 42.

Although not shown, the electronic board 36 is equipped with a control unit including a CPU and memory, and a wireless communication unit including a wireless communication module. The control unit is electrically connected to the motor 40, operation panel 48, wireless communication unit, water level gauge 50, and other components. The CPU of the control unit is responsible for overall control of the electric actuator 16 and controls the drive of the motor 40 and other components. Memory is a comprehensive term that includes ROM, RAM, and HDD, and stores control programs that control the operation of the electric actuator 16 and functions as a work area when the CPU is operating. The wireless communication unit is also connected to an antenna (not shown), and communicates wirelessly with external devices such as repeaters via this antenna.

The storage battery 38 stores the electricity generated by the solar panel 32. The motor 40 is driven by the electricity stored in the storage battery 38. A small gear 44 is provided at the tip of the output shaft 40a of the motor 40, and the main gear 42, coupled to this small gear 44, receives driving force from the motor 40 and rotates around its axis.

The main gear 42 is a double-boss gear, and a roughly cylindrical rotating shaft 46 is inserted into the shaft portion of the main gear 42. A coupling portion 46a is formed at the lower end of this rotating shaft 46, which connects to the valve shaft of the water faucet 12. A key groove 42a extending along the axial direction is formed on the inner surface of the shaft portion of the main gear 42, and a sliding key 46b that fits into the key groove 42a is formed on the outer surface of the rotating shaft 46 so as to extend along the axial direction. This allows the rotating shaft 46 to rotate as the main gear 42 rotates, and to slide axially relative to the shaft portion of the main gear 42.

An operation panel 48 for manually (electrically operated) operating the motor 40 is provided on the outer surface of the main body case 30. The operation panel 48 is appropriately provided with a main power switch, an up button, a down button, and a selection button for switching the operating mode of the electric actuator 16 (remote mode, automatic mode, manual mode, etc.). This operation panel 48 is also provided with connection terminals for connecting the wiring 58 extending from the water level gauge 50.

In a water faucet 12 equipped with an electric actuator 16 as described above, for example, a user accesses a management server using a remote control terminal and sends an operation instruction (control signal) to set the water faucet 12 to fully close, fully open, or an arbitrary opening position. A control signal corresponding to this operation instruction is then sent from the management server via a relay to the electric actuator 16. The control unit of the electric actuator 16 drives the motor 40 in response to the received control signal. The driving force of this motor 40 is transmitted to the main gear 42, causing the rotating shaft 46 to rotate together with the main gear 42. This imparts a rotational force to the valve shaft of the water faucet 12, which is fixedly connected to the rotating shaft 46. The valve shaft to which the rotational force is applied is moved up and down by a feed screw mechanism, and the valve disc is moved to a fully open position, a fully closed position, or the like.

Similarly, in the case of a water outlet 14 equipped with an electric actuator 16, when a user sends an operation command to set the outlet height of the water outlet 14 (height position of the partition body 18), the control unit of the electric actuator 16 drives the motor 40 in response to the control signal to change the outlet height of the water outlet 14.

Returning to FIG. 1, the field 100 is provided with a water level meter 50 at a position near the water tap 12 and the water outlet 14 to detect the water level in the field 100. Although not shown, the field 100 may also be provided with sensors as appropriate, such as a water temperature sensor to detect the temperature of the field water, an air temperature sensor to detect the air temperature, a humidity sensor to detect humidity, a pressure sensor to detect air pressure, a soil moisture sensor to detect soil moisture, and a soil temperature sensor to detect the soil temperature. In this embodiment, the water level meter 50 (sensor body 52, described below) is a water level and water temperature sensor that can detect not only the water level in the field 100 but also its temperature.

The water level gauge 50 is connected to the electronic board 36 (controller) of the electric actuator 16 via wiring 58 (signal cable) that complies with the RS-485 standard, for example. Sensor information related to the water level and water temperature detected by the water level gauge 50 is input to the electronic board 36 of the electric actuator 16. The power source for operating the water level gauge 50 is power stored in the storage battery 38 of the electric actuator 16, and this power is supplied from the electronic board 36 to the water level gauge 50. Using the solar cell panel 32 and storage battery 38 provided on the electric actuator 16 as the power source for the water level gauge 50 eliminates the need for a separate power source such as dry batteries in the water level gauge 50 and eliminates the need for battery replacement. However, the power source for operating the water level gauge 50 can also be provided in the water level gauge 50, or the water level gauge 50 and the electric actuator 16 can be connected wirelessly.

However, with conventional water level gauges, where the sensor directly contacts the field water, impurities can easily adhere to the sensor, which can lead to measurement errors. Furthermore, the sensor easily becomes dirty, requiring frequent maintenance.

In this embodiment, the water level gauge 50 employs the following configuration to prevent the sensor unit from becoming dirty and to enable accurate and stable measurement of the water level in the field 100. The configuration of the water level gauge 50 will be described in detail below with reference to Figures 3 to 7.

As shown in Figures 3 and 4, the water level gauge 50 comprises a sensor body 52 including a sensor unit 60 and an inner cover 62, and a water level gauge housing member 54 including a sensor case 70, a shielding membrane 72, and a protective member 74.

Referring to Figures 3, 4, and 5, the sensor main body 52 includes a sensor unit 60 (sensor board) that detects the water level in the field 100. The sensor unit 60 can be a known water level sensor, such as a capacitance type, pressure type, electrical resistance type, float type, or ultrasonic type. In this embodiment, a capacitance type sensor formed in the shape of a rectangular plate that is long in the vertical direction is used. The sensor unit 60 is housed within a vertically tubular (cylindrical in this embodiment) inner cover 62, secured by screws or the like. The inner cover 62 is a member that surrounds and protects the sensor unit 60, and is made of a synthetic resin such as rigid polyvinyl chloride or polyethylene. The nominal diameter (inner diameter) of the inner cover 62 is, for example, 40 mm.

A circular marking 62a is provided on the outer peripheral surface of the lower end of the inner cover 62, aligned with the height of the zero point 60a of the sensor unit 60. When installing the water level gauge 50, the height of this marking 62a is aligned with the height of the top surface (paddy field surface) of the field 100. A cylindrical cap 64 with a top is attached to the upper end of the inner cover 62 to seal the upper opening of the inner cover 62. The lower end of this cap 64 serves as a locking portion 64a that locks onto the upper end (support portion 70d) of the sensor case 70, described below. The lower opening of the inner cover 62 is left open and serves as a water passage 62b, which serves as an entrance and exit for fresh water C (see Figure 8), described below, into the inner cover 62.

Referring to Figures 6 and 7 as well as Figures 3 and 4, the water level gauge housing member 54 includes a vertically tubular (cylindrical in this embodiment) sensor case 70 that houses the sensor unit 60 of the sensor main body 52. The sensor case 70 is made of synthetic resin such as hard polyvinyl chloride and polyethylene. The sensor case 70 is preferably made of transparent resin so that the internal condition can be seen.

The sensor case 70 has an air vent 70a formed at the top and a first water vent 70b formed at the bottom. The air vent 70a is formed above the upper measurement limit 60b of the sensor unit 60, and the first water vent 70b is formed below the lower measurement limit 60c of the sensor unit 60. In this embodiment, a hole formed at the top end of the sensor case 70 is used as the air vent 70a, and the bottom opening of the sensor case 70 is used as the first water vent 70b. However, the top opening 70c of the sensor case 70 can also be used as the air vent by, for example, forming a notch in the bottom end of the cap 64 of the sensor body 52 or in the top end of the sensor case 70. It is also preferable that the air vent 70a be sloped downward toward the outside to prevent rainwater from entering the sensor case 70.

The upper end of the sensor case 70 serves as a support portion 70d that supports the lower end (locking portion 64a) of the cap 64 from below. The lower end of the sensor case 70 is tapered, increasing in diameter as it extends downward. In other words, the sensor case 70 has a tapered portion 70e at its lower end. The tapered lower end of the sensor case 70 allows clean water C to flow smoothly into the sensor case 70 when the water level inside the blocking membrane 72 rises. The sensor case 70 also has a cylindrical clamping portion 70f that rises from the lower end of the tapered portion 70e. The nominal diameter of the portion of the sensor case 70 above the tapered portion 70e is, for example, 50 mm, and the nominal diameter of the clamping portion 70f is, for example, 100 mm.

The water level gauge housing member 54 is also equipped with a bag-shaped shielding membrane 72 having an opening 72a at its upper end, the interior of which is in communication with the first water passage port 70b (and thus the interior of the sensor case 70). The shielding membrane 72 is formed into a bag-like shape that can expand and contract (expand) using a water-tight, flexible membrane-like material such as rubber or a synthetic resin such as polyethylene. The inner perimeter of the opening 72a is set to approximately the same size as the outer perimeter of the clamping portion 70f of the sensor case 70. In this embodiment, a standard polyethylene bag No. 10 (width 180 mm, length 270 mm) is used as the shielding membrane 72. When using a standard polyethylene bag, the thickness of the shielding membrane 72 is preferably 0.06 mm to 0.10 mm, taking into account strength and conformability (expansion and contraction). In this embodiment, the thickness of the shielding membrane 72 is 0.08 mm.

The opening 72a of the shielding membrane 72 is watertightly connected to the lower end of the sensor case 70. By connecting the shielding membrane 72 to the lower end of the sensor case 70, the shielding membrane 72 (and protective member 74) can be made as small as possible. In this embodiment, the opening 72a of the shielding membrane 72 is sandwiched and fixed between the clamping portion 70f provided at the lower end of the sensor case 70 and the upper end of the side wall 80 of the protective member 74 (described below), thereby watertightly connecting the opening 72a of the shielding membrane 72 to the sensor case 70.

The water level gauge storage member 54 also includes a cylindrical protective member 74 with a bottom that surrounds the entire shielding membrane 72. This protective member 74 protects the shielding membrane 72 and ensures a predetermined space around it (i.e., prevents the shielding membrane 72 from being buried in the soil). The protective member 74 also functions as a restraining member that restrains the shielding membrane 72 to a fixed shape when expanded. In this embodiment, the protective member 74 is formed by combining multiple short tube members and disk members made of synthetic resins such as hard polyvinyl chloride and polyethylene, and fixing them together by adhesive, screws, or the like. The protective member 74 is preferably formed from a transparent resin so that the internal condition (particularly the condition of the shielding membrane 72 and the water level) can be seen.

Specifically, the protective member 74 comprises a cylindrical side wall 80 and a disk-shaped bottom wall 82. The nominal diameter of the central portion of the side wall 80 (the portion surrounding the shielding membrane 72) is, for example, 100 mm. A raised bottom portion 80a is formed at the lower portion of the side wall 80, protruding downward from the bottom wall 82, and the bottom wall 82 is formed with multiple mud drainage holes 82a that penetrate the bottom wall 82 in its thickness direction. As a result, even if mud gets inside the protective member 74, the mud is discharged from the mud drainage holes 82a below the bottom wall 82, preventing any adverse effects on the operation (expansion/contraction) of the shielding membrane 72.

The upper part of the side wall 80 is also formed with multiple air vent holes 80b spaced apart circumferentially. These air vent holes 80b also serve as entrances and exits for field water D (see Figure 9) into the protective member 74. The lower part (raised bottom portion 80a) of the side wall 80 is also formed with multiple second water passage holes 80c spaced apart circumferentially. These second water passage holes 80c serve as entrances and exits for field water D into the protective member 74, and are located below the lower measurement limit position 60c of the sensor unit 60. The side wall 80 is also provided with a marked line 80d indicating the appropriate amount of clean water C (described below) (the appropriate water level when there is no field water D around the blocking membrane 72).

An annular support portion 80e that protrudes inward is formed on the upper inner surface of the side wall 80. When attaching the sensor case 70 and the shielding film 72 to the protective member 74, the opening 72a of the shielding film 72 is sandwiched between the clamping portion 70f of the sensor case 70 and the upper end of the side wall 80, and the lower end of the clamping portion 70f is engaged with the support portion 80e. The upper end of the clamping portion 70f is then pressed down from above using a screw 88 or the like, thereby securing the sensor case 70 and the shielding film 72 to the protective member 74. The sensor case 70 and the shielding film 72 can be detached from the protective member 74 by removing the screw 88, facilitating tasks such as replacing the shielding film 72.

When attaching the sensor body 52 to the water level gauge housing member 54, the sensor section 60 and inner cover 62 of the sensor body 52 are inserted through the upper opening 70c of the sensor case 70, and the lower end (locking section 64a) of the cap 64 is locked onto the upper end (support section 70d) of the sensor case 70. This holds the sensor body 52 upright in the water level gauge housing member 54 so that the sensor section 60 is positioned at a predetermined height. In other words, the sensor body 52 is detachable from the sensor case 70, and can be easily attached and detached by simply inserting and removing it from the sensor case 70. Because the sensor body 52 is detachable from the sensor case 70 (water level gauge housing member 54), flexible operation is possible, such as removing only the sensor body 52 from the field 100 and storing it in a storage shed during agricultural off-seasons such as winter.

In this embodiment, the height position of the upper end of the side wall 80 of the protective member 74 is aligned with the height position of the marked line 62a of the sensor body 52 (i.e., the zero point 60a of the sensor unit 60). When the water level gauge 50 is installed in the field 100, the height position of the upper end of the side wall 80 of the protective member 74 is aligned with the height position of the top surface of the field 100.

Returning to Figure 1, such a water level gauge 50 is installed in a manhole 56 provided in the field 100 to form a water level gauge installation structure 120. In other words, the water level gauge installation structure 120 comprises the water level gauge 50 and a manhole 56 provided to surround the water level gauge 50.

The manhole 56 is formed in a cylindrical shape with a bottom, and is erected in the field 100 by embedding its lower end in the field 100. The side and bottom walls of the manhole 56 have multiple holes that penetrate the manhole in the thickness direction and are distributed throughout the entire pipe wall. The multiple holes are used as inlets and outlets for field water D into the manhole 56. The height position of the bottom surface (top surface of the bottom wall) of the manhole 56 is set so that when the water level meter 50 is installed in the manhole 56, the zero point 60a of the sensor unit 60 coincides with the height position of the top surface of the field 100. Furthermore, the height position of the upper end of the side wall of the manhole 56 is set to be the same as or slightly above the maximum water level of the field water D that can be stored in the field 100.

When the water level gauge 50 is installed in the field 100, fresh water C is stored inside the blocking membrane 72 (see Figure 8). The blocking membrane 72 is also installed so that its outer surface comes into contact with field water D. In this embodiment, the field water D that flows into the manhole 56 passes through the second water passage 80c and mud drainage port 82a of the protective member 74 and reaches the periphery of the blocking membrane 72, bringing the outer surface of the blocking membrane 72 into contact with the field water D.

The amount of fresh water C is set to a value greater than the volume of space within the sensor case 70 below the upper measurement limit 60b of the sensor unit 60 (i.e., from the upper measurement limit 60b to the bottom of the sensor case 70) (the volume of the space excluding the volume of the sensor unit 60 and the inner cover 62). The amount of fresh water C is also set so that the water level (upper surface) of the fresh water C is below the lower measurement limit 60c of the sensor unit 60 when there is no field water D around the shielding membrane 72. In this invention, fresh water C refers to water such as tap water that does not contain impurities (foreign matter) such as mud, straw, or fallen leaves. Therefore, agricultural water or other sources of fresh water C can also be used as long as they are free of impurities (or have been removed). To prevent slime formation due to bacterial proliferation, a slime inhibitor or other additive can be added to the fresh water C, provided that it does not affect water level measurement.

When filling the inside of the blocking membrane 72 with fresh water C, it is advisable to visually confirm that the fresh water C has been filled up to the position of the marked line 80d on the protective member 74. However, if the protective member 74 is not transparent, a hole (peephole) can be formed in the side wall 80 at a position that indicates the appropriate amount of fresh water C, and visually confirm that the fresh water C has been filled up to the position of the hole. Alternatively, a hole can be formed in the side wall 80 at a position that indicates the appropriate amount of fresh water C, and a small valve that communicates with the inside of the blocking membrane 72 can be installed in that hole. In this case, the correct amount of fresh water C can be achieved by filling the tank with fresh water C with the valve open, and closing the valve when fresh water C starts to leak out from the valve.

Next, the operation of the water level meter 50 will be described with reference to Figures 8-10. As shown in Figure 8, when there is no field water D around the blocking membrane 72, or when the level of the field water D is lower than the appropriate level (i.e., the minimum water level) of the clear water C when there is no field water D around the blocking membrane 72, the clear water C maintains its minimum water level and the blocking membrane 72 is in a maximum expanded state. At this time, the protective member 74 constrains the shape of the blocking membrane 72 (the expanded shape) to a fixed shape. This stabilizes the expanded shape of the blocking membrane 72, thereby stabilizing the minimum water level of the clear water C. Furthermore, because the protective member 74 bears the water pressure within the blocking membrane 72, no force is applied to the blocking membrane 72, improving the durability of the blocking membrane 72.

Furthermore, as shown in FIG. 9 , when the level of the field water D rises above the minimum level of the fresh water C, the water pressure of the field water D that flows around the blocking membrane 72 through the second water inlet 80c and the mud drainage outlet 82a causes the blocking membrane 72 to contract (shrink). As a result, the level of the fresh water C rises, and fresh water C flows into the sensor case 70 and the inner cover 62, i.e., around the sensor unit 60. At this time, air that had accumulated in the protective member 74 is discharged through the air vent 80b, and air that had accumulated in the sensor case 70 and the blocking membrane 72 is discharged through the air vent 70a. As a result, the air in the sensor case 70 and the blocking membrane 72 is either maintained at atmospheric pressure or completely discharged. When the internal and external pressures acting on the blocking membrane 72 reach equilibrium—that is, when the level of the fresh water C and the level of the field water D are equal—the blocking membrane 72 stops contracting.

As shown in Figure 10, the level of the clear water C and the level of the field water D remain equal until the level of the field water D reaches or exceeds the upper measurement limit 60b of the sensor unit 60. If the level of the field water D drops, the water pressure of the clear water C causes the blocking membrane 72 to expand. As a result, the level of the clear water C drops, and when the level of the clear water C and the level of the field water D become equal, the expansion of the blocking membrane 72 stops. At this time, air flows into the protective member 74 through the air vent 80b and into the sensor case 70 and the blocking membrane 72 through the ventilation opening 70a, maintaining the air inside the sensor case 70 and the blocking membrane 72 at atmospheric pressure.

In other words, in the water level meter 50, the blocking membrane 72 expands and contracts in response to fluctuations in the level of the field water D, thereby maintaining the level of the fresh water C consistent with the level of the field water D. Therefore, by detecting the level of the fresh water C using the sensor unit 60, the water level of the field water D (field 100) can be detected.

As described above, according to this embodiment, the water level of the field 100 is detected by bringing fresh water C, rather than field water D, into contact with the sensor unit 60 using a blocking membrane 72 that stores fresh water inside. This makes it possible to prevent the sensor unit 60 from becoming soiled, allowing for accurate and stable measurement of the water level of the field 100. Furthermore, because the sensor unit 60 is less likely to become soiled, the frequency of maintenance of the water level gauge 50 can be significantly reduced.

In addition, according to this embodiment, a protective member 74 is provided that surrounds the shielding membrane 72, thereby providing proper protection for the shielding membrane 72 and allowing it to operate (expand and contract) appropriately. Furthermore, since the water level gauge 50 is installed within the manhole 56, the water level gauge 50 itself is also properly protected, and the manhole 56 prevents large debris, mud, etc. from entering the area around the water level gauge 50, making it even more difficult for the sensor unit 60 to become dirty.

Next, with reference to Figure 11, a water level indicator 50 according to another embodiment of the present invention will be described. Note that parts common to the above-described embodiment (the embodiment shown in Figure 1) will be given the same reference numerals, and duplicated descriptions will be omitted or simplified. Omitting duplicated descriptions will also be applied to other embodiments described below.

In the embodiment shown in FIG. 11 , the shielding membrane 72 is disposed to cover the lower portion of the sensor case 70, and the opening 72a of the shielding membrane 72 is watertightly connected to the center or upper portion of the sensor case 70. The sensor case 70 also has an air vent 70g (second air vent) formed directly below the connection position with the shielding membrane 72. This air vent 70g is used as an air vent for releasing air that has accumulated above the shielding membrane 72 when the shielding membrane 72 contracts. The air discharged from the air vent 70g is then discharged to the outside through the air vent 70a of the sensor case 70. When the shielding membrane 72 expands, outside air is drawn into the shielding membrane 72 through the air vents 70a and 70g. This maintains the air inside the shielding membrane 72 at atmospheric pressure, allowing the shielding membrane 72 to operate (expand and contract) appropriately.

The protective member 74 includes a cylindrical side wall 80, a disk-shaped bottom wall 82, and an annular top wall 84, and is arranged to surround the entire shielding membrane 72. An air vent 84a is formed in the top wall 84, and a second water passage 80c is formed in the side wall 80 at a position below the lower measurement limit position 60c of the sensor unit 60.

In the embodiment shown in Figure 11, as in the embodiment shown in Figure 1, the water level in the field 100 is detected by bringing fresh water C into contact with the sensor unit 60, which makes it difficult for the sensor unit 60 to become dirty and allows for accurate and stable measurement of the water level in the field 100.

In the embodiment shown in FIG. 1, the sensor main body 52 is provided with an inner cover 62, but as in the embodiment shown in FIG. 11, the sensor main body 52 does not necessarily have to be provided with an inner cover 62. Furthermore, the water level meter 50 does not necessarily have to be installed inside the manhole 56; as in the embodiment shown in FIG. 11, the water level meter 50 can also be installed in a dug hole or the like provided in the field 100. Furthermore, in the embodiment shown in FIG. 1, the manhole 56 is formed into a cylindrical shape with a bottom, but the manhole 56 does not necessarily have to have a bottom wall.

In addition, although not shown in the figures, the central lower end of the shielding membrane 72 can also be connected (fixed) to the bottom wall 82 of the protective member 74. This causes the expansion/contraction (deformation) direction of the shielding membrane 72 to be horizontal, eliminating deformation that causes the lower end of the shielding membrane 72 to float (separate) from the bottom wall 82. This makes it difficult for mud to accumulate between the lower end of the shielding membrane 72 and the bottom wall 82, and also prevents air from becoming trapped. This prevents accumulated mud and trapped air from adversely affecting the operation (expansion/contraction) of the shielding membrane 72.

Furthermore, as in the embodiment shown in Figure 12, the water level gauge 50 (or water level gauge housing 54) can also be equipped with a second shielding membrane 90 and a second protective member 92. The second shielding membrane 90 is formed in a bag shape with an opening, which is airtightly connected to the ventilation hole 70a so as to communicate with the interior of the sensor case 70. Like the shielding membrane 72, the second shielding membrane 90 is formed from a standard polyethylene bag or the like that is expandable and contractible. The volume of this second shielding membrane 90 when expanded is set to be larger than the volume of the space within the sensor case 70. The second protective member 92 is also provided so as to completely surround the second shielding membrane 90. A ventilation hole 92a (third ventilation hole) is formed in a predetermined position in this second protective member 92.

In the embodiment shown in FIG. 12, when the shielding membrane 72 contracts and the level of the fresh water C rises, the air inside the sensor case 70 and the shielding membrane 72 flows through the vent 70a into the second shielding membrane 90, causing the second shielding membrane 90 to expand. On the other hand, when the shielding membrane 72 expands and the level of the fresh water C drops, the air inside the second shielding membrane 90 flows into the sensor case 70 and the shielding membrane 72, causing the second shielding membrane 90 to contract. In this way, the air inside the sensor case 70 and the shielding membrane 72 simply moves within the sensor case 70, the shielding membrane 72, and the second shielding membrane 90 without being discharged to the outside. This prevents the fresh water C from decreasing due to evaporation (a decrease in the amount of fresh water), eliminating the need to replenish the fresh water C.

Furthermore, as in the embodiment shown in Figure 13, a horizontal pipe section 86 can be provided on the protective member 74. The horizontal pipe section 86 protrudes laterally from the side wall 80 and extends into an excavated hole 130 (or pit) provided in the field 100 at a position away from the sensor body 52. The tip (tip opening) of the horizontal pipe section 86 serves as a second water passage port 86a, which is the entrance and exit for field water D into the protective member 74. The length of the horizontal pipe section 86 is set to, for example, 3 to 10 meters.

In the embodiment shown in Figure 13, field water D is drawn from a location away from the sensor body 52, which is installed in a peripheral position of the water tap 12. In other words, a stable water level can be detected at a location that is less affected by water level fluctuations during water supply, thereby further improving the detection accuracy of the water level meter 50.

Also, as in the embodiment shown in Figure 14, a horizontally extending cylindrical extension portion 70h can be formed at the bottom of the sensor case 70. The extension portion 70h extends into an excavated hole 130 (or manhole) formed in the field 100 at a position away from the sensor main body 52, and a first water passage port 70b is formed at the tip of this extension portion 70h. The length of the extension portion 70h is set to, for example, 3m to 10m. The shielding membrane 72 and protective member 74 are also placed within the excavated hole 130 and are connected to the tip of the extension portion 70h (i.e., the lower end of the sensor case 70) within this excavated hole 130.

According to the embodiment shown in Figure 14, similar to the embodiment shown in Figure 13, it is possible to detect a stable water level at a position that is less affected by water level fluctuations during water supply, thereby further improving the detection accuracy of the water level meter 50.

In the embodiment shown in Figure 14, the tip of the extension 70h is connected to the upper ends of the shielding film 72 and the protective member 74, but as shown in Figure 15, the tip of the extension 70h can also be connected to the side of the shielding film 72 and the protective member 74.

Note that the specific configurations of the sensor body 52, water level gauge housing member 54 (sensor case 70, shielding membrane 72, protective member 74, etc.), and manhole 56 shown in the above-mentioned embodiments are merely examples and can be modified as appropriate.

For example, the protective member 74 can be formed using a Netron (registered trademark) pipe or Netron sheet, which has a mesh structure with countless holes formed in the pipe wall. The shapes of the shielding film 72 and the protective member 74 can also be modified as appropriate; for example, increasing the width (diameter) of the shielding film 72 and the protective member 74 can reduce their vertical length. Furthermore, the protective member 74 does not necessarily have to be arranged to surround the entire shielding film 72; for example, it may be arranged to cover only the lower half of the shielding film 72. Furthermore, as long as a predetermined space can be secured around the shielding film 72, the protective member 74 does not necessarily have to be arranged.

Furthermore, in each of the above-described embodiments, the sensor case 70 (and inner cover 62) is formed in a cylindrical shape, but the shape of the sensor case 70 (and inner cover 62) is not particularly limited as long as it can secure the water area necessary for measurement by the sensor unit 60 used. In this case, by adopting a shape that reduces the internal volume of the sensor case 70, the shielding membrane 72 can be made smaller, and ultimately the water level gauge 50 can be made more compact.

For example, as shown in Figures 16 and 17, when using a sensor formed as a vertically elongated rectangular plate, such as a capacitance or electrical resistance sensor, as the sensor unit 60, the sensor case 70 can be formed into a rectangular tube that fits along the outer surface of the sensor unit 60 with a specified gap. By forming the sensor case 70 into a rectangular tube, as in the example shown in Figure 16, the internal volume can be reduced, and the shielding membrane 72 can also be made smaller. This allows for the water level gauge 50 to be made more compact.

However, if the passage for fresh water C within the sensor case 70 (the gap X between the outer surface of the sensor unit 60 and the inner surface of the sensor case 70) becomes too small, capillary action may cause the water level within the sensor case 70 to rise or fall below the surrounding water surface. Experiments conducted by the inventors revealed that capillary action is hardly affected when the gap X is 3 mm or larger, so in this embodiment, gap X is set to 5 mm to allow for some leeway. Furthermore, the effect of capillary action can be reduced by using a material for the sensor case 70 that has a contact angle of close to 90 degrees when it comes into contact with water (for example, polyethylene with a contact angle of approximately 100 degrees, or rigid polyvinyl chloride with a contact angle of approximately 75 degrees). Furthermore, by forming the sensor case 70 from a material whose contact angle with water is significantly different from 90 degrees, even if a large water level difference occurs between the water surface inside the sensor case 70 and the surrounding water surface, if the cross-sectional shape of the sensor case 70 is the same in the top and bottom directions, the water level difference will be constant, so this can be addressed by performing a correction to subtract the water level difference from the measurement value.

16, the sidewall 80 of the protective member 74 is configured to surround the entire shielding membrane 72 and sensor case 70. A flange-shaped mounting portion 70i for mounting the shielding membrane 72 is formed at the lower end of the sensor case 70, and the opening 72a of the shielding membrane 72 is watertightly connected to the lower end of the sensor case 70. The upper opening of the sensor case 70 is sealed by a canopy 70j having an air vent 70a. A second shielding membrane 90 is connected to this air vent 70a via a connecting pipe 94. A second protective member 92 in the shape of a vertical cylinder with a top is connected to the upper end of the sidewall 80 of the protective member 74. The upper end of the sensor unit 60 (the non-measurement portion above the upper measurement limit 60b) is configured to penetrate the canopy 70j and protrude upward. However, the portion where the upper end of the sensor unit 60 penetrates the canopy 70j is airtight.

18 and 19, if a pressure-type sensor formed in a short cylindrical shape is used as the sensor unit 60, the sensor case 70 may have any shape that allows the sensor unit 60 and a connector (not shown) to pass through. In the embodiment shown in FIG. 18, the sensor unit 60 is housed at the bottom end of the sensor case 70. The wiring 58 is arranged to pass through the sensor case 70 and penetrate the canopy 70j. In this case, since the wiring 58 is thinner (has a smaller cross-sectional area) than the sensor unit 60, an appropriate water area necessary for transmitting water pressure is secured around the wiring 58. However, the portion where the wiring 58 penetrates the canopy 70j is airtight. In the embodiment shown in FIG. 18, the sensor case 70 may have any shape that allows the sensor unit 60 and a connector to pass through, so its internal volume can be reduced. This allows the shielding membrane 72 to be made smaller, thereby enabling the water level gauge 50 to be made more compact.

In the embodiment shown in Figure 18, the wiring 58 is passed through the sensor case 70, but as shown by the dashed line in Figure 18, the wiring 58 may also be routed out from the bottom of the sensor case 70. However, the portion where the wiring 58 passes through the sensor case 70 is made airtight.

Furthermore, in each of the above-described embodiments, the opening 72a of the shielding membrane 72 is watertightly connected to the sensor case 70, but this is not limited to this. For example, if the shielding membrane 72 is provided to cover the periphery of the sensor case 70 and the opening 72a is positioned above the maximum water level of the field water D that can be stored in the field 100, the opening 72a can be left open without being connected to the sensor case 70. However, in this case, a cover or eave must be provided to cover the top of the opening 72a to prevent rainwater and other substances from entering the shielding membrane 72.

Furthermore, in each of the above-described embodiments, the water level gauge 50, the sump 56, etc. are provided within the cultivated area of the field 100 divided by the ridges 102, but this is not limited to this. Although not shown, it is also possible to excavate the ridges 102 or otherwise provide a field extension section on the ridges 102 that connects to the cultivated area of the field 100, and provide the water level gauge 50, the sump 56, etc. in this field extension section.

Note that the specific numerical values and shapes of the dimensions listed above are merely examples and can be changed as needed depending on the product specifications, etc.

REFERENCE SIGNS LIST 10... Field water management system 12... Water supply tap 14... Water outlet 16... Electric actuator 50... Water level gauge 52... Sensor main body 54... Water level gauge storage member 60... Sensor unit 62... Inner cover 62a... Water passage port 70... Sensor case 70a... Ventilation port 70b... First water passage port 70h... Extension portion 70g... Second ventilation port 72... Shielding membrane 72a... Opening 74... Protective member 80a... Raised bottom portion 80b, 84a... Air vent 80c, 86a... Second water passage port 82a... Mud drain port 90... Second shielding membrane 92... Second protective member 92a... Third ventilation port 100... Field 102... Ridge 120... Water level gauge installation structure

Claims (22)

A water level meter for detecting the water level in a field,
a sensor body having a sensor portion for detecting the water level;
a vertically tubular sensor case having an air vent formed at an upper portion and a first water passage formed at a lower portion, and accommodating the sensor unit; and a sealing membrane formed in an expandable and contractible bag shape having an opening, the interior of which is provided so as to communicate with the first water passage,
A water level meter in which fresh water is stored inside the blocking membrane and the blocking membrane is provided so that its outer surface comes into contact with field water. The water level gauge of claim 1, wherein the opening of the shielding membrane is watertightly connected to the sensor case. the vent hole is formed at a position above an upper measurement limit position of the sensor unit,
The water level meter according to claim 1 or 2, wherein the first water passage port is formed at a position below a lower measurement limit position of the sensor unit. The water level gauge of claim 1 or 2, further comprising a second water passage opening that opens below the lower measurement limit position of the sensor unit and a cylindrical protective member with a bottom that surrounds the blocking membrane. The water level gauge of claim 4, wherein the protective member is arranged to surround the entire shielding membrane. The water level gauge of claim 5, wherein the protective member has an air vent formed in its upper portion. A water level gauge as described in claim 4, wherein the protective member has a raised bottom portion provided at the bottom of the side wall and a mud drain port formed in the bottom wall. A water level gauge according to claim 1 or 2, wherein the opening of the shielding membrane is connected to the lower end of the sensor case. A water level gauge as described in claim 8, wherein the lower end of the sensor case is tapered, increasing in diameter as it extends downward. A water level gauge as described in claim 4, wherein the lower end of the shielding membrane is connected to the bottom wall of the protective member. The protective member has a horizontal tube portion that protrudes laterally,
The water level meter according to claim 5 , wherein the second water passage port is formed at a tip end of the horizontal pipe portion. the sensor case has a horizontally tubular extending portion at a lower portion thereof,
The water level meter according to claim 1 or 2, wherein the first water passage port is formed at a tip end of the extension portion. A water level meter according to claim 1 or 2, wherein the sensor body is detachably attached to the sensor case. A water level meter according to claim 1 or 2, wherein the sensor body is provided with an inner cover that protects the sensor unit. A water level gauge as described in claim 1 or 2, wherein the amount of fresh water is greater than the volume of space within the sensor case below the upper measurement limit position of the sensor unit. the shielding film is provided to cover a lower portion of the sensor case,
The water level gauge according to claim 2 , wherein the sensor case has a second vent hole formed immediately below the position where the sensor case is connected to the shielding film. 3. The water level gauge according to claim 2, further comprising: a second shielding membrane formed in an inflatable bag shape and airtightly connected to the ventilation hole; and a second protection member having a third ventilation hole and provided so as to surround the second shielding membrane. A water level gauge as described in claim 4, wherein the protective member restricts the shape of the shielding membrane to a fixed shape when expanded. The sensor unit is formed in a rectangular plate shape,
The water level meter according to claim 1 or 2, wherein the sensor case is formed in a rectangular cylindrical shape that fits along the outer surface of the sensor unit with a predetermined gap therebetween. A water level gauge according to claim 1 or 2, wherein the sensor unit is a pressure-type sensor housed in the lower end of the sensor case. A water level meter housing member that constitutes a water level meter that detects the water level of a field together with a sensor main body having a sensor unit,
A water level gauge storage member comprising: a vertical cylindrical sensor case having an air vent formed at an upper part and a first water passage formed at a lower part, and in which the sensor unit is housed; and a sealing membrane formed in the shape of an expandable and contractible bag having an opening, the interior of which is provided so as to communicate with the first water passage. An installation structure for a water level meter that detects the water level in a field,
A water level gauge installation structure comprising: the water level gauge according to claim 1; and a cylindrical or bottomed cylindrical box having a plurality of holes penetrating in the thickness direction and provided in the field so as to surround the water level gauge.