LEVEL METER

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims foreign priority based on Japanese Patent Application No. 2023-072443, filed Apr. 26, 2023, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION
1. Technical Field

The present invention relates to a level meter that measures a level of an object.

2. Description of the Related Art

In a container that stores a flowable substance such as a liquid, a powder, or a granular material, a level meter that measures a height of an interface of the substance, that is, a level (liquid level, powder upper surface level, etc.) may be used. Such a level meter has a function of displaying the measured level to the user.

For example, a level meter described in JP 2014-002091 A includes a display unit that displays a measured liquid level.

In the conventional level meter, the measured level is displayed as a numerical value. For example, in the level meter of JP 2014-002091 A, a 5-digit 7-segment LED (light emitting diode) for displaying the measurement result of the liquid level as a numerical value is provided on the display unit.

However, when the level is displayed as a numerical value, it is difficult for the user to visually grasp the state of the object to be measured. For example, a level of an object contained in a tank is measured by a level meter, and a user may monitor how close the measured level is to a predetermined full-volume value. In this case, the user must calculate and determine what percentage of the current level is relative to the full value, based on the displayed numerical value and the full-volume value. That is, the user cannot visually grasp the state of the object such as the ratio of the current level to the full-volume value only by looking at the displayed numerical value of the level.

SUMMARY OF THE INVENTION

In view of the above problems, an object of the present invention is to provide a level meter that allows a user to easily visually grasp the state of the level of the object.

In order to solve the above problem, a level meter as an example of an embodiment according to the present invention is a level meter for measuring a level of an object, the level meter including: a sensor unit that is disposed on one end side along a measurement axis and measures the level along the measurement axis; a housing that is disposed on another end side different from the one end side; and a display unit that is provided in the housing and displays the level measured by the sensor unit with respect to a color graph together with the color graph having a plurality of level ranges color-coded with different colors.

According to the present invention, the display unit displays the level measured by the sensor unit with respect to the color graph together with the color graph having a plurality of level ranges color-coded with different colors. As a result, the user can easily visually grasp the state of the level of the object by checking the display unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating a level meter;

FIG. 2 is a cross-sectional view of the level meter;

FIG. 3 is a view illustrating a state in which a level meter is attached to a tank that houses an object;

FIG. 4A is a view illustrating a traveling path of a transmission wave;

FIG. 4B is a view illustrating a traveling path of a reflected wave;

FIG. 5 is a block diagram schematically illustrating an example of a relationship between components of the level meter;

FIG. 6 is a view illustrating an example of a configuration of a radar control unit and a transmission/reception unit;

FIG. 7 is a view illustrating a relationship between a transmission wave and a reflected wave;

FIG. 8 is a view illustrating a first display mode of a display unit;

FIG. 9 is a view illustrating a second display mode of the display unit;

FIG. 10 is a view illustrating a third display mode of the display unit;

FIG. 11 is a view illustrating a fourth display mode of the display unit;

FIG. 12 is a view for explaining mode transition of the display unit;

FIG. 13 is a perspective view illustrating another example of the level meter;

FIG. 14 is a cross-sectional view of another example of the level meter; and

FIG. 15 is a view illustrating a display unit in a case where a level range is changed.

DETAILED DESCRIPTION

Hereinafter, a level meter 10 as an example of an embodiment according to the present invention will be described with reference to the drawings. In the perspective view of FIG. 1, the level meter 10 of the present embodiment is illustrated. The level meter 10 is a device that measures the level of an object to be measured (for example, liquid, powder, granular material, and the like). The measured level is the height of the interface of the object. Specific examples of the level include the height of the liquid level of the liquid contained in a container.

The level meter 10 has a longitudinal direction A. In FIG. 1, the level meter 10 has a generally cylindrical shape extending in the longitudinal direction A. The level meter 10 includes a housing 15 and a sensor unit 16, and the housing 15 and the sensor unit 16 are arranged along the longitudinal direction A. The sensor unit 16 is disposed on one end side (lower side in FIG. 1) in the longitudinal direction A of the level meter 10, and the housing 15 is disposed on the other end side (upper side in FIG. 1) in the longitudinal direction A. One end of the sensor unit 16 in the longitudinal direction A is a measurement end unit 40.

Hereinafter, one end side in the longitudinal direction A of the level meter 10 may be referred to as a lower side, and the other end side in the longitudinal direction A may be referred to as an upper side. The sensor unit 16 measures the level of the object with the lower side in the longitudinal direction A facing the object. The sensor unit 16 of FIG. 1 measures the level of the object in a state where the measurement end unit 40 faces the object. A measurement axis is set in the sensor unit 16 of FIG. 1. The sensor unit 16 measures the level along the measurement axis. Here, when the level meter 10 measures the level of the object, it is preferable that a change direction of the level of the object to be measured (for example, liquid such as water) and the longitudinal direction A are the same direction. That is, the direction of the measurement axis of the sensor unit 16 (the direction along the measurement axis) and the longitudinal direction A are preferably the same direction. For example, when the level meter 10 measures the height (level) of the liquid level of the liquid, the longitudinal direction A is preferably the same direction as the change direction of the height of the liquid level of the liquid, that is, the vertical direction (height direction, gravitation direction). When the direction of the measurement axis and the longitudinal direction A are the same direction, the sensor unit 16 is disposed on one end side along the measurement axis, and the housing 15 is disposed on the other end side different from the one end side.

In the level meter 10 of FIG. 1, a radio wave serving as a transmission wave is transmitted from the measurement end unit 40 toward the object, and a reflected wave reflected by the object is received by the measurement end unit 40. The level meter 10 calculates the level of the object based on the transmission wave and the reflected wave.

An attachment screw portion 18 in which a thread is engraved on the surface of the cylinder is provided above the measurement end unit 40 in the sensor unit 16. An attachment portion 17 having a diameter larger than that of the attachment screw portion 18 is provided above the attachment screw portion 18. The attachment portion 17 in FIG. 1 has a nut shape. Note that the attachment portion 17 is not limited to a nut shape as long as it has a structure capable of attaching the level meter 10 to an attachment object (such as a tank that stores liquid). For example, the attachment portion 17 may have a cylindrical shape in which an anti-slip projection is formed. The anti-slip projection of the attachment portion 17 serves as an anti-slip portion when the level meter 10 is attached or detached (rotationally attached or detached) while rotating around the longitudinal direction A with respect to the attachment object. An attachment flange for attaching the level meter 10 to an attachment object may be formed instead of the attachment portion 17 and the attachment screw portion 18. Even when the attachment flange is formed, the attachment portion 17 and the attachment screw portion 18 may be provided in addition to the attachment flange.

The housing 15 disposed above the sensor unit 16 is provided with a display unit 20. The display unit 20 is disposed on an outer peripheral surface of the housing 15 extending along the longitudinal direction A. In FIG. 1, a flat portion along the longitudinal direction A is provided in a part of the outer peripheral surface of the housing 15, and the display unit 20 is disposed in the flat portion. Specifically, the lower portion of the housing 15 has a cylindrical shape surrounded by a curved outer peripheral surface (circular cross section) overlapping the sensor unit 16 along the longitudinal direction, and the upper portion of the housing 15 has a shape surrounded by an outer peripheral surface (D-shaped cross section) including a flat surface and a curved surface. Since the cylindrical portion of the housing 15 overlaps the sensor unit 16 along the longitudinal direction, the cylindrical portion and the sensor unit 16 appear to overlap when viewed from the longitudinal direction. The flat surface of the housing 15 is formed at a position offset toward the measurement axis of the sensor unit 16. The display unit 20 preferably includes an active matrix type display device (active matrix display) capable of displaying various types of information. For example, the display unit 20 includes a liquid crystal display (LCD). In particular, the display unit 20 preferably includes an LCD capable of color display (display with a plurality of colors). The display unit 20 may have a rectangular active matrix display that is long along the longitudinal direction A. That is, the long side of the rectangular active matrix display is preferably along the longitudinal direction A. The outer peripheral surface (flat portion) of the housing 15 on which the display unit 20 is disposed is preferably parallel to the longitudinal direction A (parallel to the direction of the measurement axis), but the outer peripheral surface may be slightly inclined with respect to the longitudinal direction A. Even when the outer peripheral surface is inclined with respect to the longitudinal direction A, if the angle between the outer peripheral surface and the longitudinal direction A is small (for example, 45 degrees or less), it can be said that the outer peripheral surface spreads along the longitudinal direction A.

The display unit 20 displays the level of the object measured by the sensor unit 16. In FIG. 1, a bar graph 22 whose length expands and contracts along a gauge direction B according to the value of the level is displayed on the display unit 20. The display unit 20 also displays a color gauge 24 color-coded with a plurality of colors. The color gauge 24 is an example of a color graph having a plurality of level ranges each color-coded with a different color. The display unit 20 displays the level of the object measured by the sensor unit 16 on the color graph together with the color graph. The color gauge 24 as a color graph indicates which level range the measured level belongs to among a plurality of predetermined level ranges. The color gauge 24 includes a plurality of sections. The plurality of sections of the color gauge 24 are divided into a plurality of level ranges. The sections of the color gauge 24 divided into the respective level ranges of the plurality of level ranges are arranged along the increasing/decreasing direction of the level in the display unit 20. The bar graph 22 is displayed next to the color gauge 24 (side by side with the color gauge 24). In addition, an auxiliary display unit 26 indicating information other than the bar graph 22 and the color gauge 24 is also displayed on the display unit 20.

An operation unit 30 is also disposed in a portion of the outer peripheral surface of the housing 15 where the display unit 20 is disposed. The operation unit 30 of FIG. 1 is disposed adjacent to the rectangular active matrix display elongated along the longitudinal direction A, and includes a setting key 32 and a direction key 33 arranged along the longitudinal direction A. The direction key 33 includes an up key 34 and a down key 35 arranged along the longitudinal direction A. The user of the level meter 10 can change the operation parameter of the level meter 10 by operating the operation unit 30. In particular, the user can change the setting of the display content and the level range on the display unit 20 by operating the operation unit 30.

A connection portion 12 is provided on the upper side of the housing 15. The connection portion 12 in FIG. 1 has a cylindrical shape extending in the longitudinal direction A. An outer peripheral surface of the cylindrical connection portion 12 is a connection screw portion 14 in which a thread is cut.

In addition, a state lamp 52 is provided between the connection portion 12 and the display unit 20 so as to surround the lower side (root) of the connection portion 12. The lighting state of the state lamp 52 changes according to the measured level of the object. The user can roughly know the state of the object by visually observing the lighting state of the state lamp 52.

An internal structure of level meter 10 will be described with reference to FIG. 2. FIG. 2 is a cross-sectional view illustrating a cross section of the level meter 10 in FIG. 1 taken along a plane (and a plane parallel to the longitudinal direction A) intersecting the display unit 20.

Inside the sensor unit 16, a sensor IC 41 (IC: Integrated Circuit) and a sensor board 42 that supports the sensor IC 41 are arranged. The sensor IC 41 performs transmission and reception of radio waves and signal processing for measuring the level of the object. The signal processed by the sensor IC 41 is transmitted to a display board 60 of the housing 15.

As the sensor IC 41, for example, MMIC (Monolithic Microwave Integrated Circuit) is used. The MMIC is an IC in which a plurality of semiconductor components that perform transmission of radio waves, reception of radio waves, signal processing based on transmitted and received radio waves, and the like are integrated into a single semiconductor device (one chip). In the sensor IC of FIG. 2, an antenna is integrated with the MMIC by using an antenna in package (AiP) technology or an antenna on package (AoP) technology. That is, in FIG. 2, the sensor IC 41 is an antenna-integrated package (antenna on package) in which a transmission unit that transmits a radio wave and a reception unit that receives a radio wave are integrated in a single semiconductor device. Since the antenna-integrated MMIC is used as the sensor IC 41, the volume occupied by the configuration for transmitting and receiving radio waves is reduced, and the entire dimension of the level meter 10 becomes compact. Note that the sensor IC 41 is not limited to the antenna-integrated MMIC alone, and may include a plurality of ICs. The sensor IC 41 may include, for example, an MMIC and a microcomputer. Then, the antenna-integrated MMIC may include a radio wave transmission antenna, a radio wave reception antenna, and a circuit that executes radio wave transmission/reception control, and the microcomputer may include a circuit that executes signal processing or arithmetic processing based on a reception signal received from the antenna-integrated MMIC.

The sensor IC 41 is mounted on the lower surface of the sensor board 42. The sensor board 42 is an electronic circuit board in which various electronic circuit elements are arranged on a plate made of an insulator such as glass or resin. In FIG. 2, the sensor board 42 is disposed in a direction orthogonal to the longitudinal direction A (horizontal direction in FIG. 2).

The measurement end unit 40 is located below the sensor board 42. The measurement end unit 40 of FIG. 2 includes a waveguide 45, a horn antenna 46, and a dielectric lens 48 as internal structures. In a case where the sensor IC 41 is an antenna-integrated MMIC, a radio wave serving as a transmission wave is transmitted from the sensor IC 41. The transmission wave transmitted from the sensor IC 41 is guided toward the object through the waveguide 45, the horn antenna 46, and the dielectric lens 48 in this order. The reflected wave reflected by the object and incident on the measurement end unit 40 is guided toward the sensor IC 41 through the dielectric lens 48, the horn antenna 46, and the waveguide 45 in this order. Here, when the portion where the attachment screw portion 18 is provided on the lower side of the sensor unit 16 is cylindrical, the cross section thereof is circular. In this case, the circular dielectric lens 48 can be disposed on the lower side (one end side in the longitudinal direction A) of the cylindrical portion. That is, when the sensor unit 16 has a cylindrical portion on the lower side, the cylindrical portion can serve as both a portion to be attached to an installation target (such as a tank) of the level meter 10 and an arrangement place of the dielectric lens 48, and the entire dimension of the level meter 10 becomes compact.

On the other hand, a rotation mechanism 19 is provided inside the housing 15 disposed above the sensor unit 16. The rotation mechanism 19 in FIG. 2 is disposed at a lower end (one end in the longitudinal direction A) of the housing 15, that is, between the housing 15 and the sensor unit 16. The rotation mechanism 19 can relatively rotate the housing 15 with respect to the sensor unit 16 about a rotation axis 19A. For example, the rotation mechanism 19 is a mechanism having a shaft extending along the rotation axis 19A between the housing 15 and the sensor board 42. The shaft is connected to the housing 15 via a bearing or the like arranged around the axis, and is configured such that the rotation of the housing 15 about the rotation axis 19A is not transmitted to the sensor unit 16. In addition, it is preferable that the rotation mechanism 19 can hold the housing 15 and the sensor board 42 in a state where a relative rotation angle between the housing and the sensor board becomes a desired angle. For example, the rotation mechanism 19 may include components such as a damper element serving as a rotational resistance and a rotation lock that prevents rotation so as to be held at a specific rotation angle. In addition to the above configuration, the rotation mechanism 19 may include an engagement protrusion formed on the sensor unit 16 and a plurality of hooks provided on the housing 15. The engagement protrusion is disposed on the outer periphery of the cylindrical portion in the upper portion of the sensor unit 16, and is formed long along the circumferential direction. The engagement protrusion of the sensor unit 16 may have a continuous shape so as to make one round in the circumferential direction. The plurality of hooks of the housing 15 are arranged at intervals in an annular shape corresponding to the engagement protrusion of the sensor unit 16. Each hook engages a lower surface of the engagement protrusion. Each hook rotates while sliding in the circumferential direction when receiving an external force. In addition, in a case where the rotation mechanism 19 includes the engagement protrusion and the hook, the housing 15 may be provided with an elastic body that generates a pressing force that pushes and spreads between the sensor unit 16 and the housing 15. Since the elastic body is provided, sliding resistance between the engagement protrusion and each hook is adjusted. The rotation mechanism 19 of FIG. 2 is disposed such that the rotation axis 19A is in a direction (vertical direction in FIG. 2) parallel to the longitudinal direction A (and the direction of the measurement axis). The display unit 20 is arranged on a flat surface formed at a position offset toward the rotation axis 19A in the housing 15. That is, the flat surface of the housing 15 is located away from the plane including the rotation axis 19A. Since the rotation mechanism 19 is provided, the user can rotate the display unit 20 about the rotation axis 19A parallel to the direction of the measurement axis by rotating the housing 15, and can direct the display unit 20 in a direction in which it is easy to see. In particular, when the level meter 10 is attached to a container (such as a tank) including a measurement target by the attachment screw portion 18, the user can direct the display unit 20 in a direction in which the user can easily see the display unit without moving the entire level meter 10.

In the housing 15, the display board 60 is disposed above the rotation mechanism 19. The display board 60 is an electronic circuit board in which various electronic circuit elements are arranged on a plate made of an insulator such as glass or resin. In FIG. 2, the display board 60 is disposed in a direction parallel to the longitudinal direction A (vertical direction in FIG. 2). A signal processing circuit for controlling the display unit 20 is mounted on the display board 60. The display board 60 receives a signal from the sensor IC 41, and converts the level of the object measured by the sensor unit 16 into a signal for displaying the level on the display unit 20. The display board 60 of FIG. 2 is disposed on the back side of the display unit 20 (inside the housing 15 in FIG. 2).

The display unit 20 in FIG. 2 includes a display device 28 and a transparent display window 29. The display device 28 is, for example, an LCD, particularly an LCD capable of color display. The display window 29 is, for example, a plate made of an optically transparent material such as glass, acrylic, polyarylate, or polycarbonate, and optically transmits the display content of the display device 28 to the outside of the housing 15. The display device 28 is directed in the direction (vertical direction) of a display surface 20A parallel to the longitudinal direction A. In FIG. 2, the display board 60 is directed in a direction parallel to the display surface 20A.

Since the display device 28 and the display board 60 are directed in the direction parallel to the longitudinal direction A, the components for operating the display device 28 of the display unit 20 are arranged along the longitudinal direction A (height direction) inside the level meter 10. Therefore, the area occupied by the components for operating the display unit 20 over the direction (radial direction) perpendicular to the longitudinal direction A is reduced, and the entire dimension of the level meter 10 is made compact. In FIGS. 1 and 2, the diameter dimension of the cylindrical housing 15 is smaller than that of the sensor unit 16. Note that the diameter dimension of the housing 15 is not necessarily smaller than that of the sensor unit 16, and the diameter dimensions of the housing 15 and the sensor unit 16 may be the same, or the sensor unit 16 may be smaller.

The state lamp 52 provided between the display unit 20 and the connection portion 12 includes a plurality of state LEDs 50 (Light Emitting Diodes (LEDs)) and a transmission window 53. The plurality of state LEDs 50 are disposed above the display board 60 and the display unit 20. The lighting state of the state LED 50 changes according to the level of the object measured by the sensor unit 16. A transmission window 53 including a member (such as a light diffusion film) that diffuses light is disposed above the state LED 50. The light emitted from the state LED 50 is guided to the outside of the housing 15 through the transmission window 53. Therefore, as the lighting state of the state LED 50 changes according to the level of the object, the lighting state of the state lamp 52 changes. In addition, since the transmission window 53 includes a member that diffuses light, the light emitted from the state LED 50 is uniformly diffused in all directions around the connection portion 12. The state LED 50 may emit light in a single color (for example, red, yellow, green, and the like) or may emit light by switching a plurality of colors (for example, red, yellow, green, and the like). When the state LED 50 emits light by switching a plurality of colors, a plurality of light emitting elements that emit light in different colors may be included in one LED, or a combination of a plurality of LEDs that emit light in different colors may be arranged as the state LED 50. Then, the state LED 50 may emit light by mixing a plurality of colors. When the state LED 50 emits light by switching a plurality of colors, the state LED 50 may emit light in a color corresponding to the color of the section of the color gauge 24 corresponding to the level range to which the measured level belongs.

The connection portion 12 provided at the upper end (the other end in the longitudinal direction A) of the housing 15 includes an external input terminal 12C and an external output terminal 12D serving as connection terminals with an external device. The external input terminal 12C is a terminal for inputting a signal or power, or both, from the outside to the level meter 10. The external output terminal 12D is a terminal for outputting a signal from level meter 10 to the outside. The external output terminal 12 may include a plurality of signal lines or a plurality of output terminals. For example, signals may be output from different signal lines or different output terminals to the outside according to the level range to which the measured level belongs. As a specific example, four or five signal lines (or output terminals) may be included in the external output terminal 12 in correspondence with a case where the measured level exceeds or falls below four thresholds described later, a high upper-limit value HH, an upper limit value H, a lower limit value L, and a low lower-limit value LL.

Next, an example of a use state of the level meter 10 will be described with reference to FIG. 3. FIG. 3 is a view illustrating a state in which the level meter 10 is attached to a tank 70 that houses an object 72. The object 72 is, for example, a liquid such as water, and a level Y of the object 72 is a height from the bottom of the tank 70 to an interface 74 (liquid level) of the object 72.

The tank 70 contains water to be the object 72 in, for example, a water treatment facility. For example, when the object 72 in the tank 70 is supplied to a water treatment process or the like, the level Y of the object 72 in the tank 70 decreases. In addition, as the tank 70 is replenished with the object 72, the level Y of the object 72 in the tank 70 increases. For example, a water injection port 75 is provided in an outer wall (an upper wall in FIG. 3) of the tank 70. A water injection pipe 76 is fluidly connected to the tank 70 via the water injection port 75. The water injection pipe 76 is connected to a water injection device 78 (device including, for example, a pump, a valve or the like) provided outside the tank 70. The water injection device 78 is a device that supplies (injects) the object 72 from the outside of the tank 70 into the tank 70. The water injection device 78 adjusts the amount of water injected into the tank 70 according to the level Y of the object 72 in the tank 70. In addition, the water injection device 78 stops the water pouring depending on the level Y of the object 72 in the tank 70. The water injection device 78 controls the replenishment of the object 72 to the tank 70 according to the level Y of the object 72 in the tank 70 such that the level Y of the object 72 in the tank 70, which decreases as the object 72 is consumed, for example, by the water treatment process, falls within a predetermined range.

The level meter 10 in FIG. 3 is attached to the upper side of the tank 70. An attachment hole 71 is provided above the tank 70. The attachment hole 71 is a screw hole, and the attachment screw portion 18 of the level meter 10 is screwed into the attachment hole 71, whereby the level meter 10 is attached to the tank 70. For example, the user of the level meter 10 can screw the attachment screw portion 18 into the attachment hole 71 by rotating the nut-shaped attachment portion 17 with the tip of the attachment screw portion 18 aligned with the attachment hole 71. The structure for attaching the level meter 10 to the tank 70 is not limited thereto. For example, the attachment hole 71 is not threaded, and a nut is separately screwed to the attachment screw portion 18 exposed to the inside of the tank 70, whereby the level meter 10 may be attached to the tank 70. Further, the level meter 10 may be attached to a mounting bracket which is provided above the tank 70 with an upper surface of the tank 70 opened by using a nut and the attachment screw portion 18. In addition, the method of attaching the level meter 10 to the tank 70 is not limited to the screwing using the attachment screw portion 18, and the thread may not be formed on the outer peripheral surface of the sensor unit 16. For example, a flange may be provided on one or both of the level meter 10 and the tank 70, and the level meter 10 may be attached to the tank 70 by fixing the flange to the level meter 10 or the tank 70 with a bolt.

In FIG. 3, the longitudinal direction A of the level meter 10 in a state of being attached to the tank 70 is the same direction as the change direction of the level Y of the object 72. In addition, the length direction (gauge direction B) of the bar graph 22 and the color gauge 24 displayed on the display unit 20 is also the same direction as the change direction of the level Y.

The level meter 10 transmits a radio wave to be a transmission wave Tx from the measurement end unit 40 toward the object 72. Then, a reflected wave Rx resulting from reflection of the transmission wave Tx at the interface 74 of the object 72 is received by the measurement end unit 40. The level meter 10 calculates the level Y of the object 72 based on the transmission wave Tx and the reflected wave Rx. For example, in the case of performing the measurement using the time of flight (ToF) method, the level meter 10 calculates a distance YA from the measurement end unit 40 to the interface 74 based on the difference between the transmission wave Tx and the reflected wave Rx, and calculates the level Y based on the distance YA. In addition, for example, in a case where measurement is performed by a radar method using a frequency modulated continuous wave (FMCW), the level meter 10 calculates the distance YA from the measurement end unit 40 to the interface 74 based on a frequency of a waveform obtained by mixing the transmission wave Tx and the reflected wave Rx, and calculates the level Y based on the distance YA.

A connection cable 92 is connected to the connection portion 12 of the level meter 10. The connection cable 92 connects a control device 90 (such as a programmable controller) provided outside the tank 70 and the level meter 10. An analog signal indicating the level Y of the object 72 measured by the level meter 10 or a control signal based on a comparison result between the level Y of the object 72 measured by the level meter 10 (sensor unit 16) and each threshold is transmitted (output) to the control device 90 via the external output terminal 12D (a part of an output unit 66 to be described later) of the connection portion 12 and the connection cable 92. The control device 90 controls the operation of the water injection device 78 according to the measured level Y.

FIG. 4A is a view illustrating a traveling path of transmission wave Tx. FIG. 4B is a view illustrating a traveling path of the reflected wave Rx. Referring to FIGS. 4A and 4B, the transmission wave Tx is guided to the object 72 through the horn antenna 46 and the dielectric lens 48, and the reflected wave Rx is guided to a reception unit 43R.

The sensor unit 16 includes a transmission unit 43T that transmits the transmission wave Tx and a reception unit 43R that receives the reflected wave Rx. Specifically, the sensor IC 41 disposed inside the sensor unit 16 includes the transmission unit 43T and the reception unit 43R. The transmission unit 43T and the reception unit 43R are a semiconductor electromagnetic wave generating device and a semiconductor electromagnetic wave receiving device mounted on a chip of the sensor IC 41, respectively.

A surrounding wall 47, a waveguide 45, a horn antenna 46, and a dielectric lens 48 are provided between the transmission unit 43T and the object 72 in order of proximity to the transmission unit 43T. The surrounding wall 47 surrounds a space that the transmission unit 43T and the reception unit 43R on the sensor board 42 face and communicates with the waveguide 45. The surrounding wall 47 has conductivity. A radio wave absorber that absorbs radio waves may be provided on the inner wall surface of the surrounding wall 47. The waveguide 45 is a hollow pipe formed of a conductor. The horn antenna 46 is surrounded by a tapered wall surrounding a space communicating with the waveguide 45. The tapered wall of the horn antenna 46 has conductivity, and a radio wave absorber that absorbs radio waves may be provided on an inner wall surface thereof. These are arranged such that the directions of the directivities of the waveguide 45 and the horn antenna 46 coincide with the optical axis 40A of the dielectric lens 48. In FIGS. 4A and 4B, the measurement end unit 40 is disposed such that the optical axis 40A is parallel to the longitudinal direction A (the length direction of the level meter 10). Hereinafter, the directions of the directivities of the waveguide 45 and the horn antenna 46 may also be referred to as an optical axis 40A.

The transmission wave Tx transmitted from the transmission unit 43T passes through the space in the surrounding wall 47 and the waveguide 45, and then is incident on the dielectric lens 48 via the horn antenna 46. In FIGS. 4A and 4B, the equiphase surface of the radio wave is indicated by a broken line in the surrounding wall 47, in the horn antenna 46, and below the measurement end unit 40. Note that, in the waveguide 45, the equiphase surface should originally be shown linearly, but a curved broken line bulging toward the traveling direction side (lower side in FIG. 4A, upper side in FIG. 4B) is shown in order to make the traveling direction of the radio wave easy to understand. The waveguide 45 converts the transmission wave Tx such that the transmission wave Tx becomes a spherical wave traveling in a spherical shape along the optical axis 40A from the emission end of the waveguide 45 regardless of the relative positional relationship between the transmission unit 43T and the waveguide 45. As a result, the emission end of the waveguide 45 can be regarded as a dot-liked transmission source. The diameter of the waveguide 45 may be set to a diameter that allows only the radio wave in the fundamental mode to pass through the waveguide 45 so that the emission end of the waveguide 45 becomes an ideal dot-like transmission source. On the other hand, when the diameter of the waveguide 45 is smaller than half the wavelength of the radio wave, the radio wave does not pass through the waveguide 45. For example, when the frequency of the radio wave is 50 GHz to 70 GHz, the wavelength is about 4.3 mm to about 6.0 mm, and the half wavelength is about 2.15 mm to about 3.0 mm. In this case, when a diameter larger than 3 mm and smaller than 4.3 mm is selected as the diameter of the waveguide 45, only the radio wave in the fundamental mode can pass through the waveguide 45. The diameter of the waveguide 45 satisfying the above condition is, for example, 4 mm. When the dimension of the waveguide 45 in the direction along the optical axis 40A is short, even if the diameter of the waveguide 45 satisfies the above condition, radio waves other than the fundamental mode also pass through the waveguide 45. For example, the dimension of the waveguide 45 in the direction along the optical axis 40A may be set to a length equal to or longer than one wavelength of the wavelength of the radio wave. Note that the longer the dimension of the waveguide 45 in the direction along the optical axis 40A, the longer the dimension of the level meter 10 in the longitudinal direction A. After passing through the waveguide 45, the transmission wave Tx travels as a spherical wave in the horn antenna 46 and is converted into a plane wave via the dielectric lens 48.

As illustrated in FIG. 4A, the transmission wave Tx travels as a spherical wave in the horn antenna 46, and then the transmission wave Tx incident on the dielectric lens 48 is refracted between the horn antenna 46 and the dielectric lens 48 and between the dielectric lens 48 and ambient air (atmosphere), and is guided in a direction parallel to the optical axis 40A. Since the optical axis 40A is parallel to the longitudinal direction A, the transmission wave Tx is guided in a direction in which one end (lower side) of the sensor unit 16 in the longitudinal direction A is directed, that is, in a direction of the object 72. The transmission wave Tx travels as a plane wave corresponding to the effective diameter of the dielectric lens 48 and a diffracted wave around the plane wave. The transmission wave Tx forms a radio wave beam having high directivity. Therefore, since the region of the detection target surface (the region on which the transmission wave Tx strikes in the interface 74 of the object 72) is narrowed, unnecessary reflection due to surrounding obstacles or the like is reduced.

The transmission wave Tx guided to the object 72 is reflected at the interface 74 of the object 72 and becomes a reflected wave Rx. As illustrated in FIG. 4B, the reflected wave Rx traveling as a plane wave is received at the measurement end unit 40. The reflected wave Rx received by the measurement end unit 40 first enters the dielectric lens 48. The reflected wave Rx incident on the dielectric lens 48 is refracted between the ambient air and the dielectric lens 48 and between the dielectric lens 48 and the horn antenna 46, and travels in the horn antenna 46 as a spherical wave approaching the optical axis 40A. As a result, the reflected wave Rx is guided to the reception unit 43R as a radio wave emitted from a dot-liked transmission source at the end portion on the surrounding wall 47 side via the waveguide 45.

The waveguide 45, the horn antenna 46, and the dielectric lens 48 arranged inside the sensor unit 16 guide the traveling direction of the radio wave to the direction of the optical axis 40A by each directivity with respect to the radio wave, and thus they exhibit strong directivity with respect to the radio wave as a whole by combining them. Therefore, the sensor unit 16 can appropriately guide the transmission wave Tx and the reflected wave Rx even if the length direction dimension (length along the longitudinal direction A) is small. In addition, by appropriately guiding the transmission wave Tx and the reflected wave Rx, the transmission of the transmission wave Tx and the reception of the reflected wave Rx can be performed by the common measurement end unit 40 even though the position of the transmission unit 43T and the position of the reception unit 43R are different in the sensor IC 41. Therefore, by using the waveguide 45, the horn antenna 46, and the dielectric lens 48, the designer of the level meter 10 can reduce the dimension in the length direction of the level meter 10 including the sensor unit 16, and the dimension of the entire level meter 10 can be made compact.

Next, a relationship between the components of the level meter 10 will be described with reference to FIG. 5. FIG. 5 is a block diagram schematically illustrating an example of a relationship between the components of the level meter 10. As illustrated in FIG. 5, the sensor IC 41 of the sensor unit 16 includes a transmission/reception unit 43, a radar control unit 44, a storage unit 63, and a calculation unit 64. The transmission/reception unit 43 includes a transmission unit 43T that transmits the transmission wave Tx and a reception unit 43R that receives the reflected wave Rx. The sensor IC 41 may include a plurality of ICs. For example, the sensor IC 41 may include an antenna-integrated MMIC and a microcomputer.

The radar control unit 44 includes a transmission control unit 80 that determines the waveform of the transmission wave Tx, a radar transmission/reception circuit 81 that performs mutual conversion between a digital signal and a radio wave, and a signal processing unit 89 that performs signal processing based on the transmission wave Tx and the reflected wave Rx. When the sensor IC 41 includes the antenna-integrated MMIC and the microcomputer, the antenna-integrated MMIC may include a portion (the transmission control unit 80 and the radar transmission/reception circuit 81) of the radar control unit 44 excluding the signal processing unit 89 and the transmission/reception unit 43, and the microcomputer may include the signal processing unit 89, the storage unit 63, and the calculation unit 64.

The storage unit 63 stores various setting values (data) related to the operation of the level meter 10. The calculation unit 64 performs various calculations relating to the operation of the level meter 10 based on the setting values stored in the storage unit 63, the signal processing result of the signal processing unit 89, and the like. The storage unit 63 includes a storage device such as a random access memory (RAM) and a read only memory (ROM). The calculation unit 64 includes a processor such as a central processing unit (CPU). Note that the storage unit 63 and the calculation unit 64 may be provided on the display board 60 of the housing 15. Alternatively, the storage units 63 and the calculation units 64 may be separately provided in the sensor unit 16 and the housing 15, respectively, and stored data and responsible arithmetic processing may be shared by the sensor unit 16 and the housing 15.

On the other hand, the display board 60 of the housing 15 includes an input unit 65 and an output unit 66. The input unit 65 is an interface circuit that inputs an input provided from the outside of the level meter 10 to the level meter 10 as a signal. The input provided from the outside of the level meter 10 is, for example, a user's operation on the operation unit 30, a control signal provided from an external device (such as the control device 90 or the like) via the external input terminal 12C, and the like. The input unit 65 causes the storage unit 63 to store, for example, flag information indicating that the operation unit 30 has been operated, and data such as a setting value provided via the external input terminal 12C.

The output unit 66 is an interface circuit that outputs a signal generated inside the level meter 10 to the outside. The output unit 66 changes, for example, the display content of the display unit 20, the lighting state of the state lamp 52, and the like according to the calculation result (such as the value of the level Y) by the calculation unit 64. In addition, the output unit 66 transmits the calculation result by the calculation unit 64 to an external device via the external output terminal 12D.

The measurement of the level Y by the level meter 10 will be described in more detail with reference to FIGS. 6 and 7. FIG. 6 is a view illustrating an example of configurations of the radar transmission/reception circuit 81 and the transmission/reception unit 43 included in the sensor IC 41. FIG. 7 is a view illustrating a relationship between a transmission wave Tx and a reflected wave Rx.

As illustrated in FIG. 6, the radar transmission/reception circuit 81 includes a ramp wave generator 82, a power amplifier 83, a low noise amplifier 84, a mixer 85, a low-pass filter 86, and an analog-to-digital converter 87.

The level meter 10 of the present embodiment measures the level Y by a radar method using FMCW. The ramp wave generator 82 is connected to the transmission control unit 80. When receiving data indicating the waveform of the transmission wave Tx determined by the transmission control unit 80, the ramp wave generator 82 generates a transmission signal having the waveform of the transmission wave Tx according to the data. Here, as the waveform of the transmission wave Tx, a waveform that repeats increase and decrease in frequency is used.

FIG. 7 is a graph illustrating a change in frequency of the transmission wave Tx (and the reflected wave Rx) with respect to time. In FIG. 7, the frequency of the transmission wave Tx increases linearly with time from a minimum value (Min), and returns to the minimum value again when reaching a maximum value (Max). In this manner, the frequency of the transmission wave Tx repeatedly increases and decreases. The increasing/decreasing pattern of the frequency is not limited to this, and for example, a pattern may be used in which the frequency decreases linearly with time from the maximum value and returns to the maximum value again when reaching the minimum value. In addition, a pattern of repeating linear increase/decrease and decrease between the maximum value and the minimum value may be used. The transmission wave Tx used in the present embodiment is a radio wave in the 60 GHz band, and the minimum value of the frequency is, for example, 58 GHz and the maximum value is, for example, 69 GHZ. The frequency band to be used is not limited thereto, and for example, a frequency of 77 GHz to 81 GHz may be used.

The transmission signal generated by the ramp wave generator 82 in FIG. 6 is amplified by the power amplifier 83 and sent to the transmission unit 43T. The transmission unit 43T generates a radio wave having a waveform corresponding to the transmission signal and transmits the radio wave as a transmission wave Tx to the object 72. The transmission wave Tx is reflected by the interface 74 of the object 72 to become a reflected wave Rx, and is received as a reception signal by the reception unit 43R. The reflected wave Rx is a wave out of phase with respect to the transmission wave Tx.

As indicated by a broken line in FIG. 7, the reflected wave Rx is a wave shifted from the transmission wave Tx by a time difference Δt. The time difference Δt is a value corresponding to the distance YA (FIG. 3) from the measurement end unit 40 to the interface 74 of the object 72. Since the reflected wave Rx reciprocates between the measurement end unit 40 and the object 72, there is a relationship of Δt=2×YA/c where c is the speed of light.

Then, a frequency difference ΔF corresponding to the magnitude of the time difference Δt is generated between the transmission wave Tx and the reflected wave Rx. There is a certain relationship between the frequency difference ΔF and the time difference Δt depending on the waveform of the transmission wave Tx. The waveform of the transmission wave Tx is a waveform whose frequency linearly changes with the lapse of time. That is, there is a certain relationship between the frequency difference ΔF and the time difference Δt according to the frequency change per unit time in the waveform of the transmission wave Tx. For example, the frequency of the transmission wave Tx increases linearly from the minimum value (Min) as time elapses, and reaches the maximum value (Max). In this case, the relationship between the frequency difference ΔF and the time difference Δt is uniquely determined by the difference between the maximum value and the minimum value of the frequency of the transmission wave Tx, which is the bandwidth of frequency modulation, and the relationship of the frequency change with time. Therefore, the level meter 10 can calculate the time difference Δt based on the frequency difference ΔF that is a difference between the transmission wave Tx and the reflected wave Rx. Then, the level meter 10 can calculate the distance YA(Δt×c/2) from the time difference Δt. Further, the level meter 10 can calculate the value of the level Y based on the distance YA. Specifically, the difference between the depth of the tank 70 (the distance from the bottom of the tank 70 to the measurement end unit 40) and the distance YA is the value of the level Y. Since there is a certain relationship between the frequency difference ΔF and the time difference Δt depending on the waveform of the transmission wave Tx, the correspondence relationship between the frequency difference ΔF and the distance YA can be obtained in advance. The correspondence relationship between the frequency difference ΔF and the distance YA may be stored in advance in the storage unit 63.

As illustrated in FIG. 6, the reception signal corresponding to the reflected wave Rx received by the reception unit 43R is input to the mixer 85 via the low noise amplifier 84. A transmission signal corresponding to the waveform of the transmission wave Tx output from the ramp wave generator 82 is also input to the mixer 85, and the mixer 85 generates a signal corresponding to a mixed wave Mx obtained by mixing the waveforms of the transmission wave Tx and the reflected wave Rx. Specifically, the mixer 85 mixes the transmission signal and the reception signal to generate an IF signal (IF: intermediate frequency) corresponding to the mixed wave Mx.

The IF signal corresponding to the mixed wave Mx has a waveform including a high frequency component derived from the frequency of the 60 GHz band of the transmission wave Tx and the reflected wave Rx and a low frequency component corresponding to the frequency difference ΔF between the transmission wave Tx and the reflected wave Rx. The IF signal corresponding to the mixed wave Mx is input to the low-pass filter 86, and a low-frequency waveform according to the frequency difference ΔF is extracted. The extracted low-frequency waveform is input to the analog-to-digital converter 87. The analog-to-digital converter 87 converts a low-frequency waveform into a digital value and outputs the digital value to the signal processing unit 89.

The signal processing unit 89 converts the low-frequency waveform output from the analog-to-digital converter 87 into a frequency signal Px by fast Fourier transform frequency signal Px or the like. The frequency signal Px is a signal indicating wave intensity for each frequency, and a frequency corresponding to the maximum peak PS of the frequency signal Px is a frequency difference ΔF between the transmission wave Tx and the reflected wave Rx. The signal processing unit 89 transmits the frequency signal Px to the calculation unit 64 in FIG. 5.

The calculation unit 64 calculates the values of the distance YA and the level Y based on the frequency signal Px. In calculating the values of the distance YA and the level Y, the calculation unit 64 refers to the setting values stored in the storage unit 63. For example, the storage unit 63 stores a correspondence relationship between the frequency difference ΔF and the distance YA, a value (depth of the tank 70) for calculating the level Y from the distance YA, and the like.

Depending on the measurement environment, a peak other than the maximum peak PS may appear in the frequency signal Px due to an element other than the interface 74 of the object 72 (for example, a device such as a stirrer provided in the tank 70). Even if there are a plurality of peaks in the frequency signal Px, the calculation unit 64 can specify only the maximum peak PS derived from the object 72 by appropriately performing calculation. For example, the data of the frequency signal Px obtained in advance in a state where there is no object 72 (state where the tank 70 is empty) may be stored in the storage unit 63. The calculation unit 64 can specify the maximum peak PS derived from the object 72 by examining a difference between the frequency signal Px obtained in a state where the object 72 does not exist and the frequency signal Px obtained in a state where the object 72 exists.

After calculating the frequency difference ΔF corresponding to the maximum peak PS of the frequency signal Px, the calculation unit 64 calculates the values of the distance YA and the level Y based on the frequency difference ΔF and the setting value stored in the storage unit 63. The calculation unit 64 transmits the calculated value of the level Y to the output unit 66. The output unit 66 changes the display content of the display unit 20 and the lighting state of the state lamp 52 according to the value of the level Y. The value of the level Y is sent to the control device 90 (FIG. 3) through the external output terminal 12D. The output unit 66 may output a binary or multi-valued control signal based on the comparison result between the calculated value of the level Y and the threshold to the control device through the external output terminal 12D. In addition, instead of the value of the level Y itself, a signal indicating that specific control according to the state of the level Y is to be executed may be sent to the control device 90. For example, when the level Y is above a certain threshold or below a certain threshold, a signal indicating that the operation of the pump, valve or the like should be changed may be sent to the control device 90.

Next, display contents of the display unit 20 will be described with reference to FIG. 8. FIG. 8 is a view illustrating a first display mode of the display unit 20. The display unit 20 displays a color graph indicating, by a plurality of colors, which level range the measured level Y belongs to among a plurality of predetermined level ranges. As illustrated in FIG. 8, in the first display mode, the color graph including the color gauge 24 is displayed on the display unit 20. In addition to the color gauge 24, a bar graph 22 and an auxiliary display unit 26 are displayed on the display unit 20. The bar graph 22 and the color gauge 24 are displayed as bars extending along the gauge direction B.

The color gauge 24 is displayed with a predetermined length (length specified by the setting value) according to the setting value stored in the storage unit 63 (FIG. 5). The color gauge 24 is divided into a plurality of sections along its length direction (gauge direction B). In FIG. 8, the color gauge 24 is divided into five sections. These sections are separated (defined) based on one or more thresholds set by the user. The threshold is a part of the setting value stored in the storage unit 63. The threshold is a value determined with respect to the level Y of the object 72, and a numerical range between the thresholds is a plurality of predetermined level ranges. In FIG. 8, four thresholds (HH, H, L, LL) and an upper limit (YM) and a lower limit (Y0) of the measurement range are set, and a numerical range between these values is set as five level ranges for level Y. Each section of the color gauge 24 corresponds to each level range. The number of sections of the color gauge 24 is not limited to 5. For example, in a case where only either the upper limit or the lower limit of level Y is displayed, the number of sections is two. In addition, in a case where the upper limit and the lower limit of the level Y are displayed, the number of sections is three. As such, the separators of the color gauge 24 may have various patterns depending on the elements to be displayed.

Hereinafter, the central section among the five sections illustrated in FIG. 8 is referred to as a standard section 24a. Two sections vertically adjacent to the standard section 24a are referred to as a warning section 24b, and sections vertically separated from the standard section 24a with the warning section 24b interposed therebetween (sections located at upper and lower ends of the color gauge 24) are referred to as dangerous sections 24c. When the five sections are distinguished from each other, the upper dangerous section 24c, the upper warning section 24b, the standard section 24a, the lower warning section 24b, and the lower dangerous section 24c are referred to in order from the top of the color gauge 24. The five level ranges corresponding to these five sections are referred to as an upper dangerous range, an upper warning range, a standard range, a lower warning range, and a lower danger range, respectively.

Each section of the color gauge 24 is color-coded with a color corresponding to each level range. For example, the standard section 24a may be displayed in green corresponding to the standard range, the warning section 24b may be displayed in yellow corresponding to the warning range, and the dangerous section 24c may be displayed in red corresponding to the dangerous range. Note that the upper warning section 24b and the lower warning section 24b may have different colors. Similarly, the upper dangerous section 24c and the lower dangerous section 24c may have different colors. Furthermore, the color of each section may be changed by the operation of the operation unit 30 by the user. In this case, the setting of the color assigned to each section may be selected from a plurality of assignment patterns (combinations) prepared in advance by the operation of the operation unit 30 by the user, or the color assigned to each section may be individually selected. In addition, the lighting state of each section may be selected by the operation of the operation unit 30 by the user. In this case, the lighting state may be selected from among turn-on, turn-off, and blinking.

The bar graph 22 is displayed next to the color gauge 24, and its length expands and contracts along the gauge direction B according to the measured value of the level Y. When the color gauge 24 is color-coded, the bar graph 22 is preferably displayed in a color (for example, blue) different from each section of the color gauge 24 so that the user can easily distinguish the bar graph 22 and the color gauge 24 even from a long distance. In FIG. 8, the bar graph 22 extends from the lower side to the upper side as the value of the level Y is larger. Here, as illustrated in FIG. 1, in a mode in which the display unit 20 is disposed in the housing 15 above the sensor unit 16, the display unit 20 is farther from the sensor unit 16 toward the upper side. Therefore, the bar graph 22 shows a larger value as it extends to a position (upper side in FIG. 8) farther away from the sensor unit 16. Similarly, the color gauge 24 also corresponds to a larger value at a position farther from the sensor unit 16.

An example of setting the upper limit and the lower limit of the measurement range will be described. The measurement range indicates the range of the level Y measured by the level meter 10, and for example, the lower limit of the measurement range is a value (zero point Y0, e.g. 0 mm) indicating that the object 72 does not exist in the tank 70 (the tank 70 is empty). The upper limit of the measurement range is a value (full-volume value YM, e.g. 1000 mm) indicating that the tank 70 cannot accommodate the object 72 any more (the tank 70 is full). The upper limit and the lower limit of the measurement range may be set by the user operating the operation unit 30.

An example of setting the threshold will be described. For example, the threshold is set as a value indicating that “If the level Y exceeds or falls below this value, the amount of the object 72 needs to be adjusted” with respect to the object 72 in the tank 70. The threshold may be set by the user operating the operation unit 30. Four thresholds, that is, a high upper-limit value HH (first threshold), an upper limit value H (second threshold), a lower limit value L (third threshold), and a low lower-limit value LL (fourth threshold) are set in order from the full-volume value YM that is the upper limit of the measurement range. The supply of the object 72 in the tank 70 to, for example, a water treatment process lowers the level Y of the object 72 in the tank 70. On the other hand, as the tank 70 is replenished with the object 72, the level Y of the object 72 in the tank 70 rises. In this case, the water injection device 78 controls the replenishment of the object 72 to the tank 70 according to the level Y of the object 72 in the tank 70 such that the level Y of the object 72 in the tank 70 that decreases according to the water treatment process falls within a predetermined range. Specifically, the water injection device 78 controls the replenishment of the object 72 to the tank 70 such that the level Y of the object 72 in the tank 70 is between the upper limit value H (second threshold) and the lower limit value L (third threshold). When the water injection device 78 normally operates, the level Y of the object 72 in the tank 70 falls within the range of the upper limit value H (second threshold) and the lower limit value L (third threshold). However, when the level Y of the object 72 deviates from the predetermined range by a certain amount or more although the water injection device 78 controls the level Y of the object 72 in the tank 70, it is determined that an abnormality has occurred, and the entire operation of facilities (for example, water treatment facilities) including the water injection device 78, the water treatment process device, and the like is stopped. The high upper-limit value HH is a value (for example, 800 mm) at which the entire water treatment facility should be stopped immediately when the level Y exceeds this value. The upper limit value H is a value (for example, 600 mm) at which the water injection into the tank 70 should be stopped when the level Y exceeds this value. The lower limit value L is a value (for example, 400 mm) at which the water injection into the tank 70 should be started when the level Y falls below this value. The low lower-limit value LL is a value (for example, 200 mm) at which the amount of water injected into the tank 70 should be maximized immediately when the level Y falls below this value.

The upper dangerous section 24c corresponds to a level range (upper dangerous range) between the full-volume value YM, which is the upper limit of the measurement range, and the high upper-limit value HH. The upper warning section 24b corresponds to a level range (upper warning range) between the high upper-limit value HH and the upper limit value H. The standard section 24a corresponds to a level range (standard range) between the upper limit value H and the lower limit value L. The lower warning section 24b corresponds to a level range (lower warning range) between the lower limit value L and the low lower-limit value LL. The lower dangerous section 24c corresponds to a level range (lower danger range) between the low lower-limit value LL and the zero point Y0 which is the lower limit of the measurement range. A range of each section of the color gauge 24 is defined by each corresponding threshold. The display range of each section may have a length corresponding to a threshold defining each section. In this case, when the threshold is changed by the operation of the operation unit 30 by the user, the display range of each section is changed to a length corresponding to the section defined by the changed threshold.

In FIG. 8, the level range to which the level Y belongs is illustrated depending on which position of the section of the color gauge 24 the length of the bar graph 22 has reached. More specifically, as the length of the bar graph 22 displayed next to the color gauge 24 expands and contracts according to the value of the level Y, the distal end portion (upper end) moves along the gauge direction B. The gauge direction B indicates a direction in which the length of the bar graph 22 increases or decreases in the display in the display unit 20. The direction in which the length of the bar graph 22 increases or decreases is a direction along the direction in which the level Y of the measurement target increases or decreases. In the display in the display unit 20, the bar graph 22 and the color gauge 24 have a common coordinate system along the direction in which the level Y increases or decreases. That is, the bar graph 22 and the color gauge 24 have a common coordinate system along the increasing/decreasing direction of the level in the display unit 20. Then, the level range to which the level Y belongs is indicated depending on which section of the color gauge 24 the distal end portion of the bar graph 22 is located next to. Note that an arrow shape 22a (an arrow indicated by a two-dot chain line in FIG. 8) extending toward the color gauge 24 may be displayed at the distal end portion of the bar graph 22 so that it is easy to visually understand which section of the color gauge 24 the tip of the bar graph 22 corresponds to.

Here, the level range to which the level Y belongs is specifically information indicating between which two thresholds the measured value of the level Y is. In FIG. 8, which level range the level Y belongs to is displayed depending on which section of the color gauge 24 the distal end portion of the bar graph 22 is located next to.

For example, in FIG. 8, the distal end portion of the bar graph 22 is located next to the standard section 24a. In this case, the level Y belongs to a level range (standard range) between the upper limit value H and the lower limit value L. Therefore, the user of the level meter 10 can easily visually grasp that the level Y of the object 72 is in a state between the upper limit value H and the lower limit value L by visually observing the bar graph 22 and the color gauge 24 of the display unit 20. As described above, according to the level meter 10 of the present embodiment, the user can easily visually grasp the state of the level Y of the object 72 to be measured at the site where the tank 70 is installed. Furthermore, it is preferable that the state (status) of the object 72 based on the comparison result between the level Y measured by the sensor unit 16 and each threshold is also indicated by the lighting state of the state lamp 52. For example, when the level Y belongs to a level range (standard range) corresponding to the standard section 24a, the state lamp 52 may be turned on in green. Further, when the level Y belongs to the level range (warning range) corresponding to the warning section 24b, the state lamp 52 may be turned on in yellow. Further, when the level Y belongs to the level range (danger range) corresponding to the dangerous section 24c, the state lamp 52 may be turned on in red. As described above, when the lighting state of the state lamp 52 changes depending on the level range to which the level Y belongs, the user can more easily and visually grasp the state of the level Y of the object 72. The color of each section of the color gauge 24 may be changed by the user operating the operation unit 30. That is, the operation unit 30 may change the color of each section of the color gauge 24. In this case, the lighting state of the state lamp 52 may also be changed according to the display state of each section of the gauge 24. For example, it is assumed that there are five sections of the color gauge 24, and red lighting, yellow lighting, green lighting, yellow lighting, and red lighting are allocated to each section in order from the top. Then, it is assumed that a change is made such that red lighting, yellow blinking, green lighting, turning-off, and red blinking are assigned to each section in order from the top by the user's operation. In this case, if the distal end portion of the bar graph 22 is located next to the second section from the top of the color gauge 24, the state lamp 52 lights up in yellow before the assignment is changed, and blinks in yellow after the assignment is changed. The lighting color of the state lamp 52 may also be changed according to the color of each section of the color gauge 24. Here, the color of each section of the color gauge 24 and the lighting color of the state lamp 52 are preferably set in correspondence with each other. For example, it is assumed that there are four sections of the color gauge 24, and red, yellow, green, and yellow are assigned to each section in order from the top. Then, it is assumed that a change is made by the user's operation so that yellow, green, yellow, and red are assigned to each section in order from the top. In this case, if the distal end portion of the bar graph 22 is located next to the uppermost section of the color gauge 24, the state lamp 52 is lit in red before the assignment is changed, and is lit in yellow after the assignment is changed. As described above, the state lamp 52 may emit the color corresponding to the color of the section of the color gauge 24 corresponding to the level range to which the level Y measured by the sensor unit 16 belongs to display the state (status) of the object 72. When the color of each section of the color gauge 24 is changed by the operation unit 30, the state lamp 52 may emit a color corresponding to the color after the change by the operation unit 30 of the section of the color gauge 24 corresponding to the level range to which the level Y measured by the sensor unit 16 belongs, and display the status. Note that the color of each section of the color gauge 24 and the color of the state lamp 52 corresponding to each section may not necessarily match. For example, when the distal end portion of the bar graph 22 corresponds to a section displayed in yellow, the state lamp 52 may blink in red.

In FIG. 8, the auxiliary display unit 26 is displayed above the bar graph 22 and the color gauge 24. The auxiliary display unit 26 displays information different from the bar graph 22 and the color gauge 24. In FIG. 8, the number (1, 2, 3, 4, 5) of the output port that outputs a signal in the level meter 10 is highlighted on the auxiliary display unit 26. For example, each number is displayed in white if the corresponding output port is not outputting a signal, and the number of the output port that is outputting a signal is displayed in red.

The output port is an individual signal line output from the external output terminal 12D of FIG. 2 to the outside of the level meter 10, and for example, a signal of a type corresponding to the level range to which the level Y belongs is output from the output port corresponding to the type of each signal. For example, when the level Y is within the range of the standard section 24a, a signal indicating that “the level Y is within the standard range” is output from the first output port to the outside of the level meter 10 (for example, the control device 90). At this time, the number “1” is displayed in red on the auxiliary display unit 26.

When the level Y is in the range of the upper warning section 24b, a signal indicating that “the level Y exceeds the upper limit value H” (in the upper warning range) is output from the second output port, and the number “2” is displayed in red. When the level Y is in the range of the lower warning section 24b, a signal indicating that “the level Y is below the lower limit value L” (in the lower warning range) is output from the third output port, and the number “3” is displayed in red.

When the level Y is in the range of the upper dangerous section 24c, a signal indicating that “the level Y exceeds the high upper-limit value HH” (in the upper dangerous range) is output from the fourth output port, and the number “4” is displayed in red. If the level Y is in the range of the lower dangerous section 24c, a signal indicating that “the level Y is below the low lower-limit value LL” (in the lower danger range) is output from the fifth output port, and the number “5” is displayed in red.

Each output port may be associated with each of four thresholds, that is, a high upper-limit value HH (first threshold), an upper limit value H (second threshold), a lower limit value L (third threshold), and a low lower-limit value LL (fourth threshold). For example, if the level Y falls within the range of the standard section 24a, the level Y exceeds the lower limit value L (third threshold) and the low lower-limit value LL (fourth threshold), and thus a signal indicating that the threshold is exceeded is output from the third output port and the fourth output port to the outside of the level meter 10 (for example, the control device 90). At this time, the numbers “3” and “4” are displayed in red on the auxiliary display unit 26. In addition, when the level Y is in the range of the upper warning section 24b, signals indicating that the threshold has been exceeded are output from the second, third, and fourth output ports, and the number “2”, the number “3”, and the number “4” are displayed in red. When the level Y is in the range of the lower dangerous section 24c, the level Y is below any of the high upper-limit value HH (first threshold), the upper limit value H (second threshold), the lower limit value L (third threshold), and the low lower-limit value LL (fourth threshold). Therefore, a signal indicating that the level Y exceeds the threshold is not output from any of the first, second, third, and fourth output ports, and any of the number “1”, the number “2”, the number “3”, and the number “4” is not displayed in red. Each output port is preferably connected to, for example, the water injection device 78 (FIG. 3). When signals are output from these output ports, the water injection device 78 adjusts the amount of water injected into the tank 70 according to the number of the output port. For example, when a signal is output from the second output port corresponding to the upper limit value H (second threshold), the water injection device 78 immediately stops water injection.

Next, the display mode transition of the display unit 20 will be described with reference to FIGS. 9, 10, 11, and 12. FIGS. 9, 10, and 11 illustrate the second display mode, the third display mode, and the fourth display mode of the display unit 20, respectively. FIG. 12 illustrates a transition relationship between modes included in the display unit 20.

The display unit 20 includes a plurality of display modes, and the display unit 20 can display the level range to which the level Y belongs in a different format depending on the display mode. For example, when the user operates the direction key 33 (FIG. 1) of the operation unit 30, the display mode of the display unit 20 is switched.

For example, when the up key 34 of the direction key 33 is operated in a state where the first display mode of FIG. 8 is displayed on the display unit 20, the display of the display unit 20 is switched to the second display mode of FIG. 9. Further, every time the up key 34 is operated, the display on the display unit 20 is switched to the third display mode in FIG. 10 and the fourth display mode in FIG. 11. When the up key 34 is further operated from the state in which the fourth display mode is displayed, the display on the display unit 20 returns to the first display mode.

On the other hand, each time the down key 35 is operated, the display mode is switched in the reverse order of the up key 34. That is, every time the down key 35 is operated from the state in which the first display mode is displayed, the display of the display unit 20 is sequentially switched to the fourth display mode, the third display mode, the second display mode, and the first display mode.

In addition, in each display mode, when the setting key 32 is operated, the display of the display unit 20 is switched to a setting mode (not illustrated). In the setting mode, the user can change the setting value related to the operation of the level meter 10 by operating the direction key 33 (up key 34, down key 35). In particular, the user can change the setting of the threshold of level Y in the setting mode. By changing the setting of the threshold of the level Y, the setting of the level range is also changed. That is, the user can change the setting of the level range by operating the operation unit 30 including the setting key 32 and the direction key 33.

Then, when the setting key 32 is operated again in the setting mode, the display of the display unit 20 returns to the original display mode. Therefore, as illustrated in FIG. 12, the display on the display unit 20 is cyclically switched among a plurality of display modes (first display mode, second display mode, third display mode, fourth display mode) by the operation of the direction key 33, and the display on the display unit 20 is switched between each display mode and the setting mode by the operation of the setting key 32.

The second display mode of FIG. 9 will be described. In FIG. 9, the bar graph 22 and the color gauge 24 are reduced as compared with the first display mode of FIG. 8 and displayed at the lower left of the screen. In the auxiliary display unit 26 above the bar graph 22 and the color gauge 24, the measured level Y is displayed as a numerical value in addition to the display of the output port. Here, it is displayed that the numerical value of the level Y is 550 mm, that is, the height from the bottom of the tank 70 to the interface 74 is 550 mm. As described above, depending on the display mode, the display unit 20 can display the measured level Y not only by the bar graph 22 but also by a numerical value.

Furthermore, a second auxiliary display unit 27 is displayed on the right side of the bar graph 22 and the color gauge 24. On the second auxiliary display unit 27 in the second display mode, some of the plurality of thresholds determined for the level Y are displayed as numerical values. Here, the second auxiliary display unit 27 displays that the high upper-limit value HH is 800 mm, the upper limit value H is 600 mm, the lower limit value L is 400 mm, and the low lower-limit value LL is 200 mm. Note that the zero point Y0 and the full-volume value YM are basically constant values that depend on the dimensions of the tank 70, and thus are not displayed on the second auxiliary display unit 27 in FIG. 9.

The third display mode in FIG. 10 will be described. In FIG. 10, the arrangement of the bar graph 22, the color gauge 24, the auxiliary display unit 26, and the second auxiliary display unit 27 is the same as that in the second display mode in FIG. 9, but the level Y and each threshold are indicated not by a numerical value but by a ratio with respect to the full-volume value YM (the upper limit of the measurement range).

In FIG. 10, a case where the full-volume value YM is 1000 mm is displayed. On the auxiliary display unit 26, “55%” is displayed as the ratio of the value (550 mm) of the level Y to the full-volume value YM (1000 mm). As described above, depending on the display mode, the display unit 20 can display not only the bar graph 22 but also the ratio of the measured level Y to the full-volume value YM that is the upper limit of the measurement range.

In the second auxiliary display unit 27, “80%”, “60%”, “40%”, and “20%” are displayed as the ratios of the high upper-limit value HH (800 mm), the upper limit value H (600 mm), the lower limit value L (400 mm), and the low lower-limit value LL (200 mm) to the full-volume value YM (1000 mm).

The fourth display mode in FIG. 11 will be described. In FIG. 11, the sizes of the bar graph 22 and the color gauge 24 are the same as those in the first display mode of FIG. 8, but the auxiliary display unit 26 is displayed not above but below the bar graph 22 and the color gauge 24. In addition, four lamps indicating stability are displayed on the auxiliary display unit 26 instead of the number of the output port.

Note that the stability displayed on the auxiliary display unit 26 in FIG. 11 indicates how stably the measurement of the level Y by the level meter 10 is performed. For example, when the level meter 10 is attached to be inclined with respect to the tank 70 (FIG. 3), a radio wave other than the reflected wave Rx from the interface 74 is received by the measurement end unit 40 due to reflection of the transmission wave Tx on the inner wall surface of the tank 70 or the like. Then, the measurement value of the level Y greatly changes each time of measurement, and a stable measurement value cannot be obtained. When a stable measurement value cannot be obtained, display indicating low stability is performed on the auxiliary display unit 26. For example, a state in which all four lamps disappear is displayed. On the other hand, when a stable measurement value is obtained, display indicating high stability is performed on the auxiliary display unit 26. For example, a state in which all four lamps are turned on is displayed.

Next, another example of the level meter 10 will be described with reference to FIGS. 13 and 14. FIG. 13 is a perspective view illustrating another example of the level meter 10. FIG. 14 is a cross-sectional view of another example of the level meter 10. In FIGS. 13 and 14, components having the same functions as those of the level meter 10 in FIGS. 1 and 2 are denoted by the same reference numerals as those in FIGS. 1 and 2, and the description thereof will not be repeated unless necessary.

In FIGS. 13 and 14, the housing 15 includes a base 15a and a terminal unit 21. The base 15a is disposed on one end side (lower side) in the longitudinal direction A (the direction of the measurement axis) in the housing 15. The terminal unit 21 is disposed on the other end side in the longitudinal direction A. In FIGS. 13 and 14, the display unit 20 is provided in the terminal unit 21. The terminal unit 21 can be separated from the base 15a. The base 15a has a cylindrical shape, while the terminal unit 21 has a prismatic shape.

As illustrated in FIGS. 13 and 14, the terminal unit 21 is provided with a separation operation knob 39. The user can separate the terminal unit 21 from the base 15a by operating the separation operation knob 39. For example, a claw portion (not illustrated) is provided on the terminal unit 21, and the terminal unit 21 is attached to the base 15a by the claw portion being caught on the base 15a. The separation operation knob 39 is interlocked with the claw portion, and when the user operates the separation operation knob 39, the claw portion is separated from the base 15a, and the terminal unit 21 can be separated from the base 15a. The terminal unit 21 may be fixed to the base 15a by a fastening screw on the back surface side with respect to the display unit 20. In addition, a connection connector that transmits an electric signal between the base 15a and the terminal unit 21 is preferably provided. For example, one of the pair of connection connectors may be provided on the base 15a, and the other of the pair of connection connectors may be provided on the terminal unit 21. Connecting the pair of connection connectors enables transmission and reception of an electric signal between the base 15a and the terminal unit 21. When the terminal unit 21 is separated from the base 15a, the connection connectors are connected between the base 15a and the terminal unit 21 via a cable that transmits and receives an electric signal. As a result, even in a state where the terminal unit 21 is separated from the base 15a, the display unit 20 can display the bar graph 22 corresponding to the measured level Y. In this way, when the terminal unit 21 can be separated from the base 15a, the user can confirm the display of the display unit 20 at a position away from the base 15a. For example, in a case where the level meter 10 is disposed at a position higher than the viewpoint of the user, the user may have difficulty in confirming the display of the display unit 20. Here, when the terminal unit 21 can be separated from the base 15a, the user can easily confirm the display unit 20 at the site where the tank 70 is installed by pulling the terminal unit 21 to the height of his/her viewpoint.

In FIG. 13, since the display surface of the display unit 20 is inclined with respect to the longitudinal direction A, the bar graph 22 and the gauge direction B of the color gauge 24 are also inclined with respect to the longitudinal direction A. In FIG. 13, the angle between the longitudinal direction A and the gauge direction B (the inclination angle of the display unit 20) is an acute angle. When the inclination angle of the display unit 20 is an acute angle, the vertical component of the gauge direction B has a relatively large value. Therefore, also in FIG. 13, the bar graph 22 shows a larger value as it extends to a position away from the sensor unit 16 (the upper side in FIG. 13). Similarly, the color gauge 24 also corresponds to a larger value at a position farther from the sensor unit 16.

In FIGS. 13 and 14, the connection portion 12 is disposed in a portion of the terminal unit 21 opposite to the display unit 20. Also in FIGS. 13 and 14, since the rotation mechanism 19 is provided inside the housing 15, the user can turn the connection portion 12 in a direction in which handling is easy by rotating the housing 15.

In FIGS. 13 and 14, the state lamp 52 is disposed on an outer peripheral surface of the base 15a in the housing 15. Therefore, the state lamp 52 in FIGS. 13 and 14 is provided on one end side (lower side) in the longitudinal direction A with respect to the display unit 20. As illustrated in FIG. 14, the state LED 50 is disposed on the upper side of the sensor board 42, that is, on the surface opposite to the sensor IC 41. The transmission window 53 of the state lamp 52 is disposed above the state LED 50. The light emitted from the state LED 50 is guided to the outside of the housing 15 through the transmission window 53 including a member that diffuses the light. Since the state LED 50 is disposed on the same sensor board 42 as the sensor IC 41, the dimension in the length direction of the entire level meter 10 becomes small, and the level meter 10 becomes compact.

The direction keys 33 in FIG. 13 include a left key, a right key, and a center key in addition to the up key 34 and the down key 35. The user can easily switch the display mode of the display unit 20 by operating these keys, and can easily change various setting values (in particular, a threshold affecting the level range) in the setting mode. For example, each key is associated with each of the plurality of display modes, and when any key is operated, the display of the display unit 20 is preferably directly switched to the display mode corresponding to the key.

Next, changing the setting of the level range by the operation of the operation unit 30 (FIG. 1) will be described with reference to FIG. 15. FIG. 15 illustrates the display unit 20 in a case where the level range is changed. It is assumed that the second display mode (FIG. 9) is selected as the display mode in order to indicate the change of the numerical value. In FIG. 9, the high upper-limit value HH are 800 mm, the upper limit value H is 600 mm, the lower limit value L is 400 mm, and the low lower-limit value LL is 200 mm. The user operates the operation unit 30 to switch the display mode of the display unit 20 to the setting mode, and changes the setting of the level range by changing the threshold. For example, the user changes the high upper-limit value HH to 820 mm, the upper limit value H to 640 mm, the lower limit value L to 270 mm, and the low lower-limit value LL to 180 mm. Note that it is assumed that the zero point Y0 remains at 0 mm and the full-volume value YM remains unchanged at 1000 mm. When the threshold is changed in the setting mode, the level range is also changed, so that the display of the color gauge 24 changes as illustrated in FIG. 15 according to the changed level range. As described above, when the user changes the setting of the level range on the operation unit 30, the content displayed on the display unit 20 changes.

In the above description, the position of the zero point Y0 (distance from the level meter 10 to the zero point Y0) is fixed, and the full-volume value YM remains unchanged at 1000 mm. However, the position of the zero point Y0 and the full-volume value YM may change. For example, the level meter 10 may be removed from the tank 70 of FIG. 3 and attached to another tank.

When the level meter 10 is attached to another tank, the user sets a setting value corresponding to the tank in the setting mode of the display unit 20. For example, the level meter 10 receives designation of the position of the zero point Y0 from the user. The level meter 10 sets the level Y of another tank to indicate 0 mm at a designated position (distance from the level meter 10 to the zero point Y0). In addition, setting values related to display on the display unit 20, such as a depth of another tank (a value for calculating the level Y from the distance YA) and the full-volume value YM, may be appropriately changed. In addition, when the tank is considered empty even if the interface 74 has not reached the bottom of the tank (for example, in a case where a drain port is provided on a side surface of the tank, and the tank is regarded as empty if the interface 74 becomes lower than the drain port), the zero point Y0 may be set at a position where the tank is considered empty.

The user can also change the display formats of the bar graph 22 and the color gauge 24 in the setting mode. For example, as illustrated in FIG. 15, the display format of the bar graph 22 may be changed such that the arrow shape 22a extending toward the color gauge 24 is displayed at the distal end portion of the bar graph 22. Furthermore, as illustrated in FIG. 15, the display format of the color gauge 24 may be changed so that the scale 25 indicating the value of the level Y is displayed to be superimposed on the color gauge 24.

Note that, in the above description, the combination of the bar graph 22 and the color gauge 24 is illustrated as the color graph indicating the level range to which the level Y belongs, but the display of the display unit 20 may be any display as long as the level range to which the level Y belongs is visually easy to understand. For example, the bar graph 22 and the color gauge 24 may be integrated, and the level Y may be displayed as a figure such as a point that moves up and down according to the value of the level Y in the color gauge 24.

In the above description, the level meter 10 measures the level Y by the radar method using the transmission wave Tx and the reflected wave Rx. However, the level meter 10 is not limited to the radar method as long as it can measure the value of the level Y. The level meter 10 may be, for example, a so-called ultrasonic measurement device that transmits an ultrasonic wave to the object 72 and measures the level Y based on the ultrasonic wave reflected by the object 72. In addition, the level meter 10 may be, for example, a so-called guide pulse type measurement device that includes a probe to be immersed in the object 72 and measures the level Y based on the transmission pulse input to the probe and the reflection pulse reflected by the interface 74 of the object 72.

LEVEL METER

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CPC

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