Level meter

Abstract

To provide a level meter which allows a user to easily grasp the amount of change of a level visually.SOLUTION: A level meter 10 measures a level Y of an object 72 to be contained in a container 70. On the basis of the level Y at a plurality of points in time, a level change amount indicating the amount of change a level between the plurality of points in time is determined. A display displays the measured level and the determined level change amount.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a level meter for measuring the level of a contained object. [Background technology]

[0002] In containers that store fluid substances such as liquids, powders, and granules, level gauges are sometimes used to measure the height of the interface of the substance, that is, the level (liquid surface level, powder top surface level, etc.). Such level gauges have a function to display the measured level to the user. For example, the level gauge described in Patent Document 1 has a display unit that displays the measured liquid surface level. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-002091 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the level meter of Patent Document 1, the current value of the measured interface level is displayed as a numerical value on the display. However, if the current level value is only displayed on the level meter, it is difficult for the user to visually grasp the amount of change in the level. For example, when liquid flows out of a container, the user must make a calculation based on the numerical value displayed on the level meter and past numerical values ​​to determine how quickly the level of the liquid in the container is decreasing. In other words, the user cannot visually grasp how much the level has changed compared to past times just by looking at the numerical value displayed on the level meter.

[0005] In order to automatically detect the amount of change in level, the user needs to connect an external device to the level meter to record the time series data of the measured level value and calculate the amount of change. In addition, when measuring the flow rate of the liquid flowing out of the container, the user can check the flow rate by connecting a flow meter to the container, but in either case, a separate device from the level meter is required.

[0006] 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 amount of change in level using the level meter alone. [Means for solving the problem]

[0007] In order to solve the above problems, a level meter as an example of an embodiment of the present invention is a level meter that measures the level of contents contained in a container, and is equipped with a transceiver unit that includes a transmitting circuit that transmits a measurement signal for measuring the level and a receiving circuit that receives a reflected signal resulting from the measurement signal being reflected by the contents, a level determination unit that determines the level based on the reflected signal received by the receiving circuit and container information related to the container, a change amount determination unit that determines a level change amount that represents the amount of change in level between multiple times based on the levels at multiple times, and a display unit that displays the level determined by the level determination unit and the level change amount determined by the change amount determination unit. Effect of the Invention

[0008] According to the present invention, a user can easily visually grasp the amount of change in the level of the contents of the container using the level meter alone by checking the display unit. [Brief description of the drawings]

[0009] [Figure 1] FIG. [Diagram 2] Cross-sectional view of a level meter. [Diagram 3] FIG. 2 is a diagram showing a state in which a level gauge is attached to a container that contains an object. [Figure 4]FIG. 2 is a block diagram illustrating an example of the relationship between components of a level meter. [Diagram 5] FIG. 2 is a diagram showing an example of the configuration of a radar control unit and a transmitting / receiving unit. [Figure 6] FIG. 4 is a diagram showing the relationship between a measurement signal and a reflected signal. [Figure 7] FIG. 4 is a diagram showing state transitions of a level meter. [Figure 8] FIG. 13 is a flow diagram of the period change amount mode. [Figure 9] Flow diagram of the instantaneous change amount mode. [Figure 10] FIG. 13 is a diagram showing an example of a screen of a display unit in a period change amount mode. [Figure 11] FIG. 13 is a diagram showing another example of the screen of the display unit in the period change amount mode. [Figure 12] FIG. 13 is a diagram showing an example of a screen of a display unit in an instantaneous change amount mode. [Figure 13] FIG. 13 is a diagram showing another example of the screen of the display unit in the instantaneous change amount mode. [Figure 14] FIG. 11 is a perspective view showing another example of a level meter. [Figure 15] FIG. 13 is a diagram showing an example of a screen of a display unit in another example of a level meter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference symbols, and basically the description will not be repeated. In the following description, terms meaning positions or directions such as front, back, left, right, up, and down may be used, but these terms are used for convenience to facilitate understanding of the embodiment. Unless otherwise clearly stated, these terms are not limited to front, back, left, right, up, and down in the strict geometric sense.

[0011] Hereinafter, a level meter 10 as an example of an embodiment of the present invention will be described with reference to the drawings. First, an example of the structure and usage state of the level meter 10 will be described with reference to Figs. 1, 2, and 3. Fig. 1 shows a perspective view of the level meter 10 of this embodiment. Fig. 2 shows a cross-sectional view of the level meter 10 of Fig. 1. Fig. 3 shows a state in which the level meter 10 is attached to a container 70 (e.g., a tank) that contains an item 72.

[0012] The level meter 10 is a device that measures the level Y of the contained object 72 (e.g., liquid, powder, granules, etc.) that is the measurement target. The level Y to be measured is the height of the interface 74 of the contained object 72 in the container 70. A specific example of the level Y is the distance from the bottom of the container 70 to the liquid surface of the liquid contained in the container 70. A measurement axis is set in the level meter 10, and the level meter 10 measures the level Y along the measurement axis.

[0013] As an example of a usage state of the level meter 10, a container 70 in FIG. 3 contains a liquid (water, oil, chemical liquid, etc.) that becomes the contents 72 in a liquid treatment facility. For example, when the contents 72 in the container 70 are supplied to a liquid treatment process, the level Y of the contents 72 in the container 70 decreases. Also, when the contents 72 are replenished to the container 70, the level Y of the contents 72 in the container 70 increases. For example, a water inlet 75 is provided on the outer wall (upper wall in FIG. 3) of the container 70. A water inlet pipe 76 is fluidly connected to the container 70 through the water inlet 75. The water inlet pipe 76 is connected to a water inlet device 78 (e.g., a device including a pump, a valve, etc.) provided outside the container 70. The water inlet device 78 is a device that supplies (injects) the contents 72 into the container 70 from outside the container 70. The water inlet device 78 adjusts the amount of water to be poured into the container 70 according to the level Y of the contents 72 in the container 70. The water injection device 78 also stops pouring water depending on the level Y of the contents 72 in the container 70. The water injection device 78 controls the replenishment of the contents 72 to the container 70 depending on the level Y of the contents 72 in the container 70, which decreases as the contents 72 is consumed by, for example, a liquid treatment process, so that the level Y of the contents 72 in the container 70 is within a predetermined range.

[0014] The level meter 10 in Fig. 1 has a housing 15 including a base portion 15a and a terminal portion 21. The base portion 15a is disposed on one end side (lower side) of the housing 15 in the longitudinal direction A (direction of the measurement axis). The terminal portion 21 is disposed on the other end side in the longitudinal direction A. In Fig. 1, the display portion 20 is provided on the terminal portion 21. Moreover, the terminal portion 21 is separable from the base portion 15a. The base portion 15a is cylindrical, while the terminal portion 21 is prismatic.

[0015] The terminal unit 21 may be fixed to the base unit 15a by a fastening screw on the rear side of the display unit 20. In addition, a connection connector that transmits an electric signal between the base unit 15a and the terminal unit 21 may be provided. For example, one of a pair of connection connectors may be provided on the base unit 15a, and the other of the pair of connection connectors may be provided on the terminal unit 21. By connecting the pair of connection connectors to each other, it becomes possible to transmit and receive electric signals between the base unit 15a and the terminal unit 21.

[0016] The sensor unit 16 is disposed at one end side in the longitudinal direction A of the housing 15 (the lower side in FIG. 1). Hereinafter, one end (lower end) of the sensor unit 16 in the longitudinal direction A will be referred to as the measurement end 40. As shown in FIG. 2, a dielectric lens 48 is disposed at the measurement end 40. Hereinafter, the one end side in the longitudinal direction A of the level meter 10 may be referred to as the lower side, and the other end side in the longitudinal direction A may be referred to as the upper side.

[0017] 3, the sensor unit 16 in Fig. 1 measures the level Y of the contained item 72 with one end in the longitudinal direction A facing the contained item 72. For example, when the level meter 10 measures the height of the liquid surface (interface 74) of the liquid, the longitudinal direction A of the level meter 10 is oriented in the same direction as the change in the height of the liquid surface, i.e., the vertical direction (height direction, gravity direction).

[0018] The level meter 10 in FIG. 3 transmits radio waves serving as a measurement signal Tx from the measurement end 40 toward the contained object 72. Then, a reflected signal Rx resulting from the measurement signal Tx being reflected by an interface 74 of the contained object 72 is received by the measurement end 40. The level meter 10 calculates the level Y of the contained object 72 based on the measurement signal Tx and the reflected signal Rx. For example, when performing measurement using a Time of Flight (ToF) method, the level meter 10 calculates a distance YA from the measurement end 40 to the interface 74 based on the difference between the measurement signal Tx and the reflected signal Rx, and calculates the level Y based on the distance YA. Also, for example, when performing measurement using a radar method using a Frequency Modulated Continuous Wave (FMCW), the level meter 10 calculates a distance YA from the measurement end 40 to the interface 74 based on the frequency of a waveform obtained by mixing the measurement signal Tx and the reflected signal Rx, and calculates the level Y based on the distance YA.

[0019] As shown in FIG. 1, the sensor unit 16 has a mounting screw portion 18 with a thread engraved on the surface of a cylinder, above the measurement end 40. Furthermore, a mounting portion 17 with a diameter larger than that of the mounting screw portion 18 is provided above the mounting screw portion 18. The mounting portion 17 in FIG. 1 has a nut-like shape. Note that the mounting portion 17 may have any structure that allows the level gauge 10 to be mounted to an object (such as a container 70 that contains liquid), and is not limited to a nut-like shape. For example, the mounting portion 17 may have a cylindrical shape with a non-slip protrusion. The non-slip protrusion of the mounting portion 17 serves as a non-slip protrusion when the level gauge 10 is mounted or removed (rotational attachment / detachment) while rotating around the longitudinal direction A relative to the object. In addition, instead of the mounting portion 17 and the mounting screw portion 18, a mounting flange for mounting the level gauge 10 to the object may be formed. In addition, even when a mounting flange is formed, the mounting portion 17 and the mounting screw portion 18 may be provided in addition to the mounting flange.

[0020] The level gauge 10 in FIG. 3 is attached to the upper side of the container 70. An attachment hole 71 is provided on the upper side of the container 70. The attachment hole 71 is a screw hole, and the level gauge 10 is attached to the container 70 by screwing the attachment screw portion 18 of the level gauge 10 into the attachment hole 71. For example, a user of the level gauge 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. Note that the structure for attaching the level gauge 10 to the container 70 is not limited to this. For example, the attachment hole 71 may not have a thread, and a separate nut may be screwed into the attachment screw portion 18 exposed inside the container 70, thereby attaching the level gauge 10 to the container 70. Also, the top surface of the container 70 may be open, and the level gauge 10 may be attached to a mounting fixture provided above the container 70 using a nut and the attachment screw portion 18. Furthermore, the method of attaching the level meter 10 to the container 70 is not limited to screwing using the mounting thread portion 18, and threads do not have to be formed on the outer circumferential surface of the sensor portion 16. For example, the level meter 10 may be attached to the container 70 by providing a flange on either or both of the level meter 10 and the container 70 and fastening the flange to the level meter 10 or the container 70 with a bolt.

[0021] A display unit 20 is provided on the surface of the terminal unit 21 arranged on the upper side of the housing 15. The display unit 20 preferably includes an active matrix display device (active matrix display) capable of displaying various information. For example, the display unit 20 includes an LCD (Liquid Crystal Display). In particular, the display unit 20 preferably includes an LCD capable of color display (display in multiple colors).

[0022] The display unit 20 may also be a two-line reflective color liquid crystal display that transmits and receives power and communicates data using two power lines. A two-line display communicates data by varying the magnitude of the current that travels through the power lines. For example, the current consumption of the power lines varies in the range of 4-20 mA. The content of the data being transmitted and received is represented by the magnitude of this current consumption. A reflective display allows a user to view the displayed content by external light reflected on its surface. A two-line display requires a small amount of power to be used, but a two-line reflective color liquid crystal display can display a variety of information with a small amount of power consumption.

[0023] The display unit 20 displays the level Y of the contained items 72 measured by the sensor unit 16. In Figs. 1 and 3, a bar display 22 whose length expands or contracts according to the value of the level Y is displayed on the display unit 20. The display unit 20 also displays a color gauge 24 that is color-coded in a plurality of colors. The length direction of the color gauge 24 is arranged along the expansion and contraction direction of the bar display 22. The color gauge 24 includes a plurality of sections (three in Fig. 1) arranged along the expansion and contraction direction of the bar display 22. The sections of the color gauge 24 correspond to a plurality of level ranges set for the level Y of the contained items 72, and the level ranges are defined by a plurality of level setting values ​​(e.g., threshold values) set for the level Y.

[0024] Display unit 20 displays the relative position of level Y with respect to container 70 that contains contents 72, together with bar display 22. Specifically, the length of bar display 22 expands or contracts according to the value of level Y of contents 72 within container icon 25 that resembles container 70. The length of bar display 22 with respect to the size of container icon 25 corresponds to the relative position of level Y of contents 72 with respect to the entire container 70.

[0025] A bar arrow 22a is displayed at the tip (top end) of the extension / contraction direction of the bar display 22. The bar arrow 22a indicates a position within the color gauge 24 that corresponds to the length of the bar display 22. The color gauge 24 indicates to which level range the measured level Y belongs, among a plurality of level ranges defined by level setting values.

[0026] 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 plurality of sections of the color gauge 24 are arranged along the direction of increase and decrease of the level Y on the display unit 20. The container icon 25 and the bar display 22 are displayed next to the color gauge 24 (alongside the color gauge 24). Since the color gauge 24 is displayed along with the container icon 25 and the bar display 22 on the display unit 20, the relative position of the level setting value with respect to the container 70 is displayed together with the bar display 22.

[0027] The display unit 20 also displays an auxiliary display unit 26 that shows information other than the bar display 22 and the color gauge 24. In Fig. 1, the measured value of level Y is displayed in the auxiliary display unit 26 as a height value (in mm, millimeters).

[0028] The display unit 20 also displays an output status display section 27. The output status display section 27 displays the status of a signal line whose output changes depending on the relationship between the measured level Y and the level setting value. For example, if a signal is sent from a specific signal line when the level Y exceeds a threshold value set as the level setting value, a number corresponding to that signal line is displayed on the output status display section 27. For example, in FIG. 1, the bar arrow 22a indicates the topmost section of the three sections of the color gauge 24. This state of the display unit 20 indicates that two threshold values ​​are set as the level setting value and that the measured level Y exceeds both of the two threshold values.

[0029] If a signal line is provided that outputs a signal when the measured level Y exceeds a threshold value, a signal is output from each of the two signal lines corresponding to the two threshold values ​​in the state shown in Fig. 1. In order to indicate that signals are being output from two signal lines in Fig. 1, numbers corresponding to the two signal lines that are outputting signals (here, "1" and "2") are displayed in output status display section 27.

[0030] In addition, an operation unit 30 is also arranged on the same outer surface of the terminal unit 21 as the display unit 20. The operation unit 30 in FIG. 1 is arranged below the display unit 20. The operation unit 30 includes a menu key 32 and a directional key 33. The directional key 33 has an up key 36 (up key) and a down key 35 (down key) arranged along the longitudinal direction A. The directional key 33 also has a left key 38 (left key) and a right key 37 (right key) arranged in a direction intersecting the longitudinal direction A. Furthermore, a center key 39 (center key) is provided in the directional key 33 at a position surrounded by the up key 36, down key 35, left key 38, and right key 37.

[0031] A connection part 12 is provided on the rear surface of the terminal part 21 (the part opposite to the display part 20). As shown in Figs. 1 and 2, the connection part 12 is cylindrical and protrudes from the rear surface of the terminal part 21. The outer peripheral surface of the cylindrical connection part 12 is a connection screw part 14 with threads. As shown in Fig. 2, an external input terminal 12C and an external output terminal 12D are included inside the connection part 12. 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 the level meter 10 to the outside. The external input terminal 12C and the external output terminal 12D may each include multiple signal lines or multiple terminals. For example, a signal may be output to the outside from different signal lines or different output terminals depending on the level range to which the measured level Y belongs.

[0032] A connection cable 92 shown in Fig. 3 is connected to the connection unit 12. The connection cable 92 connects the level meter 10 to a management device 90 (such as a programmable controller) provided outside the container 70. A signal indicating the level Y of the contained item 72 measured by the level meter 10 is transmitted (output) to the management device 90 via an external output terminal 12D (part of an output unit 66 described below) of the connection unit 12 and the connection cable 92. The management device 90 manages the operation of the entire facility including the container 70 based on the signal received from the level meter 10.

[0033] As shown in FIG. 1, an indicator light 52 is provided on the outer peripheral surface of the base unit 15a connected to the lower side of the terminal unit 21. The indicator light 52 changes its lighting state according to the measured level Y of the contained contents 72. The user can roughly know the state of the contained contents 72 by visually checking the lighting state of the indicator light 52. In FIG. 1, the indicator light 52 is disposed between the terminal unit 21 and the sensor unit 16. The indicator light 52 can emit light in various lighting colors (e.g., green, yellow, red, etc.). It is preferable that the indicator light 52 emits light in a lighting color corresponding to the level range to which the level Y measured by the level meter 10 belongs. For example, it is preferable that the indicator light 52 emits light in the same color as the color of the section indicated by the bar arrow 22a in the color gauge 24, which is color-coded by a plurality of colors for each section.

[0034] 2, a sensor IC 41 (IC: Integrated Circuit) and a sensor board 42 supporting the sensor IC 41 are disposed inside the sensor unit 16 below the base 15a. The sensor IC 41 transmits and receives radio waves and processes signals to measure the level Y of the contained item 72. The signal processed by the sensor IC 41 is transmitted to a display board 60 provided in the terminal unit 21.

[0035] For example, a monolithic microwave integrated circuit (MMIC) is used as the sensor IC 41. The MMIC is an IC in which a plurality of semiconductor components that transmit and receive radio waves, and perform signal processing based on the transmitted and received radio waves are integrated into a single semiconductor device (one chip). In the sensor IC 41 in FIG. 2, an antenna is integrated into the MMIC using antenna in package (AiP) technology or 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 transmitting circuit 43T that transmits radio waves and a receiving circuit 43R that receives radio waves are integrated into a single semiconductor device. By using an antenna-integrated MMIC as the sensor IC 41, the volume occupied by the configuration for transmitting and receiving radio waves is reduced, and the overall dimensions of the level meter 10 are made compact. The sensor IC 41 is not limited to a single antenna-integrated MMIC, and may include a plurality of ICs. The sensor IC 41 may include, for example, an MMIC and a microcomputer. The antenna-integrated MMIC may include a radio wave transmitting antenna, a radio wave receiving antenna, and a circuit that controls the transmission and reception of radio waves, and the microcomputer may include a circuit that performs signal processing and arithmetic processing based on a signal received from the antenna-integrated MMIC.

[0036] 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 arranged so as to be oriented perpendicular to the longitudinal direction A (horizontal direction in Fig. 2).

[0037] The measurement end 40 is located below the sensor substrate 42. The measurement end 40 in FIG. 2 includes, as an internal structure, a waveguide 45, a horn antenna 46, and a dielectric lens 48. When the sensor IC 41 is an antenna-integrated MMIC, a radio wave serving as a measurement signal Tx is transmitted from a transmission circuit 43T of the sensor IC 41. The measurement signal Tx transmitted from the sensor IC 41 is guided toward the contained object 72 through the waveguide 45, the horn antenna 46, and the dielectric lens 48 in this order. The reflected signal Rx reflected by the contained object 72 and incident on the measurement end 40 is guided toward the receiving circuit 43R of the sensor IC 41 through the dielectric lens 48, the horn antenna 46, and the waveguide 45 in this order.

[0038] The waveguide 45, the horn antenna 46, and the dielectric lens 48 arranged inside the sensor unit 16 guide radio waves in the longitudinal direction A by their respective directivities for radio waves, and when combined, they show strong directivity for radio waves as a whole. Therefore, even if the sensor unit 16 has a small longitudinal dimension (length along the longitudinal direction A), it can properly guide the measurement signal Tx and the reflected signal Rx. Furthermore, because the measurement signal Tx and the reflected signal Rx are properly guided, the measurement signal Tx can be transmitted and the reflected signal Rx can be received by the common measurement end 40, even if the position of the transmitting circuit 43T and the position of the receiving circuit 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 longitudinal dimension of the level meter 10 including the sensor unit 16, and the overall dimension of the level meter 10 can be made compact.

[0039] On the other hand, a rotation mechanism 19 is provided inside the base portion 15a arranged above the sensor portion 16. The rotation mechanism 19 in FIG. 2 is arranged at the lower end (one end in the longitudinal direction A) of the housing 15, that is, between the housing 15 and the sensor portion 16. The rotation mechanism 19 can rotate the base portion 15a and the terminal portion 21 connected to the base portion 15a relative to the sensor portion 16. The rotation mechanism 19 is arranged so that the rotation axis is parallel to the longitudinal direction A. By providing the rotation mechanism 19, the user can rotate the housing 15 to orient the display portion 20 in a direction that is easy to view. In particular, when the level gauge 10 is attached to a container 70 (such as a tank) containing the contents 72 by the mounting screw portion 18, the user can orient the display portion 20 in a direction that is easy to view without moving the entire level gauge 10.

[0040] A display board 60 is disposed inside the terminal unit 21. The display board 60 is an electronic circuit board in which various electronic circuit elements are disposed on a plate made of an insulating material such as glass or resin. 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 Y of the contained item 72 measured by the sensor unit 16 into a signal for display on the display unit 20. The display board 60 in FIG. 2 is disposed on the back side of the display unit 20 (inside the housing 15 in FIG. 2).

[0041] 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 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.

[0042] The indicator lamp 52 arranged between the terminal unit 21 and the sensor unit 16 includes a plurality of status LEDs 50 (LEDs: Light Emitting Diodes) and a transmission window 53. The plurality of status LEDs 50 are arranged 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 indicator lamp 52 is arranged on the outer peripheral surface above the status LEDs 50. The transmission window 53 arranged on the outer peripheral surface of the base portion 15a has a surface along the longitudinal direction A (vertical surface) facing the outside of the housing 15. The light emitted from the status LEDs 50 is guided to the outside of the housing 15 through the transmission window 53 including a member that diffuses the light. Here, the member that diffuses the light included in the transmission window 53 is preferably a doughnut-shaped disk. In addition, it is preferable that a tapered surface 53a having a tapered shape is formed on the inner peripheral surface of the doughnut-shaped member that diffuses the light. When the tapered surface 53a is formed on the inner periphery side of the transmission window 53, the light emitted from the status LED 50 is reflected by the tapered surface 53a and is guided to the outside of the housing 15 reliably.

[0043] The lighting state of the status LED 50 changes according to the level Y of the contained contents 72 measured by the sensor unit 16. The light emitted from the status LED 50 is guided to the outside of the housing 15 through the transparent window 53. Therefore, as the lighting state of the status LED 50 changes according to the level Y of the contained contents 72, the lighting state of the indicator light 52 changes. In addition, since the transparent window 53 contains a material that diffuses light, the light emitted from the status LED 50 is diffused in a direction intersecting with the longitudinal direction A. Therefore, the user can easily visually grasp the lighting state of the indicator light 52 from a long distance.

[0044] The status LED 50 may emit light in a single color (e.g., red, yellow, green, etc.) or may emit light by switching between multiple colors (e.g., red, yellow, green, etc.). When the status LED 50 emits light by switching between multiple colors, multiple light-emitting elements that emit light in different colors may be included in one LED, or a combination of multiple LEDs that emit light in different colors may be arranged as the status LED 50. The status LED 50 may emit light by mixing multiple colors. When the status LED 50 emits light by switching between multiple colors, the status LED 50 may emit light in a color corresponding to the color of the section of the color gauge 24 that corresponds to the level range to which the measured level Y belongs.

[0045] Next, the relationship between the components of the level meter 10 will be described with reference to FIG. 4. FIG. 4 is a block diagram that shows an example of the relationship between the components of the level meter 10. As shown in FIG. 4, the sensor IC 41 of the sensor unit 16 includes a transmitting / receiving unit 43, a radar control unit 44, and a processing unit 62. The transmitting / receiving unit 43 has a transmitting circuit 43T that transmits a measurement signal Tx and a receiving circuit 43R that receives a reflected signal Rx. The sensor IC 41 may include multiple ICs. For example, the sensor IC 41 may include an antenna-integrated MMIC and a microcomputer.

[0046] The radar control unit 44 has a transmission control unit 80 that determines the waveform of the measurement signal Tx, a radar transmission and reception circuit 81 that performs mutual conversion between digital signals and radio waves, and a signal processing unit 89 that performs signal processing based on the measurement signal Tx and the reflected signal Rx. When the sensor IC 41 includes an antenna-integrated MMIC and a microcomputer, the antenna-integrated MMIC may have the parts of the radar control unit 44 excluding the signal processing unit 89 (the transmission control unit 80 and the radar transmission and reception circuit 81) and the transceiver unit 43, and the microcomputer may be configured to have the signal processing unit 89 and the processing unit 62.

[0047] The processing unit 62 includes a storage unit 63 and a calculation unit 64. The storage unit 63 stores various set values ​​(data) related to the operation of the level meter 10. The calculation unit 64 performs various calculations related to the operation of the level meter 10 based on the set values ​​stored in the storage unit 63 and the signal processing results of the signal processing unit 89. The storage unit 63 includes a storage device such as a RAM (Random Access Memory) and a ROM (Read Only Memory). The calculation unit 64 includes a processor such as a CPU (Central Processing Unit). The storage unit 63 and the calculation unit 64 may be provided on the display board 60 of the housing 15. Alternatively, the sensor unit 16 and the housing 15 may be provided with separate storage units 63 and calculation units 64, respectively, and the stored data and the calculation processing in charge may be shared between the sensor unit 16 and the housing 15. As shown in FIG. 4, the calculation unit 64 and the radar transmission / reception circuit 81 and the signal processing unit 89 of the radar control unit 44 function together as a level determination unit 88. The level determining unit 88 performs a process of determining the level Y based on the reflected signal Rx received by the receiving circuit 43R and container information related to the container 70 (eg, the height of the container 70, etc.).

[0048] The calculation unit 64, the radar transmission / reception circuit 81, and the signal processing unit 89 also function as a change amount determination unit 788. The change amount determination unit 788 determines a level change amount representing the amount of change in the level Y between multiple times, for the level Y (measured level Y) determined by the level determination unit 88, based on the level Y at multiple times.

[0049] On the other hand, the display board 60 of the terminal unit 21 has a setting unit 61, an input unit 65, and an output unit 66. The setting unit 61 performs a process of sequentially setting container information related to the container 70 and a plurality of level setting values ​​related to the level Y. The input unit 65 is an interface circuit that inputs an input provided from outside the level meter 10 as a signal to the level meter 10. Examples of the input provided from outside the level meter 10 include a user's operation on the operation unit 30 and a control signal provided from an external device (such as the management device 90) via the external input terminal 12C. The input unit 65 stores, 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 in the storage unit 63.

[0050] The output unit 66 is an interface circuit that outputs to the outside a signal generated inside the level meter 10. For example, the output unit 66 changes the display content of the display unit 20 and the lighting state of the indicator lamp 52 according to the calculation result (such as the value of the level Y) by the calculation unit 64. The output unit 66 also transmits the calculation result by the calculation unit 64 to an external device via the external output terminal 12D.

[0051] Measurement of the level Y by the level meter 10 will be described in more detail with reference to Fig. 5 and Fig. 6. Fig. 5 is a diagram showing an example of the configuration of the radar transmission / reception circuit 81 and the transmission / reception unit 43 included in the sensor IC 41. Fig. 6 is a diagram showing the relationship between the measurement signal Tx and the reflected signal Rx.

[0052] As shown in FIG. 5, the radar transmission / reception circuit 81 includes a ramp 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.

[0053] The level meter 10 of this embodiment measures the level Y by a radar method using FMCW. The ramp generator 82 is connected to the transmission control unit 80. When the ramp generator 82 receives data indicating the waveform of the measurement signal Tx determined by the transmission control unit 80, it generates a signal having a waveform according to the data. In this embodiment, a waveform that repeatedly increases and decreases in frequency is used as the waveform of the measurement signal Tx.

[0054] FIG. 6 shows a graph showing the change in frequency of the measurement signal Tx (and the reflected signal Rx) over time. In FIG. 6, the frequency of the measurement signal Tx increases linearly from the minimum value (Min) as time passes, and when it reaches the maximum value (Max), it returns to the minimum value again. In this way, the frequency of the measurement signal Tx repeatedly increases and decreases. Note that the frequency increase / decrease pattern is not limited to this, and it is sufficient that the level determination unit 88 can calculate the level Y based on the comparison between the measurement signal Tx and the reflected signal Rx. For example, a pattern may be used in which the frequency decreases linearly from the maximum value as time passes, and when it reaches the minimum, it returns to the maximum value again. Also, a pattern in which the frequency increases and decreases linearly between the maximum value and the minimum value may be used. The measurement signal Tx used in this 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. Note that the frequency band used is not limited to this, and a frequency of, for example, 77 GHz-81 GHz may be used.

[0055] The signal generated by the ramp wave generator 82 in Fig. 5 is amplified by a power amplifier 83 and sent to the transmission circuit 43T. The transmission circuit 43T generates radio waves with a waveform corresponding to the sent signal and transmits the radio waves as a measurement signal Tx to the contained item 72. The measurement signal Tx is reflected by the interface 74 of the contained item 72 to become a reflected signal Rx, which is received as a received signal by the receiving circuit 43R. The reflected signal Rx becomes a wave out of phase with the measurement signal Tx.

[0056] As shown by the dashed line in Fig. 6, the reflected signal Rx is a wave that is shifted from the measurement signal Tx by a time difference Δt. This time difference Δt is a value that corresponds to the distance YA (Fig. 3) from the measurement end 40 to the interface 74 of the contents 72. Because the reflected signal Rx travels back and forth between the measurement end 40 and the contents 72, there is a relationship of Δt = 2 × YA / c, where c is the speed of light.

[0057] Then, a frequency difference ΔF occurs between the measurement signal Tx and the reflected signal Rx according to the magnitude of the time difference Δt. There is a certain relationship between the frequency difference ΔF and the time difference Δt that depends on the waveform of the measurement signal Tx. The waveform of the measurement signal Tx is a waveform in which the frequency changes linearly with the passage of time. In other words, there is a certain relationship between the frequency difference ΔF and the time difference Δt that depends on the frequency change per unit time in the waveform of the measurement signal Tx. For example, the frequency of the measurement signal Tx increases linearly from the minimum value (Min) as time passes, 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 and minimum values ​​of the frequency of the measurement signal Tx, which is the bandwidth of the frequency modulation, and the relationship of the frequency change with the passage of time. Therefore, the level meter 10 can calculate the time difference Δt based on the frequency difference ΔF, which is the difference between the measurement signal Tx and the reflected signal Rx. Then, the level meter 10 can calculate the distance YA (Δt×c / 2) from the time difference Δt. Furthermore, the level meter 10 can calculate the value of the level Y based on the distance YA. Specifically, the difference between the height of the container 70 (the distance from the bottom of the container 70 to the top surface inside the container 70) and the distance YA is the value of the level Y. Therefore, the level determination unit 88 can determine the level Y of the contents 72 based on the reflected signal Rx received by the receiving circuit 43R and the container information about the container 70 (such as the height of the container 70). It is preferable that the container information about the container 70, such as the height of the container 70, the bottom distance Y0 from the level meter 10 to the bottom of the container 70, and the top distance Y1 from the level meter 10 to the top surface inside the container 70 (the thickness of the top plate of the container 70 in FIG. 3), be set in advance by the setting unit 61 before the measurement of the level Y is started. It is preferable that the distance from the level meter 10 is, to be precise, the distance from the measurement reference plane (a plane on which the distance value is treated as zero) that is the measurement reference in the level meter 10. The position of the measurement reference plane is determined in advance before the use of the level meter 10 (for example, when the level meter 10 is designed). For example, the position where the level meter 10 is attached to the container 70 (the position of the outer upper surface of the container 70 in FIG. 3) is determined as the measurement reference surface. In terms of the position inside the level meter 10, the lower surface of the attachment part 17 (the upper end of the attachment screw part 18) becomes the measurement reference surface.In addition, since there is a certain relationship between the frequency difference ΔF and the time difference Δt that depends on the waveform of the measurement signal 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 the storage unit 63 in advance.

[0058] 5, a received signal corresponding to the reflected signal Rx received by the receiving circuit 43R is input to a mixer 85 via a low-noise amplifier 84. A signal corresponding to the waveform of the measurement signal Tx output from the ramp generator 82 is also input to the mixer 85, and the mixer 85 generates a mixed signal Mx by mixing the waveforms of the measurement signal Tx and the reflected signal Rx. The mixer 85 included in the radar transmitting and receiving circuit 81 functioning as a part of the level determining unit 88 specifically mixes the measurement signal Tx and the reflected signal Rx to generate an IF signal (IF: Intermediate Frequency) as the mixed signal Mx.

[0059] The IF signal (intermediate frequency signal) has a waveform that includes high frequency components originating from the 60 GHz band frequencies of the measurement signal Tx and the reflected signal Rx, and low frequency components corresponding to the frequency difference ΔF between the measurement signal Tx and the reflected signal Rx. The IF signal is input to a low-pass filter 86, which extracts a low frequency waveform corresponding to the frequency difference ΔF. The extracted low frequency waveform is input to an analog-to-digital converter 87. The analog-to-digital converter 87 converts the low frequency waveform into a digital value and outputs it to a signal processing unit 89.

[0060] A signal processing unit 89, which functions as part of the level determination unit 88, converts the low-frequency waveform output from the analog-digital converter 87 into a frequency signal Px by fast Fourier transform processing or the like. The frequency signal Px is a signal that indicates the wave strength for each frequency, and the frequency corresponding to the maximum peak PS of this frequency signal Px is the frequency difference ΔF between the measurement signal Tx and the reflected signal Rx. The signal processing unit 89 transmits the frequency signal Px to the calculation unit 64 in FIG. 4.

[0061] The calculation unit 64, which functions as a part of the level determination unit 88, calculates the values ​​of the distance YA and the level Y based on the frequency signal Px. When calculating the values ​​of the distance YA and the level Y, the calculation unit 64 refers to information stored in the storage unit 63. For example, the storage unit 63 stores the correspondence between the frequency difference ΔF and the distance YA, values ​​for calculating the level Y from the distance YA (container information such as the height of the container 70), and the like.

[0062] 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 contents 72 (for example, equipment such as a stirrer provided in the container 70). Even if multiple peaks exist in the frequency signal Px, the calculation unit 64 can identify only the maximum peak PS originating from the contents 72 by performing appropriate calculations. For example, data on the frequency signal Px obtained in a state where there is no contents 72 (a state where the container 70 is empty) may be stored in advance in the storage unit 63. The calculation unit 64 can identify the maximum peak PS originating from the contents 72 by examining the difference between the frequency signal Px obtained in a state where there is no contents 72 and the frequency signal Px obtained in a state where there is the contents 72.

[0063] After calculating the frequency difference ΔF corresponding to the maximum peak PS of the frequency signal Px, the calculation unit 64 calculates the distance YA and the value of the level Y based on the frequency difference ΔF and the information stored in the storage unit 63. In this way, the calculation unit 64, which functions as a part of the level determination unit 88, determines the level Y of the contained item 72 based on the intermediate frequency signal. 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 indicator lamp 52 according to the value of the level Y. The value of the level Y is also sent to the management device 90 (FIG. 3) through the external output terminal 12D. The output unit 66 may output a binary or multi-value control signal based on the result of comparing the calculated value of the level Y with a threshold value to the management device 90 through the external output terminal 12D. Also, instead of the value of the level Y itself, a signal indicating that a specific control should be executed according to the state of the level Y may be sent to the management device 90. For example, when level Y rises above or falls below a particular threshold a signal may be sent to management device 90 indicating that operation of pumps, valves, etc. should be altered.

[0064] Next, state transitions of the level meter 10 will be described with reference to Fig. 7. First, when the level meter 10 is started, an initial setting 100 is started. In the initial setting 100, various setting screens for sequentially setting the operating conditions of the level meter 10, including container information (such as the height of the container 70) and level setting values ​​(such as threshold values), are sequentially displayed on the display unit 20. Note that in the initial setting 100, operating conditions of the level meter 10, such as whether the level meter 10 outputs an analog signal for the measured value or performs serial communication with an external device, may be set.

[0065] Once the initial setting 100 is complete, the level meter 10 enters the measurement mode 500. In the measurement mode 500, the level meter 10 measures the level Y of the contained content 72. In the measurement mode 500, the relative position of the level setting value with respect to the container 70 is displayed on the display unit 20 together with the bar display 22, as shown in FIG.

[0066] In the measurement mode 500, the display unit 20 can display a menu screen 600. The display screen of the measurement mode 500, which displays the bar display 22 and the like, and the menu screen 600 can transition back and forth. For example, each time the user operates the menu key 32 in the measurement mode 500, the display content of the display unit 20 may be switched between the display screen of the measurement mode 500 and the menu screen 600.

[0067] A menu screen 600 displays a plurality of options corresponding to individual setting contents. In response to a user's selection, the display content of the display unit 20 transitions from the menu screen 600 to an individual setting screen such as a container setting screen 610, a setting value change screen 620, or a various setting screen 630. The menu screen 600 and the individual setting screens can transition to each other. For example, when the left key 38 is operated on an individual setting screen, the display unit 20 may be configured to return to the menu screen 600.

[0068] Furthermore, the level meter 10 is capable of transitioning from the measurement mode 500 to a period change amount mode 700 and an instantaneous change amount mode 750. For example, the level meter 10 may be capable of transitioning between the measurement mode 500 and the period change amount mode 700 in response to a user's operation of the menu key 32, the down key 35, the up key 36, etc. Furthermore, the level meter 10 may be capable of transitioning between the period change amount mode 700 and the instantaneous change amount mode 750 in response to a user's operation of the right key 37, the left key 38, etc.

[0069] In the period change amount mode 700 and the instantaneous change amount mode 750, the level change amount is displayed on the display unit 20. The level change amount is determined by the change amount determination unit 788 (FIG. 4). The change amount determination unit 788 acquires the level Y (value determined by the level determination unit 88) at a plurality of times, and determines the level change amount by examining the change amount of the level Y between the plurality of times. For example, the change amount determination unit 788 acquires the level Y (previous level value) determined by the level determination unit 88 at a certain time (previous time) and stores it in the storage unit 63. Thereafter, the change amount determination unit 788 acquires the level Y (present level value) at a time (present time) different from the previous time, and determines the difference between the previous level value and the present level value as the level change amount.

[0070] It is preferable that various operating conditions related to the determination and display of the amount of change in level, such as the interval between multiple times at which the level Y is acquired (change amount update interval), are previously determined by the user. For example, the various operating conditions are previously determined in the initial setting 100 of the level meter 10, or in a setting value change screen 620 to which a transition can be made from a menu screen 600. Initial setting values ​​for the various operating conditions may also be previously determined.

[0071] Next, the operation of the change amount determination unit 788 in the period change amount mode 700 will be described with reference to the flow diagram of Fig. 8. The change amount determination unit 788 repeats the operation according to the flow diagram of Fig. 8 at predetermined change amount update intervals (e.g., every 30 seconds or every 5 minutes).

[0072] In the period change amount mode 700, the change amount determination unit 788 first measures the level Y of the contents 72 in the container 70 by acquiring the value of the level Y determined by the level determination unit 88 in step 721. Then, in step 722, the change amount determination unit 788 determines the level change amount by calculating the amount of change in the level Y measured this time compared to the level Y measured last time (when the flow of FIG. 8 was previously executed). Note that when the change amount determination unit 788 executes the flow of FIG. 8 for the first time (when the value of the previous level Y has not been recorded), it is preferable that the change amount determination unit 788 determines the current level change amount to be zero.

[0073] Next, in step 723, the change amount determination unit 788 calculates an integrated amount of change by integrating the amount of level change for each change amount update interval within a predetermined integration period (for example, 1 hour, 10 hours, 24 hours, 100 hours, etc.). For example, if the previous integrated amount of change has already been stored in the storage unit 63, the change amount determination unit 788 calculates the integrated amount of change by adding the level change amount calculated in this step 722 to the stored integrated amount of change. Note that if the previous integrated amount of change has not been recorded, the change amount determination unit 788 sets the current level change amount as the value of the integrated amount of change.

[0074] Here, when the change amount determination unit 788 calculates the accumulated change amount, it accumulates only the level change amount obtained within the accumulation period, and does not include the level change amount outside the accumulation period in the accumulated change amount. For example, if the accumulation period is one hour and the change amount update interval is 30 seconds, the change amount determination unit 788 combines the elapsed time from the start of calculation (the time when the level change amount is determined) and the level change amount every 30 seconds until one hour after the start of calculation of the accumulated change amount, and stores it in the storage unit 63 as a change amount history. Then, the change amount determination unit 788 determines the total (accumulated amount) of the level change amount stored as the change amount history as the accumulated change amount. Here, the change amount determination unit 788 may combine the determined accumulated change amount with the time of the accumulation period (information indicating when the accumulation period is, such as date and time zone), and record it as included in the change amount history.

[0075] On the other hand, if a time equal to or longer than the integration period has elapsed since the start of calculation, the change amount determination unit 788 determines the total amount of level change from the current time to a time going back by the integration period as the integrated change amount, and does not include any level change obtained earlier in the integrated change amount. For example, a ring buffer capable of storing data for the integration period may be provided in the storage unit 63. If the elapsed time and the level change amount are recorded in combination in the ring buffer, data before the integration period is automatically deleted, so that the change amount determination unit 788 can easily integrate only the level change amount within the integration period. Note that data before the time going back by the integration period is not included in the integrated change amount, but may be used for other processing. Therefore, data for a period longer than the integration period may be stored in the storage unit 63.

[0076] When the change amount determination unit 788 calculates the accumulated change amount, in step 724, the calculated accumulated change amount (calculated value) is displayed on the display unit 20. The accumulated change amount is updated at each change amount update interval, but the update interval for the display of the calculated value (accumulated change amount) in step 724 does not necessarily have to be the same as the change amount update interval. For example, a display response interval (e.g., 10 minutes) may be set separately from the change amount update interval. Then, the display unit 20 may update the display of the accumulated change amount at each predetermined display response interval. If the display response interval is set longer than the change amount update interval, the display of the accumulated change amount on the display unit 20 is updated after the accumulated change amount has been updated several times. In this case, the frequency of changes in the accumulated change amount displayed to the user decreases, and the user does not need to frequently check the display unit 20.

[0077] Furthermore, the change amount determination unit 788 causes the display unit 20 to display the calculated value of the accumulated change amount, and in step 725 causes the calculation value (or a combination of the time elapsed since the start of calculation and the amount of level change) to be stored in the storage unit 63. In Fig. 8, step 725 (storage) is performed after step 724 (display), but step 725 may be performed first, or steps 724 and 725 may be performed in parallel. The value stored in step 725 is used for the next calculation of the accumulated change amount.

[0078] As described above, in the period change amount mode 700, the level change amount and the accumulated change amount are calculated at each change amount update interval, and the calculated accumulated change amount is displayed on the display unit 20. Note that it is preferable that the change amount determination unit 788 calculates and stores the level change amount and the accumulated change amount even in the measurement mode 500 in which the measured value of level Y is displayed on the display unit 20. When the level meter 10 is switched from the measurement mode 500 to the period change amount mode 700, the level change amount and the accumulated change amount that were determined by the change amount determination unit 788 during the measurement mode 500 are displayed on the display unit 20.

[0079] In this way, when the accumulated amount of change within the accumulation period is displayed on the display unit 20, the user can understand that the level Y is fluctuating over a long period of time, even if the level Y does not fluctuate significantly over a short period of time.

[0080] For example, in a tank that supplies lubricating oil to a machine tool, the amount of lubricating oil consumed per unit time is small, so in the past, a highly accurate flow meter had to be attached to the tank in order for a user to quantitatively grasp the amount of lubricating oil consumed. On the other hand, in such a tank, a certain amount of lubricating oil is consumed in total in one day. Therefore, when the level meter 10 of this embodiment is attached to a lubricating oil supply tank and the consumption amount for one day (accumulation period) is displayed on the display unit 20 as the accumulated amount of change, the user can quantitatively and visually grasp the speed at which the lubricating oil is consumed from the tank.

[0081] In an environment in which the contents 72 in the container 70 are consumed, such as a lubricating oil supply tank, the consumed contents 72 may be replenished during operation of the container 70. When the contents 72 are replenished, the level Y increases, but if the user only wants to know the amount of the contents 72 consumed, it is preferable that the replenishment of the contents 72 is not reflected in the displayed integrated change amount.

[0082] Therefore, when the change amount determination unit 788 determines the level change amount at each change amount update interval, it checks whether the level Y has decreased from the previous time (when the previous level change amount was calculated). Then, it is preferable that the accumulated change amount is accumulated (added) only when the level Y has decreased from the previous time. In this way, if the accumulated change amount is accumulated only when the level Y has decreased, even if the contents 72 are replenished during operation of the container 70, only the consumption amount of the contents 72 is reflected in the accumulated change amount displayed on the display unit 20, and the user can correctly grasp the consumption amount. Here, if the interface 74 of the contents 72 to be measured vibrates, the level Y may repeatedly increase and decrease within a short period of time due to the influence of the vibration, and the accumulated change amount may be accumulated even though the level Y has not actually changed. Therefore, it is preferable that the level meter 10 is capable of receiving a vibration amplitude setting value related to the vibration amplitude, which is previously determined by the user, for example. When the change amount determination unit 788 determines the level change amount, if the increase or decrease in level Y (level change amount) exceeds the fluctuation width setting value, the accumulated change amount is accumulated only if the level Y has decreased from the previous time. On the other hand, for an increase or decrease in level Y whose absolute value is smaller than the fluctuation width setting value of level Y (does not exceed the fluctuation width setting value), not only the decrease in level Y but also the increase is accumulated. In this way, it is preferable to calculate the accumulated change amount so that the increase and decrease in level Y due to fluctuation cancel each other out.

[0083] Furthermore, the data (combination of level change amount and elapsed time, integrated change amount, etc.) stored in storage unit 63 in period change amount mode 700 is preferably stored in a non-volatile memory such as a flash memory. If the data is stored in a non-volatile memory, even if level meter 10 is turned off during the integration period, level meter 10 can resume integration of the integrated change amount when the power is turned on again.

[0084] For example, when the integration period is set to a very long period (e.g., 100 hours), the operating time zone of the entire facility including the container 70 to which the level meter 10 is attached may end during the integration period, and the operation of the entire facility may be stopped. When the operation of the entire facility is stopped, the power of the level meter 10 is turned off, but if the level Y of the contained item 72 in the container 70 does not change while the operation of the entire facility is stopped, the integrated amount of change during that time does not need to be stored. After that, when the operation of the entire facility resumes and the level Y of the contained item 72 resumes changing, the power of the level meter 10 is turned on, and the integration of the integrated amount of change may be resumed using the data stored in the non-volatile memory.

[0085] Next, the operation of the change amount determination unit 788 in the instantaneous change amount mode 750 will be described with reference to the flow diagram of Fig. 9. The change amount determination unit 788 repeats the operation according to the flow diagram of Fig. 9 at predetermined change amount update intervals (for example, every 30 seconds or every 5 minutes).

[0086] In the instantaneous change amount mode 750, the change amount determination unit 788 first measures the level Y of the contents 72 in the container 70 by acquiring the value of the level Y determined by the level determination unit 88 in step 771. Then, in step 772, the change amount determination unit 788 stores the current measurement value of the level Y in the storage unit 63. The value stored in step 772 is used to calculate the next level change amount. Note that in the instantaneous change amount mode 750, the data stored in the storage unit 63 may be stored in a volatile memory.

[0087] Next, in step 773, the change amount determination unit 788 determines the amount of level change by calculating the difference between the level Y measured last time (when the flow of FIG. 9 was previously executed) and the level Y measured this time. When the change amount determination unit 788 executes the flow of FIG. 9 for the first time (when the value of the previous level Y has not been recorded), the change amount determination unit 788 may determine the amount of level change this time to be zero. In FIG. 9, step 773 (calculation) is performed after step 772 (storage), but step 772 may be performed first, or steps 772 and 773 may be performed in parallel.

[0088] Once the change amount determination unit 788 has calculated the level change amount, in step 774, the calculated level change amount (calculated value) is displayed on the display unit 20. Note that the level change amount is updated at each change amount update interval, but the update interval for the display of the calculated value (level change amount) in step 774 does not necessarily have to be the same as the change amount update interval. For example, a display response interval (e.g., 2 seconds) may be set separately from the change amount update interval. Then, the display unit 20 may update the display of the level change amount at each predetermined display response interval.

[0089] When the display response interval is set longer than the change amount update interval (e.g., 500 milliseconds), the level change amount is calculated multiple times at each change amount update interval (e.g., 2 seconds) during the change amount update interval. In this case, the value displayed on the display unit 20 may be a value calculated based on the level change amount calculated multiple times. For example, the sum of the multiple calculated values ​​obtained during the display response interval, or the average value of the multiple calculated values, may be displayed on the display unit 20 as the level change amount.

[0090] To accurately measure the change in level Y, it is preferable that the change amount update interval is short, but if the display on display unit 20 is updated at each change amount update interval, the displayed value will change frequently, making it difficult for the user to visually grasp the amount of level change. Therefore, if the display response interval is set longer than the change amount update interval and a value calculated based on the amount of level change calculated multiple times is displayed on display unit 20, the value displayed on display unit 20 will be stable, making it easier for the user to visually grasp the amount of level change.

[0091] In this way, in the instantaneous change amount mode 750, if the level change amount is determined at each change amount update interval and the display of the level change amount is updated at each display response interval, the user can easily visually grasp, by looking at the display unit 20, how much the level Y has changed in a short period of time.

[0092] In the instantaneous change amount mode 750, the change amount determination unit 788 may record a combination of the time when the level change amount was determined and the value of the level change amount as a change amount history. For example, a real-time clock indicating the current time may be built into the level meter 10 (such as in the sensor IC 41), and the change amount determination unit 788 may store data in the storage unit 63 that combines the determined level change amount and the time indicated by the real-time clock.

[0093] Next, an example of a screen of the display unit 20 in the period change amount mode 700 will be described with reference to Fig. 10. In Fig. 10, a period change amount display screen 701 in the period change amount mode 700 is shown.

[0094] The period change amount display screen 701 displays the value of level Y (here, "6230 mm") determined by the level determination unit 88 (measured by the level meter 10) and the value of the level change amount determined by the change amount determination unit 788 (here, "7777 mm / 100 h").

[0095] Here, the accumulation period of the period change amount mode 700 is set to 100 hours (100h). The display value of the level change amount "7777mm / 100h" indicates that the level Y has decreased by 7777mm during the past 100 hours (7777mm of the contents 72 has been consumed). This level change amount indicates the amount of change in the level Y, depending on how much the level Y has decreased in total during the accumulation period. The period change amount display screen 701 may display whether the level Y has increased or decreased. For example, it is preferable to display a positive value when the level Y has increased and a negative value when the level Y has decreased, in comparison with a preset level reference value (such as the value of the level Y at the start of the display of the amount of change). In addition, in FIG. 10, thresholds related to the level change amount are also displayed. For example, a value "10000" for "Hi" representing a high threshold and a value "5000" for "Lo" representing a low threshold are displayed. These thresholds indicate that the amount of level change per 100 hours (100h) should be between these values. For example, when the amount of level change falls below a low threshold and when the amount of level change exceeds a high threshold, the level meter 10 outputs a signal. A user who confirms that a signal has been output from the level meter 10, for example, checks the state of the facility including the container 70, and adjusts or stops the operation of the facility in some cases. In addition, when the amount of level change falls below a low threshold and when the amount of level change exceeds a high threshold, a signal may be output from the external output terminal 12D so that the fact that the amount of level change falls outside the range between the thresholds is transmitted to an external device connected to the level meter 10. In FIG. 10, the number "1" corresponding to the signal line through which a signal is output when the amount of level change falls outside the range between the thresholds is displayed together with the thresholds.

[0096] In FIG. 10, the amount of level change is shown in the same unit as the level Y (millimeter value of height), but the display unit 20 can also convert the amount of level change into the flow rate of the contained contents 72, such as the volume change per hour or the weight change per hour, and display it. For example, the change amount determination unit 788 may calculate how much the amount of level change is converted into the flow rate of the contained contents 72 (the amount flowing out of the container 70 or the amount flowing into the container 70) based on container information such as the volume of the container 70 and data such as the specific gravity of the contained contents 72. Note that data required for this conversion may be set in advance by the user in the initial setting 100 (FIG. 7), etc. The display unit 20 may also convert the amount of level change into the amount of change in volume or weight of the contained contents 72 and display it. Here, the amount of change in volume or the amount of change in weight may be not only the amount of change per hour (flow rate) but also the total amount of change within a specific period (integrated value). The display unit 20 may be able to display at least one of the flow rate, the amount of change in volume, and the amount of change in weight, but may also display a combination of these.

[0097] In Fig. 10, the level Y and the level change amount are displayed simultaneously on the display unit 20, but the display format of the level change amount on the display unit 20 is not limited to this, and the level Y and the level change amount (or a value based on the level change amount) may be displayed by switching between them. Furthermore, the display format of the level change amount is not limited to a numerical value, and the level change amount may be displayed as a graph. Fig. 11 shows a period change amount graph screen 702 in which the level change amount is displayed as a bar graph 711.

[0098] The period change amount graph screen 702 in FIG. 11 is another example of the screen of the display unit 20 in the period change amount mode 700. In FIG. 11, only a value based on the level change amount (accumulated change amount) is displayed in a graph, and the current level value is not displayed. The display unit 10 can display the period change amount graph screen 702 as a display in which the accumulated change amount and the date (time) are associated with each other based on the change amount history including a combination of the accumulated change amount and the time of the accumulation period of the accumulated change amount. It is preferable that the display format and the display unit of the level change amount can be switched by a user's operation. For example, it is preferable that the display format and the display unit of the level change amount can be switched by the user operating any of the directional keys 33 (FIG. 1) during the period change amount mode 700.

[0099] 11, dates (periods) such as "8 / 1" (August 1) and "8 / 2" (August 2), a bar graph 711 showing the magnitude of the accumulated amount of change on each date, and a scale showing a numerical value corresponding to the length of the bar graph 711 (such as "1000mm" and "2000mm"). In order to display such a bar graph 711, for example, the accumulation period may be set to 24 hours (one day) in the period change mode 700, and at the end of the day (for example, working hours of the facility where the level meter 10 is operated), the final value of the accumulated amount of change of that day may be combined with the date and stored as part of the change amount history in the storage unit 63. Then, when a display format for displaying the bar graph 711 is selected, the display unit 20 may display the bar graph 711 based on the combination of the date and the accumulated amount of change stored in the storage unit 63.

[0100] In this way, when the cumulative amount of change is displayed in correspondence with the date (time period) in a graph, the user can easily visually grasp the difference in the cumulative amount of change during the accumulation period (for example, one day) depending on the time period. In particular, when the cumulative amount of change corresponds to the consumption amount of the contained items 72, the user can easily visually grasp in which time period the consumption amount is high (or low).

[0101] Next, an example of a screen of the display unit 20 in the instantaneous change amount mode 750 will be described with reference to Fig. 12. In Fig. 12, an instantaneous change amount display screen 751 in the instantaneous change amount mode 750 is shown.

[0102] The instantaneous change amount display screen 751 displays the value of level Y (here, "623 mm") determined by the level determination unit 88 (measured by the level meter 10) and the value of the level change amount determined by the change amount determination unit 788 (here, "-44 mm / min").

[0103] In the instantaneous change amount display screen 751, a negative sign "-" is added before the numerical value of the level change amount to indicate that the level Y has decreased from a preset level reference value. Here, the time unit of the display value of the level change amount is set to one minute. The time unit of this display value may be set by the user. The display value of the level change amount "-44 mm / min" indicates that the level Y is fluctuating at a speed at which the level Y decreases by 44 mm per period (here, one minute) set as the time unit of the display value. This level change amount represents the change amount of the level Y depending on how much the level Y changes per set time unit. Note that the change amount determination unit 788 may convert the amount of change of the level Y within the display response interval into a value (here, the decrease rate) displayed on the instantaneous change amount display screen 751 according to the ratio between the display response interval and the time unit of the display value of the level change amount.

[0104] On the instantaneous change amount display screen 751, the display unit 20 may also convert and display the level change amount into the flow rate of the contents 72 (such as liters or kilograms per unit time) instead of just the height in millimeters.

[0105] Furthermore, the level change amount (or flow rate, etc.) in the instantaneous change amount mode 750 may be displayed not only numerically but also as a graph. Fig. 13 shows an instantaneous change amount graph screen 752 in which the level change amount in the instantaneous change amount mode 750 is displayed as a line graph 761.

[0106] An instantaneous change amount graph screen 752 in Fig. 13 is another example of the screen of the display unit 20 in the instantaneous change amount mode 750. In Fig. 13, only a graph based on the level change amount is displayed, and the current level value is not displayed. Note that during the instantaneous change amount mode 750, the user may operate any of the direction keys 33 (Fig. 1) to switch the display format and display unit of the level change amount.

[0107] In the instantaneous change amount graph screen 752 of FIG. 13, a date such as "8 / 2" (August 2), a time such as "7:21" (7:21) on that date, a line graph 761 showing the magnitude of the level change amount at each time, and a scale showing a numerical value corresponding to a position in the line graph 761 (such as "100 mm / h") are displayed. If a change amount history combining the time when the level change amount was determined (measured) in the instantaneous change amount mode 750 and the value of the level change amount is recorded, the display unit 20 can display the line graph 761 as a display in which the time included in the change amount history is associated with the level change amount determined at that time. Note that not only the level change amount, but also at least one of the flow rate, volume change amount, and weight change amount (or a combination of these) of the contained contents 72 converted from the level change amount may be associated with the time.

[0108] The instantaneous change amount graph screen 752 also shows a line representing a first threshold value 762 (here, a line of 30 mm / h) set as a threshold value for the level change amount, and a line representing a second threshold value 763 (here, -30 mm / h). The threshold value for the level change amount is set, for example, as a value at which the operation of the facility including the container 70 should be changed when the level change amount exceeds or falls below the threshold value. For example, when the level change amount is excessive (or too small), the operation of the facility is stopped, and it is checked whether an abnormality has occurred in the container 70 or the level meter 10. By checking the instantaneous change amount graph screen 752, the user can visually grasp whether an event has occurred in which the level change amount exceeds or falls below the threshold value.

[0109] Next, another example of the level meter 10 will be described with reference to Fig. 14. Fig. 14 is a perspective view showing another example of the level meter 10. In Fig. 14, components having the same functions as those in the level meter 10 in Fig. 1 are denoted by the same reference numerals as in Fig. 1, and descriptions thereof will not be repeated unless necessary.

[0110] In the level meter 10 in Fig. 14, the housing 15 has a generally cylindrical shape extending in the longitudinal direction A. The housing 15 in Fig. 14 is functionally an integrated unit of the base portion 15a and the terminal portion 21 in the level meter 10 in Fig. 1. The level meter 10 in Fig. 14 has smaller dimensions than the level meter 10 in Fig. 1.

[0111] In the level meter 10 of FIG. 14, the connection unit 12 is provided on the upper side of the housing 15. The display unit 20 is disposed on an outer peripheral surface of the housing 15 that extends along the longitudinal direction A. The indicator lamp 52 is provided between the connection unit 12 and the display unit 20 so as to surround the lower side (base) of the connection unit 12. The operation unit 30 is disposed adjacent to the display unit 20, and includes a menu key 32 and a direction key 33 that are aligned along the longitudinal direction A. The direction key 33 also has an up key 36 and a down key 35 that are aligned along the longitudinal direction A.

[0112] Display unit 20 of level meter 10 in Figure 14 displays various information in the same manner as display unit 20 in level meter 10 in Figure 1. However, since display unit 20 in Figure 14 is smaller than display unit 20 in Figure 1, the amount of level change and the like are displayed in a different display format than that of level meter 10 in Figure 1.

[0113] An example of a screen of the display unit 20 in the level meter 10 in Fig. 14 will be described below with reference to Fig. 15. Fig. 15 is an example of a period change amount display screen 705 displayed on the display unit 20 when the level meter 10 in Fig. 14 is in the period change amount mode 700.

[0114] 15, the change amount over time display screen 705 displays a value (here, "777L / 100h") of the change amount of the contents 72 based on the level change amount and its integrated value determined by the change amount determination unit 788. This value represents the volume (integrated value) of the contents 72 that has decreased during the integrated period (here, 100h) in liters (L).

[0115] The period change amount display screen 705 also displays a change amount bar graph 706 that indicates the amount of change (here, the amount of change in volume) in the contents 72 in the past. Due to space limitations on the display screen, each bar displayed in the change amount bar graph 706 is a bar that extends horizontally. The length of each bar indicates the magnitude of the integrated value of the amount of change for each cycle of the integration period (e.g., 100 hours). For example, the level meter 10 performs measurement over a period longer than the integration period, and the integrated value of the amount of change (such as the amount of change in volume) of the contents 72 during the integration period is recorded each time the integration period elapses (each cycle). Then, bars of lengths according to the magnitude of the integrated values ​​recorded in the past may be displayed side by side in the change amount bar graph 706.

[0116] The display of this change amount bar graph 706 can be scrolled up and down by the user operating the up key 36 and down key 35. For example, when any bar in the change amount bar graph 706 is in a selected state, the user operates the up key 36 or down key 35, and the bar above or below the selected bar changes to a selected state. Note that in FIG. 15, the selected bar is shown by hatching. When the up key 36 or down key 35 is operated while the bar at the top or bottom end of the screen is selected, the bar that was not displayed (the bar outside the screen) moves into the screen, and the bar at the opposite end of the screen disappears off the screen.

[0117] The time elapsed since the start of measurement (here, "0h"), which corresponds to the top bar on the screen, is displayed above the change amount bar graph 706. The time elapsed since the start of measurement (here, "500h"), which corresponds to the bottom bar on the screen, is displayed below the change amount bar graph 706.

[0118] The period change amount display screen 705 also displays thresholds related to the level change amount. For example, a "Hi" numerical value "800.0" representing a high threshold and a "Lo" numerical value "750.0" representing a low threshold are displayed. These thresholds indicate that the change amount of the contained contents 72 per integrated period (for example, 100 hours) should be between these values. For example, the level meter 10 outputs a signal when the change amount falls below a low threshold and when the change amount exceeds a high threshold. A user who has confirmed that a signal has been output from the level meter 10, for example, checks the state of the facility including the container 70, and adjusts or stops the operation of the facility in some cases. In FIG. 15, the number "1" corresponding to the signal line from which a signal is output when the change amount of the contained contents 72 falls outside the range of the thresholds is displayed together with the thresholds.

[0119] By displaying the above information on period change amount display screen 705, the user can visually grasp the information relating to the level change amount even if the display space of display unit 20 is small. [Explanation of symbols]

[0120] 10 Level gauge 15. Cabinet 15a Pedestal 16 Sensor section 17 Mounting part 19 Rotation mechanism 20 Display section 21 Terminal Unit 22 Bar Display 24 Color Gauge 26 Auxiliary display 30 Control section 41 Sensor IC 43 Transmitter / receiver 43T Transmitter circuit 43R Receiver circuit 52 Indicator light 61 Setting section 63 Memory section 64 Arithmetic section 65 Input section 66 Output section 70 containers 72 Contents 74 Interface 88 Level Determination Department 788 Change amount determination unit

Claims

1. A level meter for measuring the level of an object contained in a container, A transceiver unit including a transmission circuit for transmitting a measurement signal for measuring the level, and a reception circuit for receiving a reflected signal resulting from the measurement signal being reflected by the contained object; a level determination unit that determines the level based on the reflected signal received by the receiving circuit and container information related to the container; a change amount determination unit that determines a level change amount representing a change amount of the level between the plurality of times based on the level at the plurality of times; a display unit that displays the level determined by the level determination unit and the level change amount determined by the change amount determination unit; A level meter equipped with

2. The level meter according to claim 1 , wherein the display unit displays the level and the amount of change in level simultaneously or in a switchable manner.

3. the change amount determination unit determines the level change amount for each predetermined change amount update interval, and calculates an integrated change amount by integrating the level change amount for each change amount update interval within a predetermined integration period; The level meter of claim 1 , wherein the display unit displays the integrated amount of change and updates the display of the integrated amount of change at each predetermined display response interval.

4. The level meter according to claim 3 , wherein the change amount determining unit accumulates the accumulated amount of change only if the level has decreased compared to the previous time when the level change amount is determined for each change amount update interval.

5. A fluctuation range setting value for the fluctuation range of the level is predetermined, 4. The level meter of claim 3, wherein when the level change amount is determined for each change amount update interval, if the level change amount exceeds the fluctuation width set value, the change amount determination unit accumulates the accumulated change amount only if the level has decreased compared to the previous time, and when the level change amount does not exceed the fluctuation width set value, the change amount determination unit accumulates the accumulated change amount regardless of whether the level has increased or decreased compared to the previous time.

6. the change amount determination unit determines the level change amount at each predetermined change amount update interval; The level meter according to claim 1 , wherein the display unit updates the display of the amount of level change at each predetermined display response interval.

7. 2. The level meter according to claim 1, wherein the display unit converts the amount of change in level into at least one of a flow rate, a volumetric change, and a weight change of the contained content and displays the converted amount.

8. The level meter according to claim 1 , wherein the change amount determination unit records a time when the level change amount was determined in combination with a value of the level change amount as a change amount history.

9. 9. The level meter of claim 8, wherein the display unit displays, for the change amount history recorded by the change amount determination unit, a time included in the change amount history in association with the level change amount determined at that time, or at least one of a flow rate, a volume change, and a weight change of the contained contents converted from the level change amount.

10. the change amount determination unit calculates an integrated change amount by integrating the amount of change in the level within a predetermined integration period, and records the integrated change amount in combination with a time of the integration period as part of the change amount history; The level meter according to claim 9 , wherein the display unit displays the integrated amount of change in association with a time of the integration period based on the history of the amount of change.

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