JPH1137825A - Throwing type water level gauge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To arrange a repeater at positions which sink in water or at positions of high humidity BY measuring water level with atmospheric pressure introducing inlet of the repeater removed and without introducing atmospheric pressure into a case of a pressure detector. SOLUTION: In a differential pressure sensor 31 of a pressure detector 21, belows 32 are expanded and contracted by pressure difference between the inside and outside of an airtight chamber inside a case 27, namely between the upper side and lower side from a bottom part of the belows 32, and a mover 35 is vertically moved and an electric signal from a coil 34 is changed, and a pressure signal corresponding to a differential pressure is output. This pressure signal and a temperature signal in the airtight chamber detected by a temperature sensor 39 are respectively transmitted from pressure signals 37a, 37b and a temperature signal line 37c into a cable 42, they are input into a repeater 22. The repeater 22 houses a substrate 63 inside a cylinder main body airtightly sealed, and after a pressure signal and a temperature signal input are amplified, a temperature correction of the pressure signal is carried out. The pressure signal is span-adjusted so as to conform to a measurement range of water level and is converted into a two-wire instrumentation signal and is transmitted to a converter 23.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plunge type water level meter for measuring the water level of a water channel, a river or the like of a water supply and sewerage facility by detecting a water pressure.

[0002]

2. Description of the Related Art As shown in FIG. 14, this type of throw type water level gauge includes a pressure detector 1, a repeater 2, and a converter 3.

[0003] The pressure detector 1 detects the water pressure by being put into the water 5. The pressure detector 1 faces a pressure inlet 6 a provided in a case 6, and has a bellows 7, a spring 8, a movable element 9 and a coil 10. And a differential transformer type differential pressure sensor 12 having In this differential pressure sensor 12, the movable element 9 moves against the urging force of the spring 8 in accordance with the difference between the pressure acting on the outside (outside of the case 6) and the inside (inside of the case 6) of the bellows 7, The pressure difference between the inside and outside of the bellows 7 can be detected from the change in the output signal of the coil 10 caused by this movement.

The pressure detector 1 is a single hollow cable having signal lines 13a and 13b for transmitting an output signal of the differential pressure sensor 12 and an atmospheric pressure introducing pipe 14 made of a flexible tube member. 15 is connected to the repeater 2.

The atmospheric pressure introduction pipe 14 has one end opened in the case 6 of the pressure detector 1 and the other end opened in the case 17 of the repeater 2. Also, the case 17 of the repeater 2
Is provided with an air inlet 18. Therefore, the atmospheric pressure is introduced into the case 6 of the pressure detector 1 through the atmospheric pressure inlet 18, the inside of the case 17 of the repeater 2, and the atmospheric pressure introducing pipe 14.

The signal lines 13a, 13 of the differential pressure sensor 12
b is connected to a board 19 in the case 17 of the repeater 2, and a circuit (not shown) provided on the board 19 outputs a current according to the output signal of the differential pressure sensor 12. The board 19 is connected to the converter 3 that performs predetermined signal correction such as zero span adjustment by a cable 22 having signal lines 21a and 21b. The converter 3 is connected to a display device (not shown) such as an instrument for displaying the measured water pressure.

In the above conventional throw-in type water level gauge, the atmospheric pressure is introduced into the case 6 of the pressure detector 1 in order to correct the influence of the fluctuation of the atmospheric pressure on the water level measurement. That is, as shown in FIG. 15, since the atmospheric pressure Pa acts on the water surface 5 a, outside the bellows 7 of the differential pressure sensor 12, the atmospheric pressure Pa and the hydraulic pressure P corresponding to the water level H Sum works. On the other hand, case 6 of the pressure detector 1
, The atmospheric pressure is introduced through the atmospheric pressure introducing pipe 14, so that the atmospheric pressure Pa acts on the inside of the bellows 7 of the differential pressure sensor 12. Therefore, the differential pressure sensor 12
Is equal to the pressure corresponding to the water level H as shown in the following equation (1).

[0008]

(Equation 1)

As described above, in this conventional throw-in type water level gauge, one end opens to the atmosphere through the atmospheric pressure inlet 18 of the repeater 2, and the other end opens in the case 6 of the pressure detector 1. The provision of the atmospheric pressure introduction pipe 14 measures the water pressure corresponding to the water level.

[0010]

However, in the above conventional throw-in type water level meter, since the inside and the outside of the case 17 of the repeater 2 communicate with each other through the atmospheric pressure inlet 18, the repeater 2 is submerged. If it is placed in a place where there is a possibility of occurrence, or in a place with high humidity, moisture may enter the case 17 through the atmospheric pressure introduction port 18, and the circuit provided on the substrate 19 may fail. In addition, moisture that has entered the case 17 of the relay device 2 may flow into the pressure detector 1 via the atmospheric pressure introduction pipe 14, and the differential pressure sensor 12 may fail. Therefore, the repeater 2 needs to be arranged separately from the pressure detector 1 to be put into water. For example, when the water level is measured by putting the pressure detector 1 from a manhole into a sewer waterway in an urban area, it is necessary to arrange the repeater 2 at a location separated from the pressure detector 1 by about 200 m or more. .
The pressure detector 1 and the relay 2 are connected by the cable 15 including the atmospheric pressure introducing pipe 14 as described above. However, if the atmospheric pressure introducing pipe 14 is long, it is inconvenient to handle. If a heavy object is erroneously placed on the cable 15, the atmospheric pressure introduction pipe 14 will be constricted, and it will be difficult to accurately measure the water level.

[0011] In order to solve the above-mentioned problem of the conventional throw-in type water level meter, the first invention of the present application employs a configuration in which the water level is measured without introducing the atmospheric pressure into the case of the pressure detector. It is an object of the present invention to eliminate an introduction pipe, an atmospheric pressure introduction port of a repeater, etc., and to be able to arrange the repeater in a place where it is submerged or a place with high humidity. Further, the second invention of the present application aims at eliminating the repeater itself.

[0012]

In order to solve the above-mentioned problems, a throw-in type water level meter according to the first invention is put into water for measuring a water level, and has a case of a waterproof structure having a closed chamber therein, A differential pressure detecting means for detecting a differential pressure of the sum of the atmospheric pressure and the water pressure corresponding to the water level with respect to the atmospheric pressure in the closed chamber, and outputting as a pressure signal; and a temperature detecting means for detecting the temperature in the closed chamber, and outputting as a temperature signal. Pressure detector comprising: a first error correction unit for correcting an error of the pressure signal due to a temperature change in the closed chamber using a temperature signal output from the temperature detection unit; A repeater having a waterproof structure including means for outputting a pressure signal, a second error correction means for correcting an error caused by atmospheric pressure fluctuation of the pressure signal to obtain a pressure signal corresponding to a water level, and The corresponding water level It is characterized by having a transducer comprising means for outputting to the level signal.

In the throw-in type water level meter according to the first invention, the pressure detector is provided with temperature detecting means, the relay is provided with first error correcting means for correcting a temperature error, and the converter is provided with an atmospheric pressure. Since the second error detecting means for correcting the fluctuation error is provided, the water pressure corresponding to the water level can be obtained from the pressure difference between the inside and outside of the closed chamber of the pressure detector detected by the differential pressure detecting means. That is, in the first aspect, the water level can be measured without introducing atmospheric pressure into the case of the pressure detector. As a result, the atmospheric pressure introduction pipe, the atmospheric pressure introduction port, and the like, which are necessary for the conventional device of this type, can be eliminated, and the repeater can have a sealed waterproof structure.

A throw-in type water level meter according to a second aspect of the present invention is placed in water for measuring a water level, and has a waterproof structure provided with an enclosed space therein, and a water pressure corresponding to the atmospheric pressure and the water pressure corresponding to the water level. A differential pressure detecting means for detecting a differential pressure with respect to the atmospheric pressure of the closed space and outputting the pressure as a pressure signal; a pressure detector including a temperature detecting means for detecting a temperature in the closed space and outputting the temperature as a temperature signal; First error correction means for correcting an error caused by a temperature change in the closed space of the pressure signal output from the pressure detection means using the temperature signal output from the temperature detection means, and a corrected pressure signal And a second error correction means for correcting an error caused by atmospheric pressure fluctuation of the pressure signal output from the pressure detector to obtain a pressure signal corresponding to the water level,
A converter having means for outputting a pressure signal corresponding to the water level.

In the throw-in type water level meter according to the second invention having the above-described structure, the pressure detector case can have a closed structure, as in the first invention, so that the atmospheric pressure introduction pipe and the like are eliminated. be able to. In addition, since the second error correction means is provided in the pressure detector in addition to the first error correction means, the repeater can be eliminated.

An atmospheric pressure detecting means is provided in the converter, and the second error correcting means utilizes an atmospheric pressure signal output from the atmospheric pressure detecting means to cause an atmospheric pressure fluctuation of the pressure signal. Error is corrected.

Alternatively, the converter has input means for inputting an atmospheric pressure signal representing the atmospheric pressure, and the second error correction means utilizes the atmospheric pressure signal input from the input means,
The error caused by the atmospheric pressure fluctuation of the pressure signal may be corrected.

[0018]

Next, an embodiment of the present invention shown in the drawings will be described. (First Embodiment) A throw-in type water level gauge 20 according to a first embodiment of the present invention shown in FIGS.
A repeater 22 and a converter 23 are provided.

As shown in FIG. 3, the pressure detector 21 includes an upper cover 25 and a pressure receiving unit main body 26, and has a closed chamber 2 therein.
7a is provided. Each of the upper cover 25 and the pressure receiving unit main body 26 has a flange 25
a, 26a, and these flange portions 25a, 2
The upper cover 2 is fixed by fixing the bolts 28 to the upper cover 2a.
5 and the pressure receiving portion main body 26 are integrally assembled. An O-ring 29 is compressed between the flanges 25a and 26a to seal a gap between the flanges 25a and 26a.

A large-diameter cylindrical portion 26c provided with a pressure inlet 26b is provided at the lower end of the pressure receiving portion main body 26, and the flange portion 26a is provided on the outer periphery of the upper wall 26d of the large-diameter cylindrical portion 26c. Is provided. The large-diameter cylindrical portion 26c
The upper wall portion 26d is provided with a communication hole 26e facing the pressure introduction port 26b. Further, the upper wall portion 26d
A small-diameter cylindrical portion 26f is provided on the opposite side (upper side in the figure) of the large-diameter cylindrical portion 26c.

A differential transformer type differential pressure sensor constituting a differential pressure detecting means is attached to the pressure receiving portion main body 26. The differential pressure sensor 31 includes a bellows 32, a spring 33,
A coil 34 and a mover 35 are provided. Bellows 3 above
Reference numeral 2 is tightly fixed to the lower surface side of the upper wall portion 26d so that its open end surrounds the periphery of the communication hole 26e. On the other hand, a rod-shaped movable element 35 projects from the closed end of the bellows 32 located at the lower end in the figure, and the tip of the movable element 35 projects into the small-diameter cylindrical portion 26f through the communication hole 26e. The coil 34 is fixed to the inner peripheral surface of the small-diameter cylindrical portion 26f, and the tip of the moving element 35 is located inside the coil 34. The pressure signal lines 37a and 37b are connected to the coil 34.

In the differential transformer type differential pressure sensor 31, the pressure inside the closed chamber 27a (above the bottom of the bellows 32) and the pressure outside the closed chamber 27a (below the bottom of the bellows 32 in the figure). Bellows 3
2 expands and contracts, and the moving element 35 moves up and down. That is, when the pressure inside the closed chamber 27a is higher than the pressure outside the closed chamber 27a, the movable element 35 moves downward in the drawing, and the pressure inside the closed chamber 27a is higher than the pressure outside the closed chamber 27a. If it is low, the moving element 35 moves upward in the figure. The electric signal output from the coil 34 changes in accordance with the vertical movement of the movable element 35, and an electric signal (pressure signal) corresponding to the differential pressure between the inside and outside of the closed chamber 27a is output.

A detachable protection frame 38 for protecting the distal end of the pressure receiving section main body 26 is provided. The protection frame 38 includes an annular member 38a surrounding the periphery of the distal end of the pressure receiving section main body 26, and a support member 38b connecting the annular member 38a and the flange portion 26a.

On the inner surface of the upper cover 25, a temperature sensor 39 constituting temperature detecting means is fixed. The temperature sensor 39 outputs a signal (temperature signal) indicating the temperature of the air in the closed chamber 27a. In the figure, reference numeral 37c denotes a temperature signal line for transmitting an output signal from the temperature sensor 39.

In the drawing of the upper cover 25, an insertion hole 25b is provided at the upper end, and a cable 4 for connecting the pressure detector 21 and the relay 22 through the insertion hole 25b.
One end of 2 is inserted into the closed chamber 27a. The cable 42 has two pressure signal lines 43a and 43b and one temperature signal line 43c. A female screw portion 25c is provided in the insertion hole 25b, and a fastening member 44 through which the cable 42 is inserted is screwed into the female screw portion 25c, and between the bottom of the insertion hole 25b and the fastening member 44, Cable packing 46 and packing retainer 47 inserted into the cable 42
Has been arranged. Therefore, by tightening the fastening fitting 44, the cable packing 46 is compressed via the packing retainer 47, and the gap between the exterior 42a of the cable 42 and the insertion hole 25b is sealed. Also, the cable 42
Of the pressure signal lines 43a, 43b
A cable sealing metal fitting 48 is attached to this portion, and an adhesive sealing material is poured into the portion, and the temperature signal line 43c is provided between the sealing chamber 27a and the repeater 22 through the inside of the sheath 42a of the cable 42. The air moves.

As shown in FIG. 4, the pressure signal lines 43a and 43b and the temperature signal line 43c included in the cable 42 are provided.
Are connected to the differential pressure sensor 31 through the printed circuit board 49.
The pressure signal lines 37a and 37b are connected to the temperature signal line 37c on the temperature sensor 39 side. Specifically, crimping connection pins 51 are crimped to the ends of the pressure signal lines 43a and 43b and the temperature signal lines 43c of the cable 42, and the crimping connection pins 51 are provided on the printed circuit board 49 through holes (not shown). ) Is connected to the upper end by soldering. On the other hand, the pressure signal lines 37a and 37b of the differential pressure sensor 31 and the temperature signal line 37c of the temperature sensor 39 are connected to the lower end side of the through hole of the printed circuit board 49 by soldering.

The upper surface side of the printed circuit board 49 is covered with a silicon tube 52, and an adhesive sealing material 53 is poured into the silicon tube 52 so that the pressure signal lines 43a and 43b and the temperature signal line 43c included in the cable 42 are formed. A seal is provided between the closed chamber 27a of the pressure detector 21 and the repeater 22 so that air does not move.

The repeater 22 shown in FIGS. 1 and 5 includes a cylindrical main body 54 and a disk-shaped lid member 55. The main body 54 has a closed end at the lower end and an open end at the upper end in FIG.
54b are provided. The upper end side flange portion 54 a and the lid member 55 are fixed by bolts 57. Flange part 5
An O-ring 58 is contracted between the cover member 4a and the lid member 55, thereby sealing the inside 22a of the repeater 22.

A pair of cable connecting portions 54d, 54d are provided on the peripheral wall 54c of the main body 54. One cable connecting portion 54d is for connecting the cable 42 from the pressure detector 21 and the other cable connecting portion 54d is for connecting a cable 69 connecting the repeater 22 and the converter 23. It is. As shown in FIG. 5B, the cable connection portion 54d is provided with a female screw portion 54e, and the female screw portion 54e has the cables 42 and 69.
Are screwed into each other, and a cable 4 is provided between the bottom of the cable connection portion 54d and the fastener 59.
2, a cable packing 61 and a packing retainer 62 inserted through are disposed. By tightening the fastening fitting 59, the cable packing 61 is compressed via the packing retainer 62, and the cable 42, 69
a, 69a and the insertion hole 54 provided in the cable connection portion 54d
The gap f is sealed. Thus, the repeater 22
The interior 22a is sealed and has a waterproof structure, and is not provided with an atmospheric pressure communication port as in a conventional throw-in type water level gauge of this type.

A board 63 is accommodated in the inside 22a of the repeater 22. As shown in FIG. 6, this substrate 63 has
The circuit includes amplification circuits 64A and 64B, a temperature correction circuit 65 constituting a first error correction unit, a span adjustment circuit 66, and a current conversion circuit 67. The pressure signal lines 43a and 43b and the temperature signal line 43c of the cable 42 connected to the pressure detector 21 are connected to amplifier circuits 64A and 64B, respectively. The functions of the various circuits provided on the substrate 63 will be described later.

Cable 69 for connecting to converter 23
Has two pressure signal lines 71a and 71b, and these pressure signal lines 71a and 71b
7 is connected.

The converter 23 is, as shown in FIGS. 1 and 2,
A terminal portion 73 is provided in a rectangular box-shaped case 72, and the pressure signal lines 71a and 71b of the cable 69 are connected to the terminal portion 73. As shown in FIG. 7, the converter 23 has input circuits 75A, 75B, A /
D conversion circuit 76, CPU constituting second error correction means
(Central processing unit) 77, an atmospheric pressure sensor 78 constituting an atmospheric pressure detecting means, a span adjusting circuit 79, and a D / A conversion circuit 80. The CPU 77 is connected via a D / A circuit 80 to a display device 81 composed of an instrument and the like, and is connected to an alarm device 82 composed of a buzzer and the like.
The functions of these devices will be described later.

In this embodiment, since the inside of the pressure detector 21 is not sealed and the atmospheric pressure is not introduced into the sealed chamber 27a, if the temperature fluctuates, the pressure of the air in the sealed chamber 27a fluctuates. Also fluctuates. Therefore, it is necessary to correct the error due to the temperature fluctuation.
Further, the atmospheric pressure when the closed chamber 27a is closed and the air is confined is not necessarily the same as the atmospheric pressure when the water level is measured. Therefore, the error due to the atmospheric pressure fluctuation is corrected. for that reason,
In the throw-in type water level meter of the first embodiment, the water level is measured based on the following principle.

The atmospheric pressure when the closed chamber 27a is closed and air is trapped is Pa ₀ , and the temperature is T ₀ . The atmospheric pressure at the time of measuring the water level is Pa, the temperature is T, and the pressure within the closed chamber at the time of measuring the water level is Pv. Also, the water pressure corresponding to the water level is P
And The closed chamber 27 in the closed chamber of the pressure detector 21
The volume V of a is negligibly constant. As shown in FIG. 3, since the atmospheric pressure Pa acts on the water surface, the pressure below the bellows 32 (outside the closed chamber 27a) is Pa + P. On the other hand, the pressure above the bellows 32 (inside the closed chamber 27a) is Pv described above. Therefore, the pressure Ps detected by the differential pressure sensor 31 at this time is represented by the following equation (2).
It is represented by

[0035]

(Equation 2)

On the other hand, when the closed chamber 27a is closed and when the water level is measured, the pressure, temperature and volume are given by the following equations (3).
There is a relationship.

[0037]

(Equation 3)

When the above equation (3) is substituted into the equation (2), the following equation (4) is obtained.

[0039]

(Equation 4)

The second term on the right side of equation (4) is the differential pressure sensor 31
Shows the correction of the temperature error with respect to the detected pressure Ps. The third term of the equation (4) shows correction of an error due to atmospheric pressure fluctuation with respect to the pressure Ps detected by the differential pressure sensor.

Next, a method of measuring the water level using the above-mentioned throw-in type water level meter will be described. First, the pressure detector 21 is arranged in water for measuring the water level, and the repeater 22 and the converter 23 are installed at predetermined locations. For example, FIG.
Shows an example in which the throw-in type water level meter of the first embodiment is used for detecting the water level of a water tank 86 of a sewerage facility that pumps water by a pump 85. The pressure detector 21 is a water tank 86
Of water 5 In this example, the protective frame 38 is removed, and is suspended from the opening 89 a provided on the floor 89 above the water tank 86 by the frame member 87 and the support shaft 88. The repeater 22 is installed near the opening 89a. The vicinity of the opening 89a has high humidity, and if the water level in the water tank 86 rises abnormally, the water overflowing from the opening 89a may cause the repeater 22 to be submerged. However, in the present embodiment, since the repeater 22 has a waterproof structure, the repeater 22 can be disposed in such a location.

At the time of measurement, first, the differential pressure sensor 31 and the temperature sensor 39 of the pressure detector 21 output signals. The pressure signal output from the differential pressure sensor 31 is expressed by the above equations (2) to (4).
, And includes an error caused by the above-described temperature fluctuation and an error caused by the atmospheric pressure fluctuation. On the other hand, the temperature signal output from the temperature sensor 39 indicates the temperature T in the closed chamber 27a at the time of measuring the water level in the equations (2) to (4).

The pressure signal and the temperature signal are respectively transmitted to the cable 4
The signal is transmitted to the repeater 22 via the pressure signal lines 43a and 43b and the temperature signal line 43c. In the repeater 22, FIG.
As shown in the flowchart of FIG. 7, the pressure signal and the temperature signal are inputted in step # 10.
Amplified at 4B. The amplified pressure signal and temperature signal are input to the temperature correction circuit 65, and the temperature of the pressure signal is corrected in step # 12. This step # 12
Is to correct an error due to temperature fluctuation from the pressure Ps detected by the differential pressure sensor 31, and performs a process of adding the second term on the right side of the equation (4) to the detected differential pressure Ps.
As a result of this temperature correction processing, the higher the temperature of the closed chamber in the pressure detector 21, the lower the output value of the pressure signal is corrected.

The pressure signal after temperature correction is sent to a span adjustment circuit 6.
6 and the span adjustment is executed in step # 13. This span adjustment is to adjust the value of the pressure signal after the temperature correction according to the measurement range of the water level.

The pressure signal after the span adjustment is supplied to the current conversion circuit 6
7 is input. The current conversion circuit 67 is connected to the converter 23 via the pressure signal lines 71a and 71b as described above.
A constant voltage is applied from the converter 23 to a and 71b. The current conversion circuit 67 converts the pressure signal into a so-called two-wire instrumentation signal, and converts the current flowing through the pressure signal lines 71a and 71b according to the output value of the pressure signal input from the span adjustment circuit 66. Adjust. The pressure signal converted to the two-wire instrumentation signal is

In the converter 23, in step # 20 of the flowchart of FIG. 10, the pressure signal output from the repeater 22 as a two-wire instrumentation signal is converted into an A / D signal by the A / D conversion circuit 76 via the input circuit 75A. After D conversion, CPU
Read in 77. Further, in step # 21, the output signal (atmospheric pressure signal) of the atmospheric pressure sensor 78 is subjected to span adjustment by the span adjusting circuit 79, and then, in step # 22, the A / D converter 23 outputs the A / D signal through the input circuit 75B. The data is D-converted and input to the CPU 77. The atmospheric pressure signal is the atmospheric pressure signal Pa at the time of measuring the water level in the equations (3) and (4).
Is equivalent to

The CPU 77 performs offset adjustment (zero point adjustment) of the pressure signal in step # 22. This offset adjustment is to adjust the output value of the pressure signal according to the offset amount of the water level measured by the water level meter before the water level measurement with respect to the actual water level.

Next, in step # 23, the CPU 77 corrects the atmospheric pressure fluctuation error of the pressure signal after the offset adjustment. This atmospheric pressure fluctuation error correction is performed by the closed chamber 27 included in the pressure signal output from the differential pressure sensor 31 of the pressure detector 21.
This is for correcting an error caused by the atmospheric pressure fluctuation at the time of sealing of “a” and at the time of measuring the water level. This atmospheric pressure correction,
The water pressure corresponding to the water level at the time of measuring the water level is obtained by the temperature correction performed by the relay 22 described above. The CPU 77
In step # 24, a signal (water level signal) representing the measured water level is output to the display device 81 via the D / A circuit 80. If the water level signal indicates that the water level is equal to or higher than the predetermined water level in step # 25, a signal for instructing the alarm device 82 to operate is output in step # 26.

FIG. 11 shows a second embodiment of the present invention. In the second embodiment, a signal from the temperature sensor 39 is input to the differential pressure sensor 31 of the pressure detector 21. In the first embodiment, the temperature correction circuit 65 (see FIG. 6) of the repeater 22 performs the operation. The temperature correction is performed by the differential pressure sensor 31. Further, the differential pressure sensor 31 has a function of performing the current conversion performed by the current conversion circuit 67 of the repeater 22 in the first embodiment. Therefore, in the second embodiment, there is no need to provide a repeater, and the pressure detector 21 and the converter 23 can be directly connected by the cable 90.

FIG. 12 shows a third embodiment of the present invention. In the third embodiment, the water pressure is detected by the absolute pressure sensor 91 instead of the differential pressure sensor. The absolute pressure sensor 91 is a sensor that detects an absolute pressure that is not affected by atmospheric pressure fluctuations, and includes elements corresponding to the temperature sensors and the temperature correction circuits of the first and second embodiments. Further, the absolute pressure sensor 91 of the present embodiment has a function of performing the current conversion performed by the current conversion circuit 67 of the repeater 22 in the first embodiment. Therefore, it is not necessary to provide a relay, and the pressure detector 21 and the converter 23 are connected to the cable 9.
0 allows direct connection.

FIG. 13 shows an example in which the throw-in type water level meter according to the third embodiment is used for measuring the water level of a water channel 97 of a sewer. The water channel 97 is suspended from a manhole 95 by a chain 96.
Of water 5 Since the repeater 22 is unnecessary as described above, the cable 90 having one end connected to the pressure detector 21 is connected to the converter 23 (not shown) via a pipe 98 provided in the ground.

The present invention is not limited to the above embodiment, and various modifications are possible. For example, an atmospheric pressure sensor is not provided in the converter, and an atmospheric pressure sensor provided separately is provided in the converter 22.
May be connected to the terminal unit 73 for atmospheric pressure correction using the input atmospheric pressure signal.

[0053]

As is apparent from the above description, in the throw-in type water level meter according to the first invention of the present application, since the temperature detecting means and the first and second error correcting means are provided, the differential pressure detecting means is provided. The water pressure corresponding to the water level can be obtained from the differential pressure of the sum of the detected atmospheric pressure and the water pressure corresponding to the water level with respect to the air pressure in the closed space. Therefore, in the first invention, it is not necessary to introduce the atmospheric pressure into the pressure detector, and the atmospheric pressure introduction pipe and the atmospheric pressure introduction port of the repeater can be eliminated, and the repeater can be made a sealed waterproof structure. for that reason. The repeater can be placed in a place where there is a possibility of being submerged or a place with high humidity.

Further, in the second invention of the present application, similarly to the first invention, the case of the pressure detector can be made to have a sealed structure, and the second error correction means can be provided in addition to the first error correction means. Since the means is also provided in the pressure detector, the repeater itself can be eliminated, and the structure of the entire apparatus can be simplified.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a throw-in type water level meter according to a first embodiment of the present invention.

FIG. 2 is a schematic partial cross-sectional view showing a throw-in type water level meter according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing a pressure detector according to the first embodiment of the present invention.

FIG. 4 is a partially enlarged sectional view of a part IV in FIG. 2;

FIG. 5A is a partial cross-sectional side view showing a repeater according to the first embodiment of the present invention, and FIG. 5B is a cross-sectional view taken along line V-V in FIG.

FIG. 6 is a schematic configuration diagram illustrating a repeater according to the first embodiment of the present invention.

FIG. 7 is a schematic configuration diagram illustrating a converter according to the first embodiment of the present invention.

FIG. 8 is a schematic sectional view showing a state where the throw-in type water level meter according to the first embodiment of the present invention is installed in a water tank of a sewerage facility.

FIG. 9 is a flowchart showing the operation of the repeater according to the first embodiment of the present invention.

FIG. 10 is a flowchart showing the operation of the converter according to the first embodiment of the present invention.

FIG. 11 is a schematic partial cross-sectional view showing a throw-in type water level meter according to a second embodiment of the present invention.

FIG. 12 is a schematic partial sectional view showing a throw-in type water level meter according to a third embodiment of the present invention.

FIG. 13 is a schematic cross-sectional view showing an example in which the second embodiment or the third embodiment is used for measuring the water level of a water channel of a sewer.

FIG. 14 is a schematic configuration diagram showing a conventional throw-in type water level meter.

FIG. 15 is a cross-sectional view showing a pressure detector in a conventional throw-in type water level gauge.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Pressure detector 22 Repeater 23 Transducer 31 Differential pressure sensor 39 Temperature sensor 91 Absolute pressure sensor 42, 69, 90 Cable

Claims (4)

[Claims] 1. A case of a waterproof structure which is put into water for measuring a water level and has a closed chamber therein, and a differential pressure of a sum of an atmospheric pressure and a water pressure corresponding to the water level with respect to an air pressure in the closed chamber is detected. A differential pressure detecting means for outputting a pressure signal, a pressure detector having a temperature detecting means for detecting the temperature in the closed chamber and outputting the temperature signal as a temperature signal, and an error caused by a temperature change in the closed chamber of the pressure signal. A first error correction unit that corrects using a temperature signal output from the temperature detection unit, a repeater having a waterproof structure including a unit that outputs a corrected pressure signal, A second error correction means for correcting a resulting error to obtain a pressure signal corresponding to the water level, and a converter having means for outputting a water level signal representing a water level corresponding to the pressure signal. Throw Water level meter. 2. A case of a waterproof structure which is put into water for measuring a water level and has a sealed space therein, and a differential pressure of the sum of the atmospheric pressure and the water pressure corresponding to the water level with respect to the air pressure of the sealed space, A differential pressure detecting means for outputting as a pressure signal,
A pressure detector having a temperature detecting means for detecting the temperature in the closed space and outputting the temperature signal as a temperature signal, and an error caused by a temperature change in the closed space of the pressure signal output from the differential pressure detecting means, A pressure detector including first error correction means for correcting using a temperature signal output from the temperature detection means, and means for outputting a corrected pressure signal; and a large pressure signal output from the pressure detector. A second error correcting means for correcting an error caused by atmospheric pressure fluctuation to obtain a pressure signal corresponding to the water level; and a converter having means for outputting a pressure signal corresponding to the water level. Water level gauge. 3. An atmospheric pressure detecting means is provided in said converter,
2. The method according to claim 1, wherein the second error correction unit uses an atmospheric pressure signal output from the atmospheric pressure detection unit to correct an error caused by an atmospheric pressure change of the pressure signal. 2. The throw-in type water level meter according to 2. 4. The converter has input means for inputting an atmospheric pressure signal representing the atmospheric pressure, and the second error correction means uses the atmospheric pressure signal input from the input means to generate the pressure signal. The throw-in type water level meter according to claim 1 or 2, wherein an error caused by the atmospheric pressure fluctuation is corrected.