JP2001194467A - Groundwater flow measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a groundwater flow measuring instrument which can stably and accurately measure groundwater flow flowing at relatively high flow velocity. SOLUTION: A float 2 of the groundwater flow measuring instrument is centered, by causing the conductor 4 of the float 2 positioned inside an electromagnetic induction coil 5 to generate an electromagnetic force toward the center by supplying an alternating current to the coil 5, while the float 2 is made to float in a measurement case 1. When the float 2 is centered, a current control means causes the float 2 to generate an electromagnetic force in a direction opposite to the direction of the groundwater flow, but thereafter, the alternating current supplied to the coil 5 is gradually reduced. A flow velocity calculating means fetches the value of the alternating current at the moment the float 2 starts the movement due to a drop in the electromagnetic force and calculates the flow velocity of the groundwater flow, based on the value of the alternating current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a float type groundwater flow measuring device for measuring the velocity and direction of groundwater flow based on the moving speed and direction of a float, and particularly to a groundwater flow suitable for measuring a groundwater flow having a relatively high flow velocity. It relates to a measuring device.

[0002]

2. Description of the Related Art Conventionally, as a single-hole type groundwater flow measuring method, a tracer such as a chemical solution or a dye is introduced into a measuring case, and the flowing direction and position of the tracer are measured to measure the flow velocity and direction of the water flow. There are known a tracer method, a camera method in which a video camera is inserted into a measurement case, a floating substance flows into the measurement case, and the movement thereof is measured.

[0003]

However, in the camera method using a video camera, since the size of the apparatus is increased and the front of the camera is brightly illuminated by the light, the water temperature partially rises due to the light and the convection current is increased. There is a problem that it is difficult to measure the accurate movement of the groundwater flow due to the occurrence of the water.

[0004] The tracer method is widely practiced at present, and can measure the trend of the groundwater flow with considerable accuracy. However, when the movement of the water flow is very slow and the water can move freely, the tracer is moved underwater. There is a problem that it is difficult to measure the groundwater flow with high accuracy due to the unstable movement of water or the diffusion phenomenon of the injected liquid.

In the method of injecting a tracer, once the tracer is injected and the measurement is performed, if it is desired to perform the measurement again, it is necessary to lift the measurement case from the boring hole and refill the tracer. There was a problem that continuous measurement was not possible.

Therefore, conventionally, a measurement case is immersed in water,
With the air layer formed on the upper part, the float of the insulator is floated at the center position of the measurement case, and four electrodes are arranged on the inner peripheral wall of the measurement case at intervals of 90 degrees. Based on the change in electrical resistance between adjacent electrodes that changes according to the position of the float, the position of the float is measured in a timely manner, and the direction and speed of the float moved by the groundwater flow are
Devices have been developed to measure the direction and velocity of groundwater flow.

[0007] This float type groundwater flow measuring device usually has a float moving range of about 5 mm in a measuring case, and based on a change in electric resistance between adjacent electrodes that changes according to the position of the float, The position of the float is measured in time, and the direction and speed of the float moved by the groundwater flow are
Measured as the direction and velocity of groundwater flow. In such a groundwater flow measuring device, the flow velocity is about 9 m to 0.9 m / day.
When measuring groundwater flow with a relatively slow flow rate during the day, the flow rate can be measured accurately without any problem.However, when measuring near a river or near groundwater pumping, the flow rate can be several tens of When the speed is very fast, i.e., m to several hundred m / day, there is a problem that the error of the flow velocity measurement value becomes very large.

That is, the bore diameter of the well for measuring the groundwater flow is usually 66 mm to 116 mm. However, a pipe is inserted into the observation well to protect the wall of the bore hole, and the bore is inserted into the observation well. The movable range of the float, that is, the float movable range is about 10 mm from the center. Excluding the unstable area near the center or the periphery, the float movable range usable for the flow velocity measurement is about 5 mm. It is limited to the extent. For this reason, the flow velocity is, for example, several tens m
When the speed is as high as several hundred m / day, there is a problem that the error of the measured flow velocity becomes very large.

By the way, if the measuring device is enlarged, the float can naturally have a large moving range.
In such a case, it is expected that the workability and economic efficiency may be deteriorated because the borehole needs to be enlarged and different measuring devices are required depending on the flow velocity.

The present invention has been made in view of the above points, and has as its object to provide a groundwater flow measuring apparatus capable of stably and accurately measuring a groundwater flow having a relatively high flow velocity.

[0011]

To achieve the above object, a groundwater flow measuring device according to the present invention comprises a measuring case having a flow port through which groundwater can flow, and a float of an insulator arranged in the measuring case. An air supply means for supplying air into the measurement case; and an air supply means disposed on the inner peripheral wall of the measurement case so as to be positioned on the X-axis and the Y-axis on an XY plane whose plane is a cross section of the measurement case. Two pairs of electrodes, a pair of electrodes X1 and X2 located on the X axis and a pair of electrodes Y1 and Y located on the Y axis.
2, a constant current circuit that supplies a constant current, a current flowing through each electrode when current is supplied from the constant current circuit, and current values of a pair of electrodes X1 and X2 located on the X axis. XY coordinate signal generating means for calculating the difference between the current values of the pair of electrodes Y1 and Y2 located on the Y axis to generate an X coordinate signal and a Y coordinate signal indicating the position of the float;
Arithmetic processing means for calculating the direction and speed of movement of the float based on the X and Y coordinate signals from the X and Y coordinate signal generating means; a conductor attached to the float; And an electromagnetic induction coil that generates an induction current in the conductor, current control means that supplies and controls an alternating current to the electromagnetic induction coil, and an electromagnetic force that opposes the direction of the water flow to the float by the current control means. And a flow velocity calculating means for calculating the flow velocity of the groundwater flow based on the value of the alternating current.

The current control means gradually reduces the current in a state where the float is centered by supplying the current to the electromagnetic induction coil, and the flow rate calculating means determines the current based on the current value at the start of the movement of the float. , The flow rate of the groundwater flow can be calculated. In another embodiment, the flow velocity calculating means includes a current control means for supplying a current to the electromagnetic induction coil to cause the float to generate an electromagnetic force opposite to the direction of the water flow, thereby causing the float to be centered on the float. It can be configured to calculate the velocity of the groundwater flow based on the moving speed of the groundwater.

[0013]

In the groundwater flow measuring device having the above-mentioned configuration, at the time of measurement, first, an AC current is supplied to the electromagnetic induction coil in a state where the float is floated in the measurement case, and the float conductor located inside the electromagnetic induction coil is supplied. Then, an electromagnetic force toward the center is generated to perform centering of the float. In the centered state, the current control means causes the float to generate an electromagnetic force in a direction opposite to the direction of the water flow. Thereafter, the current of the electromagnetic induction coil is gradually reduced. Then, the flow velocity calculating means captures the current value at the time when the float starts moving due to the decrease in the electromagnetic force, and calculates the flow velocity of the groundwater flow based on the current value.

As described above, instead of measuring the speed at which the float moves due to the water flow, the flow velocity is calculated based on the centering electromagnetic force corresponding to the force of the water flow received by the float, that is, the current value flowing through the electromagnetic induction coil. Even if the flow velocity is relatively high and the accurate flow velocity cannot be measured in a narrow float movement range, the flow velocity of the water flow can be accurately calculated by the electromagnetic force of the centering, that is, the current value flowing through the electromagnetic induction coil. it can.

On the other hand, after measuring the flow velocity,
The position (direction) of the float that is moved by the water flow in that state by interrupting the current of the electromagnetic induction coil to eliminate the electromagnetic force
Is calculated using the X / Y coordinate signal generating means and the arithmetic processing means. The XY coordinate signal generation means detects the current flowing through each electrode when the current is supplied from the constant current circuit, and
The difference between the current value of the pair of electrodes X1 and X2 located on the axis and Y
By calculating the difference between the current values of the pair of electrodes Y1 and Y2 located on the axis, an X coordinate signal and a Y coordinate signal indicating the position of the float are generated. The arithmetic processing means calculates the moving direction of the float based on the X coordinate signal and the Y coordinate signal from the X / Y coordinate signal generating means.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a measuring unit of the groundwater flow measuring device, FIG. 6 is a sectional view thereof, and FIG. 5 is a block diagram of the measuring device. Reference numeral 1 denotes a measurement case, which is attached to a lower end of an insertion tube 8 to be inserted into a boring hole or the like, as shown in FIG. 6, and inserted into the boring hole or the like.

The measuring case 1 comprises cup-shaped containers arranged at the upper and lower portions, and the upper and lower cup-shaped containers are connected by a large number of lattice frames 3, and the lattice frame 3 is formed of groundwater. It becomes a distribution department that can be distributed. An air pipe 7 for introducing air into the case is connected to the upper part of the measurement case 1.

Reference numeral 2 denotes an insulator float provided in the measurement case 1, which is formed of, for example, a polyacetal resin or the like in a columnar shape and has a closed air chamber (not shown) provided therein as shown in FIG. Then, it floats in the water in the measurement case 1 in an upright state. A conductor 4 for float centering and high flow velocity measurement is fixed to the lower part. As the conductor 4, a non-magnetic good conductor such as copper or aluminum in the form of a short pipe or a disc is preferable.

Further, the measurement case 1 around the conductor 4
Inside, an electromagnetic induction coil 5 for generating an induced current in the conductor 4 is wound. The winding diameter of the coil 5 is, for example, about 30 to 40 mm and about 1 to 1 for centering.
It is wound so as to obtain a current of 0 ampere turns and a weak current for measuring a high flow velocity. The electromagnetic induction coil 5 includes
As shown in FIG. 5, a current control circuit 18 is connected, and the current control circuit 18 is controlled by a microcomputer 15 described later.

A part of the grid frame 3 provided in the middle part of the measurement case 1 has four electrodes X at 90-degree intervals.
1, X2, Y1, and Y2 are attached, and these four electrodes are arranged on an XY plane having a horizontal section of the measuring case 1 as a plane.
Axis and the Y axis.

As shown in FIG. 5, each of the electrodes X1, X2, Y
Reference numeral 1 and Y2 are connected to an XY switching circuit 10, and a constant current circuit 11 is connected to a pair of electrodes X1 and X2 located on the X axis via the XY switching circuit 10 and a pair of electrodes X1 and X2 located on the Y axis. Are connected so as to alternately supply a constant current between the electrodes Y1 and Y2.

The XY switching circuit 10 comprises a relay circuit or a transistor switching circuit.
The electrodes X1, X2, Y1, Y at a cycle of about 0 to 50 Hz.
2, the current supply side and the current detection side are switched. In the constant current circuit 11, in order to correct a change in water conductivity,
In order to eliminate errors due to electrolysis of the electrodes, an AC power supply that outputs a rectangular wave of, for example, 2 kHz is used.

On the output side of the XY switching circuit 10, a current-voltage conversion circuit 12a is connected to a circuit for outputting a current from the electrode Y1, and a current-voltage conversion circuit is connected to a circuit for outputting a current from the electrode Y2. The circuit 12b is connected, the current-voltage conversion circuit 12c is connected to the circuit that outputs the current from the electrode X1, and the current-voltage conversion circuit 12d is connected to the circuit that outputs the current from the electrode X2.

The current-voltage conversion circuits 12a, 12b, 12
The rectifier circuits 13a and 13d are provided on the output sides of c and 12d, respectively.
b, 13c, 13d are connected, the output side of the rectifier circuit 13a is connected to the inverting input side of the comparator 14a via a smoothing circuit, and the output side of the rectifier circuit 13b is connected to the comparator 14a via a smoothing circuit. Connected to non-inverting input side.

The output side of the rectifier circuit 13c is connected to the inverting input side of the comparator 14b via a smoothing circuit, and the output side of the rectifier circuit 13d is connected to the comparator 14b via a smoothing circuit.
Is connected to the non-inverting input side. The comparator 14a has an electrode Y
1 outputs a voltage corresponding to the difference between the current of the electrode Y2 and the current of the electrode Y2, and the comparator 14b outputs a voltage corresponding to the difference between the current of the electrode X1 and the current of the electrode X2.

A microcomputer 15 is connected to the outputs of the comparators 14a and 14b as a main control circuit of the measuring device. The microcomputer 15 includes a CPU, a ROM of a fixed memory, a RAM that can be written and read at any time, and an input / output circuit, and controls a float centering, a current control of the electromagnetic induction coil 5 described later, and a current value at the start of movement of the float. Calculation of high flow rate based on each electrode X
The flow velocity and flow direction of the water flow are measured based on the current values between 1, X2, Y1, and Y2. The calculation of the flow velocity and the flow direction of the water flow is based on the difference currents Iy1, Iy2, Ix1,
After fetching each data of Ix2 and performing a predetermined correction process, the X coordinate and the Y coordinate of the float 2 are calculated. The data of the X coordinate and the Y coordinate are output to the XY recorder 16,
The flow velocity is recorded as the direction of the groundwater flow, and the flow velocity is calculated by calculating the moving distance of the float with respect to time, and the calculation result is numerically displayed on the display 17.

In order to determine the flow velocity of the high-flow water flow using the float centering device, the float movement start current with respect to the flow velocity of the water flow is measured from an experiment in advance. In other words, the float is positioned in the center of the measurement case by flowing a current through the centering induction coil in a water stream of various flow velocities, and the value of the current flowing through the induction coil is gradually reduced, and the float starts moving. Measure the current value of Then, data of current values corresponding to such a large number of flow velocities are stored in the ROM in advance as table data or the like.

Next, a case where a groundwater flow at a high flow velocity (for example, several tens m to several hundred m / day) is measured using the groundwater flow measuring device having the above-described configuration will be described. First, the measurement case 1 is inserted into a pre-drilled boring hole, and the measurement case 1 is accurately positioned with respect to the azimuth and put into groundwater.

Underground water flows into the measurement case 1 from around the lattice frame 3 and fills the case.
Then, by supplying air into the case 1 from the air pipe 7, a predetermined amount of an air layer is formed in the upper portion of the case, and the water level in the case is set to a predetermined position as shown in FIG. At this time, the water level in the case is determined by a water level sensor 9 provided on the inner peripheral surface of the case.
Is detected by

Next, at the start of the measurement, the microcomputer 15 executes the step 100 of FIG. 7 and controls the current control circuit 18 to supply a current for float centering (for example, about 1 mA) to the electromagnetic induction coil 5. Supply. Then, a magnetic field is generated around the electromagnetic induction coil 5,
At this time, an induced current (eddy current) is generated in the conductor 4 of the float 2 located inside the electromagnetic induction coil 5 in a direction to cancel a change in magnetic flux generated by the magnetic field. Further, from the relation between the induced current and the magnetic field, a force (electromagnetic force) toward the center of the electromagnetic induction coil 5 is generated in the conductor according to the Fleming's left hand rule.

Therefore, when the float 2, that is, the conductor 4 is located at the center of the measurement case 1, that is, the center of the electromagnetic induction coil 5, the float 2 receives a uniform force from all directions toward the center, and the float 2 is located at the center position of the measurement case 1. Will be retained. On the other hand, when the float 2 is deviated to any side in the measurement case 1, the conductor 4 approaches a part of the electromagnetic induction coil 5. In this case, the magnetic flux density that the conductor 4 receives from that portion increases, and the induced current generated in the conductor 4 increases,
The force (force in the central direction) generated in the conductor 4 also increases at that portion. Due to this increased force, the conductor 4, that is, the float 2, receives a force toward the center from the offset position, is returned to the center of the measurement case 1 against the water flow, and is centered.

Next, in step 110, the microcomputer 15 controls the current control circuit 18 to gradually decrease the value of the centering current supplied to the electromagnetic induction coil 5; At 120, it is determined whether the float 2 has started to move from the center position due to the water flow. Then, steps 110 and 120 are repeatedly executed, and when the force of the water flow exceeds the electromagnetic force of the centering (the force holding the center position), the float 2 starts moving from the center position. Proceeding to step 130, the current value is stored.

The detection of the position when the float 2 moves away from the centering position is performed by detecting the electrodes X1, X
The measurement is performed by measuring a voltage value between 2, Y1, and Y2.

That is, first, from the constant current circuit 11 to each electrode X
1, X2, Y1, and Y2 are supplied with an AC rectangular current.
As shown in FIGS. 3 and 4, the current from the constant current circuit 11 is alternately supplied to the electrodes X1, X2 and the electrodes Y1, Y2, and the current obtained from the electrodes Y1, Y2 and the electrodes X1, X2 at that time. Is sent to the current-voltage conversion circuits 12a, 12b, 12c, 12d connected to the respective circuits.

The current-voltage conversion circuits 12a, 12b, 12
c, 12d convert the current signal into a voltage signal, and these voltage signals are converted into rectifier circuits 13a, 13b, 13c, 13c.
It is converted to a DC voltage at d. Then, the current I of the electrode Y1
The voltage signal corresponding to y1 is input to the inverting input of the comparator 14a.
The voltage signal corresponding to the current Iy2 of the electrode Y2 is
a is input to the non-inverting input. The current I of the electrode X1 is
The voltage signal corresponding to x1 is supplied to the inverting input of the comparator 14b.
The voltage signal corresponding to the current Ix2 of the electrode X2 is
b is input to the non-inverting input. The comparator 14a outputs a difference voltage corresponding to the difference between the currents Iy1 and Iy2, and the comparator 14b outputs a difference voltage corresponding to the difference between the currents Ix1 and Ix2.

For example, as shown in FIG. 2, when the float 2 moves in the direction of the electrode Y1, the electric resistance R1 of the electrode Y1 as viewed from the electrodes X1 and X2 increases because the current is interrupted by the float 2, and conversely. Meanwhile, the electric resistance R2 of the electrode Y2 as viewed from the electrodes X1 and X2 decreases because the influence of the float 2 decreases. Similarly, when the float 2 moves in the direction of the electrode X1, the electric resistance R3 of the electrode X1 as viewed from the electrodes Y1 and Y2 increases because the current is interrupted by the float 2, and conversely, the electrode as viewed from the electrodes Y1 and Y2. The electric resistance R4 of X2 decreases because the influence of the float 2 decreases.

Here, since the resistors R1 and the like are combined resistors, 1 / R1 = 1 / {R (X1, Y1)} + 1 / ｛R
(X2, Y1)}, and the resistance R2 is 1 / R2 = 1 /
{R (X2, Y2)} + 1 / {R (X1, Y2)}. Further, the resistance R3 is 1 / R3 = 1 / ｛R (X1, Y
1) {+ 1 / {R (X1, Y2)} and the resistance R4
Is 1 / R4 = 1 / {R (X2, Y2)} + 1 / {R
(X2, Y1)}.

Therefore, as shown in FIG. 3, a power source is connected between the electrodes X1 and X2 and the electrodes Y1 and Y2 to supply a current, and the current Iy1 flowing through the electrode Y1 and the current Iy2 flowing through the electrode Y2 are measured. Then, the difference between the currents Iy1 and Iy2 is determined, and the movement of the float in the Y-axis direction is measured. Similarly, as shown in FIG. 4, power is supplied to electrodes X1 and X2 and electrodes Y1 and Y2.
And a current Ix1 flowing through the electrode X1 and a current Ix2 flowing through the electrode X2 are measured.
The difference between x1 and Ix2 is determined, and the movement of the float in the X-axis direction is measured.

Next, in step 140, the microcomputer 15 sets the float 2 in step 130.
Is based on the current value at the start of movement,
The flow velocity corresponding to the current value is calculated by searching a data table of the flow velocity for the current value stored in advance in the data table. The calculated flow velocity data is written into a memory or the like and displayed on the display 17.

As described above, while the float 2 is centered, the current of the electromagnetic induction coil 5 is gradually reduced.
The electromagnetic force is gradually lowered, the current value when the float 2 starts moving is determined, and based on this current value, the flow velocity of the water flow is measured. For example, the flow velocity is several tens m to several hundred m / day. Even if the speed is very fast, the moving range of the float 2 is about 5
The flow rate can be measured accurately with a measuring device with a narrow range of mm.

Next, at step 150, the microcomputer 15 controls the current control circuit 18 to cut off the current supplied to the electromagnetic induction coil 5. As a result, the electromagnetic force applied to the conductor 4 (the float 2) by the electromagnetic induction coil 5 disappears, and the float 2 is in a state where it can move freely.

Then, in the next step 160, the flow direction of the water flow is measured from the moving direction of the float 2. That is, the microcomputer 15 determines whether the electrodes X1, X2
A constant current circuit 11 is connected between the electrodes Y1 and Y2 to supply a current, a current Iy1 flowing to the electrode Y1 and a current Iy2 flowing to the electrode Y2 are measured, and a difference between the currents Iy1 and Iy2 is obtained. Is measured in the Y-axis direction. Similarly, a constant current circuit 11 is connected between the electrodes X1 and X2 and the electrodes Y1 and Y2 to supply a current, and a current Ix1 flowing to the electrode X1 and a current Ix2 flowing to the electrode X2 are measured.
The difference between x1 and Ix2 is determined, and the movement of the float in the X-axis direction is measured. The X-coordinate and Y-coordinate data thus obtained are output to the XY recorder 16 at predetermined time intervals.
The direction of the groundwater flow is recorded on XY coordinates, and the flow direction of the water flow is determined.

On the other hand, the flow rate is about 9 to 0.9 m / day.
When measuring the groundwater flow at a relatively slow speed of the day, after supplying an alternating current to the electromagnetic induction coil 5 and centering the float 2, the current supply to the electromagnetic induction coil 5 is cut off, and then the above step is performed. Similarly to the process 160, the current Iy1 flowing to the electrode Y1 and the current Iy2 flowing to the electrode Y2
Is measured, the difference between the currents Iy1 and Iy2 is determined, and the movement of the float in the Y-axis direction is measured. Similarly, the current Ix1 flowing through the electrode X1 and the current Ix2 flowing through the electrode X2 are measured, and the current Ix1 and Ix2 are measured. The difference is obtained, the movement of the float in the X-axis direction is measured, and the flow velocity is calculated from the moving time and distance.

In the above embodiment, the current of the electromagnetic induction coil is gradually reduced while the float 2 is centered, and the current value when the float 2 starts moving is determined. The flow rate of the electromagnetic induction coil 5 was measured while the float 2 was centered.
The current supplied to the float 2 is reduced to a constant weak current, and while the float 2 is generating an electromagnetic force in the direction of the center, the float 2 loaded by the electromagnetic force moves with the water flow and the moving distance. From the current value, the flow velocity of the high-velocity water flow can also be obtained.

[0045]

As described above, according to the underground water flow measuring device of the present invention, the current control means for supplying and controlling the current to the electromagnetic induction coil for centering the float allows the float to be opposed to the direction of the water flow. To calculate the velocity of the groundwater flow based on the current value, instead of measuring the speed at which the float moves,
Since the flow velocity is calculated based on the electromagnetic force of the centering corresponding to the force of the water flow received by the float, that is, the current value flowing through the electromagnetic induction coil, the flow velocity is relatively high, so that accurate flow velocity cannot be measured in a narrow float movement range. Even so, the flow velocity of the water flow can be accurately calculated.

[Brief description of the drawings]

FIG. 1 is a perspective view of a groundwater flow measuring device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a basic relationship between an electrode and an electric resistance in a measurement case.

FIG. 3 is an explanatory diagram of current detection from electrodes Y1 and Y2.

FIG. 4 is an explanatory diagram of current detection from electrodes X1 and X2.

FIG. 5 is a block diagram of a groundwater flow measuring device.

FIG. 6 is a longitudinal sectional view of the measurement case 1.

FIG. 7 is a flowchart showing an operation of measuring flow velocity and flow direction.

[Explanation of symbols]

 1-measurement case, 2-float, 3-grid frame, 4-conductor, 5-electromagnetic induction coil, 7-air tube, 15-microcomputer 18-current control circuit X1, X2, Y1, Y2-electrode.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor, Toshimasa Takemura 2-23 Higashishinmachi, Yokkaichi-shi, Mie Tohoku Chisui Co., Ltd. In company

Claims (3)

[Claims] 1. A measurement case having a flow port through which groundwater can flow, an insulator float disposed in the measurement case, air supply means for supplying air into the measurement case, On the inner peripheral wall, two pairs of electrodes disposed on the X-axis and the Y-axis on an XY plane having a horizontal cross section of the measurement case as a plane, and a pair of electrodes X1 positioned on the X-axis , X2 and a pair of electrodes Y1 and Y2 located on the Y axis, a constant current circuit for supplying a constant current, and detecting a current flowing to each electrode when the current is supplied from the constant current circuit, A pair of electrodes X1 and X located on the X axis
2 and a pair of electrodes Y1 and Y located on the Y-axis.
X and Y coordinate signal generating means for calculating an X coordinate signal and a Y coordinate signal indicating the position of the float by calculating the difference between the two current values, and an X coordinate signal from the XY coordinate signal generating means. Arithmetic processing means for calculating the direction and speed of movement of the float based on the Y coordinate signal; a conductor attached to the float; and a conductor disposed around the conductor inside the measurement case and guided by the conductor An electromagnetic induction coil for generating an electric current, current control means for supplying and controlling an alternating current to the electromagnetic induction coil, and an electromagnetic force opposite to the direction of the water flow is generated in the float by the current control means, and And a flow rate calculating means for calculating a flow rate of the groundwater flow based on the value. 2. The method according to claim 1, wherein the current control means supplies the current to the electromagnetic induction coil and gradually lowers the current in a state where the float is centered. 2. The groundwater flow measuring device according to claim 1, wherein the flow velocity of the groundwater flow is calculated based on the current value. 3. The current value when the current control means supplies a current to the electromagnetic induction coil to generate an electromagnetic force in the float opposite to the direction of the water flow to center the float. The groundwater flow measuring device according to claim 1, wherein the flow velocity of the groundwater flow is calculated based on the moving speed of the float.