JPH0259620A - Water level sensor - Google Patents

Abstract

PURPOSE:To measure the settlement by a leveling system whose structure is simple and which scarcely causes a measurement error by obtaining an output being proportional to a water level in a transparent measuring tube by receiving a current output of a one-dimensional light position sensor. CONSTITUTION:A light beam from a light source 2 lighted by a constant-current circuit 1 is made incident on the inside of a tube from the bottom part of a transparent measuring tube 3. To the inside of the tube, water at the time of measuring the settlement of the ground is applied from an inlet/outlet 3a through a communication tube, and in accordance with its hydraulic pressure, a water level in the tube moves. To the inside surface of the transparent measuring tube 3, hydrophilic coating is applied in advance, therefore, water of a part brought into contact with the inside surface of the tube of the peripheral part of the water level swells, and the light beam from the light source 2 is refracted and emitted to the outside of the tube. As for the outside surface of the transparent measuring tube 3, the length direction is finished partially to a plane, and a refracted light is received by a one-dimensional light position sensor 4 fixed to this plane part and converted to a current value being proportional to a water level generated in the tube. The converted current value is converted to a voltage value by a current/voltage converting means and obtained as a measured value from an output side.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a water level sensor used when measuring subsidence using a water mounding method.

[Prior Art] Conventionally, when measuring ground subsidence using a water embankment method, it is necessary to measure changes in water level. To measure this change in water level, we took advantage of the fact that the dielectric constant of water is larger than that of air. The so-called electric capacitance 11i1!1 constant method and the float position measurement method in which a float is floated on the water surface and the position of the float is detected by control by a servo system are often used.

[Problems to be Solved by the Invention] However, in the above-mentioned electric capacitance ff1U1 constant method, the dielectric constant of water changes depending on the water temperature, so a correction electrode must be provided in the measurement section to correct for temperature changes.
This has the disadvantage that not only the regular shape becomes larger, but also one circuit becomes more complicated.

In addition, with the float position measurement method, if the water level changes faster than the operating temperature of the servo system, or if the water level changes during a power outage, it will not be able to follow the changes and measurement will not be possible. Of course, there was a drawback in that the float itself came into contact with the tube wall, causing measurement errors.

[Means for Solving the Problems] A water level sensor according to the present invention includes a transparent measuring tube whose inner surface is coated with a hydrophilic coating, and a light source for allowing light to enter the tube from outside the bottom of the transparent measuring tube.

The length direction of the outer surface of the transparent measuring tube is partially finished as a flat surface, and the refracted light obtained from the periphery of the water level inside the transparent main tube is converted into a current value proportional to the water level by fixing it to the flat surface. It is characterized by comprising a one-dimensional optical position sensor for detection, and current-voltage conversion means for receiving the current output detected from the optical position sensor and converting it into voltage.

[Operation] According to the water level sensor of the present invention, since the inner surface of the transparent measuring tube is coated with a hydrophilic coating, the light source is generated at the periphery of the water level surface that has entered the tube, that is, at the bulge of water close to the inner surface of the tube. Light entering the tube is refracted and emitted outside the tube. This refracted light is received by a one-dimensional optical position sensor attached to the outer surface of the transparent 1ffj fixed tube and converted into a current value proportional to the water level generated inside the tube. This converted current value is further converted into a voltage value by a current-voltage conversion means and obtained as a measured value from the output side.

[Embodiments of the Invention] Next, an embodiment of a water level sensor according to the present invention will be given.
This will be explained with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment according to the present invention. In this figure, a light source 2 is turned on with a current supplied from a constant current circuit 1, and the light from the light source 2 is transmitted to a transparent measuring tube 3.
enters the tube from the bottom of the tube.

Water for determining ground subsidence M is added to the pipe from the inlet/outlet 3a through the communication pipe, causing the water level to shift within the pipe in accordance with the water pressure. Since the inner surface of the transparent measuring tube 3 has been previously coated with a hydrophilic coating, the water in the area around the water level that contacts the inner surface of the tube bulges, and the light coming from the light source 2 is refracted here and absorbed into the tube. released outside. This refracted radiation becomes uniform in the surrounding direction. As shown in FIG. 2, the outer surface of the transparent measuring tube 3 is partially finished with a flat surface 3c in the longitudinal direction, and the refracted light is transmitted to a one-dimensional optical position sensor fixed to this flat surface. 4 and is converted into a current value proportional to the water level generated in the pipe.

FIG. 3 is a sectional view showing a specific example of the configuration of the one-dimensional optical position sensor 4. As shown in FIG. This optical position sensor consists of two layers 4c on the front surface of a flat silicon plate, an N layer 4d on the back surface, and one layer 4c in the middle.
It is composed of three layers: e. When a light beam is incident on the P layer as shown in the figure, a charge proportional to the light energy is generated at the incident position and flows out as a photocurrent through the P layer (resistance layer) to the electrodes 4a and 4b. Since this P layer is made to have a uniform resistance value over the entire surface, the photocurrent is divided and extracted in inverse proportion to the distances from the incident position to the electrodes 4a and 4b, respectively.

Here, the distance between 9 electrodes is 2L, and the complete current is 'Or electrode 4
The current taken out from a is II + If the current taken out from 4b is 12. If the distance from the position of the incident light to the origin is set to X when the midpoint of the P layer is set as the origin, the following equation is obtained.

r+ -10(L-X)/2L... (1)1
2-1. (L+X)/2L-(2)(12If
) / (If + 12) =X/
L... (
3) As can be seen from this equation (3), the electrodes 4b and 4a
By determining the difference and sum of the currents I2 and 11 obtained from , it is possible to calculate the light incident position regardless of the energy of the incident light.

Referring again to FIG. 1, a current-voltage conversion circuit 5 is connected to the electrode 4a side of the optical position sensor 4, and a current-voltage conversion circuit 6 is connected to the electrode 4b side.

Current 11 on the electrode 4a side and current I2 on the electrode 4b side, respectively.
is converted into a voltage value. Current! The output of the current-voltage conversion circuit 5 corresponding to , and the output of the current-voltage conversion circuit 6 corresponding to the current I2 are added to a subtraction circuit 7, and the difference between the two is determined. On the other hand, the output of the current-voltage conversion circuit 5 and the output of the current-voltage conversion circuit 6 are also added to the addition circuit 8,
Here, the sum of both is found. The division circuit 9 is the subtraction circuit 7
The output value of the subtraction circuit 7 is divided by the output value of the addition circuit 8. These subtraction circuits7. The series of functions performed by the addition circuit 82 and the division circuit 9 means the processing of equation (3) above. Thus.

The output of the division circuit 9 allows the light incident position to be known.

In this way, the 1 division circuit has a differential voltage on the numerator side input.

By inputting the sum voltage to the denominator side input, fluctuations in the output of the optical position sensor due to changes in the amount of light are corrected.

Further, a constant current is supplied to the light source 2 by a constant current circuit 1, and the brightness of the light source is maintained stably.

In addition, in the above embodiment, formula (3) was applied, but in addition to this, the following formula is applied from formulas (1) and (2).

II /12 - (L-X)/ (L+X)
...By deriving (4), the subtraction circuit and addition circuit can be omitted.

It can also be used for calculations in addition to the direct division circuit.

[Effect of the invention〕 As is clear from the above description, there are two aspects of the present invention.

a transparent NJ fixed tube with a hydrophilic coating, a light source for allowing light to enter the tube from outside the bottom of the transparent measurement tube, a one-dimensional optical position sensor fixed to the outside of the transparent measurement tube; The main element is a means for receiving the current output from the dimensional optical position sensor and outputting a voltage proportional to the water level in the transparent measuring tube. The advantages of this method are that it eliminates drawbacks, has a simple structure, has good connectivity, and can reduce measurement errors.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment according to the present invention;
FIG. 2 is a perspective view showing the attachment relationship between the transparent measuring tube and the one-dimensional optical position sensor in FIG. 1, and FIG. 3 is a sectional view showing an example of the configuration of the one-dimensional optical position sensor. In the figure, 1 is a constant current circuit, 2 is a light source, 3 is a transparent measuring tube, 3a and 3b are entrances and exits, and 3c is a flat surface. 4 is a one-dimensional optical position sensor, 4a and 4b are electrodes, 4c is a P layer, 4d is an N layer, and 4e is! layer, 5.6 is a current-voltage conversion circuit, 7 is a subtraction circuit, and 8 is an addition circuit.

Claims (1)

[Claims] 1. A transparent measuring tube with a hydrophilic coating on the inside,
A light source for inputting light into the tube from outside the bottom of the transparent measuring tube, and a light source fixed to the transparent measuring tube to convert refracted light obtained from the area around the water level surface generated in the transparent measuring tube to a current value proportional to the water level. A water level sensor comprising: a one-dimensional optical position sensor that converts and detects; and current-voltage conversion means that receives a current output detected from the optical position sensor and converts it into voltage.