JP7636611B2 - Non-contact height measurement method using capacitance - Google Patents

Description

The present invention relates to a non-contact height measurement method using electrostatic capacitance, and more specifically, to a non-contact height measurement method that detects the height level of a dielectric material on the opposite side of a wall based on the value of the electrostatic capacitance between electrodes.

Conventionally, there have been known capacitance-based liquid level sensors that detect the liquid level in a dielectric substance present inside a nonmetallic material body that forms a space, for example, a container that holds a liquid, based on changes in capacitance (see, for example, Patent Document 1 and Patent Document 2).

The proposal in the above-mentioned Patent Document 1 is to measure the storage level or amount of a tank container or the like containing a liquid or powder, etc., using a sensor body, and this sensor body is formed by arranging two membrane-like electrode bodies at a distance from each other between two films made of an insulating material, connecting lead wires to each of these two electrode bodies, and bonding the two films to each other to form a flexible sensor body. The lead wires connected to the electrode bodies are then connected to an electric circuit such as a signal amplifier. It is also described that a flexible signal processing electric circuit unit may be inserted and connected to the lead wires to form a flexible sensor body, and the detection signal may be processed in this sensor body.

This sensor body is used to measure the liquid level of objects the size of irregular containers or glass bottles, and the detection signal detected by the sensor body is connected to an electrical circuit such as a signal amplifier for signal processing, but there is no description of the input voltage to the sensor body, the output signal, or the processing of those signals.

In the proposal of Patent Document 2, the liquid level sensor includes a sensor body and a sensor circuit, and the sensor body includes an insulating sheet made of a flexible material, a detection electrode formed on one side of the insulating sheet, a guard electrode formed on the other side facing the detection electrode and wide enough to include the area of the detection electrode, and a pair of ground electrodes formed symmetrically with respect to the detection electrode or guard electrode at a predetermined distance from either side of the insulating sheet, and detects the electrostatic capacitance between the detection electrode and the ground electrode and the guard electrode. In addition, the sensor circuit is connected to the sensor body, converts the electrostatic capacitance detected by the sensor body into an electric signal, and detects the liquid level by signal processing the electric signal.

This liquid level sensor requires three electrodes to detect the liquid level in a container that holds the liquid based on changes in capacitance: a detection electrode, a guard electrode, and a ground electrode. The liquid level is also detected through a sensor circuit that converts the capacitance detected by the sensor body into an electrical signal and processes the signal, resulting in a complex and expensive sensor.

Patent Document 3 describes a device that detects concrete defects such as junks before the concrete hardens, applying a high-frequency current between a pair of side points on the outer surface of the formwork before and after pouring the concrete, measuring the capacitance of the concrete formwork and the outer part of the concrete, and detecting concrete defects inside the formwork based on the difference in capacitance. This detection method involves bringing both terminals of the device into contact with measuring points, but it only detects junks between the two terminals, which is a partial detection method.

The product described in Non-Patent Document 1 is a capacitance type liquid level sensor, in which a film-like electrode is attached to the outside of a tank made of resin or the like, and the level of the liquid inside the tank is detected by changes in capacitance. In this case, the maximum detection height is 250 mm, which is relatively low. The power supply voltage is a DC 12V/DC 245V DC power supply.

Furthermore, Non-Patent Document 2 describes a method in which a metal tape is attached to the outside of a container, the capacitance of the metal tape is measured with a capacitance sensor, and the capacitance value is converted into a change in water level (cm) to calculate the water level. The principle of detecting this change in water level is to use a capacitance sensor (Texas Instruments FDC2214) that captures the change in capacitance value at the resonant frequency, to cause LC resonance between an arbitrary capacitor and coil, and to capture the change in capacitance value associated with the change in dielectric constant occurring in the sensor part (metal part) as a change in resonant frequency.

This uses the detection principle that as the water level rises, the sensor's capacitance value increases and the resonant frequency decreases; however, as shown in the graph of the relationship between water level and capacitance value in the literature, this is only applicable to measuring water levels up to about 20 cm, and the measurement height is relatively limited.

Patent Document 4 also describes an interface measurement sensor for measuring the height of an interface of a measurement object, which has first and second electrodes that have a length corresponding to the measurement range in which the height of the interface is measured and are attached vertically to a structure into which the measurement object is introduced, and which calculates the capacitance between these electrodes and has a wireless tag that wirelessly transmits the calculated result to the outside.

In this case, the interface measurement sensor is installed in a direction extending vertically inside the formwork (a tubular structure such as a pile or pillar), and the object to be measured (e.g. concrete) is in direct contact with the level sensor for measurement.

In addition, in Patent Document 5, a level sensor consisting of a pair of electrode wires that are parallel to each other at a fixed horizontal distance and extend vertically and are covered with an insulating material is installed in the void inside the formwork, and as concrete is poured into the void, the rise height of the concrete poured into the void is calculated based on the change in capacitance that occurs between the pair of electrode wires according to the dielectric constant of the concrete.

In this case, the level sensor is installed extending vertically within the empty space inside the formwork, so the concrete comes into direct contact with the level sensor for measurement.

In Patent Document 6, a long and narrow level sensor consisting of a pair of electrode wires covered with an insulating material, whose detection amount changes depending on the length of contact with the concrete, is attached to the formwork surface installed inside the tunnel so that its longitudinal direction extends along the length or width of the formwork surface. When the level sensor comes into contact with the concrete, it detects the electrostatic capacitance generated between the pair of electrode wires depending on the relative dielectric constant of the concrete, and the height of the poured concrete is determined from this detection amount.

This level sensor is attached to the outside of the formwork, extending along its width, so the sensor makes direct contact with the concrete when making measurements.

JP 2007-303982 A JP 2013-167651 A JP 2005-300482 A JP 2011-174718 A JP 2012-172375 A JP 2019-78047 A

Kameoka Electronic Catalog (Capacitive Liquid Level Sensor CLA Series Internet <URL: https://www.ipros.jp/popup/download/catalog/?objectExpression=2-1447607&sourceObjectId=1447607&sourceObjectType=2&hub=45+bing>) Macnica ([IoT/M2M Exhibition 2017 Report] IoT PoV Verification Model Exhibition Corner Water Level Measurement Example Internet <URL: https://www.macnica.co.jp/business/semiconductor/articles/texas_instruments/122549/>)

The present invention aims to provide a non-contact height measurement method using capacitance that can measure the height level of a dielectric material on the opposite side of a wall based on the value of the capacitance between electrodes, and that can measure the height level of liquid or powder in a container up to a high height level without requiring a circuit to process complex electrical signals, and that can be manufactured at low cost and is easy to use.

The non-contact height measurement method using capacitance of the present invention has been developed to solve the above technical problems, and has the following features:

First, the non-contact height measurement method using capacitance of the present invention is a method in which a pair of electrode bodies connected to a conductor are arranged in close contact or spaced apart from each other at an interval on the outer side of a non-metallic material body having a space in the vertical direction, and the height of a dielectric material to be introduced into the non-metallic material body having a space is measured based on the value of the capacitance between the electrode bodies,
A measurement AC signal of an arbitrary measurement frequency is input to the pair of electrodes,
The impedance and phase angle between the electrodes are measured to calculate the capacitive reactance, and the value of the electrostatic capacitance is calculated, and the height of the dielectric material is obtained from the calculated value.
Secondly, in the non-contact height measurement method using electrostatic capacitance according to the first invention, it is preferable that the pair of electrode bodies is strip-shaped.
Thirdly, in the non-contact height measurement method using electrostatic capacitance according to the first or second invention, it is preferable that the measuring AC signal is in the range of 5 mVrms to 5 Vrms, and the measuring frequency is in the range of 1 KHz to 20 MHz.
Fourthly, in the non-contact height measurement method using electrostatic capacitance according to the first to third aspects of the present invention, it is preferable that an initial value of the electrostatic capacitance during measurement is set to a zero value.
Fifth, in the non-contact height measurement methods using electrostatic capacitance of any one of the first to fourth inventions, it is preferable that the non-metallic material having a space is a formwork, and the dielectric material introduced into the formwork is a cement-based material.
Sixth, in the non-contact height measurement method using electrostatic capacitance of any one of the first to fifth inventions, it is preferable that the non-metallic material body having the space is a formwork, and that the formwork is a formwork in which a height measurement formwork with a sensor in which the electrode body is attached and integrated with the non-metallic material body is connected to another formwork.
Seventh, in the non-contact height measurement method using electrostatic capacitance of any one of the first to sixth inventions, it is preferable that the pair of electrode bodies are elongated electrode bodies, and that a predetermined portion of the elongated electrode body in the longitudinal direction is formed wide.
Eighth, in any of the first to seventh inventions, in the non-contact height measurement method using electrostatic capacitance, it is preferable that a plurality of the pairs of electrode bodies are connected by a conductor.
Ninthly, in the non-contact height measurement method using electrostatic capacitance according to the fifth or sixth invention, it is preferable that the pair of electrode bodies are connected to each other by a connector at the connection portion of the formwork.
Tenthly, in any of the first to ninth inventions, in the non-contact height measurement method using electrostatic capacitance, it is preferable that the pair of electrode bodies is waterproof.
Eleventhly, in any of the first to tenth aspects of the present invention, in the non-contact height measurement method using electrostatic capacitance, it is preferable that data relating to the measurement is transmitted to a display device by a wireless communication device.
Twelfthly, in any of the first to eleventh aspects of the present invention, in the non-contact height measurement method using electrostatic capacitance, it is preferable that a numerical value or a chart of the height is displayed by a display device.

According to the non-contact height measurement method using electrostatic capacitance of the present invention, the height level of a dielectric substance such as a liquid or powder within a space formed by a non-metallic material body can be easily detected by a simple and inexpensive sensor placed on the outside of the non-metallic material body without the need for a circuit to process complex electrical signals, and can even be detected at relatively high height levels.

FIG. 1A is a schematic perspective view showing an embodiment of the non-contact height measurement method using capacitance of the present invention, in which the non-metallic material body forming the space is a square container and a pair of band-shaped electrode bodies are arranged on the same side of the container, and FIG. 1B is a top view of FIG. FIG. 1A is a schematic perspective view showing an embodiment of the non-contact height measurement method using electrostatic capacitance of the present invention, in which the non-metallic material body forming the space is a rectangular container and a pair of band-shaped electrode bodies are arranged on adjacent side surfaces of the container, and FIG. 1B is a top view of FIG. FIG. 1A is a schematic perspective view showing a height measurement situation when the non-metallic material forming the space is a circular acrylic pipe when viewed from above and the dielectric substance is water, and FIG. 1B is a graph showing the measurement results of the relationship between electrostatic capacitance and height measured using FIG. 1A. FIG. 1A is a schematic perspective view showing a height measurement situation when the non-metallic material forming the space is an FRP formwork and the dielectric substance is fresh concrete, and FIG. 1B is a graph showing the measurement results of the relationship between height and capacitance measured using FIG. 1A. FIG. 1A is a schematic perspective view showing a height measurement situation when the non-metallic material forming the space is a wooden formwork and the dielectric material is fresh concrete, and FIG. 1B is a graph showing the measurement results of the relationship between height and capacitance in FIG. FIG. 1A is a schematic front view of an embodiment in which an FRP formwork with an electrode body attached is used as a formwork for height measurement with a sensor, and FIG. 1B is a schematic oblique view showing an embodiment in which an FRP formwork with an electrode body attached as a formwork for height measurement with a sensor is connected to a wooden formwork as another formwork. FIG. 1A is a perspective view showing a height measurement situation when the non-metallic material forming the space is an FRP formwork used for the secondary lining of a tunnel and fresh concrete is poured as a dielectric material, and FIG. 1B is a cross-sectional view of FIG. 1A. 1A is a front view of an embodiment in which a pair of electrode bodies, consisting of a long electrode body and an electrode body with an electrode width increased at a specified position, are arranged to measure the height, and FIG. 1B is a graph showing the measurement results of the relationship between height and capacitance in FIG. 1A is a schematic front view showing an embodiment in which a pair of electrode bodies and a measuring device are connected by conductors, and FIG. 1B is a graph showing the measurement results of the relationship between height and capacitance in FIG. 1A is a schematic front view showing an embodiment in which a pair of upper and lower electrode bodies are vertically connected by a connector at the vertical connection portion of the upper and lower formwork, and FIG. 1B is an enlarged cross-sectional view of the connection portion of the electrode bodies in FIG. FIG. 13 is a top view showing an embodiment in which a pair of electrode bodies is waterproofed. 11 is a schematic perspective view showing an embodiment in which data measured by a measuring device is transmitted to a display device by a wireless communication device. FIG. FIG. 1 is an explanatory diagram of an embodiment in which the pouring height of concrete in the secondary lining of a tunnel is displayed on a monitor. This is a schematic oblique view showing an embodiment in which a height measurement formwork with multiple sensors, in which electrode bodies are attached in the vertical direction to the outside of each side of an FRP formwork, is connected between wooden formwork. FIG. 15 is an explanatory diagram of an embodiment in which the pouring height of the concrete in FIG. 14 is displayed on a monitor screen.

The non-contact height measurement method using capacitance of the present invention is a method in which a pair of electrodes connected to a conductor are arranged close together or spaced apart at a distance on the outer side of a non-metallic material body having a space, in the vertical direction, and the height of a dielectric material introduced into the non-metallic material body having a space is measured based on the value of the capacitance between the electrodes.

Below, one embodiment of the non-contact height measurement method using electrostatic capacitance according to the present invention will be described in detail with reference to the drawings. Fig. 1(a) is a schematic perspective view of the non-contact height measurement method using electrostatic capacitance according to the present invention, in which a pair of electrode bodies are strip-shaped and arranged on the same side of a container in which the non-metallic material body forming the space has a square shape, and Fig. 1(b) is a top view of Fig. 1(a). Note that the present invention is not limited to this embodiment.

The operating principle of the non-contact height measurement method using capacitance of the present invention is that an alternating current is applied between a pair of electrodes 11 separated by a distance and insulated by air, generating an electric field between the electrodes 11 and generating capacitance like a capacitor, and when a dielectric material 20 with a higher dielectric constant than air is introduced into this electric field, the capacitance increases.

The dielectric material 20 is not particularly limited as long as it has a high and measurable relative dielectric constant, and may be any of liquids, fluids, powders, etc., and specific examples include cement-based materials 22 such as fresh concrete and fresh mortar, and water. The material of the non-metallic material body 2 having a space is an insulator, and examples of organic materials include plastic, rubber, wood, leather, etc., and examples of inorganic materials include fine ceramics, glass, ceramics, refractories, cement-based materials, FRP, etc., as well as composite materials of these.

The input signal to the pair of electrode bodies 11 is a measurement AC signal of a predetermined frequency, and the impedance and phase angle between the electrode bodies 11 are measured to calculate the capacitive reactance, and the capacitance value is calculated using the following equation, and the height level of the dielectric material 20 is determined from this value.
X _C =1/(2πfC)
( _XC : capacitive reactance, f: frequency of AC voltage, C: electrostatic capacitance)
It is preferable that the measurement AC signal is 5 mvV to 5 vVrms and the measurement frequency is in the range of 1 KHz to 20 MHz. By setting the measurement frequency in a high frequency range, the detection sensitivity to electric field fluctuations is improved, minute changes in capacitance can be detected, and the device has relatively high resistance to noise and can suppress the effects of external interference and electromagnetic noise.

As the capacitance measuring device 3, an instrument capable of measuring the capacitance of an AC input signal, such as an LCR meter, multimeter, or impedance analyzer, can be suitably used. As the thickness of the nonmetallic material body 2 increases, it becomes more difficult to detect the capacitance, so it is considered that the thickness should be within a detectable range. Furthermore, the measurement data measured by the measuring device 3 can be displayed on the display device 5.

As shown in FIG. 1(b), a pair of electrode bodies 11 connected to conductive wires 10 are closely spaced apart on the outer side of a rectangular container as viewed from above, which is a non-metallic material body 2. When a dielectric material 20 is filled inside the rectangular container, the capacitance between the electrode bodies 11 increases as the filling height increases. This makes it possible to measure the height of the dielectric material 20 based on the capacitance value. In FIG. 1(a), the two conductive wires 10 are each connected to the upper ends of the pair of electrode bodies 11, but the connection to the electrode body 11 may be at any height position of the electrode, for example, the lower end of the electrode.

The electrode body 11 may be a conductive metal plate, and is particularly suitable for its light weight and thin plate or film shape made of copper, aluminum, or other materials. The electrode body 11 can be attached to the container by, for example, attaching it to the contact surface of the container side with double-sided tape or an insulating adhesive, or by using a conductive copper foil adhesive tape or a conductive aluminum foil adhesive tape with an adhesive applied to one side of the electrode body 11. It is desirable to protect the outer surface of the electrode body 11 by covering it with an insulating one-sided adhesive tape, for example.

A pair of electrode bodies 11 can also be formed on an insulator in advance. Specifically, for example, two plate- or film-shaped electrode bodies 11 can be arranged at a distance from each other on one side of a film made of an insulating material, or two film-shaped electrode bodies 11 can be arranged at a distance from each other between two films made of an insulating material to form a pair of electrode bodies 11 as a single body. In addition, the container may be made of a composite material as long as the contact surface with the electrode bodies 11 is the non-metallic material body 2. The film-shaped electrode body 11 may be formed on the film by printing, vapor deposition, or plating.

The conductor 10 may be a lead wire or a coaxial cable, and the lead wire may be a solid wire or a twisted wire. However, in the case of a lead wire, the higher the frequency, the more susceptible it is to the effects of electromagnetic waves coming from the outside. Therefore, when the transmission length is long, it is preferable to use a coaxial cable, which is used as a cable for transmitting high-frequency signals and is less susceptible to the effects of electromagnetic waves.

2(a) is a schematic perspective view of an embodiment of the non-contact height measurement method using capacitance of the present invention, in which the non-metallic material forming the space is a rectangular container, and a pair of strip-shaped electrodes are arranged on adjacent sides of the container, and FIG. 2(b) is a top view of FIG. 2(a). In the present invention, the pair of strip-shaped electrodes 11 can be arranged in a row on adjacent sides, rather than on the same side. In this case, too, by applying an alternating current between the pair of electrodes 11, which are separated by air and insulated from each other by a distance, an electric field can be generated between the electrodes 11, generating electrostatic capacitance like a capacitor. In addition, as long as the distance between the pair of strip-shaped electrodes is not too far and the electric field can reach them, the pair of strip-shaped electrodes 11 can be arranged on opposing surfaces.

The following are experiments (Experiments 1 to 3) for confirming the effects of the non-contact height measurement method using capacitance according to the present invention.
<Experiment 1>
3(a) is a schematic perspective view of a height measurement situation when the non-metallic material body 2 forming the space is an acrylic pipe that is circular when viewed from above, and the dielectric substance 20 is water. This acrylic pipe is cylindrical in shape, but if the pair of electrode bodies 11 are flexible band-like electrode bodies 11, it can flexibly accommodate tanks or containers of various shapes with curves, or objects that form a space such as objects in the shape of a formwork, and can detect the height level of the substance in the container.

Figure 3(b) is a graph showing the relationship between the water level and the capacitance when the dielectric material 20 in Figure 3(a) is water. The capacitance was measured under conditions of a measurement AC signal of 0.63 Vrms and a measurement frequency of 100 kHz. The capacitance at the start of the measurement was set to zero as the initial value, since the capacitance value is determined by the surrounding environment when the electrode body 11 was installed. The same measuring device was used in the following experiments, and measurements were made with the initial value set to zero.

The thickness of the acrylic pipe is 3 mm, and the width of the conductive copper foil tape can be appropriately determined according to conditions such as measurement accuracy and installation space restrictions, as the proportionality constant increases as the thickness is increased. In this experiment 1, a 20 mm width was used. The conductive copper foil tape used in this experiment 1 was also used in the following experiments. The measurement results showed that the capacitance increased almost in proportion to the water level, so measurements were taken up to a water level of 8 m. The proportionality constant was approximately 0.53 pF/cm.

<Experiment 2>
4(a) is a schematic perspective view of a height measurement state when the non-metallic material 2 forming the space is an FRP formwork 464 and the dielectric material 20 is fresh concrete 22. A structure to be constructed in civil engineering, construction work, etc. is constructed by installing a formwork 46 and pouring fresh concrete 22 into the formwork 46. At that time, the electrode body 11 is attached to the top and bottom of the outside of the formwork 46, and the pouring height of the concrete 22 is measured. The FRP (fiber reinforced plastic) formwork 464 has excellent heat retention compared to a steel formwork, has excellent peelability so that scraping work can be reduced, and has features such as the face plate 48 not rusting. In this experiment 2, four sides were formed with a formwork with a thickness of 6 mm, fresh concrete 22 was poured inside the formwork 46, and the relationship between the pouring height of the fresh concrete 22 and the electrostatic capacitance was investigated.

Fig. 4(b) is a graph showing the measurement results of the relationship between the pouring height and the capacitance in Fig. 4(a). From this measurement result, the capacitance increases almost in proportion to the pouring height of the fresh concrete 22 up to a height of 1.7 m, as in the case of the water level. The proportionality constant was about 0.32 pF/cm. The thickness of the FRP formwork 464 used in this experiment 2 was 6 mm.
<Experiment 3>

Figure 5(a) is a schematic perspective view of the height measurement situation when a wooden formwork 466 is used as the non-metallic material 2 forming the space and the dielectric substance 20 is fresh concrete 22, and Figure 5(b) is a graph showing the measurement results of the relationship between capacitance and height when fresh concrete is poured using Figure 5(a). According to the measurement results, the capacitance increases almost in proportion to the pouring height of the fresh concrete 22 up to a height of 1.7 m. The proportionality constant was approximately 0.27 pF/cm. The thickness of the wooden formwork 466 used in this experiment 3 was 12 mm.

From the results of Experiment 1 (Fig. 3(b)), Experiment 2 (Fig. 4(b)), and Experiment 3 (Fig. 5(b)), it was confirmed that the height level of the dielectric material 20 (water and fresh concrete 22) in a container made of a non-metallic material 2 can be measured in a non-contact manner by arranging a pair of electrode bodies 11 in close contact with each other at a distance from each other on the outside of the non-metallic material 2 of an acrylic pipe, an FRP formwork 464, or a wooden formwork 466, connecting conductors 10 and applying a predetermined AC voltage, measuring the capacitance and the impedance and phase angle generated between the electrode bodies 11, calculating the capacitive reactance, and calculating the value of the capacitance.

In addition, in experiment 2, an FRP formwork 464 was used as the formwork 46, and in experiment 3, a wooden formwork 466 was used, but the formwork 46 is not particularly limited as long as it is made of a non-metallic material, and for example, a transparent formwork, a plastic formwork, etc. can also be used. Note that a wooden formwork 466 is particularly suitable for use because it is easy to process, has a beautiful finish, and is generally inexpensive.

6(a) is a schematic front view showing an embodiment of the sensor-equipped height measurement formwork 463. In this embodiment, an FRP formwork 464 with an electrode body 11 attached thereto is used as the sensor-equipped height measurement formwork 463. In the sensor-equipped height measurement formwork 463 of this embodiment, the electrode body 11, which is the height detection unit, is attached and integrated with the FRP formwork 464, which is a non-metallic material body, and is used exclusively as the sensor-equipped height measurement formwork 463, and is configured to be connected to another formwork 465. More specifically, the electrode body 11 is covered with a protective material 467 such as an acrylic plate, or is protected by being in close contact with it. The frame 468 is provided with fastening holes 469 so that it can be fixed to another formwork 465 with bolts. By setting it in another formwork 465 and repeatedly measuring, the concrete pouring height can be functionally measured when pouring concrete at multiple locations or pouring concrete sequentially from the lower layer to the upper layer in a columnar structure such as an elevated bridge. The non-metallic material used for the sensor-equipped height measurement formwork 463 may be a non-metallic material other than the FRP formwork 464, and examples of such materials include wooden formwork, transparent formwork, and plastic formwork, and these may be used in appropriate combinations.

6(b) is a schematic perspective view showing an embodiment in which the FRP formwork 464 to which the electrode body 11 is attached as the sensor-equipped height measurement formwork 463 in FIG. 6(a) and another formwork 465 are connected to each other at their sides. In this embodiment, the FRP formwork 464 to which the electrode body 11 is attached as the sensor-equipped height measurement formwork 463 and the wooden formwork 466 as the other formwork 465 are connected to each other at their sides, and the electrode body 11 is attached above and below the outside of the FRP formwork 464. In this embodiment, it is preferable to prevent the joints between the FRP formwork 464 and the wooden formwork 466 from shifting. Specifically, for example, a single pipe can be fastened with a home tie, or in order to tighten more reliably, a fastening hole 469 can be provided at the connection portion 471 of the FRP formwork 464 and the wooden formwork 466 to fix with a bolt or clamp it. To make the joints more waterproof, waterproof tape can be applied to the joints between the FRP formwork 464 and the wooden formwork 466, or a seal can be placed between the joints. In this case, it is preferable to apply a waterproof sealant to the frame 468 of the FRP formwork 464 in advance.

Below is a detailed description of an embodiment in which the non-contact height measurement method using capacitance of the present invention is applied to tunnel construction.

Figure 7 (a) is a perspective view showing the height measurement situation when the non-metallic material 2 forming the space is an FRP formwork 464 used for the secondary lining of the tunnel 4, and fresh concrete 22 is poured as the dielectric material 20. In the embodiment of the secondary lining of the tunnel 4, the electrode body 11 is attached in the circumferential direction toward the tunnel top end 41 on the inside of the FRP center 44, and the conductor 10 connected to the electrode body 11 is aligned along the longitudinal direction of the tunnel 4 from near the ceiling of the center 44, and is connected to the measuring device 3 and the display device 5 outside the gable formwork side 43 for measurement and display. The electrode body 11 is attached to the center 44 in close contact with the inner surface of the center 44. The ribs and other components of the center 44 may be machined, such as by drilling holes, to be in close contact with the center 44.

Fresh concrete 22 is poured into the concrete pouring space 21 between the waterproof sheet 42 and the center 44. Since the difference in pouring height will vary depending on the fluidity of the fresh concrete 22 being poured, the number of detection conductors 10 is determined according to the fluidity of the fresh concrete 22, but typically 2 to 4 are placed on each side of the tunnel 4.

Figure 7(b) is a cross-sectional view of Figure 7(a). The electrode body 11 is installed in close contact with the inner surface of the center 44 from bottom to top. In Figure 7(a), the conductor 10 extending from the ceiling of the center 44 to the gable formwork side 43 is connected to the measuring device 3, but this is omitted in Figure 7(b). Fresh concrete 22 is poured into the concrete pouring space 21 between the waterproof sheet 42 and the center 44, and as the concrete is poured in sequence upward, the capacitance increases as the concrete 22 is filled, and the filling height of the poured concrete 22 in the circumferential direction is measured based on this value.

At this time, it is taken into consideration that the relative dielectric constant of the fresh concrete 22 depends on the temperature, and the higher the temperature of the fresh concrete 22, the lower the relative dielectric constant, and the proportionality constant fluctuates slightly. In addition, when pouring the fresh concrete 22, if the pouring takes a long time depending on the pouring conditions, the water content of the fresh concrete 22 already poured in the lower part will decrease as the hardening progresses over time, and the proportionality constant between the height and the capacitance will fluctuate slightly. Therefore, when actually carrying out construction, the proportionality constant between the height and the capacitance of the fresh concrete 22 to be used, taking into account the characteristics such as the heat generation temperature and hardening time, can be found in advance, and reflected in the calculation of the actual height measurement.

8(a) is a front view of another embodiment, showing a case where a pair of electrode bodies 11 consisting of a long electrode body 11 and an electrode body 12 with a larger width at a predetermined position is arranged to measure the height. In this embodiment, the pair of electrode bodies 11, the electrode body 12 with a fixed height section in the center formed wide, is arranged to be located at a fixed point height on the side of the FRP formwork 464, so that it can be confirmed that the fresh concrete 22 is filled up to the position of the wide electrode body 12, and more accurate measurement can be performed. The long electrode body 11 has a width of 20 mm, and the short and wide electrode body 12 in the middle has a width of 80 mm and a length of 20 mm, and is attached at a position from 50 cm to 52 cm in height. It can also be applied to casting when the proportional constant changes due to the hardening of the cast concrete 22 when the casting time is long. The wide electrode body 12 can be installed in multiple places as necessary.

Figure 8 (b) is a graph showing the relationship between concrete height and capacitance in Figure 8 (a). The measurement results show a constant rate of increase from 0 to 50 cm in height, then the rate of increase increases from 50 to 52 cm, and returns to the previous rate of increase after about 52 cm. As a result, the change in the rate of increase at the 50 to 52 cm point confirms that concrete has been poured up to this height. From that point on, the height can continue to be measured based on the proportionality constant.

Figure 9 (a) is a front view of another embodiment, showing a case where a pair of electrode bodies 11 connected in multiples with a conductor 10 is arranged to measure the height. In this embodiment, a pair of short electrode bodies 11 connected in multiples are arranged at a fixed height on the side of the FRP formwork 464, and the height level of the material is measured intermittently. In this way, by arranging the short electrode bodies 11 at a fixed height, it is also possible to measure the height intermittently. The electrode bodies 11 are 80 mm wide and 20 mm long, and are attached at 10 cm intervals from a height of 10 to 60 cm. It can also be applied to pouring when the proportional constant becomes 9 due to the hardening of the poured concrete 22 when the pouring time is long.

Figure 9(b) is a graph showing the measurement results of the relationship between height and capacitance in Figure 9(a). In this measurement result, the capacitance does not increase when the height is 0 to 10 cm, increases when the height is 10 to 12 cm, and barely increases when the height is 12 to 20 cm, and then repeats the same situation up to a height of 70 cm. As a result, the capacitance increases every 10 cm, making it possible to measure the pouring height, albeit intermittently.

Figure 10 (a) is a front view of an embodiment in which a pair of upper and lower electrode bodies 11 are connected vertically by a connector 13 at the vertical connection part of the upper formwork 461 and the lower formwork 462. If the height of the formwork 46 is set to 1.8 m, and concrete is poured higher than that height, the upper formwork 461 and the lower formwork 462 are connected to raise the formwork and pouring is performed. In this case, in order to measure the pouring height, the upper and lower electrode bodies 11 can be connected at the connection part 47 of the formwork. The connection method is to connect the electrode bodies 11 attached along the top and bottom of the face plate 48 (back side) of the upper formwork 461 and the lower formwork 462 using the connector 13 at the location of the horizontal frame 482 where the upper formwork 461 and the lower formwork 462 are connected.

Figure 10(b) is an enlarged cross-sectional view of the electrode body connection part in Figure 10(a). At the connection part of the electrode body 11, the connector 13 is connected through the conductor 10 attached along the face plate 48 (back side) across the upper formwork 461 and the lower formwork 462 at the position of the horizontal frame 482 with respect to the vertical frame 481. In this way, the casting height is continuously measured at the connection part 47 of the formwork, but since the electrode body 11 is not as thick as the horizontal frame 482 at the connection part 47 of the upper formwork 461 and the lower formwork 462, when the casting part moves from the lower formwork 462 to the upper formwork 461, the thickness of the horizontal frame 482 is added to the height value at the part of the conductor 10 where the electrode body 11 is not connected.

Figure 11 is a plan view showing an embodiment in which the pair of electrode bodies 11 is waterproofed. It is believed that the capacitance of the pair of electrode bodies 11 will increase and cause an error in the height value if a dielectric substance such as water is attached to the electric field outside the non-metallic material body 2 that forms the space 21. It is therefore preferable to cover the periphery of the electrode body 11 with a waterproof enclosure 49. The waterproof enclosure 49 is placed at a certain distance from the electrode body 11, and an air layer, which is an insulator, is provided between them. The waterproof enclosure 49 also serves to prevent contact with other dielectric substances. It is also possible to attach a plate such as an acrylic plate directly to the copper sheet instead of the waterproof enclosure 49. In this case, the attachment method is to use double-sided tape or adhesive.

Figure 12 is a perspective view of an embodiment in which data measured by the measuring device 3 is transmitted to the display device 5 by the wireless communication device 6. This embodiment is for the case where the pouring height is measured and the filling of the tunnel top end 41 is detected in the secondary lining of the tunnel 4. The measuring device 3 connected to the conductor 10 is installed on the outside of the gable formwork side 43, and the measurement data can be wirelessly transmitted to the display device 5 of a personal computer or the like by the wireless communication device 6. By using the wireless communication device 6 in this way, communication in a narrow space can be changed from wired to wireless, eliminating the risk of cutting the conductor 10 and improving workability.

Figure 13 is an explanatory diagram showing the pouring height of concrete 22 in the secondary lining of tunnel 4 displayed on the screen of monitor 5. Here, a pair of electrode bodies 11 are attached to the inside of center 44 at three locations on the existing side, center, and end side, and are measured from above, below, left and right. The upper image in Figure 13 is a view of tunnel 4 from the side, and the lower image is a view of tunnel 4 from the cross section. By displaying and illustrating the height of poured concrete 22 in this way, the pouring situation can be visually grasped in real time. In this case, since the cross-sectional shape of tunnel 4 is arch-shaped, the relationship between the length of immersion of electrode body 11 in concrete 22 in accordance with the arch shape and the pouring height at that time is calculated in advance, and the pouring height can be calculated.

Figure 14 is a schematic perspective view of an embodiment in which a plurality of height measuring formworks 463 with sensors are attached to the outside of each side of an FRP formwork 464 in the vertical direction and connected between wooden formwork 466. In this embodiment, when the pouring area is large and the pouring height at multiple positions is to be known, the parts close to the formwork can be grasped at the same time. In addition, when pouring is performed by switching valves using piping rather than pouring by moving the boom of a ready-mixed concrete pump vehicle, the pouring height of the concrete at the pouring location can be known, so the timing of each valve switching can be grasped in a timely manner. Here, a pair of electrode bodies 11 are attached to a total of eight places on the four sides of the FRP formwork 464 for measurement. In addition, the data can be transmitted by a wireless communication device 6 and displayed on a display device 5 such as a personal computer. The transmission destination may be within the work site where the concrete is poured, or to a distant office, etc.

Figure 15 is an explanatory diagram of an embodiment in which the pouring height of the concrete in Figure 14 is displayed on a monitor screen. In this embodiment, the pouring height at each of eight positions is displayed. By displaying this display on a large screen in the work site, those involved in the work can keep track of the progress of the concrete pouring, which can help with preparations for the next work, etc.

REFERENCE SIGNS LIST 10 Conductor 11 Electrode body 12 Wide electrode body 13 Connector 2 Non-metallic material body having space 20 Dielectric material 21 Concrete casting space 22 Cement-based material (fresh concrete)
3 Measuring device 4 Tunnel 41 Tunnel top end 42 Waterproof sheet 43 Gable formwork side 44 Center 45 Natural ground 46 Formwork 461 Upper formwork 462 Lower formwork 463 Formwork for height measurement with sensor 464 FRP formwork 465 Other formwork 466 Wooden formwork 467 Protective material 468 Frame 469 Fastening hole 47 Connection part of upper and lower formworks 471 Connection part of formwork for height measurement with sensor (FRP formwork) and other formwork (wooden formwork) 48 Face plate 481 Vertical frame 482 Horizontal frame 49 Waterproof enclosure 5 Display device (monitor)
6. Wireless communication device

Claims (9)

A method for measuring the height of a dielectric substance to be introduced into a non-metallic material body having a space based on a value of electrostatic capacitance between the electrodes, the method comprising the steps of: disposing a pair of electrodes connected to a conductor in close contact with each other or at a distance from each other at an outer portion of a non-metallic material body having a space in the vertical direction; and measuring the height of a dielectric substance to be introduced into the non-metallic material body having a space based on a value of electrostatic capacitance between the electrodes, the method comprising the steps of
The pair of electrode bodies are strip-shaped,
the non-metallic material body having the space is a formwork;
the dielectric material introduced into the formwork is a cement-based material;
Using a capacitance measuring device, a measurement AC signal having a measurement frequency in the range of 1 KHz to 20 MHz and 5 mVrms to 5 Vrms is directly input from the measuring device through a conductor to the pair of electrodes;
A non-contact height measurement method using capacitance, characterized in that the impedance and phase angle between the electrodes are measured to calculate capacitive reactance, a capacitance value is calculated, and the height of the dielectric material is determined by utilizing the fact that the capacitance value is proportional to the height of the dielectric material. A method for measuring the height of a dielectric substance to be introduced into a non-metallic material body having a space based on a value of electrostatic capacitance between the electrodes, the method comprising the steps of: disposing a pair of electrodes connected to a conductor in close contact with each other or at a distance from each other at an outer portion of a non-metallic material body having a space in the vertical direction; and measuring the height of a dielectric substance to be introduced into the non-metallic material body having a space based on a value of electrostatic capacitance between the electrodes, the method comprising the steps of:
The pair of electrode bodies are strip-shaped,
the non-metallic material body having the space is a formwork, the formwork being formed by connecting a sensor-equipped height measurement formwork in which the electrode body is attached to the non-metallic material body and integrated with the formwork to another formwork,
Using a capacitance measuring device, a measurement AC signal having a measurement frequency in the range of 1 KHz to 20 MHz and 5 mVrms to 5 Vrms is directly input from the measuring device through a conductor to the pair of electrodes;
A non-contact height measurement method using capacitance, characterized in that the impedance and phase angle between the electrodes are measured to calculate capacitive reactance, a capacitance value is calculated, and the height of the dielectric material is determined by utilizing the fact that the capacitance value is proportional to the height of the dielectric material. 3. A non-contact height measurement method using electrostatic capacitance according to claim 1, wherein an initial value of the electrostatic capacitance during measurement is set to zero. 3. A non-contact height measurement method using capacitance according to claim 1 or 2, characterized in that the pair of electrode bodies are long electrode bodies, and a predetermined portion of the long electrode body in the longitudinal direction is formed to be wide. 3. The non-contact height measurement method using electrostatic capacitance according to claim 1, wherein a plurality of pairs of the electrode bodies are connected to each other by a conductor. A non-contact height measurement method using capacitance as described in claim 1 or 2, characterized in that the formwork consists of an upper formwork and a lower formwork connected vertically, and the pair of electrode bodies are connected to each other by a connector at the connection between the upper formwork and the lower formwork. 3. A non-contact height measurement method using capacitance according to claim 1, wherein the pair of electrodes is waterproof. 3. The non-contact height measurement method using capacitance according to claim 1, wherein the data relating to the measurement is transmitted to a display device by a wireless communication device. 3. A non-contact height measurement method using capacitance according to claim 1 or 2 , characterized in that a numerical value or a chart of the height is displayed on a display device.