JPS59109835A - Converter for engineering work - Google Patents

Abstract

PURPOSE:To attain a converter for engineering works which can detect the changed state of an object to be measured stably without the electric influence of noise, floating capacity, thunder, etc., by transmitting and receiving signals between a detecting part, which detects the deformation of a distortion causing body, and a measurer through an optical cable. CONSTITUTION:A primary diaphragm 8 which deforms in accordance with the distortion causing body and a secondary diaphragm 21 are allowed to face each other through a gap 9, and the reflected light, which is changed by the deformation of the secondary diaphragm 21 corresponding to the deformation of the diaphragm 8, from the diaphragm 21 of the irradiating light passing through an optical fiber bundle 14 from a light projector 18 is received by a photoelectric converter 19 through an optical fiber bundle 15. An electric signal corresponding to the distortion of the distortion causing body is outputted from the converter 19. By this constituting using optical fibers, the converter for engineering works is attained which can detect the changed state of the object to be measured stably without the electric influence of noise, floating capacity, the damage of thunder, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a civil engineering converter that is installed on objects to be measured, such as buildings and underground, and converts deformations thereof into electrical quantities and measures them.

Here, civil engineering transducers are, for example, inclinometers, earth pressure meters, friction force meters, displacement meters, load meters, reinforcing steel needles, water pressure gauges, etc., and the deformation (or behavior) of objects to be measured such as rock, soil, and concrete. ) is observed.

Conventionally, there is a Carlson type civil engineering converter as a converter used for such a purpose, and as an example, the configuration of a Carlson type soil pressure gauge will be explained with reference to FIG.

FIG. 1 is a schematic cross-sectional view of the Carlson type earth pressure gauge, in which a cable 1 connected to an external measuring device (not shown) is inserted into a steel cylinder 2 and passed through the cable 1. A lead wire 3 is connected via a terminal plate 4 to terminals 6 and 6' fixed to a steel frame 5.5'. One end of the steel frame 5 is fixed to the center of a secondary diaphragm, which will be described later, and the other steel frame 5' is fixed to a fixed part of the steel cylinder 2, and both steel bars 5°5 ' are arranged parallel to each other and close to each other. two terminals 6.6 and 6' on both steel bars 5 and 5', respectively;
Resistance wires 7, 7 forming the sensing part so as to intersect between 6'
' is hung. When earth pressure is applied to the primary diaphragm 8, the earth pressure is transmitted to the secondary diaphragm 10, which has a smaller pressure receiving area than the secondary diaphragm 8, via the mercury sealed in the gap 9. Then, the secondary diaphragm lO is displaced more than the -order diaphragm 8, and this displacement becomes the displacement of the steel frame 5 connected to the secondary diaphragm 10, and the distance between it and the fixed @@ shaft rod 5'. A relative shift occurs between the two. Due to this relative shift, the resistance wires 7 and 7' stretched between both terminals 6 and 6' are expanded and contracted, and the resistance of the resistance wires 7 + 7' changes, so the resistance change can be measured using an external measuring device. Detect and measure earth pressure. In order to prevent the resistance wires 7 and 7' from rusting due to long-term measurements, a small amount of air is added to the inner space 11 of the steel cylinder 2 with non-volatile oil that does not change easily over time. It is enclosed.

Next, a conventional earth pressure gauge using a strain gauge as a sensing part will be described with reference to FIG. 2, which shows a schematic cross-sectional view thereof. Incidentally, the same members (or portions) as in the embodiment shown in the first figure are given the same reference numerals, and their explanations will be omitted. In this conventional example, a strain gauge 12 is bonded to the inner surface of the secondary diaphragm 10 instead of using the steel frames 5, 5' and resistance wires 7, 7' shown in FIG. Therefore,
- The earth pressure applied to the secondary diaphragm 8 is transmitted through the mercury in the gap 9 to the secondary diaphragm 10 with amplified displacement, changing the resistance of the strain gauge 12 bonded on the secondary diaphragm 10. , the strain gauge 12
This constitutes a Wheatstone bridge, where it is converted into a signal corresponding to the earth pressure.

However, the conventional earth pressure gauges shown in Figures 1 and 2 above both use electrical elements such as resistance wires and strain gauges in the detection part, and also use electric cables to connect the detection part and the measuring instrument. However, since the wires are used for heating, there is a drawback that the resistance wires, electric cables, etc. are susceptible to poor insulation, disconnection, etc. due to moisture or external force. In particular, a problem unique to civil engineering converters is that most of the electrical elements mentioned above are placed outdoors, so they are easily damaged by lightning strikes, and civil engineering converters are mainly located underground or in concrete. Since the converter or cable is buried inside the converter, there is a major problem in that even if the converter or cable breaks down, it cannot be replaced. In addition, since civil engineering converters are generally installed at a location far from the measuring instrument and use long electrical cables (sometimes as long as 1-2) between them, the effects of internal resistance and stray capacitance of the electrical cables There was an unavoidable difficulty.

The present invention was made in order to solve the above-mentioned problems in conventional civil engineering converters, and its purpose is to have a simple configuration, extremely few failures, and to reduce the insulation loss in at least the converter and signal transmission cable. To provide a civil engineering transducer that is completely free from electrical influences such as noise, stray capacitance, and lightning damage, and can stably detect deformations in objects to be measured over a long period of time. be.

That is, in order to achieve the above object, the present invention includes an optical fiber cable consisting of a plurality of optical fibers, a projector and a photoelectric converter placed opposite to one end surface of the optical fiber cable, and the other end surface of the optical fiber cable. It is composed of a strain-generating body whose surface facing the other end surface is a reflective surface and which deforms according to the deformation of the object to be measured, and the reflective surface of the strain-generating body is used in the projector via the optical fiber cable. The deformation of the object to be measured is detected by projecting light onto the object and converting the reflected light from the reflective surface of the strain-generating body into an electrical quantity by the photoelectric converter via the optical fiber cable. It is characterized by what it did.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 3 is a sectional view schematically showing the configuration of an embodiment in which the present invention is applied to an earth pressure gauge. In FIG. 3, the same members as those shown in FIGS. 1 and 2 are designated by the same reference numerals, and their explanations will be omitted.

In the figure, ] 3 is an optical fiber cable as a signal transmission cable, which is made by converging a plurality of optical fibers (fibers), and one end is connected to at least an optical fiber bundle 14 for transmitting light and an optical fiber bundle 15 for receiving light. It is branched, and the other end is inserted into the steel cylinder 2 and fixed to the main body rigid part 16 by a fixing member 17. A light projector 18 such as an LED (light emitting diode) or tungsten lamp is attached to the end face of the light projecting optical fiber bundle 4 at one end of the optical fiber cable 13, either directly or via a condenser lens, a diaphragm (not shown), etc. The optical fiber bundle 15 for receiving light is placed oppositely (opposed to each other).
A photoelectric converter 19 such as a photo)-transistor QclS ((cadmium oxide) COD (charge transfer device) is mounted on the end face of the
Direct or condensing lens, aperture, filter (not shown)
It is opposed through etc. On the other hand, on the other end surface of the optical fiber cable 13, a secondary diaphragm 2 as a strain body is provided with a reflective surface 20 that is mirror-finished by plating or the like.
1 is placed opposite. The internal space 22 of the secondary diaphragm 21 is filled with inert gas such as crab gas to prevent the other end surface (light emitting/receiving surface) 23 of the optical fiber cable 13 and the reflective surface 20 of the secondary diaphragm 21 from becoming cloudy or oxidizing. Filled with gas and sealed.

Next, the operation of the embodiment having the above configuration will be explained with reference to FIGS. 3 to 6. Here, Fig. 4 is a diagram to explain a state in which no earth pressure is applied to the negative diaphragm, Fig. 5 is a diagram to explain a state in which a part of the diaphragm is affected by soil pressure, and Fig. 6 is a diagram to explain a state in which earth pressure is applied to a part of the diaphragm. FIG. 3 is a characteristic diagram showing the relationship between the amount of deflection of the secondary diaphragm and the attenuation ratio of the amount of light (ratio of the amount of received light to the amount of emitted light).

First, when earth pressure is not built up in the partial diaphragm 8 of the earth pressure gauge, neither the secondary diaphragm 8 nor the secondary diaphragm 21 is deformed, and both diaphragms 8 and 21 have a flat plate shape. Therefore, the beam emitted from the light projector 18 enters the light projecting optical fiber bundle 14 from the first surface, and is repeatedly reflected within the light projecting optical fiber of the optical fiber cable 13 until it reaches the other end surface 23. The light is transmitted and illuminates the reflective surface 20 of the secondary diaphragm 21. Since the cast-finished reflective surface 20 has a flat plate shape in this case, the light irradiated thereon is reversed by approximately 18 degrees and enters the other end surface (light emitting/receiving surface) of the optical fiber cable 13 again. The light is then repeatedly reflected on the inner surface of the light-receiving optical fiber, exits from one end face of the light-receiving optical fiber bundle 15, and enters the photoelectric converter 19, changing the resistance value of ads as a photoelectric conversion element, for example. Here, if the ratio (attenuation ratio) between the amount of light received by the photoelectric converter 19 and the amount of light projected by the light projector 180 is A, the value to this value indicates the maximum value when the earth pressure is not high.

Next, when earth pressure is applied to the secondary diaphragm 8 and the secondary diaphragm 8 slightly deflects, the pressure is transferred to the secondary diaphragm 21 using mercury sealed in the gap 9 as a transmission medium, as shown in FIG. causes a large deflection. Since the pressure receiving area of the secondary diaphragm 21 is smaller than the pressure receiving area of the -order diaphragm 8, the displacement due to the earth pressure is amplified and transmitted to the secondary diaphragm 21. At this time, the secondary diaphragm 21 liquid forms so that the reflected rotation bulges out toward the optical fiber cable 13, so that it is emitted from the projector 18 via the optical fiber cable 13 and from the other end surface 23. A part of the emitted light beam does not enter the inside of the optical fiber cable I3 due to the reflective surface 20, but leaks to the side. This amount of leakage corresponds to the amount of deformation of the secondary diaphragm 21. In other words, the amount of deflection of the secondary diaphragm 21 is inversely proportional to the amount of light received at the exit surface of the light-receiving optical fiber bundle 14, that is, the amount of light received by the photoelectric converter 19, and ultimately the amount of electricity obtained from the photoelectric converter 19.

Since it is known that the earth pressure and the deflection of the diaphragm are proportional, the soil pressure can be determined by measuring the ratio A between the projector and the amount of light received. FIG. 6 is a graph showing the relationship between the upper pressure and the damping ratio A, and the two are exactly inversely proportional.

However, it is desirable to have an even distribution with as little bias as possible. In addition, the reflective surface 20 in the secondary diaphragm 21
It is desirable to apply anti-reflection treatment, such as matte coating, to walls other than those in the room to eliminate measurement errors due to diffused reflection, flare, etc.

Furthermore, in the above-described embodiments, the light emitting optical fiber and the light receiving optical fiber are used separately, but the same optical fiber may be used for light emitting and receiving.

That is, a half mirror (or half prism) is disposed obliquely on one end surface side of the optical fiber cable 13, a light projector 18 for projecting a light beam to the optical fiber 13 is arranged behind it, and a light projector 18 is disposed on the side of the half mirror. A photoelectric converter 19 is disposed at , and the other end surface of the optical fiber 13 is configured to be opposed to the secondary diaphragm 21 as in the above embodiment. With this configuration, the beam emitted from the projector 18 hits the secondary diaphragm 21 via the half-mirror-single fiber cable 13, and the light beam reflected by the reflective surface 20 travels inside the optical fiber cable 13 again. The light travels backward, is reflected by a half mirror, and enters the photoelectric converter 19. Therefore, in this case, a beam splitter such as a half mirror is required, but since there is no need to branch the optical fiber cable into two systems, the optical fiber cable can be manufactured at low cost.

In addition, the converter of the present invention is not limited to the above-mentioned earth pressure meter, but can detect physical changes by converting them into electrical quantities by using the deflection of a plate such as a diaphragm. It is highly suitable as a civil engineering transducer to be buried or installed underground or in concrete structures, such as force meters, load meters, reinforcing bar gauges, water pressure gauges, etc.

As detailed above, according to the present invention, an electric element is used as a detection section for detecting deformation of a strain-generating body and a cable for transmitting a detection signal from the detection section to a measuring instrument installed at a remote location. Since it is not used, there is no risk of poor insulation due to moisture absorption in the detection section, damage caused by lightning, or the effects of stray capacitance of the cable, etc. Therefore, deformation of the temporary measurement target can be detected stably over a long period of time. Since there are almost no failures of the parts, I installed it underground or in concrete, etc., and spent the afternoon on it. It is suitable as an eye changer that cannot be replaced, and since the floodlight and photoelectric converter are usually placed in an observation room above the ground, they can be easily repaired or replaced even if one of them breaks down. A civil engineering converter that is easy to maintain and manage can be provided.

[Brief explanation of drawings]

Figure 1 is a schematic cross-sectional view of a conventional Carlson soil pressure gauge, Figure 2
The figure is a schematic cross-sectional view of a conventional strain gauge type soil pressure meter.
The figure is a cross-sectional view schematically showing the configuration of an embodiment when the present invention is applied to a soil pressure gauge, and Figures 4 and 5 are cross-sectional views for explaining the present invention in detail. Figure 5 shows the state where no earth pressure is applied, and Figure 5 shows the state where earth pressure is applied. Figure 6 is a characteristic diagram showing the relationship between the amount of deflection of the secondary diaphragm and the attenuation ratio of the amount of light that changes depending on the deflection. It is. 2...Steel cylinder, 8...Next diaphragm, 9...Gap, 13...Optical fiber cable, 14...Light emission Optical fiber bundle for use, 15... Optical fiber bundle for light reception, 16...
・・・・Main body rigid body part, 18...・・・Floodlight, 19
...Photoelectric converter, 20...Reflection surface, 2
1...Secondary diaphragm. Figure 7 Figure 2 Cause Figure 3 Figure 4 Figure 5 Figure G Earth pressure

Claims (3)

[Claims] (1) In a civil engineering converter that is installed on an object to be measured such as a structure or underground and converts the deformation into an electrical quantity and measures it, an optical fiber cable consisting of a plurality of optical fibers and a A projector and a photoelectric converter are placed opposite to one end surface of the cable, and a surface that is placed opposite to the other end surface of the optical fiber cable and faces the other end surface is a reflective surface and deforms according to the deformation of the object to be measured. The light projector projects light onto the reflective surface of the strain body through the fiber cable, and the reflected light from the reflection surface of the strain body is transmitted through the fiber cable to the photoelectric transformer. 1. A converter for civil engineering, characterized in that the deformation of the object to be measured is detected by converting the deformation into an electrical quantity using a heat exchanger. (2) The civil engineering converter according to claim 1, wherein the optical fiber cable has at least one end side of an optical fiber bundle made up of a plurality of optical fibers arranged in a light projection array and converged into one. (3) The civil engineering transducer according to claim 1, wherein the strain body is a thin film disc-shaped diaphragm.