WO1988005905A1 - A measuring device for the determination of deformations, relative movements or the like - Google Patents

A measuring device for the determination of deformations, relative movements or the like Download PDF

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Publication number
WO1988005905A1
WO1988005905A1 PCT/NO1988/000006 NO8800006W WO8805905A1 WO 1988005905 A1 WO1988005905 A1 WO 1988005905A1 NO 8800006 W NO8800006 W NO 8800006W WO 8805905 A1 WO8805905 A1 WO 8805905A1
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WO
WIPO (PCT)
Prior art keywords
fiber
measuring device
sensor
sensor organ
deformations
Prior art date
Application number
PCT/NO1988/000006
Other languages
French (fr)
Inventor
Arne Berg
Original Assignee
Optoplan A.S.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Optoplan A.S. filed Critical Optoplan A.S.
Publication of WO1988005905A1 publication Critical patent/WO1988005905A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/08—Testing mechanical properties
    • G01M11/083—Testing mechanical properties by using an optical fiber in contact with the device under test [DUT]
    • G01M11/086—Details about the embedment of the optical fiber within the DUT
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
    • G01B11/18—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge using photoelastic elements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/24—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet
    • G01L1/242—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet the material being an optical fibre
    • G01L1/243—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet the material being an optical fibre using means for applying force perpendicular to the fibre axis

Definitions

  • a measuring device for the determination of defotmations, relative movements or the like for the determination of defotmations, relative movements or the like.
  • the present invention concerns a measuring device for the determination of deformations, relative movements or the like, and is more specifically directed towards a fiberoptic strain sensor which is particularly adapted to detection of cracks in or between constructions. These cracks may arise as a result of overload or movement between the constructions. Examples of constructions may be concrete platforms, dams, towers, tunnels, and so on.
  • the sensor described therein comprises a sort of roller chain with an optical fiber which has been run through all of the chain links, so that the chain when subjected to a tensile stress, imparts greater or less bending to the fiber along its length. Resulting variations in the optical characteristics of the fibe may then be measured by means of per se previously known techniques.
  • the novel and particular features of the measuring device according to the present invention consists primarily in that the sensor organ is integrated with an elastically deformable element which joins in the movements of the sensor organ and which is adapted to furnish a return force attempting to bring the sensor organ back to a normal position.
  • the solution indicated here implies that the described sensor principle may be utilized in many applications and for different purposes in a similar manner as sensors and transduce based upon other physical principles, i.e. with measuring parameters which may both increase and decrease.
  • the measuring device according to the invention will be particularly favourable when the sensor organ is essentially moulded into the elastically deformable element.
  • link element is shaped like a chain of per se quite common construction, the fiber having been run through every other link of the chain.
  • Such an ordinary and simple chain may be miniaturized to quite another extent than the previously known roller chain mentioned above.
  • the senor according to the present invention is based upon utilization of inexpensive available components, which are well suited for mass production.
  • the fiber is enclosed by a chain where the chain links are placed in such a manner that they will bend the fiber when the chain is stretche
  • cracks or strain may be detected.
  • the chain will resume its original shape because of the construction of the sensor.
  • the chain is tightly moulded inside an elastic material. This material pulls the chain back to -its initial position when the strain or load ceases.
  • the fiber bend (and consequently the chain strain) may be determined by measuring induced bending losses.
  • the losses may be detected by measuring the fiber light transmission.
  • the bend positions may be determined measuring the losses by means of an optical backscattering technique (OTDR) in a known manner
  • OTDR optical backscattering technique
  • Fig. 1 shows the principle of the device according to the invention, in a schematic and simplified manner
  • Fig. 2 shows an embodiment of the measuring device without strain
  • Fig. 3 shows an embodiment of the measuring device . with strain
  • Fig. 4 shows in principle how the sensor may be located in a concrete construction
  • Fig. 5 shows in a diagram how the cracks positions may be detected by means of fiber optics.
  • a fiber 1 is shown schematically located in a ho 2 which is enclosed by a chain with links 4A-3A-4B-3B-4C.
  • the hole is formed in a surrounding elastically deformable element 5 and passes through every other link 3A, 3B, etc.
  • These link will experience a change of angle in relation to the remaining links 4A, 4B, AC , which may bend the fiber 1 when the chain is stretched.
  • a normal position as shown in Fig. 2 it is thus assumed that the fiber takes an approximately straight course.
  • the hole 2 is formed during production by threading the chain in the desired formation onto a filament or thin rod wit the selected diameter Da of the hole.
  • the filament and the chain are thereafter moulded into an elastic material 5.
  • the material acts like a "spring” pulling the chain back to its initial position (the normal position) when the possible strai or load ceases.
  • the spring stiffness and the mechanical characteristics of the sensor are determined by the composition and design of the material.
  • That sensor organ which consists of the chain or link element and the optical fiber may according to the description above be regarded as integrated with the elastically deformabl element 5.
  • This element joins in the movements of the sensor organ and supplies the return or spring force which attempts t bring the sensor organ back to its normal position.
  • the particularly described embodiment with a complete in-moulding of the sensor organ inside the elastically deformable element 5, has for one thing the substantial advantage that the delicate sensor organ is well protected against mechanical and other damages.
  • the elastically deformable element One may envisage utilization of many different materials in the elastically deformable element, but in accordance with the invention materials with relatively small moduli of elasticity are preferred, especially materials of a rubber elastic character.
  • materials which is usable for many practical applications is a silicone material.
  • the material of the deformable element is light transparent or light translucent, which for one thing leads to that light emanating from the fiber in the bending points (the loss points) will be visible from the outside.
  • the purpose of having a hole of diameter DH which is greater than the fiber diameter DF is to create a non-linear sensor characteristic.
  • the fiber 1 will not be bent until the hole 2 touches the fiber on both sides (every other link) .
  • a minimum value is determined, which value must be obtained before the sensor gives an indication. This is desirable in a number of applications (alarm when cracks exceed a certain size) .
  • Fig. 2 shows a more practical appearance of the measuring device when unstretched (normal position) .
  • width B 1,3 mm
  • length L 2,0 mm
  • wire thickness T 0,4 mm
  • the chain links 13A-B, respectively 14A-C have a per se known and quite ordinary design, constructed for instance by thin wire as already indicated above. This renders possible a very high degree of miniaturization, which may be necessary for certain 'applications.
  • the length of the links is of the same size order as the cracks.
  • Small dimensions of the chain links giv the particular advantage that the local bends appearing in th fiber 11 have smaller radius of curvature and consequently amplified optical losses. This implies enhanced sensitivity.
  • Fig. 3 shows how the measuring device may appear when it is stretched.
  • the bending radius is determined by the strain and the dimensions of the links as well as the fiber.
  • the sensor characteristic may therefore be modified and optimized to the current application
  • Fig. 4 shows how a sensor 31 may be placed inside a concrete construction 20 with a surface 21 in order to detect cracks 24 and 26.
  • Reeinforce ent is indicated by 22.
  • An alar is important if the cracks are sufficiently big to reach the reinforcement 22.
  • the sensors may be manufactured for instance in a circular fashion (in cross-section) , and they may be concreted firmly directly in the concrete 20 or they may be glued inside a hole in the concrete which is adapted for that purpose.
  • Fig. 5 shows how to localize cracks by means of an optica backscattering technique (OTDR) .
  • OTDR optica backscattering technique
  • a short light pulse is transmitted into the fiber, and the backscattered signal reflects fiber losses.
  • the abscissa indicates time, i.e. also length along the fiber, while the ordinate indicates the backscattered signal on a logarithmic scale.
  • Th significant jumps at 41 and 42 in the displayed curve 40 represent bending losses in the fiber, for instance due to cracks which have developed in a concrete construction. Bending losses induced in the sensor may be localized when the fiber path and the light speed inside the fiber are known.
  • the optical fiber of the sensor organ in contrast to that which is shown in Fig. 2, has a normal position with a series of bends, the previously mentioned deformations or the like being arranged so as to more or less straighten out at least a few of the bends. In that case measurement will be done by detecting a reduction of present losses in the fiber.
  • the regular and preferred use of the measuring device is based upon a normal position as illustrated in Fig. 2, and with deformations of the sensor organ as a consequence of external tensile stresses as illustrated in Fig. 3.
  • the arrow 19 in Fig. 3 indicates the direction of those external tensile stresses to which the measuring device is sensitive.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

A measuring device for the determination of deformations, relative movements or the like, comprising a sensor organ consisting of a link element with a series of mutually movable links (13A-B, 14A-C), and an optical fiber (11) which has been run through links (13A, 13B) of the link element in such a manner that said link element when influenced by said deformations or the like, imparts to the fiber greater or less bending in points along the fiber. Consequently variations of the optical characteristics of the fiber arise, which variations may be measured by means of per se known techniques. The sensor organ is integrated with an elastically deformable element (15) which joins in the movements of the sensor organ and is adapted to furnish a return force attempting to bring the sensor organ back to a normal or initial position. The device finds a particular application area in detection of cracks in or between constructions, for instance in reinforced concrete.

Description

A measuring device for the determination of defotmations, relative movements or the like.
The present invention concerns a measuring device for the determination of deformations, relative movements or the like, and is more specifically directed towards a fiberoptic strain sensor which is particularly adapted to detection of cracks in or between constructions. These cracks may arise as a result of overload or movement between the constructions. Examples of constructions may be concrete platforms, dams, towers, tunnels, and so on.
Among previously known methods of fiber optic strain measurement, the method described in a comparatively theoretica fashion by Marvin and Ives in Applied Optics, Vol. 23, No. 23, December 1984, page 4212, may be cited as an example. The sensor described therein comprises a sort of roller chain with an optical fiber which has been run through all of the chain links, so that the chain when subjected to a tensile stress, imparts greater or less bending to the fiber along its length. Resulting variations in the optical characteristics of the fibe may then be measured by means of per se previously known techniques.
When utilizing the described principle in practical constructions for different purposes, certain problems arise, which have not been solved or which has not been hinted at at all in the Applied Optics article above. For one thing no other situations are described therein, than movement in only one direction, or only increasing deformation. It is further clear that the described particular roller chain constitutes a rather complicated and expensive construction, which not least will be difficult to implement in small dimensions, which may be desirable in many cases.
On background of the above the novel and particular features of the measuring device according to the present invention consists primarily in that the sensor organ is integrated with an elastically deformable element which joins in the movements of the sensor organ and which is adapted to furnish a return force attempting to bring the sensor organ back to a normal position. The solution indicated here, implies that the described sensor principle may be utilized in many applications and for different purposes in a similar manner as sensors and transduce based upon other physical principles, i.e. with measuring parameters which may both increase and decrease.
The measuring device according to the invention will be particularly favourable when the sensor organ is essentially moulded into the elastically deformable element.
Another substantial feature according to the invention consists in that the link element is shaped like a chain of per se quite common construction, the fiber having been run through every other link of the chain. Such an ordinary and simple chain may be miniaturized to quite another extent than the previously known roller chain mentioned above.
Thus the sensor according to the present invention is based upon utilization of inexpensive available components, which are well suited for mass production. The fiber is enclosed by a chain where the chain links are placed in such a manner that they will bend the fiber when the chain is stretche By measuring bending losses induced in the fiber, cracks or strain may be detected. When the strain is removed, the chain will resume its original shape because of the construction of the sensor. Preferentially the chain is tightly moulded inside an elastic material. This material pulls the chain back to -its initial position when the strain or load ceases.
The fiber bend (and consequently the chain strain) may be determined by measuring induced bending losses. The losses may be detected by measuring the fiber light transmission. The bend positions may be determined measuring the losses by means of an optical backscattering technique (OTDR) in a known manner
A closer specification of the measuring device as well as the novel and particular features according to the invention, have been included into the patent claims.
The invention shall be explained more closely in the following, referring to the drawings.where:
Fig. 1 shows the principle of the device according to the invention, in a schematic and simplified manner, Fig. 2 shows an embodiment of the measuring device without strain,
Fig. 3 shows an embodiment of the measuring device . with strain,
Fig. 4 shows in principle how the sensor may be located in a concrete construction, and
Fig. 5 shows in a diagram how the cracks positions may be detected by means of fiber optics.
In Fig.l a fiber 1 is shown schematically located in a ho 2 which is enclosed by a chain with links 4A-3A-4B-3B-4C. The hole is formed in a surrounding elastically deformable element 5 and passes through every other link 3A, 3B, etc. These link will experience a change of angle in relation to the remaining links 4A, 4B, AC , which may bend the fiber 1 when the chain is stretched. In a normal position as shown in Fig. 2 it is thus assumed that the fiber takes an approximately straight course. The movement of the chain when it is subjected to strain is determined by the dimensions of the links (B = width, L = length, T = wire thickness - Fig. 1, resp. 2) .
The hole 2 is formed during production by threading the chain in the desired formation onto a filament or thin rod wit the selected diameter Da of the hole. The filament and the chain are thereafter moulded into an elastic material 5. The material acts like a "spring" pulling the chain back to its initial position (the normal position) when the possible strai or load ceases. The spring stiffness and the mechanical characteristics of the sensor (flexibility, compression, etc.) are determined by the composition and design of the material.
After moulding the filament is pulled out and the fiber 1 is threaded into the formed hole 2. Another alternative is moulding the fiber directly in with the chain threaded onto th fiber.
That sensor organ which consists of the chain or link element and the optical fiber may according to the description above be regarded as integrated with the elastically deformabl element 5. This element joins in the movements of the sensor organ and supplies the return or spring force which attempts t bring the sensor organ back to its normal position. The particularly described embodiment with a complete in-moulding of the sensor organ inside the elastically deformable element 5, has for one thing the substantial advantage that the delicate sensor organ is well protected against mechanical and other damages.
One may envisage utilization of many different materials in the elastically deformable element, but in accordance with the invention materials with relatively small moduli of elasticity are preferred, especially materials of a rubber elastic character. An example of a material which is usable for many practical applications is a silicone material. Further, for certain purposes it may be suitable that the material of the deformable element is light transparent or light translucent, which for one thing leads to that light emanating from the fiber in the bending points (the loss points) will be visible from the outside.
The purpose of having a hole of diameter DH which is greater than the fiber diameter DF , is to create a non-linear sensor characteristic. The fiber 1 will not be bent until the hole 2 touches the fiber on both sides (every other link) . Thus, a minimum value is determined, which value must be obtained before the sensor gives an indication. This is desirable in a number of applications (alarm when cracks exceed a certain size) .
Fig. 2 shows a more practical appearance of the measuring device when unstretched (normal position) . The figure is enlarged since the dimensions of the disclosed fiber 11 are typically DF = 0,25 mm. The dimensions of each chain link
14A-C may for certain applications be typically: width B = 1,3 mm, length L = 2,0 mm and wire thickness T = 0,4 mm. A typical size of the hole 12 may be DH = 0,3 mm.
In the favourable practical embodiment in Fig. 2 the chain links 13A-B, respectively 14A-C have a per se known and quite ordinary design, constructed for instance by thin wire as already indicated above. This renders possible a very high degree of miniaturization, which may be necessary for certain 'applications. For the detection of small cracks, it is essential that the length of the links is of the same size order as the cracks. Small dimensions of the chain links giv the particular advantage that the local bends appearing in th fiber 11 have smaller radius of curvature and consequently amplified optical losses. This implies enhanced sensitivity. Those links I4A-C being located alternately on each side of th fiber 11 and pressing against the fiber when a stress is applied in the direction of the chain length, are located in the same plane as the drawing paper, while the links 13A and 13B inbetween are located in a plane which is perpendicular to the paper plane. This constitutes a very favourable configurat in cooperation with the fiber 11, which thereby is led in a natural manner through every other link 13A, 13B, etc. These chain links may be regarded to constitute hinges of the composite link element.
Fig. 3 shows how the measuring device may appear when it is stretched. One may clearly see how the fiber 11 is bent when it must comply to the position of the links. The bending radius is determined by the strain and the dimensions of the links as well as the fiber. The sensor characteristic may therefore be modified and optimized to the current application
Fig. 4 shows how a sensor 31 may be placed inside a concrete construction 20 with a surface 21 in order to detect cracks 24 and 26. Reeinforce ent is indicated by 22. An alar is important if the cracks are sufficiently big to reach the reinforcement 22. The sensors may be manufactured for instance in a circular fashion (in cross-section) , and they may be concreted firmly directly in the concrete 20 or they may be glued inside a hole in the concrete which is adapted for that purpose.
Fig. 5 shows how to localize cracks by means of an optica backscattering technique (OTDR) . A short light pulse is transmitted into the fiber, and the backscattered signal reflects fiber losses. In the diagram the abscissa indicates time, i.e. also length along the fiber, while the ordinate indicates the backscattered signal on a logarithmic scale. Th significant jumps at 41 and 42 in the displayed curve 40 represent bending losses in the fiber, for instance due to cracks which have developed in a concrete construction. Bending losses induced in the sensor may be localized when the fiber path and the light speed inside the fiber are known.
It must be realized that the present invention permits different variants and modifications within the framework of the specified solution as further indicated in the patent claims. One particular possibility exists where the optical fiber of the sensor organ, in contrast to that which is shown in Fig. 2, has a normal position with a series of bends, the previously mentioned deformations or the like being arranged so as to more or less straighten out at least a few of the bends. In that case measurement will be done by detecting a reduction of present losses in the fiber. However, the regular and preferred use of the measuring device is based upon a normal position as illustrated in Fig. 2, and with deformations of the sensor organ as a consequence of external tensile stresses as illustrated in Fig. 3. The arrow 19 in Fig. 3 indicates the direction of those external tensile stresses to which the measuring device is sensitive.

Claims

P A T E N T C L A I M S
1. A measuring device for the determination of deformations relative movements or the like, comprising a sensor organ consisting of a link element with a series of mutually movabl links (3A-B, 4A-C, 13A-B, 14A-C) , and an optical fiber (1, 11) which has been run through links of the link element in such manner that said link element when influenced by said deforma tions or the like, imparts greater or less bending to the fib in points along the fiber length, with a resulting variation the optical characteristics of the fiber, which variation may be measured by means of per se known techniques, characterize in that the sensor organ is integrated with an elastically deformable element (5, 15) which joins in the movements of th sensor organ and is adapted to furnish a return force which attempts to bring said sensor organ back to a normal position.
2. A measuring device according to claim 1, characterized i that the sensor organ is essentially moulded into the elastica deformable element (5, 15) .
3. A measuring device according to claim 2, characterized in that the elastically deformable element (5, 15) , in order to accommodate the fiber (1, 11) , has a through hole (2, 12) with larger cross-section than the fiber cross-section.
4. A measuring device according to claim 1, 2 or 3, charac¬ terized in that the elastically deformable element (5, 15) consists of a material of rubber elastic character.
5. A measuring device according to one of claims 1 to 4, characterized in that the elastically deformable element is transparent or translucent.
6. A measuring device according to one of claims 1 to 5, characterized in that the link element has the shape of a chai (13A-B, 14A-C) , and that the fiber (11) has been run through every other link (13A, 13B) of the chain.
7. A measuring device according to one of claims 1 to 6, characterized in that the optical fiber of the sensor organ ha a series of bends in its normal position and is adapted to, when subjected to said deformations or the like, having at least a few of said bends more or less straightened.
PCT/NO1988/000006 1987-01-29 1988-01-18 A measuring device for the determination of deformations, relative movements or the like WO1988005905A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NO870370 1987-01-29
NO870370A NO870370D0 (en) 1987-01-29 1987-01-29 Measuring device.

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0867688A2 (en) * 1997-03-25 1998-09-30 GLÖTZL GESELLSCHAFT FÜR BAUMESSTECHNIK mbH Displacement measuring device
CN102494629A (en) * 2011-12-16 2012-06-13 上海诚诚欣信息科技有限公司 Method and device for detecting transmission chain of assembling line

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3047308A1 (en) * 1979-12-21 1981-09-17 Honeywell Inc., Minneapolis, Minn. Optical fibre acoustic sensor - with optical fibre spiral embedded in low elasticity modules block
EP0118592A1 (en) * 1983-02-16 1984-09-19 Felten & Guilleaume Energietechnik AG Tensile strength cable incorporating an optical fibre sensor
US4488040A (en) * 1982-11-19 1984-12-11 Gte Products Corporation Fiber optic sensor
US4513200A (en) * 1983-01-24 1985-04-23 Occidental Research Corporation Fiber optic movement measuring sensor
EP0182030A1 (en) * 1984-11-14 1986-05-28 Felten & Guilleaume Energietechnik AG Traction force-sensitive optical fibre cable and its manufacturing process
DE3443949A1 (en) * 1984-12-01 1986-06-05 AEG KABEL AG, 4050 Mönchengladbach Light guide as force sensor

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3047308A1 (en) * 1979-12-21 1981-09-17 Honeywell Inc., Minneapolis, Minn. Optical fibre acoustic sensor - with optical fibre spiral embedded in low elasticity modules block
US4488040A (en) * 1982-11-19 1984-12-11 Gte Products Corporation Fiber optic sensor
US4513200A (en) * 1983-01-24 1985-04-23 Occidental Research Corporation Fiber optic movement measuring sensor
EP0118592A1 (en) * 1983-02-16 1984-09-19 Felten & Guilleaume Energietechnik AG Tensile strength cable incorporating an optical fibre sensor
EP0182030A1 (en) * 1984-11-14 1986-05-28 Felten & Guilleaume Energietechnik AG Traction force-sensitive optical fibre cable and its manufacturing process
DE3443949A1 (en) * 1984-12-01 1986-06-05 AEG KABEL AG, 4050 Mönchengladbach Light guide as force sensor

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Applied Optics, Vol. 23, No. 23, 1984, (DEAN C. MARVIN and NEIL A. IVES), "Widerange Fiber-Optic Strain Sensor", pages 4212-4217. *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0867688A2 (en) * 1997-03-25 1998-09-30 GLÖTZL GESELLSCHAFT FÜR BAUMESSTECHNIK mbH Displacement measuring device
EP0867688A3 (en) * 1997-03-25 1999-07-07 GLÖTZL GESELLSCHAFT FÜR BAUMESSTECHNIK mbH Displacement measuring device
CN102494629A (en) * 2011-12-16 2012-06-13 上海诚诚欣信息科技有限公司 Method and device for detecting transmission chain of assembling line

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