1.
Extensometer with long base, tensioned optical fibre and bragg rating, and manufacturing process for this extensometer
Abstract
According to the invention, that relates particularly to monitoring of structures, part of the optical fiber (4) containing a Bragg grating (R) is arranged in a tube (16); this part is tensioned between the two ends of the tube; the ends of this part are fixed to the ends of the tube; this tube will be rigidly fixed to a host material (2).
Long base, stretched fiber-optic Bragg network extensometer and production method for same
US Patent 6,956,981/ Dewynter-Marty , et al./ October 18, 2005
Abstract
An extensometer including a base, a tensioned optical fiber, and a Bragg grating. The extensometer relates particularly to monitoring of structures. Part of the optical fiber containing the Bragg grating is arranged in a tube. This part is tensioned between the two ends of the tube. The ends of this part are fixed to the ends of the tube, and the tube is rigidly fixed to a host material.
3.
Bragg network extensometer and measurement device comprising at least one such extensometer
EP1992906 (A1) — 2008-11-19/ ROUGEAULT STEPHANE [FR] ; FERDINAND PIERRE [FR] (+1)
Abstract:
The sensor i.e. Bragg grating extensometer (2), has a Bragg grating (8) i.e. periodic refraction index disturbance zone, formed in an optical conductor i.e. optical fiber (10), which is integrated to a monolithic support (12) e.g. microtube, of a test body (13). An elastic unit i.e. helical spring (14), transfers displacement of a movable object i.e. contact wire, with amplitude reduced with respect to object displacement amplitude, to an end of the support. The spring is interposed between the support end and the object for permitting the sensor to monitor the displacement of the object.
4.
Temperature sensor and extensometer
Abstract
A thermometer and extensometer for cables and conductors is described. The travel time of one or more acoustic signals along a conductor is used to determine the temperature along the conductor and the length of the conductor. The acoustic frequency is selected to minimize temporal dispersion of the propagating acoustic energy. The technique can be used to measure the temperature and sag of an overhead power line, the temperature of the windings in a transformer, or the temperature of the central conductor in a coaxial power cable.
5.
Bragg network extensometer and method for the production of said extensometer
Applicant: COMMISSARIAT ENERGIE ATOMIQUE [FR] ; BUGAUD MICHEL [FR]
Publication info: WO0060312 (A1) — 2000-10-12
Abstract:
A Bragg network extensometer and a method for the production of said extensometer. The extensometer comprises an optical fiber (4) in which at least one Bragg network (R1 ... RN) is formed, in addition to a core (6) which encases the fiber and is buried in a host material (2). Two anchoring means (A1 ... AN) are provided for each Bragg network so that the proof body can be anchored in the host material. Said anchoring means are firmly connected to the core and are placed on each side of the Bragg network corresponding thereto. According to the inventive method, the core is formed around the fiber by co-extrusion. The invention is particularly suitable for use in surveillance of works of art.
6.
ULTRASONIC EXTENSOMETER
Abstract
An ultrasonic extensometer for measuring the elongation of a bolt or the like being tightened against structure which it fastens, the extensometer including a transducer magnetically coupled to one end of the bolt, a pulser/receiver for generating a periodic pulse signal which energizes the transducer that is subsequently energized by the echo pulse from the far end of the bolt to provide an echo signal which is received and amplified, indicating circuit means for detecting and providing a correct couple indication between the transducer and its associated bolt end, and measuring circuit means for displaying a variable duration meter signal responsively produced by the amplified echo signal and controlled in duration by a vernier signal responsively produced by the pulse signal after a predetermined delay which is adjustable to index the vernier signal a desired amount with respect to the meter signal so that when the bolt has been elongated the proper amount, the amplified echo signal then coincides with the indexing vernier signal and the duration of the meter signal is reduced to zero.
7.
Extensometer comprising a flexible sensing element and Bragg gratings
Abstract
Extensometer with flexible test specimen and Bragg gratings applied in particular to the monitoring of concrete structures, is configured to measure deformations of a host material and comprises at least one test specimen which undergoes linear bending stresses, and at least one Bragg grating formed in an optic fibre and fixed to the test specimen. The extensometer configured such that any deformation of the host material is transmitted to the grating via the test specimen. The extensometer also comprises mechanical means which transform deformation of the material into bending of the test specimen, which deforms the grating.
Horizontal extensometer
Abstract
Disclosed is a horizontal extensometer for measuring strain on specimens in cryogenic to elevated temperatures with zero frictional and activation forces. The extensometer has first and second elongate hollow arms which are adapted to pivot in relation to one another in response to the increase in length of a test specimen when a strain is applied thereto. An increase between the points of attachment on the specimen produces a corresponding decrease in length at the opposite ends of the two arms, thereby producing movement through a standard linear variable differential transformer. A connecting rod which is highly rigid in the Y-axis but readily flexible in the Z and X-axes is adapted to pass through the center of the linear variable differential transformer to a moveable core and produce a measurement of the differential. The extensometer also employs a unique clamping mechanism which substantially reduces error caused by external forces. The extensometer of the present invention has near zero hysteresis.
9.
US2814883 (A) — 1957-12-03 / STRIMEL ROBERT S
Abstract not available for US2814883
Multirange extensometer
Abstract not available for US2578066
Probe for an extensometer
Abstract
Disclosed herein are probes for mounting on an extensometer used in conjunction with a materials testing machine, and can be used in high temperature applications. Each probe includes a probe shaft with a tip and a probe support body mounted to a hollow shield tube over the probe shaft. The probe support body includes a tipped segment which is biased toward the tip of the probe shaft. A longitudinal axis passes through the tips and tipped segment, respectively. The hollow shield tube mounted over the probe shaft is made of a high temperature material having a low thermal conductivity coefficient. The sleeve prevents excessive temperature transients from affecting the probe shaft.
Externsometer
Abstract not available for US 3319338 (A)
High temperature extensometer system
Abstract
A high temperature extensometer system carries specimen contact rods of substantial length which pass through openings in a furnace to engage a specimen in such furnace. The rods are supported at the exterior of the furnace on a paralleogram linkage support frame made to provide an output indicating specimen strain as the contact rods separate and also made with parallel beams which shift so the rods can move differentially in longitudinally axial direction. The rods shift axially when the specimen and test loading grips shift in position, for example when the grips and specimen are initially heated.
14.
Extensometer
Abstract not available for US 2543429 (A)
15.
Extensometer
Abstract
A strain gage extensometer used for measuring uniaxial and biaxial strains in material test specimens. The extensometer is composed of two independent axial strain measuring sensors joined together by a resilient member which is instrumented to provide transverse strain data. All compliant, instrumented members are coupled to the deformations of the specimen, which thus causes strain in the instrumented members which is sensed by suitable strain gages and instruments. A special attachment mechanism is provided by the thin, parallel elements machined into one of the sensors.
16.
Extensometer
Abstract
An extensometer for detecting traumatized ligaments where the elongation of the ligament is either abnormally large or abnormally small compared to the elongation measured on a healthy ligament for an angle of flexion of the knee. The extensometer includes at least one flexible member having a strain gauge secured thereto to measure deflexion of the flexible member from its normal configuration. The flexible member has a free end and is secured at its opposed end to a support base. A clamping member is provided to retain the free end of the flexible member on a ligament while maintaining the support base substantially stationary with respect to the ligament whereby elongation of the ligament is detected by the deformation of the flexible member from its initial configuration.
Extensometer
Abstract
An extensometer capable of simultaneous measurement of axial strain and torsional deflection of a specimen subjected to axial or torsional load. A pair of gauge members define reference plane surfaces, one extending parallel and another extending perpendicular to the test axis. For each reference plane surface there is a follower capable of sensing only the component of relative displacement that lies in the direction normal to the reference plane surface. The sensed values of these followers represent relative axial and torsional displacement of the gauge members. The followers of the embodiment comprise cantilevers extending from ends fixed on one gauge member to ends biased against and freely riding upon the respective reference plane surfaces on the other gauge member. A calibration stand is also shown, comprising a two-part dummy specimen, the parts aligned to define a test axis. One dummy part, which is mounted for rotation on the axis and fixed against axial displacement along the axis, has a torque arm which a micrometer displaces to rotate the dummy part for calibration of the torsional sensing system of the extensometer. The second dummy part, which is fixed against rotation about the axis, is moved along the axis by a second micrometer for calibration of the axial strain sensing system of the extensometer. The parallelogram linkage of the embodiment employs resilient flexures. Clamps join the two gauge members when not in use.
18.
EXTENSOMETER
Abstract
A strain gage extensometer used for measuring and controlling strain in tensile tests, compression tests and fatigue tests on specimens. The extensometer has a pair of arms that are connected together with a flexible element. The arms are coupled to move with the specimen when the specimen is subjected to strain and thus cause a strain in the flexible element supporting the arms. Suitable strain gages are utilized on the flexible element so that the strain in the specimen can be determined. As shown, the arms are also coupled with a cross flexure element to stabilize the arms.
High-temperature extensometer
Abstract
The invention relates to an apparatus for the one-dimensional, highly precise measurement of extension at the surfaces of hot specimens. The working range extends from normal temperature to about 1800.degree. C., but measurements are also possible up to 2300.degree. C. With respect to atmospheric pressure, the application range extends from vacuum up to pressures of several bar. The high-temperature extensometer in accordance with the invention is distinctly more cost-effective than previous extensometers for hot test specimens, despite its considerably larger measurement range.
Averaging axial-diametral strain measuring extensometer
Abstract
An extensometer is used for measuring axial and diametral strains in a material test specimen. The extensometer comprises an assembly of extensometer sections positioned on diametrally opposite sides of the specimen with specimen engaging points spaced axially along the specimen. The extensometer assembly is arranged so that the two extensometer sections will average the axial strain measured by the two extensometer sections. Also, if desired, the two extensometer sections may provide an indication of the average change in diameter of the specimen at the location of the upper contact points and at the location of the lower contact points of the extensometer sections on opposite sides of the specimen. The support system between the extensometer sections provides for the necessary degrees of freedom to provide measuring only in the axis desired, and sufficient restraint in other axes to insure that accurate measurements are obtained.
EXTENSOMETERS
Abstract
Two pairs of specially shaped bar members are attached to either side of a specimen respectively in such a manner that pointers attached to the two bar members in each pair are caused to be relatively longitudinally displaced to an extent proportional to the specimen strain. The bar members are constrained so as to be capable of relative movement which takes place only in the direction of specimen strain. The two members of at least one pair thereof carry respective diffraction gratings through which a light source is arranged to direct a beam of light whereby to generate a moire fringe pattern. A photoelectric cell is provided for receiving at least a part of the fringe pattern. The cell is thus successively subjected to a plurality of light and dark bands which results in a plurality of electrical pulses proportional in number to the change in the gauge length.
EXTENSOMETER
Abstract not available for US 3514864 (A)
23.
EXTENSOMETER FOR LARGE DIAMETER RODS
Abstract not available for US 3614834 (A)
Extensometers
Abstract not available for US 3402472 (A)
25.
EXTENSOMETER FOR HIGH TEMPERATURES
Abstract:
The invention relates to a device for measuring a change in length of a sample, i.e. to an extensometer. The device comprises at least two measuring rods (1) disposed next to each other in a plane of measurement and received in separate first bearings (3) in a bearing block (5) so as to be rotatable about parallel first axes of rotation that extend at a right angle to the plane of measurement. The bearing block (5) is received in a second bearing (6) in a suspension (7) so as to be rotatable about a second axis of rotation that extends in parallel to the first axes of rotation. The device also comprises at least one measuring sensor for detecting a change in a distance between the measuring rods (1). The inventive device is characterized in that the measuring rods (1) are configured from a high-temperature resistant material having a low thermal expansion coefficient. The first bearings (3) and the second bearing (6) are configured as prismatic bearings. The inventive device allows to carry out measurements at high temperatures and high frequencies.
Extensometer
Abstract not available for CZ 18992 (U1)
Laser monitoring extensometer
Abstract:
The utility model relates to an improved type laser monitoring extensometer. When a steel plate and other metal plates are rolled, the elongation of the utility model can be monitored. The utility model is composed of two laser detector heads, two signal processors, a data processor, and a display unit. The detector heads of the utility model use a self correcting type light path, and namely the optic axis emitted by a laser device is perpendicular to the steel plate which is measured. An emitting lens is used as a receiving lens, a flat reflection mirror with 45DEG and an imaging lens are additionally arranged, the projection light path and the receiving light path are coaxial, and thereby, the receiving efficiency and the signal-to-noise ratio of signal light can be effectively improved. When the utility model is in use and does not need to adjust the optical path, the utility model has stable and reliable performance, and strong interference rejection, and the utility model is convenient for operation and maintenance.
Landslide early-warning extensometer
Abstract:
The utility model discloses a landslide early-warning tensometer, which comprises a cabinet and a built-in alarm circuit board, and further comprises an alarm loudspeaker and a power supply battery, wherein a band tape unit device is arranged in the cabinet, a measuring rule fixed head of the outermost end cap of the band tap unit is connected with a rope measuring unit which is used to detect on site, a vernier scale is arranged on a straight measuring rule segment of the band tap unit, a magnet is embedded in the vernier scale, an on-and-off switch in the alarm circuit is a group of tongue tubes, and the tongue tubes are arranged on the outer side of the vernier scale, a vernier scale fixing device is further arranged in the cabinet, which is arranged on the lower portion of the straight measuring rule segment, and an instrument protective casing is further added out of a landslide monitoring tensometer. The utility model is a group-measuring group-preventing monitoring and early-warning instrument used for abrupt geological hazards, and is mainly used to comprehensively control geological hazards.
Bragg network extensometer and measurement device comprising at least one such extensometer
Abstract:
The sensor i.e. Bragg grating extensometer (2), has a Bragg grating (8) i.e. periodic refraction index disturbance zone, formed in an optical conductor i.e. optical fiber (10), which is integrated to a monolithic support (12) e.g. microtube, of a test body (13). An elastic unit i.e. helical spring (14), transfers displacement of a movable object i.e. contact wire, with amplitude reduced with respect to object displacement amplitude, to an end of the support. The spring is interposed between the support end and the object for permitting the sensor to monitor the displacement of the object.
30.
A EXTENSOMETER FOR LARGE DIAMETER IN LOW TEMPARUTURE
Abstract not available for KR 20070046468 (A)
HIGH TEMPERATURE EXTENSOMETER WITH ADJUSTABLE GAGE LENGTH
Abstract not available for KR 20070044910 (A)
EXTENSOMETER
Abstract:
PROBLEM TO BE SOLVED: To provide an extensometer capable of accurately measuring extension over a range from a high-temperature region to a low-temperature region under simple constitution.
33.
THREE-POINT EXTENSOMETER
Abstract:
An instrument mounting system for repeatable field testing of equipment or other test object, comprising a frame and an inner surface defined at least in part by the frame. Exactly three object contact points are disposed upon the inner surface, the three object contact points defining a plane.
34.
OPTICAL LASER EXTENSOMETER BY USING LASER DISPLACEMENT SENSOR FOR MEASURING EXACT DISTANCE BETWEEN DIFFUSED REFLECTION TAPES BY MEANS OF LASER DISPLACEMENT SENSOR
Abstract:
PURPOSE: An optical laser extensometer by using a laser displacement sensor is provided to exactly measure the distance between diffused reflection tapes by maintaining a uniform velocity for a scanning speed through a laser displacement sensor. CONSTITUTION: An optical laser extensometer by using the laser displacement sensor includes a light source(11), a laser displacement light source, a condenser lens(12,14), a beam splitter(18), a double-sided rotation mirror(20), a laser displacement sensor(19), and a photodiode(16). The light source(11) generates light. The laser displacement light source detects laser displacement. The condenser lenses(12,14) condense the light. The beam splitter(18) splits the light in a desired direction. The photodiode(16) condenses reflected light. The double-sided rotation mirror allows a test sample to be scanned using the split light and provides light to the beam splitter if diffused reflection exists in the test sample.
EXTENSOMETER
Abstract:
PROBLEM TO BE SOLVED: To provide an extensometer capable of being easily attached to a test piece in a single step operation.
36.
Extensometer comprising a flexible sensing element and bragg gratings
Abstract:
This extensometer, applied in particular to the monitoring of concrete structures, is intended to measure deformations of a host material and comprises at least one test specimen ( 18 ) which undergoes linear bending stresses, and at least one Bragg grating ( 14 ) formed in an optic fibre ( 16 ) and fixed to the test specimen. Any deformation of the host material is transmitted to the grating via the test specimen. The extensometer also comprises mechanical means ( 20, 22 ) which transform deformation of the material into bending of the test specimen, which deforms the grating.
37.
Temperature-compensated extensometer
Abstract:
An extensometer having two spaced-apart mounting bases adapted to be mounted on a load-bearing structure with its axis of sensitivity intersecting the axis along which load-induced strains are generated at 45 DEG . The extensometer includes a pair of parallel links connecting the mounting bases through respective flexure hinges. In one embodiment, one of the links is also connected to one of the bases through an intermediate flexure hinge so that the link deforms responsive to relative movement applied between the bases along the axis of sensitivity. A strain gauge mounted on this link measures the magnitude of the deformation. In a second embodiment, a strain-instrumented measurement beam extends between the two links so that it deforms responsive to pivotal movement of the links as the mounting bases move in opposite directions along the axis of sensitivity. This embodiment of extensometer may be mounted on the load-bearing structure through three or more mounting points. In order to facilitate mounting of the extensometer on a structure without pre-straining the extensometer, a rigid plate may be connected to the extensometer through a plurality of pins, each of which extends from the plate through the extensometer at each of the mounting points. The pins terminate in a point and they are biased against the structure by a threaded fastener extending from the plate, through the extensometer, and into the structure.
38.
STRAIN GAGE EXTENSOMETER
Abstract not available for US 2921282 (A)
Extensometer
Abstract not available for US 2663085 (A)
Extensometer
Abstract not available for US 2543429 (A)
EXTENSOMETERS
Abstract not available for US 2744181 (A)
EXTENSOMETER COMPRISING A FLEXIBLE SENSING ELEMENT AND BRAGG GRATINGS
Abstract:
The invention relates to an extensometer comprising a flexible sensing element and Bragg gratings. The inventive extensometer, which is intended to measure deformations in a host material, is particularly suitable for monitoring concrete structures. The invention comprises at least one sensing element (18) which is subjected to linear bending and at least one Bragg grating (14) which is formed in an optical fibre (16) and which is fixed to the aforementioned sensing element. In this way, any deformation in the host material is transmitted to the grating by means of the sensing element. The extensometer also comprises mechanical means (20, 22) which transform a deformation in the material into a sensing element bending motion which deforms the grating.
43.
BOREHOLE ULTRA-LONG-TERM GROUND CREEP EXTENSOMETER
Abstract:
PROBLEM TO BE SOLVED: To solve the problem of the measurement of long-term ground displacement since the fracture of time dependency of the ground due to long-time stress, namely creep fracture, occurs through a certain determined creep deformation process of the ground and hence the stability of the ground can be evaluated and the fracture time of the ground can be predicted to some degrees by measuring the deformation of the ground for a long term and grasping a speed change in the movement of the ground, but the long-term displacement measurement of the ground that extremely slowly moves due to the ground creep cannot be made by the conventional technique. ; SOLUTION: Both the ends of a measurement probe are fixed to an immovable ground 1 and a movable ground 2 in a boring hole 4 by a grout 7, and the displacement between the fixing is measured with time by an optical fiber displacement sensor 8 built into the probe. The probe is made of stainless steel to withstand a long-term measurement, and a slide section is provided for expansion and contraction. Additionally, the conventional optical fiber sensor that has a high measurement precision and is rich in durability is used. ; COPYRIGHT: (C)2004,JPO
44.
TARGET OF NON-CONTACT EXTENSOMETER AND NON-CONTACT EXTENSOMEMTER
Abstract:
PROBLEM TO BE SOLVED: To provide a target of a non-contact extensometer suitable for being attached to a test piece to be used as a marked line for the optical displacement measurement, and especially for detecting the position without any influence of shifting and noise in the extending direction of the test piece. SOLUTION: This target M of the non-contact extensometer is formed by a pattern different in optical property from the surface of the test pieces, which has an elliptical edge shape taking the extension direction (longitudinal direction) of the test piece S as a minor axis and the direction (cross direction) orthogonal to the extension direction as a major axis. The center of gravity of the target M of the non-contact extensometer is obtained from a projective component in the major axis direction of the target M of the non-contact extensometer or in the direction right-angled to the direction of tensile load applied to the test piece in an image signal obtained by imaging the surface of the test piece.
45.
Optical extensometer and reference line mark therefor
Abstract:
A reference line mark for an optical extensometer of the invention has a mark main body with a boundary shape, in which a reflectance of light is different from other portions. The boundary shape is arranged such that when the mark main body is integrated in a direction perpendicular to the deformation direction under the condition that the mark is attached to a test piece, results of the integration constitute an isosceles triangle having a base in a deformation direction of the test piece. Thus, data points for obtaining edge portions of the mark can be increased, and error-free approximation can be available. Elongation of the test piece can be measured with high accuracy at high computing speed.
46.
CALIBRATION DEVICE FOR OPTICAL EXTENSOMETER
Abstract:
PROBLEM TO BE SOLVED: To provide a calibration device for an optical extensometer wherein error-less accurate calibration is performed at low cost. SOLUTION: With the calibration device, comprising a reference surface 1A which provides a length reference, under such condition as a test piece W (or a plate of the same thickness as the test piece W, held between holders 11 and 12 of a tester, a distance L between the reference surface 1A and a camera is equal to a distance L between a surface comprising a mark of the test piece W at actual measurement and the camera.; A calibrator for providing a length reference and a regulating means for regulating a fitting position of the calibrator to the tester are provided, and the regulating means is so configured as to move the fitting position of the calibrator by a half of tester's thickness relative to a position when a test piece's thickness is 0, according to the thickness or the test piece.
47.
REFERENCE LINE MARK BODY FOR OPTICAL EXTENSOMETER
Abstract:
PROBLEM TO BE SOLVED: To provide a reference mark body for optical extensometer, by which a reference line mark is prevented from becoming obscure owing to the influence of the deformation of a test piece without being affected by the ground of the test piece and a material. SOLUTION: A reference line mark pattern 11 is given to one face of a film 10. A first permanent magnet 2 is fixed to the back side. The film 10 is held by the test piece W by the suction force of the magnets 2 and 3 by sandwiching the test piece W with the first permanent magnet 2 and the second permanent magnet 3 which has a form almost similar to the magnet 2 and which sucks each other with the magnet 2. Since the film 10 is not adhered to the test piece W, it is prevented from deforming even if the test piece W is deformed and the clarity of the mark pattern 11 is maintained.
48.
OPTICAL EXTENSOMETER
Abstract:
PROBLEM TO BE SOLVED: To exert no influence on measurement of extension even if a marking seal to a test body by sticking a marking seal where a reference line is drawn on the surface, and an adhesive part is provided only on one side, taking the position of a reference line as a boundary on the backside in such a manner that the adhesive part is positioned in the end direction of the test body. SOLUTION: A set of marking seals 3 are stuck to the vicinity of the upper and lower ends of a test body. One lateral reference line 11 is drawn in the lower part of the approximately square marking seal on the surface of the marking seal 3. The background color is white or the like, and the marking line 11 is black. Paste or the like is applied to the upper side from the position of the reference line 11 on the surface, and this part serves as an adhesive part 12 in sticking the seal to the test body. As for the sticking of the marking seal 3 to the test body, a set of two seals are stuck near both ends of the test body. The respective sticking directions are such that the adhesive part 12 is positioned near the end of the test body, that is, near the chuck. The change in the position of the marking line 11 is measured by a television camera set or the like.
49.
OPTICAL EXTENSOMETER
Abstract:
PROBLEM TO BE SOLVED: To measure the elongation of a test piece of a rope composed of a fibrous material, etc., until the test piece is fractured even when the test piece rotates around its axial center due to a load. SOLUTION: An optical extensometer is provided with a reference line marker G for test piece composed of supporting frames 2 and 3 which are supported in a state where the frames 2 and 3 surround a test piece T in a plane perpendicular to the axial line of the test piece T by inserting and fixing the front ends of needles P1 and P2 into and in the test piece T and a reference line frame 1 which is put around the frames 2 and 3 and carries reference lines 1S on its outer peripheral surface. The elongation of the test piece T is measured by optically detecting the displacement of the optical image of the reference lines 1S of the marker G.
50.
OPTICAL EXTENSOMETER
Abstract:
PURPOSE:To measure the extension with high accuracy by a method wherein a light illuminating means is arranged on a test piece, a pair of index marks are formed by the light projected from the illuminating means, a pair of light index marks which move accompanying the extension of the test piece are detected by a photoelectric converting device, so that the extension is operated. CONSTITUTION:A pair of index marks are formed on a test piece TP by the light projected from a point light source 11. An optical axis of an image forming optical system 21b is agreed with an optical axis of the point light source 11 before starting a test. When the test piece TP is expanded by a material tester, the test piece TP is expanded and the point light source 11 is moved upward along with a fitting metal 10 accompanying the expansion of the test piece TP. A light image of the point light source 11 is formed on a line sensor 21a by the optical system 21b. A control circuit 24 moves an extensometer camera 21 upward so that the light image of the point light source 11 is always at the same position on the sensor 21a. The rotating amount of a pulse motor 23 is detected by a pulse encoder, from which the upward and downward moving amounts of the camera 21 are obtained. The difference of the moving amounts is calculated by the circuit 24, so that the extension of the test piece TP is obtained.
51.
OPTICAL EXTENSOMETER
52.
OPTICAL EXTENSOMETER
OPTICAL EXTENSOMETER
IMPROVEMENTS IN OR RELATING TO OPTICAL EXTENSOMETERS
EXTENSOMETERS
EXTENSOMETER
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