JP3049208B2 - Optical fiber pressure sensor using optical loss structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an optical fiber pressure sensor using the optical loss providing structure that can be regarded as an optical loss due to local bending of the optical fiber and converts the pressure of the fluid such as liquid or gas .

[0002]

2. Description of the Related Art An OTDR (Optical Time Domain Reflectometer) is used as a tester for measuring the loss distribution of an optical fiber.
Is widely used. In this method, an optical pulse is injected into an optical fiber, and of the scattered light generated in the optical fiber, the intensity of the light (backscattered light) returning to the incident end side is temporally sampled and measured. It is also called an area backscattered light measuring device. When the backscattered light is sampled with the time at which the light pulse was incident set to zero, the sampling delay time corresponds to the distance from the incident end to the place where the backscattered light is generated, and the intensity of the optical fiber to the corresponding place is measured. Respond to losses. Therefore, the loss distribution of the optical fiber can be expressed from the intensity distribution of the sampled backscattered light.

According to such a principle, if a mechanism for giving a loss to propagating light is provided at one or more points in the middle of an optical fiber by some physical quantity, in each case, the physical quantity at the one or more points is calculated. Can measure.

For example, in Japanese Patent Application Laid-Open No. 61-61038, a gas is sealed in a communication cable, and when the gas pressure in the cable is reduced due to an abnormality, the gas is pushed by a differential pressure between the reference gas pressure and the gas pressure in the cable. A device has been proposed in which an optical fiber is pushed into a recess with a rod, the optical fiber is bent, and the optical fiber is detected by a backscattered light detection device to detect an abnormality in the communication cable and its occurrence position.

[0005]

In the apparatus described above, the means for locally bending an optical fiber in accordance with a physical quantity will be described. The optical fiber is allowed to move freely, and when the optical fiber is pushed into the concave portion, it is impossible to always obtain a stable curvature and bending length due to the effect of loosening or loosening for the same event. Also, Japanese Patent Application Laid-Open No. 54-12217
No. 8 discloses a method in which a local bending is formed in an optical fiber by a pressure transmitting device by an applied pressure, and the pressure is measured by detecting a propagation loss of light in the optical fiber. It cannot be bent at a curvature, and a stable bending length cannot be obtained.

[0006] From such a viewpoint, it is deformed by pressure,
A structure is disclosed in which an optical fiber is wound in a coil shape around an elastic cylinder that is restored when pressure is released, and the optical fiber is bent with the deformation of the cylinder under pressure, and the pressure is detected from a change in light intensity. . However, since the curvature does not change stably, reproducibility of loss change is poor. In order to depart from such conventional technology, when repeatedly deforming the optical fiber, that is, when repeatedly applying optical loss to the optical fiber,
From the initial state in which no pressure is applied to the optical fiber, when a pressure of an arbitrary magnitude is applied within a limited range, a predetermined local bend is formed according to the applied force, and the pressure is released. Mechanism that restores the optical fiber to the initial state before pressure is not applied to the optical fiber.
It is desirable to use a fiber optic pressure sensor using an optical fiber .

[0007]

In order to solve the above-mentioned problems, a protrusion having a curved surface on a contact surface with an optical fiber is moved toward a stator having a concave curved surface facing the optical fiber, thereby forming a local portion on the optical fiber. In a light loss providing structure that bends and causes a change in transmission loss, an optical loss providing structure including a mechanism for constantly applying tension to the optical fiber is proposed. In addition, after the optical fiber is locally bent in the above-mentioned structure, a spring or the like is interposed between the protrusion and the support holding the protrusion in order to forcibly return the protrusion to the initial state. Then, an optical loss applying structure including a mechanism for forcibly returning the projection to the initial state is proposed. Next, the light loss imparting structure, the bellows for the reference fluid, and the bellows for the fluid to be detected, which are opposed to the bellows for the reference fluid, expand and contract by the differential pressure between the fluid to be detected and the reference fluid, and these bellows are connected. A connecting rod indicating the amount of movement corresponding to the amount of expansion and contraction of the bellows for the fluid to be detected due to a change in the differential pressure, and the amount of movement of the connecting rod changes the distance between the fulcrum and the operating point via the fulcrum to determine the amount of expansion and contraction. An optical fiber pressure sensor that detects a change in differential pressure between a reference fluid and a fluid to be detected as a change in loss of an optical fiber by combining a differential pressure-movement amount conversion unit including an operation plate that can be extracted as a movement amount is proposed. The remaining points will be described below.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an optical loss imparting structure is shown in Embodiment 1, and FIG. 1 (a), enlarged detailed views (b) and (c) of a circled portion in FIG. explain.

(Tension applying portion) FIG. 1C shows an inner tube 7 having a through hole 8 at the center of the cross section and a flange 9 at the center in the longitudinal direction, and an outer diameter of the inner tube 7 at the center of the cross section. An outer tube 10 having a larger through hole 11, an outer diameter equal to the outer diameter of the flange of the inner tube 7, and having a flange 12 at one end is prepared. The material of these cylindrical tubes may be either metal or plastic, and if a split type is used in the longitudinal direction, the assembling work becomes easy.

The optical fiber 2 used here is mainly a glass fiber of quartz and has a primary coating of a synthetic resin on its surface. As shown in FIG. 1 (b), an appropriate extra length is provided for the optical fiber 2, and the optical fiber 2 is passed through the through-hole 8 of the inner tube 7 and attached to the inner tube 7 using an adhesive or the like. It is fixed and integrated in the longitudinal direction. An inner cylinder in which a coil spring 6 having a diameter smaller than the diameter of the flange 12 and larger than the outer diameter of the cylindrical portion is mounted on the outer cylindrical tube 10 and the optical fiber 2 is fixed and integrated in this state. The tube 7 and the optical fiber 2 are inserted into the through hole 11 of the outer tube 10, one end of the coil spring is fixed on the flange 9 of the inner tube 7, and the other end is fixed on the tube portion of the outer tube 10. And connect them. Thus, a tension applying portion 5 circled in FIG. 1A is configured.

(Local Bending Forming Section) As shown in FIG. 1A, the surface has a predetermined convex curve in a direction orthogonal to the optical fiber 2 to be arranged, and penetrates the lower surface of the support 1. A projection 3 having legs 3 'which can be held and moved up and down, and a predetermined concave curve formed on the surface in a direction orthogonal to the optical fiber 2 in a direction orthogonal to the optical fiber 2 and fixed to the upper side of the support 1 opposite to the projection 3 The stator 4 has a local bend forming portion.

The tension applying portion 5 is positioned at a position penetrating one side surface of the support 1 in accordance with the horizontal line of the optical fiber 2 with respect to the local bend forming portion arranged on the support 1 as described above. The optical fiber 2 fixed to the support body 1 by the flange 12 of the outer tube and extending from the tip of the inner tube 7 of the tension applying portion passes between the opposed protrusion 3 and the stator 4 of the local bending portion. The projection 3 passes straight down in a state of being lowered, penetrates the other side of the support 1 and reaches the outside. At this time, the optical fiber 2
Is fixed by the fixing portion 13 in a state where tension is applied. In this case, the tension applied to the optical fiber 2 is between the other side fixing portion 13 of the support 1 and the inner tube 7. In this state, the front end of the optical fiber bending active portion according to the curves of the projection 3 and the stator 4 of the local bending forming portion is adjusted so as to be almost in contact with the optical fiber or to take a slightly distant position. If a coil spring having a different spring constant is applied, the tension changes.

According to the structure having the above-described structure, a local bend is formed in the optical fiber 2 due to the proximity of the protrusion 3 to the stator 4 due to the vertical movement of the protrusion, thereby imparting a change in transmission loss to the optical fiber 2. The optical fiber 2 is constantly tensioned in response to the vertical movement of the projection 3 and is maintained in a state of tension, and is maintained in a state where the projection 3 is applied. The quality of the reproducibility of the local bending shape produced by the stator 4 is extremely high. In FIG. 9, the relationship between the movement amount (mm) of the protrusion 3 and the transmission loss increase amount (dB) of the optical fiber was measured five times by the prototype device, and the measurement result by the repetition was the loss increase amount for the same movement amount. Is indicated by a black line, the range of variation (hereinafter the same in FIGS. 10 and 12) of the black line in the vertical direction is an extremely narrow range, that is, a small variation error and a high reproducibility.

(Embodiment 2) FIG. 2 shows an embodiment 2. The difference from the one shown in FIG. 1 is that the coil spring 14 is inserted into the support 1 at the position where the leg 3 ′ of the projection 3 penetrates outward on the lower surface of the support 1, and the threaded leg 3 ′ The position where the tip of the protruding member 3 contacts the optical fiber 2 is adjusted in a state where the nut 15 is screwed and the coil spring 14 is compressed. With such a configuration, when the protrusion 3 is located above by the additional force, and the additional force is released and descends, the descending force is caused by the own weight and the tension applied to the optical fiber 2 in the structure of FIG. However, in the case of this example, the elastic force acts on the projection 3 from the coil spring 14, and the projection 3 quickly returns to the original position without being affected by backlash.

Third Embodiment FIG. 3 shows a third embodiment. The difference from the one shown in FIG. 1 is that the local bend forming part in the one shown in FIG. 1 is arranged at two positions on the line of the optical fiber 2. According to this example, the optical fiber can be locally bent at each position to cause a change in transmission loss, and its use will be described later.

[0016] (Example 4) than on, have been described optical loss causing structures, it will now be described gas pressure sensor using the structure.

(Differential pressure-movement amount converter) FIG. 4 shows an example of this. In the figure, the structure disposed at the upper portion has already been described, and the differential pressure-movement amount converter is disposed below the structure. The movement amount generated by the differential pressure is transmitted to the projection 3 via the operation plate 29. Such a pressure sensor is applied, for example, to a monitoring device for fluctuation of insulating gas pressure of gas-insulated electric equipment. In the figure, a detected gas bellows 21 and a reference gas bellows 22, which are fluid bellows that expand and contract due to a differential pressure between the detected gas and the reference gas, are supported by a support 20, and the bellows 21 and 22 face each other. Connecting rod 2
Connect at 3. The detected gas pressure source 24 and the detected gas bellows 21, and the reference gas pressure source 25 and the reference gas bellows 22 are connected by pressure pipes 26, respectively. With such a configuration, as described later, the movement amount corresponding to the amount of expansion and contraction due to the change in the differential pressure of the bellows for detection gas is set to
By changing the distance between the fulcrum 28 and the operating point 30 of the operating plate 29 via the, the amount of expansion and contraction is taken out from the operating plate 29 as an arbitrary operating point moving amount.

A pin 27 is fixed to the connecting rod 23, a fulcrum 28 is set on the support 20 above the connecting rod 23, and the operating plate 29 is rotatably supported at a bending point of the operating plate 29 having an L-shaped cross section. . At this time, at the position where the operating plate 29 faces the pin 27, the end face of the operating plate 29 contacts the left side of the pin 27 in the drawing,
At a position facing the leg 3 ′ of the projection 3 of the local bending portion, the leg 3 ′ extends a predetermined length beyond the leg 3 ′, and when the operation plate 29 rotates about the fulcrum 28, the leg 3 ′ The end of the operating plate 29 has a length that does not come off. FIG.
An example is shown below. The operating plate 29 is a horizontal piece 3 that bends at right angles.
5, a vertical piece 36, and a support piece 37 extending in the direction parallel to the horizontal piece 35 from the middle of the vertical piece 36. The vertical piece 36 has a hole 33 formed in the center thereof. Through the support 23, at the position of the fulcrum 28, it is rotatably supported by the support 20 (FIG. 4) as described above. On the other hand, a hole is provided on the support piece 37, and around the hole, for example, a nut is fixed and a support rod 3 screwed with the nut is fixed.
8, the tip of the support rod 38 is brought into contact with the back surface of the horizontal piece 35, and the vertical height adjustment function by the rotation of the support rod 38 in the form of a thread groove (not shown) is used to adjust the height of the support piece 37. Although the horizontal piece 35 is in a small range, the height of the horizontal piece 35 can be adjusted by the bending elasticity of the horizontal piece 35, and at the same time, the horizontal piece 35 contacts the leg of the protrusion of the local bend forming part and rotates. It serves to reinforce the support piece 37 when giving. At the position behind the vertical piece 36 as shown, a nut 34 for setting the position on the connecting rod 23 is formed on the connecting rod 23 instead of the pin 27 of FIG. 4 described above. And is fixed so as to be in contact with the back surface of the vertical piece 36 in the figure. When the connecting rod 23 moves in the direction of the arrow, the vertical piece 36
, The end of the horizontal piece 35 rises while rotating upward.

In this embodiment, when the reference gas pressure and the detected gas pressure are equal and both bellows are in equilibrium,
And the operating plate 29 are just in contact with each other, and on the other hand, the operating plate 29 is in contact with or slightly apart from the leg 3 ′ of the projection 3 or its connection leg, and the pressure of the detected gas decreases. Then, the balance between the bellows is broken, and the connecting rod 23 moves to the left. By changing the distance of the operating point 30 of the operating plate 29 with respect to the leg 3 'of the projection 3 via the fulcrum 28, the amount of expansion / contraction can be taken as an arbitrary amount of movement of the operating point. Forming a moving amount conversion unit; The pressure sensor according to the present invention can be constructed by assembling the differential pressure-movement amount converter with the position of the leg of the protrusion of the light loss imparting structure facing the upper position of the operation plate of the differential pressure-movement amount converter. Is done.

FIG. 10 shows the results of measuring the relationship between the differential pressure (kgf / cm ² ) from the reference gas pressure and the increase in the transmission loss (dB) of the optical fiber using the prototype device. The transmission loss of the optical fiber hardly changes even after 600 repetitions of the measurement. Also,
The test was repeated 600 times in this manner, and it was confirmed that the optical fiber was not cut.

(Embodiment 5) Embodiment 5 is shown in FIG. FIG.
The difference from the above is that at a position surrounded by a circle on the upper side of the operation plate 29, a protrusion moving amplifying tool 31 using a snap action mechanism for the support 20 is disposed above the operation plate 29,
The lower end of the movable connecting rod 32 passing through the amplifying tool 31 is
And the upper end thereof is engaged with the leg 3 'of the projection 3 of the local bend forming portion or the connection leg thereof. Thus, the differential pressure-movement amount conversion portion including the projection moving amplifying tool is included. It can operate by forming. Thus, the lower end of the movable connecting rod 32 of the protruding member is opposed to the operating plate through the protruding member amplifying member. The snap action mechanism will be described with reference to FIG. As shown in the drawing, one end of the coil spring C and one end of the rod-shaped body B is supported between both fulcrums S and S ', and the connection point J is focused on. When an upward force is applied to the arrow shown in (a), the coil spring C is normally contracted without breaking its shape. In this way, the coil spring contracts and becomes linear between the two fulcrums S and S 'including the connection point J as shown in (b), but when a slight force is applied in the same arrow direction as before, the coil spring C is rapidly compressed. The state is released, the force of the coil spring C acts in an oblique direction, and the connection point J is rapidly displaced upward as shown in (c). The protrusion amplifier has such a function of rapidly moving the connection point J. In FIG. 6, the associated movable connecting rod 32 is rapidly moved upward.

As described above, the axle moving amount amplifying tool 31 is mounted on the upper side of the operating plate 29, and the lower end of the movable connecting rod 32 facing the operating plate 29 comes into contact by the rotation of the operating plate due to an increase in the differential pressure. The connecting rod 32 slightly rises due to an upward force on the movable connecting rod 32, and the amplifying tool 31 expresses a snap action function, rapidly raises the connecting rod 32, and connects the protrusion 3 connected thereto. (See FIG. 4) rises, giving the optical fiber local bending with large transmission losses. Although not shown, at the monitoring position where the optical fiber is wired, an abnormality can be immediately alerted by the time domain backscattered light measuring device (OTDR).

In this case, a snap action mechanism is used to move the protrusion, and the optical fiber is not moved except at an operating pressure at which an alarm is generated by adjusting the gap between the operating plate and the movable connecting rod in advance. Since it is possible to prevent an increase in transmission loss from occurring, it is possible to reliably determine an abnormal alarm. Further, at the time of the monitoring, a distributed monitoring method in which the pressure sensors are arranged in series is possible, and an abnormal pressure at the positions where a plurality of sensors are arranged can be detected with a single fiber. FIG. 11 shows the results of a test performed by a test apparatus by setting the agitator movement amount amplifying device to operate when the differential pressure from the reference gas pressure is reduced to −0.38 kgf / cm ² · G. However, the results were extremely good after 5 repetitions.

(Embodiment 6) Embodiment 6 is shown in FIG. Although the light loss imparting portion structure is omitted, in this example, each protrusion of the structure including the two local bend forming portions as shown in Embodiment 3 is connected to one of the differential pressure-movement amount converting portions. Although the one that is opposed to one of the operating plates is shown, the one near the fulcrum 28 is of the type that uses the axle moving amount amplifying tool 31 by the snap action mechanism already described in the fifth embodiment. On the other hand, the one on the side farther from the fulcrum is of a type in which the operating point changes its operating point due to the rotation of the operating plate 29 during operation, and always gives a local bending of the transmission loss to the optical fiber by the protrusion in response to the change in the differential pressure. Things. The one in which the axle moving amount amplifying tool 31 is engaged with the apron by the movable connecting rod 32 is provided between the horizontal position of the operation plate, that is, the lower end of the movable connecting rod 32 connected to the prong at the gas pressure equilibrium position. Are set so as to form a predetermined gap. When set in this way, the differential pressure between the bellows increases during operation, and when the operating plate rotates around the fulcrum, there is a gap during the initial period. Without, the operating plate in contact with the lower end of the movable connecting rod in a specified abnormally decompressed state or in advance thereof,
When the differential pressure exceeds the specified differential pressure, the axle movement amplifying device operates, and the axle rises rapidly and gives a small local bend to the optical fiber facing the stator, that is, a bend with a large transmission loss. The transmission loss suddenly increases, and the monitoring station alerts this as a gas pressure abnormality. On the other hand, as described in the fourth embodiment, the protrusion on the side not engaged with the protrusion moving amount amplifying tool has a function of constantly monitoring the pressure reduction state in an analog manner as described in the fourth embodiment. Accomplish. However, those with and without the axle moving amount amplifying device adjust the operation setting conditions in advance, and those without the axle moving amount amplifying device have a differential pressure from zero to at least an abnormally reduced pressure in an analog manner. It must be measurable. FIG. 12 shows an example in which the test is repeated five times by the prototype device of this embodiment. Looking at this graph, a pressure change is observed, and it is possible to cope with the prediction of occurrence of an abnormality.In the event of an abnormal pressure, the agitator moving amount amplifying device by the snap action mechanism operates, so that the instantaneous operation is performed at the set alarm operating point. An increase in loss occurs, and abnormal alarms can be reliably identified.On the other hand, pressure differences at each position can be monitored in an analog state, and possible situations can be predicted. Can be dealt with by the alarm. In the above embodiment, the differential pressure between the reference gas pressure and the detected gas pressure is detected, but the differential pressure between the reference liquid pressure and the detected liquid pressure can be detected instead of gas.

[Brief description of the drawings]

FIG. 1 (a) shows an embodiment of a light loss applying structure according to the present invention, and FIGS. 1 (b) and 1 (c) show explanatory views of the configuration of a tension applying section.

FIG. 2A illustrates an embodiment of the present invention, and FIG. 2B illustrates a configuration explanatory view of a tension applying unit.

3A illustrates an embodiment of the present invention, and FIG. 3B illustrates a configuration explanatory view of a tension applying unit.

FIG. 4 shows an embodiment of an optical fiber pressure sensor using the optical loss applying structure of the present invention.

FIG. 5 shows an example of an operation plate used in the present invention.

FIG. 6 shows an embodiment of a pressure sensor using an optical loss applying structure provided with a protrusion operated by the snap action mechanism of the present invention.

FIG. 7 shows an embodiment of an optical fiber pressure sensor using a protrusion operated by the snap action mechanism of the present invention and an optical loss applying structure that is used in combination with a protrusion without a snap action mechanism.

FIGS. 8A, 8B and 8C are schematic illustrations of snap action mechanism operation.

FIG. 9 shows an operation characteristic (a relationship between a loss increase amount and a movement amount) of an example of the light loss imparting structure of the present invention.

FIG. 10 shows an operation characteristic (a relationship between a loss increase amount and a differential pressure) of an example of an optical fiber gas pressure sensor using the light loss imparting structure of the present invention.

FIG. 11 shows an operation characteristic (a relationship between a loss increase amount and a differential pressure) of an example in which a protrusion moving amount amplifying tool using a snap action mechanism is provided in the differential pressure-movement amount conversion unit of the present invention.

FIG. 12 is a diagram illustrating an example of an operational characteristic (a relationship between a loss increase amount and a differential pressure) in which a differential pressure-to-movement amount conversion unit according to the present invention is provided with and without a protrusion-amplifying device for a protrusion of a snap action mechanism. Is shown.

[Explanation of symbols]

Reference Signs List 1 support 2 optical fiber 3 protrusion
3 'leg of foot 4 stator 5 tension applying part 6 coil spring 7 inner tube 8 through hole 9 flange 10 outer tube 11 through hole 12 flange 13 fixing part 14 coil spring 15 nut 20 support 21 bellows for detected gas 22
Bellows for reference gas 23 Connecting rod 24 Detected gas pressure source 25
Reference gas pressure source 26 Pipe 27 Pin 28
Supporting point 29 Operating plate 30 Operating point 31 Lever movement amplifying tool using snap action mechanism
32 Movable rod

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideaki Nishima 1-3-1 Shimaya, Konohana-ku, Osaka-shi In the Osaka Works, Sumitomo Electric Industries, Ltd. (72) Inventor Takayuki Kawai 1 Higashi-Shinmachi, Higashi-ku, Nagoya Chubu Electric Power Inside the Company (72) Inventor Akinobu Miyazaki 2-4-2, Yokota, Atsuta-ku, Nagoya-shi Inside Chubu Electric Power Co., Inc.Chuo Transmission and Substation Construction (72) Inventor Manabu Yagi 2--24, Yokota, Atsuta-ku, Nagoya No. 72 Chubu Electric Power Co., Inc.Central Transmission & Substation Construction Plant (72) Inventor Takashi Tojo 1311 Aobadai, Tokorozawa-shi, Saitama Prefecture Sagimiya Manufacturing Co., Ltd. In-house (56) References JP-A-60-211405 (JP, A) JP-A-64-29727 (JP, A) JP-A-6-34401 (JP, A ) JitsuHiraku flat 2-37394 (JP, U) JitsuHiraku flat 3-102672 (JP, U) (58 ) investigated the field (Int.Cl. ^7, DB name) G01L 11/02 G01L 1/24

Claims (3)

(57) [Claims] 1. A projection having a curved surface in contact with an optical fiber.
Moving the stator in the direction of the stator with the opposite concave curve
Causes the optical fiber to bend locally, causing transmission loss.
An optical loss providing structure for generating
Optical loss applying structure with tension applying part to apply tension to the rivet
When, The bellows for reference fluid and the fluid to be detected facing the bellows
Between the bellows to be detected that expands and contracts due to the differential pressure between
Connected by a connecting rod, and the moving amount of the connecting rod is
Change the amount of expansion and contraction by changing the distance between
Difference consisting of an operating plate that can be taken out as a point movement
A pressure-movement amount conversion unit, The legs of the protruding member are disposed so as to be opposed to and close to the operation plate.
An optical fiber pressure sensor. 2. A projection having a curve on a contact surface with an optical fiber.
Moving the stator in the direction of the stator with the opposite concave curve
Causes the optical fiber to bend locally, causing transmission loss.
An optical loss providing structure for generating
Optical loss applying structure with tension applying part to apply tension to the rivet
When, The bellows for reference fluid and the fluid to be detected facing the bellows
Between the bellows to be detected that expands and contracts due to the differential pressure between
Connected by a connecting rod, and the amount of movement of the connecting rod is
Change the amount of expansion and contraction by changing the distance between
An operation plate that can be taken out as a point movement amount and the operation
It is placed above the plate, and the lower end of the movable connecting rod is
Snap action mechanism that is placed facing and close to
A differential pressure-movement amount conversion unit including
With The other end of the movable connecting rod of the axle moving amount amplifying tool is a leg of the axle.
Optical fiber pressure sensor characterized by being engaged with
Sa. 3. A projection having a curved surface in contact with an optical fiber.
Moving the stator in the direction of the stator with the opposite concave curve
Causes the optical fiber to bend locally, causing transmission loss.
Two local bends cause transmission loss
A light loss imparting structure for extending the optical fiber.
An optical loss applying structure including a tension applying portion for applying a force, The bellows for reference fluid and the fluid to be detected facing the bellows
With the differential pressure between Between the expanding and contracting bellows
Connected by a connecting rod, and the amount of movement of the connecting rod is
Change the amount of expansion and contraction by changing the distance between
An operation plate that can be taken out as a point movement amount and the operation
It is placed above the plate, and the lower end of the movable connecting rod is
Snap action mechanism that is located opposite and close to
The differential pressure-movement amount conversion unit provided with the used
Prepared, The other end of the movable connecting rod of the axle moving amount amplifying tool engages with the leg of the axle.
The leg of the other head is opposed to and close to the operating plate.
An optical fiber pressure sensor, which is disposed.