JP3458291B2 - Pressure fluctuation detector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure fluctuation detector, and more particularly to a pressure fluctuation detector for detecting pressure fluctuations of gas, liquid, etc. filled in a container.

[0002]

2. Description of the Related Art Conventionally, a Bourdon tube, a bellows or the like has been known as a detector for detecting the pressure of a gas, a liquid or the like filled in a container. Each of these detectors is a device that measures a pressure by converting a change in pressure into a mechanical displacement. For example, the Bourdon tube is a semi-circular tube with an elliptical or flat cross section. One end of the tube is closed, and when pressure is applied to the inside of this tube from the other end, the tip is displaced to measure the pressure. To do.

Such a detector is simple in structure, inexpensive, and highly reliable. However, these detectors have
It has the drawbacks that the pressure detection range is narrow and the speed of tracking changes in pressure is slow. In addition, since the pressure information obtained from these detectors is mechanical displacement, it is theoretically necessary to centrally manage the pressure information from many detectors and to transmit the obtained pressure information to a remote location. It is impossible for me.

Therefore, in recent years, a detector such as a strain gauge or a semiconductor gauge, which converts a pressure change into an electric displacement, has come into use. Such a detector is
The change in pressure is detected, for example, as a change in electric resistance or a change in capacitance. This type of detector has the characteristics of high detection accuracy and the ability to follow pressure fluctuations at high frequencies. Furthermore, since transmission to a remote location can be easily performed using a conductor cable, centralized control is possible. Etc. can be easily realized.

[0005]

However, in a detector such as a strain gauge or a semiconductor gauge that detects a pressure change as an electric change, a power source for driving these detectors is required, and an object to be detected is If the object is flammable or flammable, it is necessary to take safety measures.

Further, when the information detected by these detectors is transmitted by using the conductor cable, it is unavoidable that noise invades from the surroundings into the conductor cable or leakage of information from the conductor cable. It is also necessary to take safety measures against the effects of lightning.

Furthermore, the transmission of information by a conductor cable has a problem that transmission loss is large and long-distance transmission is difficult.

The present invention provides a pressure fluctuation detector capable of accurately measuring the pressure of a combustible or flammable object to be detected in a wide detection range and capable of following a pressure change at a high frequency. To aim. It is another object of the present invention to provide a pressure fluctuation detector that can transmit a detection result to a remote place without being affected by noise.

[0009]

According to the present invention, a pressure detecting means for detecting a pressure and generating a voltage signal corresponding to the pressure, a light source for generating light, and the light incident from the light source are provided. An optical modulator that modulates based on the voltage signal and emits modulated light, a photoelectric converter that converts the modulated light into an electric signal, and a pressure that determines the pressure based on the electric signal from the photoelectric converter. Measuring means, and the optical modulation hand
A stage, and an incident optical waveguide on which light from the light source is incident,
And an incident optical waveguide for emitting modulated light,
And the output optical waveguide are connected to each other in response to the voltage signal.
Two phase-shift optical waveguides with different refractive indices and
-Type optical waveguide for Mach-Zehnder interferometer
A pressure fluctuation detector characterized by being a waveguide element is obtained.

[0010]

The piezoelectric element generates a voltage signal according to the fluctuation of the pressure of the pressure detection object. The measuring range of the piezoelectric element is wide,
The ability to follow pressure fluctuations is also high. Further, since the piezoelectric element does not require a driving power source, it is possible to detect pressure even in a flammable or explosive atmosphere. The voltage signal from the piezoelectric element is supplied to the optical modulator, and the optical modulator modulates the light transmitted through the optical fiber according to the voltage signal and sends the modulated light back through the optical fiber. . The modulated light is converted into an electric signal by the photoelectric element, and the pressure of the detection target is obtained based on the electric signal.

Since the measurement result can be transmitted to a remote place using light, it is not affected by noise, information is not leaked, and lightning is not affected.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention. The pressure fluctuation detector of this embodiment includes a light source 11 (for example, a semiconductor laser) that generates light, a light source power source 12 that drives the light source 11, an input optical fiber 13 that transmits light from the light source 11, and an input optical fiber 13. An optical modulator 14 that modulates and outputs light from
Output optical fiber 1 for transmitting modulated light from the optical modulator 14
5, a light receiver 16 for converting the modulated optical signal from the output optical fiber 15 into an electric signal, a measuring device 17 for obtaining a pressure based on the electric signal from the light receiver 16, and a pressure detected by detecting the pressure of an object to be detected. It has a pressure detection element 18 for supplying a corresponding voltage signal to the modulation electrode of the optical modulator 14.

In the pressure fluctuation detector of this embodiment, the light source 11
The light emitted from is incident on the optical modulator 14 via the input optical fiber 13. On the other hand, the pressure detection element 18 generates a voltage signal according to the pressure of the object to be detected, and supplies this voltage signal to the modulation electrode of the optical modulator 14. The optical modulator 14 is
The intensity of the light from the light source 11 is modulated according to the voltage signal from the pressure detection element 18. The modulated light is the light modulator 1
4 and the light receiver 16 through the output optical fiber 15.
Incident on. The light receiver 16 converts the incident light into an electric signal according to its intensity and outputs the electric signal to the measuring device 17. The measuring instrument 17 performs signal processing on the input electric signal to obtain the pressure. Also, the calculated pressure is displayed.

In the pressure fluctuation detector according to the present embodiment, only the pressure detecting element 18 needs to be arranged in the container accommodating the object to be detected, and it is not necessary to supply electric power to the pressure detecting element 18. Even if the material is flammable or flammable, safety measures can be taken easily. Also,
The piezoelectric element can handle a wide measurement range and can also handle pressure fluctuations at high frequencies.

Further, in the pressure fluctuation detector of this embodiment, since the optical signal is modulated by using the optical modulator, the optical signal can be transmitted when transmitting the detection result to a remote place. The influence of noise can be eliminated and information leakage can be prevented. Furthermore, there is no need for safety measures against lightning on the transmission line.

The optical modulator 14 used in this embodiment is shown in FIG.
A detailed description will be given with reference. This optical modulator 14 uses, as a substrate 21, a lithium niobate crystal that exhibits an electro-optical effect.
An optical waveguide is formed on the surface to form a Mach-Zehnder optical interferometer. That is, the two phase shift optical waveguides 2 are provided between the input waveguide 22 connected to the input optical fiber 13 and the output waveguide 23 connected to the output optical fiber 15.
4 is formed, and the modulation electrode 25 is formed on the surface of the phase shift optical waveguide 24.

The light incident on the optical modulator 14 branches into two phase shift optical waveguides 24 and travels. Modulation electrode 2
Voltage signals from the pressure detection elements are supplied to the respective 5 to apply an electric field to the phase shift optical waveguide 24. Then, due to this electric field, the refractive index of the phase shift optical waveguide 24 changes. Therefore, the two phase shift optical waveguides 24
A phase difference occurs between the two optical signals passing through, and when they merge at the emission optical waveguide 23, they interfere with each other to become light having an intensity change depending on the voltage applied to the modulation electrode 25. The optical modulator has a length of 50 mm, a width of 3 mm, and a thickness of 0.5 mm.

Next, the pressure detecting element 1 used in this embodiment
8 will be described in detail with reference to FIG. The pressure detecting element 18 is a piezoelectric element in which electrodes 32 and 33 covering the entire surface are formed on the front and back surfaces of a piezoelectric element substrate 31 made of a lithium niobate crystal (polarized in the thickness direction) which is a piezoelectric material. A diaphragm 34 is attached to one electrode 32, and a base 35 is attached to the diaphragm 34. The electrodes 32 and 33 are provided with terminals 36 and 37, respectively, and these terminals are connected to the modulation electrode 25 of the optical modulator 14 described above.

In the pressure detecting element 18, when a pressure difference occurs between the front side and the back side, the diaphragm 34 is deformed. At this time, the piezoelectric element substrate 31 forming the piezoelectric element is also deformed, and a voltage signal is generated between the electrodes 32 and 33.
Therefore, if a gas having a reference pressure is filled in one of the front and back sides of the pressure detecting element 18, the pressure fluctuation on the other side can be taken out as a voltage signal. Further, the diaphragm can cope with a sudden pressure change.

Next, a second embodiment of the present invention will be described with reference to FIG. Here, the same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

The optical modulator 41 used in this embodiment is 2
A polarizing element 43 and a transparent electrode 44 are attached to the surface of each of the glass plates 42, and a liquid crystal 45 is sandwiched between them. In this optical modulator 41, the pressure detection element 18
When a voltage signal from the liquid crystal is applied to the transparent electrode 44, the liquid crystal 4
5 is oriented according to the voltage, and the light transmittance changes. As a result, the light that has entered the optical modulator from the input optical fiber 13 is intensity-modulated and then enters the output optical fiber.

As described above, also in the optical modulator 41 of this embodiment, the intensity of the light incident on the optical modulator can be modulated based on the pressure detected by the pressure detecting element. Therefore, the pressure fluctuation can be detected as in the first embodiment.

The input optical fiber 13 and the output optical fiber 15 may be plastic optical fibers.

Next, a third embodiment of the present invention will be described with reference to FIGS. Here, the same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.
The pressure fluctuation detector of this embodiment is the optical circulator 51.
And a reflection type optical modulator 52, and a polarization maintaining fiber 53 connecting them. An optical directional coupler may be used instead of the optical circulator 51.

The optical circulator 51 causes the light emitted from the light source 11 to enter the polarization-maintaining wave holding fiber 53 and causes the light from the polarization maintaining fiber 53 to enter the light receiver 16. The polarization maintaining fiber 53 also transmits the light from the optical circulator 51 to the reflective optical modulator 52 and the light from the reflective optical modulator 52 to the optical circulator 51.

As shown in FIG. 6, the reflection type optical modulator 52 includes a substrate 61 made of a lithium niobate crystal having an electro-optical effect, and an input / output waveguide 6 formed on the surface of the substrate 61.
2 and two phase shift optical waveguides 63 connected to the input / output waveguide 62, the modulation electrode 64 formed on the surface of the phase shift optical waveguide 63, and the phase shift optical waveguide 63 formed on the end face of the substrate 61. It has a total reflection film 65 that totally reflects the incident light.

Also in this reflection type optical modulator 52, as shown in FIG.
Similarly to the optical modulator 14, the light incident from the polarization maintaining fiber 23 branches from the input / output waveguide 62 into the two phase shift optical waveguides 63 and passes near the modulation electrode 64. Further, the light that has passed through the two phase shift optical waveguides 63 is reflected by the total reflection film 65, passes through the vicinity of the modulation electrode 64 again, and joins in the input / output waveguide 62. The light undergoes modulation in accordance with the voltage signal from the pressure detection element 18 when passing through the vicinity of the modulation electrode 64. That is, a phase difference occurs between the lights passing through the two phase shift optical waveguides 63,
At the time of joining at the input / output waveguide 62, the pressure detection element 18
The light has an intensity change according to the voltage signal from.

As described above, in the pressure fluctuation detector of this embodiment, the number of optical fibers for connecting the light source 11 and the light receiver 16 to the optical modulator 52 can be one.

In the first and third embodiments, the pressure detecting element and the optical modulator are independent of each other. However, as shown in FIG. 7, the pressure detecting element and the optical modulator are independent of each other. Can be integrally formed. That is, the electrodes 72 are formed in the central portions of the front and back surfaces of the lithium niobate crystal substrate 71 polarized in the thickness direction to form a piezoelectric element, and the substrate 7
The diaphragm 73 and the base 74 are attached to the back surface side of 1 to form a pressure detecting element. Then, an optical waveguide 75 is formed on the peripheral portion of the surface of the substrate 71, a modulation electrode 76 covering a part of the optical waveguide 75 is formed, and the modulation electrode 76 and the electrode 72 are connected by a strip conductor 77. Further, in the case of a reflection type optical modulator, a reflection film 78 is formed and an optical fiber 79 is connected to the optical waveguide 75.

In this way, by integrating the pressure detecting element and the optical modulator, it is possible to reduce the size and weight and to simplify the manufacturing and assembling steps. In addition, the durability can be improved by integration. Further, it is not necessary to draw the signal line connecting the pressure detection element and the optical modulator outward from the container containing the pressure detection target, and it is possible to eliminate the influence of noise and the like.

[0031]

According to the present invention, the optical modulator is driven by the voltage signal from the pressure detecting means to modulate the light from the light source, so that the detection result can be transmitted to a remote place. Can be used and is not affected by surrounding noise or lightning. In particular, if transmission is performed using an optical fiber, there is no leakage of information to the surroundings and the loss of the transmission path is small, so that information transmission to a distant place can be realized.

Further, by using a piezoelectric element as the pressure detecting means, it is possible to cope with a wide measurement range and pressure fluctuation of a high different frequency, and since the pressure detecting portion does not require a driving power source, it is flammable or explosive. The pressure can be detected in the atmosphere.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a pressure fluctuation detector according to a first embodiment of the present invention.

2 is a configuration diagram of an optical modulator used in the pressure fluctuation detector of FIG. 1. FIG.

FIG. 3 is a partial cross-sectional perspective view showing a configuration of a pressure detection element used in the pressure fluctuation detector of FIG.

FIG. 4 is a configuration diagram of a pressure fluctuation detector according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram of a pressure fluctuation detector according to a third embodiment of the present invention.

6 is a configuration diagram of an optical modulator used in the pressure fluctuation detector of FIG.

7 is a partial cross-sectional perspective view showing a configuration of an optical modulator and a pressure detection element, which are manufactured on the same substrate and are used in the pressure fluctuation detector of FIG.

[Explanation of symbols]

11 light source 12 Light source power supply 13 Input optical fiber 14 Optical modulator 15 Output optical fiber 16 light receiver 17 measuring instruments 18 Pressure detection element 21 board 22 Incident waveguide 23 Output waveguide 24 Phase shift optical waveguide 25 modulation electrode 31 Piezoelectric element substrate 32, 33 electrodes 34 diaphragm 35 base 36, 37 terminals 41 Optical modulator 42 glass plate 43 Polarizer 44 Transparent electrode 45 LCD 51 Optical circulator 52 Reflective optical modulator 53 Polarization maintaining fiber 61 board 62 Input / output waveguide 63 Phase shift optical waveguide 64 modulation electrode 65 Total reflection film 71 Lithium niobate crystal substrate 72 electrodes 73 diaphragm 74 base 75 Optical waveguide 76 Modulation electrode 77 Strip conductor 78 Reflective film 79 optical fiber

Claims (9)

(57) [Claims] 1. A pressure detecting means for detecting a pressure to generate a voltage signal corresponding to the pressure, a light source for generating light, and the light incident from the light source is modulated based on the voltage signal to be modulated. It has a light modulating means for emitting light, and a photoelectric conversion means for converting the modulated light into an electrical signal, and a pressure measuring means for determining the pressure based on the electric signal from the photoelectric conversion means, wherein the light modulation A means connects the incident optical waveguide on which the light from the light source is incident, the outgoing optical waveguide for emitting the modulated light, the incoming optical waveguide and the outgoing optical waveguide, and has a refractive index in response to the voltage signal. Pressure fluctuation characterized by being a transmission-type optical waveguide device that constitutes a Mach-Zehnder interferometer having two phase-shifting optical waveguides that change respectively
Detector . 2. The pressure fluctuation detector according to claim 1, wherein the pressure detecting means includes a piezoelectric element. 3. A process according to claim 1, wherein the transmission optical waveguide elements are formed on a substrate of the piezoelectric element also
2 is a pressure fluctuation detector . 4. The incident waveguide of the light modulating means is first.
Claims of being connected to the light source by an optical fiber, wherein the emitting waveguide of the optical modulation means is connected to said photoelectric conversion means by the second optical fiber
1, 2 or 3 pressure fluctuation detector. 5. A pressure detecting means for detecting a pressure to generate a voltage signal corresponding to the pressure, a light source for generating light, and the light incident from the light source is modulated based on the voltage signal to be modulated. It has a light modulating means for emitting light, and a photoelectric conversion means for converting the modulated light into an electrical signal, and a pressure measuring means for determining the pressure based on the electric signal from the photoelectric conversion means, wherein the light modulation An optical waveguide on which the light is incident, and two phase-shifting optical waveguides that split the light from the optical waveguide into two, and the respective refractive indices change according to the voltage signal, and the phase-shifting optical waveguide. Pressure fluctuation which is a reflection-type optical waveguide element which constitutes an interferometer having a total reflection mirror which is formed on the end face of the optical fiber and propagates through the phase shift optical waveguide toward the optical waveguide. Detector . 6. The pressure detecting means includes a piezoelectric element.
The pressure fluctuation detector according to claim 5, wherein 7. The reflection type optical waveguide element is formed on a substrate of the piezoelectric element, according to claim 5.
6 is a pressure fluctuation detector. 8. The optical waveguide of the light modulating means is connected to an optical fiber, and the optical fiber is connected to the light source and the photoelectric converting means via an optical direction separating means. The pressure fluctuation detector according to claim 5, 6 or 7 . 9. A pressure detecting means for detecting a pressure and generating a voltage signal corresponding to the pressure, a light source for generating light, and the light incident from the light source is modulated based on the voltage signal to be modulated. It has a light modulating means for emitting light, and a photoelectric conversion means for converting the modulated light into an electrical signal, and a pressure measuring means for determining the pressure based on the electric signal from the photoelectric conversion means, wherein the light modulation 2 means for forming a polarizing element and a transparent electrode
A pressure fluctuation detector characterized in that a liquid crystal is sandwiched between two transparent bodies.