JPS60135737A - Pressure transmitter - Google Patents

Abstract

PURPOSE:To detect an increase and a decrease in pressure variation by demultiplexing light and then multiplexing light waves passed through single-mode optical fibers which vary and do not vary in length with pressure, and photodetecting obtained interference fringes at two nearby points and deciding on the moving direction of the fringes. CONSTITUTION:When pressure is applied to a pressure admitting body 1, a pressure reception part 4 increases in diameter to cause an optical path difference between single- mode optical fibers 2 and 3 because the optical fiber 2 extends while the other optical fiber 3 of a reference light part 5 does not vary in length, and interference is caused in the output light of an optical multiplexer 9 to form interference fringes at a photodetection part 10. The interference fringes move from the center of photodetection to the circumference at the time of an increase in pressure or from the circumference to the photodetection center at the time of a decrease in pressure, so the interference fringes are photodetected by photodetectors 11 and 12 and converted into a pulse signal and outputs (a) and (b) of preamplifiers 13 and 14 are supplied to monostable multivibrators 15 and 16 to decide on the before-after relation of the timing. Further, a counter 17 counts up when the pressure increases and counts down when the pressure decreases. Thus, explosion resistance and digital signal output are secured.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to an optical pressure transmitter that uses optical fibers and optical interference.

(b) Background Mechanical and electric types have traditionally been used as instruments to measure the pressure of fluids such as air and oil, but mechanical types have a complex structure and require a comprehensive control system. It is not suitable for being built into a computer, and electric types have difficulty in being explosion-proof depending on the location where they are installed.

Many of them obtain analog output, and when converting to digital for data processing, there is a problem in that an expensive A/D converter must be installed. Therefore,
In order to solve this problem, the inventors of this application created a pressure gauge that generates interference fringes according to pressure using an optical fiber and measures pressure from the number of interference fringes, and filed a separate application.

However, by simply counting the number of interference fringes, even if it is possible to know the amount of change in pressure, it is not possible to know its increase or decrease. Therefore, if you want to know not only the amount of i conversion of pressure, but also the increase or decrease in pressure.

Merely counting the number of interference fringes was not sufficient.

In view of the above, the purpose of this invention is to provide a pressure transmitter that is explosion-proof and has digital signal output, and is capable of detecting not only the amount of change in pressure but also its increase and decrease. It is to be.

B) Structure In order to achieve the above object, the 1-m pressure transmitter of the present invention includes a light source, a light splitter that branches the light from the light source, and transmits one of the lights branched by the light splitter. , transmitting a first single mode optical fiber whose length changes depending on the introduced pressure and the other light branched by the optical splitter, and whose length does not change regardless of the introduced pressure. a second single-mode optical fiber; an optical multiplexer that receives and combines light from the first and second single-mode optical fibers and outputs interference fringes; and an optical multiplexer that outputs interference fringes of light; Two light receivers that receive the interference fringes of
and a means for determining the moving direction of the meter that corresponds to the number of interference fringes t'l based on the number of interference fringes t′l, and the amount of change in pressure is determined from the counting means, and an increase or decrease in pressure is distinguished from the discrimination output of the discriminating means. ing.

(e) Examples The present invention will be explained in more detail by way of examples below.

1 and 2 show a pressure transmitter according to an embodiment of the present invention, and FIG. 1 is a (schematic diagram,
FIG. 2 is a circuit block diagram of the signal processing section.

In FIG. 1, reference numeral 1 denotes a pressure introducing body having a cylindrical outer shape, and optical fibers 2 and 3 are wound around the outer peripheral surface of this pressure introducing body 1 in close contact with it.

These optical fibers 2.3 are all single-mode optical fibers, but when pressure is introduced into the pressure introducing body 1, the optical fiber 2 is wound around a portion whose diameter changes depending on the pressure. The pressure introducing body 1 constitutes a pressure receiving part 4. The optical fiber filter is wound around a portion whose diameter does not change even when the pressure of the pressure introducing body 1 is introduced, and constitutes a reference light section 5.

6 is a laser light source, and 9 the emitted light is.

The signal is input to an optical splitter 8 via an optical fiber 7. In the optical splitter 8, the light from the laser light source 6 is split.

Optical fiber 2. It is now possible to add it to Party B.

1. Optical fiber 2. The light from B is multiplexed by an optical multiplexer 9, and is made to enter the light receiving section 1O. In the light receiving section 10, two light receivers (light receiving elements) il and 12 are arranged at two points extremely close to the center of the incident light.

This light receiver 11.1'2 is as shown in FIG.

Preamplifier 15. ．． 1.4 is connected.

The output a of the preamplifier 13 is applied to the enable input terminal EN of the monostable multivibrator multivibrator 16, and the output a of the preamplifier 14 is applied to the input terminal EN of the monostable multivibrator V-16 and monostable multivibrator 16. It is adapted to be applied to the enable input terminal EN of the multivibrator 15.

Seven Stable Multihive Soak 1.5.16 is among the outputs a and b of preamplifiers 1 and 14.

From the output end Q corresponding to the one that is output first. (output cover of a certain width) Vs is derived. output of the monostable multivibrator 15 d. The output of the monostable multi-by-break 16 is applied to the UP input terminal of the counter 17 and the DoXvN input terminal of the counter 17, so that the counter 1 counts up or down, respectively. 18 is a D/A converter, 1
9 is an output amplifier.

next. The operation of the embodiment pressure transmitter configured as above will be explained.

No pressure is introduced into the pressure introducing body 1. In the state.

Since the diameter of the pressure receiving part 4 of the pressure introducing body 1 does not increase at all, the optical fiber 2 does not stretch. Therefore, optical fiber/. There is no optical path difference between the optical fiber 2 and the optical fiber 2, and the light that passes through the optical multiplexer 9 and enters the light receiving section 1O.

No interference fringes occur, and no output change is obtained in the photoreceivers 11, 12.

However, when a change occurs in the pressure input to the pressure introduction body 1, the diameter of the pressure receiving part 4 changes according to the pressure. Become a person. As a result, the length of the optical fiber 2 also changes, e.g., elongates. On the other hand, since the length of the optical fiber 3 of the reference light section 5 does not change even when pressure is introduced, an optical path difference occurs in the optical fiber 2.3. As a result, interference occurs in the output light of the optical multiplexer 9, and interference fringes occur in the light receiving section 10. In this case, the optical path difference increases as the introduced pressure increases9. Also, when the optical path difference is 1 times the wavelength of the light, one interference fringe occurs.

The larger the optical path difference, the more interference fringes will occur.

The manner in which these interference fringes occur is shown as a light intensity change curve A in the light receiving section 10''2 of FIG. Also.

When the pressure increases, the interference fringes move from the light reception center to the periphery, and when the pressure decreases, the interference fringes move from the periphery toward the light reception center. therefore.

Distributed closely from the light receiving center of the light receiving unit 10 toward the periphery.
If the interference fringes are received by the receivers 11 and 12, which are 1"1, and converted into pulse signals, and the number of pulses is counted, the number of interference fringes, that is, the amount of change in pressure can be detected. Depending on whether the interference fringes are received first, it is possible to distinguish whether the pressure is increasing or decreasing.

For example, if the pressure changes in an increasing direction and one interference fringe moves from the light receiving center to the periphery, the light pulse due to this interference fringe is first received by the light receiver 11, and then by the light receiver 1.
2 will receive light.

Otherwise, the output a of the preamplifier 13 and the preamplifier 14
The output is as shown in the left half of Figure 5.

First, the output a rises, followed by the output A. Therefore, the seven table multivibrator 15 has terminal EN
Since it receives the signal a without receiving any signal, it is triggered, outputs a constant fan pulse signal to the output terminal Q, and adds this to the UP input terminal of the counter 17 (see UP in FIG. 6). However, at the timing when the signal a is input to the seven-number table multivibrator 16, the signal a is input to its own terminal τN, so it is not triggered. Therefore, no signal is input to the DOWN input terminal of the counter 17. Even if the pressure continues to increase and interference fringes occur continuously, the direction of movement is from the center of light reception to the periphery, so signal a always rises in the light.

As in the case of one interference fringe, pulse signals are sequentially input to the UP input terminal of the counter 17, and the counter 17 continues the up-run 1-.

On the other hand, when the pressure changes in a decreasing direction, the interference fringes move from the periphery toward the center of light reception.

First, one interference fringe is generated, and the optical pulse is transmitted to the receiver 12.
The light is first received by the light receiver 11, and then the light is received by the light receiver 11. Therefore, as shown in the right half of Fig. 3, the output a and small output of the preamplifiers 13 and 14 rise first and then the output a rises.Therefore, the monostable multi-pin inverter EN receives the signal a. Since it receives a signal in the state of
This is added to the DOWN input terminal of the counter 17 (see OWN in FIG. 6). However, at the timing at which the signal a is input to the monostable multi-layer circuit 15, the signal a is input to its own terminal EN, so the seven-stable multi-by-layer circuit 15 is not triggered. Therefore, no signal is input to the UP input terminal of the counter 17.

Subsequently, as the pressure decreases, only the 1- trigger of the monostable multi-pin regulator 16 is performed in the same manner, and the down-run 1- of the counter 17 is correspondingly connected to R)Y.

As described above, in the Nannostable Multi-Vipe V-Li 15.16, the movement direction of the interference fringes, that is, the increase in pressure and
The decrease is detected, and the amount of pressure change is obtained by increasing or decreasing the output of the mononuclear multiviprator 15, 16 with the counter 17. The count value of the counter 17 is converted into an analog value by a D/A converter 18 as required, and outputted through an output amplifier 19.

In addition, as the pressure introduction body 1 of the first embodiment, for example, the fourth
The structure shown in the figure is used. This pressure introduction body 1 includes a cylindrical portion 23 that defines an inner space 22 formed by a thin elastic wall 21, a pressure introduction port 24, and a communication path that communicates the pressure introduction port 24 with the inner space 22. 25 is integrally formed with a cylindrical portion 26 which has a cylindrical portion 26. The optical fiber 2 is wound around the cylindrical portion 23, and the optical fiber 2 is wound around the cylindrical portion 26. When pressure is introduced into the inner space 22 of the cylindrical portion 2, the elastic wall 21 tightens, and as a result, the length of the optical fiber 2 is extended.However, since the cylindrical portion 26 is thick, the pressure Even when the optical fiber is introduced, the outer periphery does not change at all, so the length of the optical fiber does not change.

(F) Effect According to the present invention, the amount of pressure change is determined by counting the number of interference fringes caused by the optical path difference of the optical fiber corresponding to the pressure change, and the increase or decrease in pressure is determined by detecting the moving direction of the interference fringes. Because it is a thing.

Good explosion proof r f? ij It is possible to simultaneously distinguish not only the amount of pressure change but also its increase/decrease while ensuring the advantage of pressure detection using an optical fiber and optical interference application that digital output is possible.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the pressure detection section of a pressure transmitter showing a one-fire embodiment of the present invention, FIG. 2 is a circuit block diagram of the signal processing section of the pressure transmitter, and FIG. FIG. 4 is a signal waveform diagram for explaining the operation, and is a sectional view specifically showing an example of a pressure introducing body used in the pressure transmitter. 1: Pressure introducing body. 2.5: Single mode optical fiber. 6: Laser light source, 8: Optical splitter. 9: Optical multiplexer, 11/12-light receiver. 15/16: Mononu table multi-by break, 17
:counter. Patent applicant U Shimadzu Corporation Patent attorney Shigeru Shin Nakamura Figure 1 Figure 3 Figure 4 Figure 2

Claims (1)

[Claims] (1) A light source and a light splitter that branches the light from the light source. This optical splitter transmits one of the split lights. A first single mode optical fiber whose length changes depending on the introduced pressure and the other light branched by the optical splitter are transmitted, and the length changes regardless of the introduced pressure. an optical multiplexer that receives and combines light from the first and second single mode optical fibers and outputs interference fringes of light; and the optical multiplexer. two light receivers that receive interference fringes of light at two adjacent points; a counting means that counts the number of interference fringes based on the outputs from these light receivers; means for determining the direction of movement of the stripes, the pressure transmitter being capable of distinguishing the amount of change in pressure from the counting means and the increase or decrease in pressure from the discrimination output of the discriminating means.