JP2006194609A - Liquid level indicator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a precise liquid level indicator that can be manufactured inexpensively since it does not cause a light reflector to be contaminated by solution, or the like, is capable of measurement stably with less maintenance, does not cause a phenomenon, such as ignition, from occurring by the electrical circuit, or the like in a measurement system, and also can be configured by a simple electrical circuit. <P>SOLUTION: The liquid level indicator has a means having a reflecting plate in a cylinder airtightly separated from liquid to be measured and moving the reflecting plate to a liquid level position by a magnet mounted to a float floating on the surface of the liquid. The height of the liquid level is determined by measuring the reflection delay time of light. A relaxation oscillator in which a frequency is determined by delay time is composed for the measurement, and the frequency is measured, thus obtaining the economical liquid level indicator. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a liquid level gauge that measures the liquid level in a container using reflection of light.

As a device for measuring the height of the liquid surface using light, either a method using direct reflection from the liquid surface, or a reflecting plate installed on a float floated on the liquid surface, and the reflected light from now on is used. A method is used.
FIG. 1 is an example of the latter. A float 105 is floated on a liquid surface 110 of a container 100 for storing liquid, and a reflector 106 is installed on the float 105 via a support 107, and light rays emitted from the light emitting unit 103 of the optical distance meter 101 are reflected on the reflector. The light is reflected by 106, received by the light receiving unit 102, and the liquid level is measured from the reciprocal propagation time of the light. In this example, a guide 104 is provided to prevent the reflector 106 from deviating from the light beam, and the float 105 moves up and down along this guide. FIG. 2 is a view of the float 105 viewed from the optical distance meter 101 side.

In addition, a cylinder equipped with a colored magnet that changes color by rotating is placed in a container containing liquid, and the colored magnet is rotated by a magnet on a float that floats on the liquid surface. A method for measuring the current is used.
FIG. 3 shows an example.
In this example, a cylinder into which liquid can flow is provided outside the container 100, and a float 111 with a magnet is floated on the liquid surface in the cylinder, and the rotating colored magnet 113 in the display 112 is rotated by the magnet on the float. The liquid level is read from the discoloration position.
Japanese Patent Application No. 9-128097 (Patent Publication No. 10-300558) Japanese Patent Application No. 8-159114 (Patent Publication No. 9-318422) http://www.kaneko.co.jp/goods.htm (Magnet float type liquid level gauge)

In the conventional method using an optical distance meter, the reflecting mirror surface is directly exposed to a liquid or gas as a measurement object. For this reason, even if the distance between the reflecting mirror surface and the liquid surface is taken, dirt adheres to the mirror surface with time, and the reflected light attenuates, making reception difficult. When a droplet adheres to the mirror surface due to vibration or the like, the reflection direction of the light changes due to refraction of the droplet, and it becomes difficult to receive the reflected light.

In order to measure the delay due to light reflection, an optical distance meter is required, and this measuring unit is expensive in the conventional method using interference due to the wavelength of light.

In the example of measurement using magnetic coupling, the colored part is visually measured, and automatic measurement and recording are impossible. To increase accuracy, the size of the rotating magnet is made thin and small. There is a hating that needs to be complicated.

  In the present invention, a cylinder whose inside is hermetically separated from the liquid to be measured is inserted into the liquid to be measured, and a float floated on the surface of the liquid to be measured is disposed on the outer periphery of the cylinder, Arranges a moving body that magnetically couples with the external float and follows this movement, and measures the position of the moving body to measure the liquid level, so that the measurement space is not directly exposed to the liquid to be measured. Like that.

At the same time, a retro-reflective mirror is installed on the moving body inside the cylinder to prevent the situation where light cannot be received even when the angle or position of the reflector is changed.

In addition, as an optical distance meter, a relaxation oscillator whose frequency is determined by the delay time including the propagation time of light from the light source to the light receiving element and the time delay in the electric circuit is constructed, and this oscillation frequency is measured. Find the liquid level. Many of these are composed of electronic circuits and can be manufactured at low cost.

Further, by providing a reference route in the apparatus, it is possible to eliminate time fluctuations in portions other than the light reflection route to be measured, enabling accurate measurement and reducing the need for maintenance.

Also, as an option, liquid can be filled inside the cylinder and the buoyancy of the moving system in the cylinder can be used to offset the weight of the moving body and magnet inside the cylinder due to gravity, making it easier to follow the external magnet. To do. Thereby, the moving body can easily follow the external float by magnetic coupling with the external magnet.

Another option is to use a cylinder as a cylinder and install spiral guides inside and outside to move the moving body up and down while rotating along the spiral. As a result, the rotational force can be used to follow the height position of the external float in the space of the moving body, enabling stable follow-up and preventing falling due to impact or the like.

In the present invention, since the position of the moving body that follows the external float inside the hermetic cylinder by the magnetic force is measured by the propagation time of the light, the light reflector is not contaminated by the solution or the like, and stable measurement can be performed with little maintenance. It is possible.

In addition, by installing the light emitting and receiving parts away from the liquid to be measured using optical fibers, it is possible to prevent the occurrence of ignition and other phenomena due to the electrical circuit of the measurement system, etc., realizing an extremely high explosion-proof system it can.

Further, the liquid surface height is obtained by measuring the oscillation frequency using the relaxation oscillation in which the oscillation frequency is determined by the time delay from the light emission source to the reception of the measurement light. Since this method can be configured with a simple electric circuit, it can be manufactured at low cost.

Furthermore, delay fluctuations other than the light reflection route can be eliminated by providing a calibration route. For this reason, measurement with extremely high accuracy is possible, and at the same time, a level gauge that is easy to maintain can be provided.

In addition, if necessary, the liquid is filled in the cylinder, and the buoyancy of the moving system in the cylinder is used to cancel the gravity, thereby facilitating the tracking of the moving body to the float and enabling accurate and stable measurement.

Furthermore, if necessary, spiral guides can be prepared inside and outside the cylinder to stabilize the follow-up to the external float position in the space of the moving system, and it is possible to prevent measurement errors due to dropping due to impact.

4 and 5 show an embodiment of the present invention. FIG. 4 is a side sectional view of the liquid to be measured and the measuring device, and FIG. 5 is a plan view of the measuring device as viewed from the BB ′ portion.
The liquid level measurement in the present invention is performed as follows.
The light emitted from the light emitting unit 103 of the optical distance meter 101 is guided to the optical cable connecting unit 114 attached to the container 100 containing the liquid to be measured by the light transmission fiber 115, where the light is collimated by the light transmission collimator 117-1. And is emitted toward the retroreflector 122 on the moving body 123 provided in the sealed cylinder 118. The light reflected by the retroreflector 122 passes through the light receiving collimator 117-2, is guided by the light receiving fiber 116, and is input to the optical distance meter 101.
The liquid level is obtained by a simple calculation described later from the difference between the time when the light is emitted from the optical distance meter 101 and the time when the light is received.

In the above measurement system, the sealed cylinder 118 is used to prevent the reflection surface of the retroreflector 122 from being contaminated by the liquid in the container 100 or from preventing the propagation of light by volatile liquid vapor, The retroreflector 122 is used to ensure that the reflected light can be received by the light receiving collimator 117-2 regardless of the inclination when the sealed cylinder 118 is attached, the inclination of the measurement liquid surface, and the like.

In the measurement method described above, it is important that the reflection surface of the retroreflector 122 and the liquid surface to be measured are on the same plane. In the present invention, this is realized as follows.
A floating cylinder 119 that rises and falls along the outer periphery of the sealed cylinder 118 is provided so as to float on the liquid surface 110, and an external permanent magnet 120 is fixed to the floating cylinder 119 on the sealed cylinder 118 side. An internal permanent magnet 121 is also fixed to the movable body 123 inside the sealed cylinder 118 on the sealed cylinder 118 side. These two permanent magnets are set so that their magnetic forces attract each other, so if the float 119 moves with the movement of the liquid level 110, the moving body 123 will also move together, eventually the liquid level position and the retroreflector The position of the reflecting surface 122 is the same. Although the actual liquid surface position and the reflective surface position may differ depending on the mounting method, it is clear that this deviation can be corrected by calibration.
Further, in this case, the sealed cylinder 118 must be one that does not block the magnetic force, but it is obvious that it can be easily realized by using a non-magnetic material. Specifically, it can be realized with plastic or the like.

In order to improve the efficiency of the magnetic force, the permanent magnet is reinforced with a magnetic yoke, and the contact surface is provided with rollers to reduce the friction between the float 119 and the moving body 123 and the sealed container 118. , Improve the followability of the liquid surface and the reflective surface.

  Various arrangement methods of the magnet for causing the moving body 123 to follow the movement of the float 119 are conceivable. FIG. 6 shows an example in which four bar magnets are arranged in a crossing manner, and FIG. 7 shows an example in which cylinder-type magnets are arranged. In either case, the external permanent magnet 120 fixed to the float 119 and the internal permanent magnet 121 fixed to the moving body 123 need to be fixed at positions where the NS poles face each other. Obviously, it can be easily realized by making the floats 119 and the movable body 123 freely rotatable with respect to the sealed cylinder 118.

In the above description, the moving body 123 is in a state of floating in space due to the magnetic force. In order to realize this stably, a strong magnet for supporting the weight of the moving body 123 is required. Otherwise, the moving body 123 may fall onto the bottom surface of the sealed cylinder 118 due to an impact or the like.
In the present invention, as one means for solving this problem, a transparent liquid 124 is filled in a sealed cylinder 118, and a moving body 123 is placed therein. In this way, it is possible to balance the gravity acting on the moving body 123 and the buoyancy caused by the transparent liquid 124, and the weight of the moving body 123 can be made equal to zero. Moreover, since the liquid can be prevented from abruptly moving due to an impact force or the like, it is easy to stably hold the moving body 123 at the same height as the float 119.

In this case, the retroreflector 122 needs to have a retroreflective property in the environment of the filled transparent liquid 124. It is also effective to prepare a liquid drain hole 125 in the moving body 123 so that the movement of the moving body 123 within the sealed cylinder 118 is less susceptible to the viscous resistance of the transparent liquid 124.
In the present embodiment, an example of measuring the liquid level in the container is shown, but it is clear that the height of the water level and the like can be measured by installing the cylinder in a river, a lake, the sea, or the like.

FIG. 8 is a diagram showing the configuration of the optical distance meter 101 and the liquid level measurement used for the liquid level gauge.
In the present invention, the light level emitted from the light source is emitted to the retroreflector, and the liquid level is measured by the time difference until the reflected light is received. Specifically, the relaxation oscillator 126 whose frequency is determined by this time difference is configured, and the liquid level is measured from the frequency. This will be described in detail below.

The relaxation oscillator 126 includes an electric circuit portion and an optical path portion with the electro-optical converter 129 and the photoelectric converters 128-2 and 128-1 as a boundary. The electric circuit portion receives the reflected light returned by the inverting amplifier 132, the photoelectric converter 129 whose light output is controlled by the level of its binary output, and the retroreflector 122, and converts it into an electrical signal. The photoelectric converters 128-2 and 128-1, the amplifiers 130-1 and 130-2 that amplify the outputs, and the switching signal 140 output from the counting operation processing unit 138, the outputs of the amplifiers 130-1 and 130-2. One of them is selected, and the output thereof is composed of a switching circuit 131 for inputting to the inverting input terminal of the inverting amplifier 132 and a reference voltage source 133 connected to the non-inverting input terminal of the inverting amplifier 132.
From the viewpoint of this electric circuit portion, the optical path portion can be regarded as a delay circuit having a time difference from light emission to light reception.

The two photoelectric converters 128-1 and 128-2 selected by the switching circuit 131 are outputs of the optical path for measuring the liquid level by 128-1, and 128-2 is the measurement of the liquid level. Is a calibration output that measures a common time delay that is not directly related to.
When the output level of the inverting amplifier 132 is high in this system, after a time delay determined in relation to the liquid level, a high level signal is input to the inverting input, and the output of the inverting amplifier 132 is set to a low level. Invert. On the contrary, when the output is at a low level, the low level is input after the time delay, and the output of the inverting amplifier 132 is inverted to a high level.
Here, whether the level is high or low is determined based on the reference voltage 133 connected to the non-inverting input of the inverting amplifier 132.
Therefore, this circuit including the optical path is a relaxation oscillator that is repeatedly turned on and off with the time delay as a half cycle.

The optical path portion is configured as follows.
The light output of the electro-optic converter 129 is guided to the light: cable coupling unit 114 installed at the head of the sealed cylinder 118 by the light transmission fiber 115, where it is converted into a parallel beam by the collimator 117-1 and the half mirror 145. In this case, half of the power of the luminous flux is emitted to the retroreflector 122, and the other half passes through the collimator 117-2 and the receiving fiber 116-1 to the photoelectric converter 128-2. Entered. Here, the light beam emitted to the retroreflector 122 is reflected in the incident direction, passes through the half mirror 145, and is input to the photoelectric converter 128-1.

Here, the lengths of the receiving fibers 116-1 and 116-2 and the collimators 117-1 and 117-2 and the distance between them and the half mirror 145 are set to be equal and pass through the fibers 116-1 and 116-2. The difference in optical path length is twice the distance between the half mirror 145 and the retroreflector 122.
Therefore, the time difference including the electric circuit portion of the calibration path passing through the fiber 116-1 and the photoelectric converter 128-2 is measured, and the time difference of the measurement path passing through the fiber 116-2 and the photoelectric converter 128-1 is measured. By subtracting from this measured value, the time difference between the half mirror 145 and the retroreflective mirror 122 can be obtained.

The frequency of this oscillator is as follows.
The output point A of the inverting amplifier 132 is considered as a time reference.
After the output of the inverting amplifier 132 changes, the time until the optical level of the output of the electro-optical converter changes, the level of the input light of the photoelectric converter 128-1 or 128-2 changes, The time until the level of the electric signal changes, the time until the output electric signal reaches the input of the inverting amplifier 132 through the amplifier 130-1 or 130-2 and the switching circuit 131, and the output from the input of the inverting amplifier 132 The sum of the time delay until is the time delay Te of the electric circuit. Here, the system passing through the photoelectric converter 128-1 and the system passing through the photoelectric converter 128-2 have the same circuit configuration, and in this case, the time delay Te is equal.

The time until the change of the output light of the electro-optic converter 129 reaches the half mirror 145 is To1, the time until it is reflected by the retroreflector 122 and reaches the half mirror 145 is To2, and the time from the half mirror 145 to the photoelectric converter If the time to reach 128-1 or 128-2 is To3, the total time delay Td1 in the measurement path is
It is given by Td1 = To1 + To2 + To3 + Te. Therefore, the period of the relaxation oscillator is 2Td1 and the frequency is
F1 = 1 / 2Td1 = 1/2 (Te + To1 + To2 + To3)
Given in.
On the other hand, the frequency in the calibration path is
F2 = 1/2 (Te + To1 + To3)
Given in.
From these two equations, the round trip time from the half mirror 145 to the retroreflector 122 is
To2 = (F2−F1) / 2F1 * F2
Given in.

The frequency is obtained by counting the number of output pulses of the inverting amplifier 132 by a frequency counter 134 for a predetermined time. This counting time is created by counting a fixed number of outputs of the oscillator 135 by the time counter 136. The counting operation processing circuit 137 and the frequency liquid level conversion circuit 138 in FIG. 8 are circuits for controlling the frequency and calculating the liquid level from the measured frequency, and the display control output 139 displays the result. It is a man-machine interface for
The switching signal for the calibration measurement and the liquid level measurement is generated in this portion by a program stored in the circuit in advance, and sent to the switching circuit 131 for control.

9 and 10 show an embodiment of the present invention. FIG. 9 is a side sectional view of the liquid to be measured and the measuring device, and FIG. 10 shows the structure of the spiral guide which is a feature of this embodiment.
The liquid level measurement in the present invention is performed as follows.
The light emitted from the light emitting unit 103 of the optical distance meter 101 is guided to an optical cable connecting unit 114 (not shown) attached to the container 100 containing the liquid to be measured by the light transmission fiber 115, where the light transmission collimator 117- 1 is converted into parallel rays and emitted toward the retroreflector 122 on the moving body 123 provided in the sealed cylinder 118. The light reflected by the retroreflector 122 passes through the light receiving collimator 117-2, is guided by the light receiving fiber 116, and is input to the optical distance meter 101.
In the above measurement system, the moving body 123 on which the retroreflector 122 is placed is attracted to the position of the liquid level by magnetic coupling with the float 119 outside the sealed cylinder 118. Further, the moving body 123 and the float 119 move up and down along the spiral guides 141 and 142 provided inside and outside the sealed cylinder 118.

This spiral guide. 10 has a structure as shown in FIG. 10, and the moving body 123 and the float 119 are moved up and down along the spiral guide.
In this way, the moving body 123 is supported by the holding force generated from the relationship between the frictional force with the inner spiral guide 143 and the magnetic rotational force between the outer permanent magnet 120 and the inner permanent magnet 121. Thus, it becomes easy to stably hold the moving body 123 at the same height as the float 119.

  In FIG. 9, the spiral guides are provided on both the inside and the outside of the sealed cylinder 118, but a substantially similar effect can be obtained with a structure in which only the inner spiral guide 141 is mounted.

Since the signal processing system that handles electrical signals can be separated from the measurement position, it is possible to provide an extremely high explosion-proof device, and it can be applied to various liquid level measurements including gasoline and other highly flammable liquids.

In addition, since the optical path including the reflecting mirror is completely sealed, this part is not contaminated and can be applied to the measurement of the liquid level of all liquids including highly volatile liquids.
Remote measurement is also possible by lengthening the optical fiber part to measure the water level of rivers, lakes, and seas.

It is a side view of an example of the conventional liquid level gauge. It is the figure which looked at the reflector, float, etc. below from A-A 'of FIG. It is a figure which shows an example of the liquid level meter using the conventional magnet. It is a figure which shows an example of a structure of a liquid level gauge, and a buoyancy support liquid level gauge in a cylinder. Example 1 FIG. 5 is a view of a reflector portion and the like below from BB ′ of FIG. Example 1 Magnet Arrangement Example 1 It is a diagram showing a bar magnet type. Example 1 It is a figure which shows the example 2 of a magnet arrangement | positioning. Example 1 It is a block diagram explaining the optical distance meter which measures a liquid level height. (Example 2) It is a figure which shows the example of a structure of the liquid level meter equipped with the spiral guide. Example 3 It is a figure which shows the outer side spiral guide of the sealing cylinder of FIG. Example 3

Explanation of symbols

100 containers
101 Optical distance meter
102 Receiver
103 Light emitter
104 Guide
105 Float
106 reflector
107 Support
108 Guide tracer
109 Guide hole
110 Liquid level
111 Float magnet
112 Display
113 Rotating colored magnet
114 Optical cable connection
115 Optical fiber
116 Receiving fiber
117 collimator
118 Sealed cylinder
119 float
120 External permanent magnet
121 Internal permanent magnet
122 Retroreflector
123 mobile
124 clear liquid
125 Fluid hole
126 Relaxation oscillator
127 Measurement controller
128 photoelectric converter
129 electro-optic converter
130 Amplifier
131 switching circuit
132 Inverting amplifier
133 Reference voltage
134 Frequency counter
135 Oscillator
136 hour counter
137 Counting processor
138 Frequency level converter
139 Display / Control output
140 Switching signal
141 Inside spiral guide
142 Outer spiral guide
143 Inner tracer
144 Outer tracer
145 half mirror
146 Measuring light

Claims (6)

  In a level gauge for measuring a liquid level, a cylinder that is secretly separated from a liquid to be measured, a float that is installed on the outer periphery of the cylinder and floats on the liquid level, a magnet fixed to the float, and the magnet Other magnets or iron pieces provided in a cylinder that are magnetically coupled to each other and follow the float position by magnetic force, a moving body coupled to the magnets or iron pieces in this cylinder, and a retroreflective mounted on the moving body A liquid level gauge comprising: a plate, a light sending mechanism for emitting light to the retroreflecting plate, and a reflection light receiving mechanism for detecting reflected light from the reflecting plate.   The transparent liquid different from a measuring object is filled in the cylinder, and a moving body including a magnet or an iron piece on which the retroreflective plate in the cylinder is placed is immersed in the transparent liquid. Liquid level indicator.   A cylinder is used as the cylinder, and the vertical movement of the moving body in the cylinder by magnetic coupling with the magnet on the external float is performed along the spiral guide provided in the cylinder. The liquid level gauge according to claim 1.   A cylinder is used as the cylinder, and the movement of the float outside the cylinder is performed along the spiral guide provided on the outer peripheral surface of the cylinder, and at the same time, the vertical movement of the moving body inside the cylinder by the magnetic coupling force is performed. The liquid level gauge according to claim 1, wherein the liquid level gauge is arranged along another spiral guide provided on the inner peripheral surface of the cylinder.   In a liquid level meter that detects the position of the liquid surface by the optical path length of the reflected light with the moving body on which the reflector that follows the liquid level is mounted, relaxation is performed by using the delay of the optical path and the electrical path including the path of the reflected light. A liquid level gauge comprising an oscillator and measuring the height of the liquid level by measuring the frequency.   6. The liquid level gauge according to claim 5, wherein the measurement value is calibrated by inserting a half mirror in the optical path and measuring light and electrical path lengths that are not directly related to the liquid level.

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