JPH0989631A - Liquid-level meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a liquid-level meter by which a measuring part can be installed inside a tank and by which a liquid level can be measured without using a glass gage. SOLUTION: In a liquid-level meter, the liquid surface level of a liquid inside a tank is measured optically. In the liquid-level meter, a longitudinally long opening 2 is arranged and formed in one face of the sidewall of a case 1 which is installed inside the tank, and a light-emitting body 3 and a light-receiving body 4 are erected and installed inside the case 1 so as to face the opening. The light-emitting body 3 is constituted so as to be provided with (n) pieces of light-emitting elements 3-1 to 3-n which are arranged and installed continuously in the vertical direction, and the light-receiving body 4 is constituted so as to be provided with a plurality of photodetectors corresponding to the light- emitting elements 3-1 , to 3-n . The light-emitting elements 3-1 to 3-n are controlled by a computing and processing part 5 so as to emit light sequentially, the liquid surface level inside the tank is computed on the basis of the output of the light-receiving body, and a computed result is displayed on a display part 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level gauge for optically measuring a liquid level in a tank.

[0002]

2. Description of the Related Art In order to measure the liquid level of water, oil or the like in a tank, a non-contact type liquid level meter using ultrasonic waves or optical sensors is used. FIG. 7 is a block diagram showing the configuration of an optical liquid level gauge which the applicant has proposed at the same time.

On one side of a glass gauge 11 connected to an oil tank (or a water tank), a plurality of light emitters 12 _{-1 to} 12 _-n are continuously arranged in the vertical direction. Furthermore, glass gauge 1
On the opposite side of the light emitting bodies 12 _{-1 to} 12 _-n with the light emitting element 1 in between, a plurality of light receiving bodies 13 _{-1 to} 13 _-n are continuously arranged in the vertical direction. A shift register 1 is provided for each of the light emitters 12 _{-1 to} 12 _-n.
4 is connected to the shift register 14 and the light receiving body 13.
_The processing calculation unit 15 is connected to _{-1 to} 13- _n .

In this structure, the processing arithmetic unit 15 controls the shift register 14 to control the light emitters 12 _{-1 to} 12 _-n.
Are sequentially turned on, and at that time, the light receiving bodies 13 _{-1 to} 13 _-n receive the light reaching through the glass gauge 11 and output an electric signal according to the received light amount. This output state is processed and calculated by the calculation unit 1
5, the light amount difference between the light receiving members 13 _{-1 to} 13 _-n , that is, the light receiving member 13 located at the boundary where the light amount changes greatly.
The position of is determined to be the liquid level. That is, when the liquid 16 in the tank is oil, the amount of received light is large because the liquid 16 portion of the glass gauge 11 has a large light-collecting effect, and the amount of received light is small because the gas portion of the glass gauge 11 has a small light-collecting effect. Less. The liquid level is measured by utilizing the difference in the amount of received light.

[0005]

However, according to this liquid level gauge, since the detection is carried out by using the lens effect of the glass gauge formed by the presence or absence of the liquid in the pipe, the existing tank having no glass gauge is used. Not applicable to. Further, since it cannot be installed in the tank, the mounting position is limited.

Therefore, an object of the present invention is to provide a liquid level gauge which can be applied to an existing tank having no glass gauge and can be installed in the tank.

[0007]

In order to achieve the above object, the present invention provides a liquid level gauge for optically measuring the liquid level of a liquid in a tank. A light-emitting body provided with a plurality of light-emitting elements, which is erected in the tank,
A light-receiving element that stands upright in the tank in the vicinity of the light-emitting body and receives light from the light-emitting element of the light-emitting element that is reflected by gas and liquid in the tank, and the light-emitting element of the light-emitting element. To emit light in a predetermined order and to detect the liquid level in the tank based on the light receiving state of the light receiving body at that time.

According to this structure, the light emitter and the light receiver are installed in the tank, and the light from the light emitter is reflected by the liquid at the predetermined position and is received by the light receiver. Therefore, the liquid level can be measured without using a glass gauge. As a result, the liquid level can be measured without being limited by the structure of the tank.

[0009]

1 is a perspective view showing an embodiment of a liquid level gauge according to the present invention, and FIG. 2 is an explanatory view showing a state of installation of the liquid level gauge of FIG. 1 in a tank. . A case 1 installed in the tank has a box shape having four side walls, and an opening 2 made of a vertically long transparent material is provided on one surface thereof.
In the vicinity of the opening 2 in the case 1, a light-emitting body 3 having substantially the same height as the opening 2 is provided upright. This light-emitting body 3 has a structure in which n light-emitting elements 3 _{-1 to} 3 _-n are continuously arranged in the vertical direction, and all the light-emitting elements emit emitted light horizontally toward the opening 2. I am trying to do it. Further, a light receiving body 4 (its light receiving surface is directed to the opening 2) is provided upright adjacent to the light emitting body 3. The light receiving body 4 may be configured to include a plurality of light receiving elements to which one light receiving element is assigned for each of the light emitting bodies 3, or an image pickup device such as a CCD.

An arithmetic processing unit 5 is connected to the light receiving body 4, and a display unit 7 (comprising a display device such as a liquid crystal display and a drive circuit) for displaying the arithmetic result is further provided on the arithmetic processing unit 5.
Is connected. A shift register 6 is connected to each of the light emitters (light receiving elements) 3, and an arithmetic processing unit 5 is also connected to the shift register 6. The arithmetic processing unit 5 and the shift register 6 are installed outside the case 1, and the light receiving unit 4
And the connection with the light-emitting body 3 is performed using a cable or a lead wire. Then, as shown in FIG. 2, the liquid level gauge shown in FIG. 1 is erected at a position where it does not interfere with other work in the tank 8 containing the liquid 8A.

FIG. 3 is an explanatory view showing the positional relationship between the light emitter 3 and the light receiver 4. The opening 2 has a refractive index n ₁ with respect to the refractive index n ₂ of the liquid in the tank. The light emitted from each of the light emitters 3 is refracted on the inner surface of the opening 2, reflected on the outer surface, refracted again on the inner surface, and reaches the light receiver 4. FIG. 4 is an explanatory diagram showing the relationship between the emitted light and the incident light with respect to the light receiver in the present invention.

From the substance D _A (optical refractive index n _A ) to the substance D
_B (optical refractive index n _B ), or substance D _C (optical refractive index n _A <n
When light is incident on _B <n _C ), at the interface, the incident angle from the substance D _A is θ _A , the refraction angle is θ _B , and θ _C (0 ≦
When θ ≦ 0.25π), the following equation holds. n _A sin θ _A = n _B sin θ _B = n _C sin θ _C (1) Since the light refractive index has a relationship of n _A <n _B <n _C , the following formula is established. _{θ A> θ B> θ C} ··· (2) Further, the energy reflectance when light is incident from the substance D _A to substance D _B (Γ _B), light is incident from the substance D _A to substance D _C In the case of S-deflection, the following equation is derived as the energy reflectance (Γ _C ). Γ _BS = sin ² (θ _B −θ _A ) / sin ² (θ _B + θ _A ) Γ _CS = sin ² (θ _C −θ _A ) / sin ² (θ _C + θ _A ) (3) In the case of P deflection, the following equation is derived. Γ _BP = tan ² (θ _A −θ _B ) / tan ² (θ _A + θ _B ) Γ _CP = tan ² (θ _A −θ _C ) / tan ² (θ _A + θ _C ) ... (4) Equation ( From (2), (3) and equation (4), Γ _BS + Γ _BP <Γ _CS + Γ _CP (5) That is, the light incident on the substance having a small optical refractive index is incident on the substance having a large optical refractive index. The energy reflectance is higher than that of the light. Since the light refractive index of gas is smaller than that of liquid, the light reflected by the opening 2 above the liquid surface is larger than the light reflected by the opening 2 below the liquid surface. Therefore, the received light intensity when the light emitters are turned on one by one is shown in FIG.
become that way. Light emitter 3 whose received light intensity changes the most
The position of is determined to be the liquid surface. The sensor resolution at this time is the width of the light emitting element. Then, as shown in FIG. 6, when the intensity of received light is changed stepwise by three or more light emitters near the liquid surface, the resolution becomes less than the width of the light emitting element.

In the above structure, the light emitting element 3 emits light in order from the lower side or the upper side by controlling the shift register 6 by the arithmetic processing section 5. The light from the light emitter 3 is reflected by the interface with oil or air in the tank and is received by the light receiver 4.
The light is received by and is output as an electric signal according to the amount of light received.
At this time, the amount of reflected light at the position above the liquid surface is larger than the amount of light reflected at the position below the liquid surface of the opening 2. Therefore, the received light intensity when the light-emitting bodies 3 are turned on one by one is as shown in FIG. This electric signal is taken into the arithmetic processing unit 5, and the position of the light emitting body where the received light intensity changes most is determined to be the liquid surface. The obtained liquid surface level is digitally displayed on the display unit 7 connected to the arithmetic processing unit 5 (note that it may be an analog display using a meter).

Although the opening 2 is provided in the side wall of the case 1 in the above embodiment, the side wall of the case 1 does not have a window shape, but the side wall of the case 1 has three sides, and a transparent window is provided on all sides. 1 may be used. Further, in the above description, the liquid level of the oil in the tank was targeted, but the present invention is not limited to the liquid level measurement in the tank, and for example, in a monitoring system in the underground hole of the underground power transmission line. Can be applied.

[0015]

As is apparent from the above, according to the present invention, the light-emitting body and the light-receiving body are installed in the tank, and the two are not directly confronted with each other, and the liquid is used as a reflector to indirectly detect the presence or absence of the liquid. Since the change in the received light is detected, the liquid level can be measured without using a glass gauge, and the liquid level can be measured regardless of the structure of the tank.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a liquid level gauge according to the present invention.

FIG. 2 is an explanatory diagram showing the installation status of the liquid level gauge of FIG. 1 in a tank.

FIG. 3 is an explanatory diagram showing an arrangement relationship between a light emitter and a light receiver in the present invention.

FIG. 4 is an explanatory diagram showing a relationship between emitted light and incident light with respect to a photoreceptor in the present invention.

FIG. 5 is a characteristic diagram showing the relationship between the position of a light emitter and the total amount of received light.

FIG. 6 is a characteristic diagram showing a state in which three or more light emitters are gradually changed near the liquid surface.

FIG. 7 is a block diagram showing a configuration of a conventional liquid level gauge.

[Explanation of symbols]

DESCRIPTION OF _SYMBOLS 1 case 2 opening 3 light-emitting body 3 _{-1 to} 3- _n light-emitting element 4 light-receiving body 5 arithmetic processing display section 6 shift register 7 display section 8 tank

Claims (1)

[Claims] 1. A liquid level meter for optically measuring the liquid level of a liquid in a tank, comprising a plurality of light emitting elements continuously arranged in a vertical direction, and standing upright in the tank. A light-emitting body, a light-receiving body standing near the light-emitting body in the tank and receiving light from the light-emitting element of the light-emitting body reflected by gas and liquid in the tank, and the light-emitting body 2. A liquid level gauge, comprising: a light emitting device that emits light in a predetermined order, and a detection unit that detects the liquid level in the tank based on the light receiving state of the light receiver at that time.