JPH0495821A - Ultrasonic level meter - Google Patents

Abstract

PURPOSE:To measure the liquid level with good accuracy by providing a float of a smaller specific gravity than a liquid in a container, and a reflecting plate of a larger specific gravity than the liquid which is suspended from the float in a swaying fashion. CONSTITUTION:An ultrasonic pulse generated from an ultrasonic probe 6 at the bottom of a container 1 is reflected by a reflecting plate 10 suspended from a float 8, and received again by the probe 6. The distance (m) between the probe 6 and reflecting plate 10 is obtained by measuring the time since the pulse is generated until it is received by the probe 6. Even when the height of the float 8 is changed in accordance with the increase/decrease of the storing amount of a liquid 2, the distance (l) between the float 8 and reflecting plate 10 is constant. Therefore, the distance between the probe 6 and liquid surface is (m+l). Moreover, as more bubbles are present near the liquid surface, it is possible to face the reflecting plate 10 to the probe 6 at the position other than where the air bubbles are present if the distance (l) between the float 8 and reflecting plate 10 is set suitably. The influences of the air bubbles can be removed. In this manner, the liquid level can be measured with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an ultrasonic level meter that measures the height of a liquid stored in a container.

<Prior Art> In order to monitor the amount of liquid stored in a container, such as petroleum, milk, beer, etc., an ultrasonic level meter is used to measure the height of the liquid level.

The conventional ultrasonic level meter, as shown in Figure 2(a),
An ultrasonic probe is placed at the top of the container a, and ultrasonic pulses are emitted vertically from the ultrasonic probe toward the liquid surface, and the reflected waves are emitted by the ultrasonic probe again. The height of the liquid level is measured based on the time required to transmit and receive ultrasonic waves.

Alternatively, as shown in Fig. 2(b), the ultrasonic probe is submerged in the liquid, and the ultrasonic pulse is emitted from the bottom of the container a, and the time required for wave transmission and reception is determined in the same way as above. Measure the height of the liquid level based on the

<Problems to be Solved by the Invention> However, the configuration shown in FIG. There are many bubbles C in
Since the ultrasonic waves are scattered by the bubbles C, stable measurement results cannot be obtained.

On the other hand, in the configuration shown in Fig. 2(b), it is not affected by bubbles on the liquid surface, but if the liquid has a high specific gravity such as heavy oil, when it is poured into the container a, it will be absorbed into the liquid. Since the existing bubbles d do not float easily, stable measurement results cannot be obtained because the ultrasonic waves are attenuated by the presence of the bubbles d.

<Means for Solving the Problems> The present invention was made in view of the above circumstances, and even when there are bubbles on the liquid surface or in the liquid, the present invention can solve the problem. This makes it possible to accurately measure the height of the liquid level without being affected by the

Therefore, the present invention has an ultrasonic probe 6 that transmits and receives ultrasonic pulses, and transmits ultrasonic waves from this ultrasonic probe 6 toward the liquid surface of the liquid 2 stored in the container l. In an ultrasonic level meter that measures the height of the liquid level based on the time it takes to emit a pulse and receive the reflected wave again by the ultrasonic probe 6, the ultrasonic probe 6 is connected to the container 1. while placing it at the bottom of the container l
The structure includes a floating device 8 having a specific gravity smaller than the liquid disposed therein, and a reflecting plate 10 swingably suspended from the floating device 8 and having a specific gravity larger than the liquid.

<Function> In the above configuration, the ultrasonic pulse emitted from the f-cos ultrasonic probe 6 disposed at the bottom of the container 1 is reflected by the reflection plate 10 suspended from the float 8 and returns to the ultrasonic probe. The wave is received by child 6. Then, if the time required for transmitting and receiving waves during this period is measured, the distance between the ultrasonic probe 6 and the reflection plate 10 is m.
Find out. Furthermore, even if the height of the float 8 changes according to the increase or decrease in the amount of liquid 2 stored, the distance ρ between the float 8 and the reflector lO remains constant. The distance between the child 6 and the liquid surface can be determined by m+ρ.

Here, the closer the bubbles are to the liquid surface, the more numerous the bubbles are, so by appropriately setting the distance 11ia between the float 8 and the reflector 10, the reflector 10 can be adjusted to avoid areas where a large number of bubbles exist. By facing the ultrasonic probe 6, it is not affected by air bubbles. Furthermore, since the ultrasonic pulse is emitted from the bottom side of the container 1, it is naturally not affected by bubbles on the liquid surface.

<Embodiment> FIG. 1 is a block diagram of an ultrasonic level meter according to an embodiment of the present invention. In the figure, reference numeral 1 is a container, 2 is a liquid stored in the container 1, 3 is an inlet for the liquid 2, and 4 is an ultrasonic level meter.

This ultrasonic level meter 4 includes an ultrasonic probe 6 that transmits and receives ultrasonic pulses, and a distance to the liquid level 2a based on the time of the ultrasonic pulses transmitted and received by this ultrasonic probe 6. It has a measuring section 7 that measures.

An ultrasonic probe 6 is attached to the bottom of the outside of the container 1. Furthermore, a floating device 8 having a specific gravity smaller than that of the liquid 2 is provided in the container 1 and floats on the liquid 2. Further, an arm 9 having a predetermined length a is attached to the lower part of the floating device 8 so as to be swingable by means of a pin connection, etc., and a reflecting plate IO made of metal or the like having a higher specific gravity than the liquid 2 is mounted on this arm 9. Fixed. This allows the inlet 3
Even if the floating device 8 swings when liquid is injected from the tank, the reflecting plate 10 remains unaffected by the swing. The reflection plate 10 and the ultrasonic probe 6 are opposed to each other.

I2 is a trigger pulse generation unit that generates a trigger pulse, 1
4 is a wave transmitter that outputs a driving pulse for excitation of the ultrasound probe 6 in response to a trigger pulse; 16 is a wave transmitter that amplifies the signal obtained by receiving the ultrasound echo from the ultrasound probe 6; The wave receiving section 18 that performs wave detection is a level comparison section that compares the signal level from the wave receiving section 18 with a preset threshold. Also,
20 is a counter that counts the transmission time of ultrasonic pulses;
The counting operation is started in response to the ) trigger pulse from the ultrasonic trigger pulse generation section, and the counting operation is stopped in response to the output signal of the level comparison section 18.

22 is a setting unit for giving a preset value to the counter according to the distance between the float 8 and the reflector 10; 24 is a calculation unit that measures the height of the liquid level based on the count output of the counter 20; 26 is a calculation unit This is a display section that displays the results.

In the above configuration, even if the height of the floating device 8 changes according to an increase or decrease in the amount of liquid 2 stored, the distance ρ between the floating device 8 and the reflecting plate 10 is kept constant.

Normally, the closer the liquid surface is, the more bubbles 30 there are, so if the distance g between the floating device 8 and the reflector 10 is set appropriately, the reflection can be avoided in a way that avoids areas where there are a lot of bubbles 30. Since the plate 10 faces the ultrasonic probe 6, it is not affected by the air bubbles 30. In addition, since the ultrasonic pulse is emitted from the bottom side of the container 1, bubbles 32 are generated on the liquid surface 2a.
Even if it exists, it will not be affected by it.

Therefore, when a trigger pulse is output from the trigger pulse generator 12, the counter 20 starts a counting operation in response to this, while a drive pulse is output from the wave transmitter 14, and this drive pulse causes the bottom of the container 2 to be Ultrasonic pulses are emitted from the placed ultrasonic probe 6. Then, this ultrasonic pulse is reflected by the reflection plate IO suspended by the float 8 without being affected by the air bubbles 30, and is received again by the ultrasonic probe 6. Then, the output from the ultrasonic probe 6 is amplified and detected by the wave receiving section 16, and then compared with a predetermined threshold value by the level comparing section 18.

When a trigger pulse is input from the trigger pulse generator 12, the counter 20 starts counting from the preset value. When the ultrasonic echo reflected by the reflection plate 10 is received, the signal level exceeds the threshold set by the level comparison section 18, so the output from the level comparison section 18 at that time is As a result, the counter 20 stops counting. As a result, the counter 20 outputs a count value corresponding to the time required for reciprocating the distance m between the ultrasound probe 6 and the reflection plate 10, and this count value is used for the next step of calculation. The information is sent to the section 24. The calculation unit 24 calculates the distance a between the floating device 8 and the reflecting plate 10 and the container! Since the correction data taking into account the thickness t of the bottom surface of The value of t is displayed on the display section 26 as the height of the liquid level 2a.

In this embodiment, the ultrasonic probe 6 is attached to the bottom of the outside of the container 1, but as in the conventional case, it is placed submerged in the liquid 2 of the container I to adjust the height of the liquid level 2a. Of course, it can also be measured.

<Effects of the Invention> According to the present invention, the height of the liquid level can be accurately measured without being affected by the presence of bubbles on the liquid surface or in the liquid. Excellent effects such as being able to do things are demonstrated.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an ultrasonic level meter according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram of a conventional ultrasonic level meter. 1... Container, 2... Liquid, 4... Ultrasonic level meter,
6. Ultrasonic probe, 8. Floating device, lO...Reflector.

Claims (1)

[Claims] (1) Ultrasonic probe that transmits and receives ultrasonic pulses (6)
The ultrasonic probe (6) emits ultrasonic pulses toward the surface of the liquid (2) stored in the container (1), and the reflected waves are sent back to the ultrasonic probe. In the ultrasonic level meter that measures the height of the liquid level based on the time until the wave is received by the probe (6), the ultrasonic probe (6) is placed at the bottom of the container (1), while a floating device (8) having a specific gravity smaller than that of the liquid disposed in the container (1); a reflecting plate (10) having a specific gravity larger than the liquid swingably suspended from the floating device (8); An ultrasonic level meter characterized by comprising: