JPH08219854A - Ultrasonic liquid level meter - Google Patents

Abstract

PURPOSE: To measure a liquid level particularly when waves or the like occurs on the liquid surface in an ultrasonic liquid level meter for measuring the inside liquid level of a vessel or the like by using ultrasonic wave. CONSTITUTION: A time interval between first echo wave (the echo wave reflected on a liquid level 2 once) and second echo wave (the echo wave reflected on the liquid 2 twice) of ultrasonic transmission in the liquid in a vessel 1 is obtained based on a detection signal from an ultrasonic transceiver 3 by an ultrasonic instrument 5. A liquid level is obtained based on the time interval between the first echo wave and the second echo wave of ultrasonic wave in the liquid obtained by the ultrasonic instrument 5 and the transmission speed of the ultrasonic wave in the liquid corrected by a temperature signal. Even if the second echo wave is not detected, the current liquid level can be computed based on the time interval proportional to the liquid level computed after obtaining only the time interval of the first echo wave by a displacement computing device 8 and the last liquid level stored in a processing unit 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid level meter for measuring the liquid level of a liquid inside a container (including piping etc.) by using ultrasonic waves, and particularly to a liquid level meter having a large wave on the liquid surface. The present invention relates to an ultrasonic liquid level meter capable of measuring a liquid level even when a second echo wave (echo of an ultrasonic wave reflected twice on a liquid surface) cannot be detected due to a factor.

[0002]

2. Description of the Related Art A conventional ultrasonic liquid level gauge is shown in FIG. 4 (longitudinal sectional view). In this example, when the temperature change range of the liquid passing through the inside of the pipe 1 is wide, The liquid level of the liquid surface 2 is measured in consideration of the temperature. By the way, the temperature of the pipe 1 itself changes due to the temperature change of the liquid inside the pipe 1, and for a long time,
Since the temperature of the pipe 1 and the temperature of the liquid become the same, a temperature measuring sensor 9 such as a thermistor is attached to the outer periphery of the pipe 1.

When measuring the liquid level of the liquid in the pipe 1 using the ultrasonic transmitter / receiver 3 mounted on the lower surface of the bottom wall of the pipe 1, the propagation velocity of the ultrasonic wave changes depending on the temperature of the liquid. Therefore, the time S ₁ when the ultrasonic wave is reflected once on the liquid surface and returns to the ultrasonic transmitter / receiver 3 and the ultrasonic wave which is reflected once on the liquid surface is reflected on the bottom of the inner wall of the pipe and further reflected on the liquid surface. To the difference (S ₂ −S ₁ ) from the time S ₂ when the item is returned,
The ultrasonic wave velocity corrected based on the temperature signal from the sensor 9 is multiplied by the arithmetic processing unit 13 to calculate the correct liquid level.

The display device 7 shown in FIG. 4 displays the liquid level calculated by the arithmetic processing device 13. The ultrasonic liquid level measuring device 12 processes the signal from the ultrasonic transmitter / receiver 3 to perform arithmetic processing. The temperature measuring instrument 10 processes the signal from the temperature sensor 9 and sends it to the arithmetic processing unit 13.

[0005]

In the conventional ultrasonic liquid level meter, when the liquid in the container is flowing, if the wave becomes large or bubbles are generated on the liquid surface, the liquid level of the ultrasonic wave is increased. The received level of the reflected echo wave from the
There is a problem that the ratio (signal ratio with respect to noise) decreases and the reflected echo wave (especially the echo wave reflected twice on the liquid surface) cannot be detected, and the liquid level cannot be measured.

The present invention is intended to solve the above-mentioned problems, and a second echo wave (at the liquid surface) from the liquid surface is caused by factors such as a large wave on the liquid surface of the liquid in the container. It is an object of the present invention to provide an ultrasonic liquid level meter capable of measuring a liquid level even if it becomes impossible to detect an echo wave reflected twice.

[0007]

In order to achieve the above-mentioned object, an ultrasonic liquid level meter of the present invention is mounted on a lower surface of a bottom wall of a liquid containing portion in order to measure the liquid level of the liquid in the liquid containing portion. Displacement transmitter that calculates the ultrasonic wave propagation time corresponding to the displacement of the liquid level based on the signal from the ultrasonic wave transmitter and the ultrasonic wave transmitter and the ultrasonic wave transmitter connected to the ultrasonic wave transmitter and receiver. And a temperature measuring device that measures the temperature of the liquid, and an arithmetic processing unit that calculates the liquid level of the liquid based on signals from the ultrasonic measuring device, the displacement calculating device, and the temperature measuring device. It is characterized by being configured as.

Further, the ultrasonic liquid level meter of the present invention is designed to measure the liquid level of the liquid in the liquid containing portion and the ultrasonic transmitter / receiver mounted on the lower surface of the bottom wall of the liquid containing portion. The first time from the transmission of the ultrasonic wave propagated from the container toward the liquid surface through the bottom wall of the liquid container and the liquid to the reception of the echo wave reflected once by the liquid surface of the ultrasonic wave. And an ultrasonic measuring device for measuring a second time from the transmission of the ultrasonic wave to the reception of an echo wave reflected twice on the liquid surface of the ultrasonic wave, and a signal from the ultrasonic measuring device. In addition to the above, a displacement calculator for calculating an ultrasonic wave propagation time proportional to the displacement of the liquid level of the liquid based on the first time and a temperature measuring device for measuring the temperature of the liquid containing portion are provided, and the same temperature measurement is performed. After receiving the temperature signal from the instrument An ultrasonic propagation velocity in the liquid, and means for calculating the liquid level of the liquid based on the difference between the first time of the received from the ultrasonic measuring device and the second time,
When the echo wave reflected twice on the liquid surface is not detected and the second time cannot be obtained, the product of the time proportional to the displacement received from the displacement calculator and the ultrasonic propagation velocity is stored. It is characterized in that it is provided with an arithmetic processing unit having means for calculating the liquid level of the liquid based on the previously measured liquid level value.

[0009]

In the above ultrasonic level meter of the present invention, the first echo wave of ultrasonic wave propagation in the liquid in the container (once at the liquid level once by the ultrasonic measuring device based on the detection signal from the ultrasonic transmitter / receiver). The time interval for the reflected echo wave) and the second echo wave (the echo wave reflected twice on the liquid surface) is obtained.

Then, from the time interval between the first echo wave and the second echo wave of the ultrasonic wave in the liquid obtained by the ultrasonic measuring device, and the propagation velocity of the ultrasonic wave in the liquid corrected by the temperature signal. Although the liquid level is obtained, even when the second echo wave is not detected, a time interval proportional to the displacement of the liquid level calculated by obtaining only the time interval of the first echo wave by the displacement calculator, and an arithmetic processing unit The current liquid level can be calculated from the previously measured liquid level stored in the memory.

[0011]

EXAMPLE As shown in FIG. 1, an ultrasonic transmitter / receiver 3 is mounted on the bottom surface of a bottom wall of a stainless steel pipe 1 serving as a liquid container, and the ultrasonic transmitter / receiver 3 has an ultrasonic measuring device 5 attached thereto. Are connected. Then, in the ultrasonic measuring device 5, based on the signal from the ultrasonic transmitter / receiver 3, from the transmission of the ultrasonic wave propagated toward the liquid surface 2 through the bottom wall of the pipe 1 and the liquid, the liquid of the ultrasonic wave is transmitted. First time S ₁ until reception of echo wave (first echo wave) reflected once on surface 2 and second time until reception of echo wave (second echo wave) reflected twice on liquid surface 2 S ₂ is measured (see FIG. 2). Reference numeral 21 in FIG. 2 (a) indicates the path length of the first echo wave, and reference numeral 22 in FIG. 2 (b).
Indicates the path length of the second echo wave.

Further, a temperature sensor 9 for measuring the temperature of the liquid in the pipe 1 is mounted on the outer periphery of the pipe 1, and a signal from the temperature sensor 9 is sent to the temperature measuring device 10 by the arithmetic processing unit 6.
Is converted into a temperature signal to be input to and the same signal is transmitted. On the basis of this temperature signal, the arithmetic processing unit 6 obtains the ultrasonic wave propagation velocity V in the liquid from the temperature characteristic of the sonic velocity in the liquid which is input in advance.

In this way, in the arithmetic processing unit 6, the first time S ₁ from the ultrasonic measuring device 5 and the second case S ₂ are transmitted.
And the ultrasonic propagation velocity V described above, the liquid level L can be obtained from the following [Equation 1].

## EQU1 ## 2L = V × (S ₂ −S ₁ ) The liquid level L thus obtained is displayed on the display device 7 connected to the arithmetic processing device 6.

Such normal measurement of the liquid level can be performed when both the first echo wave and the second echo wave, which are the reflected echo waves of the ultrasonic waves, can be detected. Is reflected by the liquid surface once more than by the first echo wave, and is also reflected once more by the bottom surface in the pipe, so the echo level becomes considerably small, and when a wave etc. occurs on the liquid surface, It becomes impossible to detect the echo wave (see FIG. 3). It should be noted that FIG. 3 (a) shows the first echo wave 31
And the state where the second echo wave 32 is detected, and FIG. 6B shows the state where only the first echo wave is detected.

In such a case, the displacement calculator 8 is adapted to continue the liquid level measurement if only the first echo wave having an echo level higher than that of the second echo wave can be detected. The displacement calculator 8 is the first measured by the ultrasonic measuring device 5.
The time S ₁ is always stored in addition to the currently measured value one time before, that is, the previous value, and the difference (S ₁ ′) between the previous first time S ₁ and the current first time S ₁ ′ is calculated. -S ₁ ) is transmitted to the arithmetic processing unit 6 as a time proportional to the liquid level displacement.

In the arithmetic processing unit 6, normally, the liquid level L is calculated by the above-mentioned means by the first time S ₁ and the second time S ₂ received from the ultrasonic measuring device 5, but the second time is calculated.
The echo wave cannot be detected, and the second time S
_{When 2} is not obtained, the calculation of the liquid level L is automatically performed by using the time signal (S ₁ ′ −S ₁ ) proportional to the liquid level displacement from the displacement calculator 8 described above. Switching is performed.

The arithmetic processing unit 6 always stores the previous value L of the currently calculated liquid level L ', and calculates the liquid level L'from the current ultrasonic propagation velocity V'by the following relational expression. It can be obtained from [Equation 2].

[Number 2] 2L '= 2L + V' × (S 1 '-S 1) thus determined was the liquid level L', the arithmetic processing unit 6
Is displayed on the display device 7 connected to.

[0018]

As described in detail above, according to the ultrasonic liquid level meter of the present invention, the following effects can be obtained. (1) Transmission of ultrasonic waves propagated from the ultrasonic transmitter / receiver to the liquid surface through the bottom wall of the liquid container and the liquid and reception of echo waves reflected once by the liquid surface of the ultrasonic waves From the transmission of the above ultrasonic wave for the first time until 2
By the second time until the reception of the echo wave reflected once,
Since the liquid level is obtained, the liquid level can be obtained accurately even if the material and wall thickness of the liquid containing portion such as the pipe and the container are changed. (2) Even if the liquid surface of the liquid in the liquid storage part is greatly shaken by the wave and the second echo wave reflected twice on the liquid surface cannot be detected, it is proportional to the displacement received from the displacement calculator. Since the means for calculating the liquid level is provided from the product of the time for which the ultrasonic wave propagates in the liquid and the liquid level value of the previous measurement, the liquid level can be accurately obtained without interrupting the measurement. .

[Brief description of drawings]

FIG. 1 is a schematic view showing an arrangement configuration of an ultrasonic liquid level gauge as an embodiment of the present invention.

2 (a) and 2 (b) are each an explanatory view showing a working state in a main part of the apparatus of FIG.

3 (a) and 3 (b) are graphs each schematically showing a detection state of an echo wave in the apparatus of FIG.

FIG. 4 is a schematic diagram showing an arrangement configuration of an example of a conventional ultrasonic water level meter.

[Explanation of Codes] 1 Piping as a liquid storage part 2 Liquid level 3 Ultrasonic wave transmitter / receiver 4 Ultrasonic waves propagating in liquid 5 Ultrasonic wave measuring device 6 Calculation processing device 7 Display device 8 Displacement calculation device 9 Temperature sensor 10 Temperature measurement Device 21 First echo waveguide step 22 Second echo waveguide step 31 First echo wave 32 Second echo wave

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[Procedure amendment]

[Submission date] March 23, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

[0013] In this manner, the arithmetic processing unit 6, a first time S ₁ and the second time S from the ultrasonic measuring device 5
_The liquid level L can be calculated by the following [Equation 1] from ₂ and the ultrasonic propagation velocity V described above.

[Equation 1] The liquid level L thus obtained is displayed on the display device 7 connected to the arithmetic processing device 6.

Claims (2)

[Claims] 1. An ultrasonic transmitter / receiver mounted on a lower surface of a bottom wall of the liquid containing portion for measuring a liquid level of the liquid containing portion, and an ultrasonic measuring device connected to the ultrasonic transmitter / receiver. A displacement calculator that calculates an ultrasonic wave propagation time corresponding to the displacement of the liquid level based on a signal from the ultrasonic meter, a temperature measuring device that measures the temperature of the liquid, and the ultrasonic measuring device. An ultrasonic liquid level gauge, comprising: an arithmetic processing unit that calculates the liquid level of the liquid based on signals from a displacement calculator and a temperature measuring device. 2. An ultrasonic transmitter / receiver mounted on a lower surface of a bottom wall of the liquid containing portion for measuring the liquid level of the liquid in the liquid containing portion, and the ultrasonic transmitter / receiver in the bottom wall of the liquid containing portion. And measuring the first time from the transmission of the ultrasonic wave propagated to the liquid surface via the liquid to the reception of the echo wave reflected once by the liquid surface of the ultrasonic wave, and the transmission of the ultrasonic wave. From the ultrasonic measuring device for measuring the second time until the reception of the echo wave reflected twice on the liquid surface of the ultrasonic wave, and receiving the signal from the ultrasonic measuring device, and based on the first time described above. It is equipped with a displacement calculator that calculates the ultrasonic wave propagation time proportional to the displacement of the liquid level of the liquid, and a temperature measuring device that measures the temperature of the liquid container, and also receives the temperature signal from the temperature measuring device to obtain the same temperature. Ultrasonic propagation velocity in the liquid obtained to correspond to the signal, A means for calculating the liquid level of the liquid based on the difference between the first time and the second time received from the ultrasonic measuring device, and an echo wave reflected twice on the liquid surface cannot be detected. When the second time is not obtained, the product of the time proportional to the displacement received from the displacement calculator and the ultrasonic wave propagation velocity and the stored last measured liquid level value are used to determine the liquid level of the liquid. An ultrasonic liquid level gauge, comprising an arithmetic processing unit having means for calculating a liquid level.