JPH0720100A - Ultrasonic liquid measuring apparatus - Google Patents

Abstract

PURPOSE:To obtain a title apparatus with the waveguide of ultrasonic waves and the receiver installed at an interval in a liquid to measure an equalized density and a level of a liquid with ununiform density distribution. CONSTITUTION:This apparatus comprises a waveguide 9 installed in a liquid tank 3 storing a liquid under test to radiate ultrasonic waves to the liquid under test, an ultrasonic transducer 8 which receives ultrasonic waves reflected from the boundary between the terminal of this waveguide 9 and the liquid under test, an ultrasonic receiver 11 which receives ultrasonic waves radiated into the liquid under test, and an arithmetic means which processes output signals from each receiver.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the measurement of liquid density and liquid level in a liquid tank, and more particularly to an ultrasonic liquid measuring device capable of uniformized density detection of the entire liquid using ultrasonic waves.

[0002]

2. Description of the Related Art Conventionally, in the case of measuring the liquid level and density of a liquid stored in a tank, an air purge type measuring device as shown in FIG. 2 is used. This measuring device has a first purge pipe 4 and a second purge pipe 5 in which air sent from the self-operated flow rate control valves 1 and 2 is installed in a liquid tank 3.
The back pressure generated in the two purge pipes 4 and 5 is released into the liquid from the tip of the two differential pressure detectors 6 in the differential pressure detecting means 6.
a and 6b are used to measure the density and liquid level. That is, according to this configuration, since the relationship of the following expression (1) is established between the liquid level and the back pressure, the liquid level can be known by measuring the back pressure.

[0003]

## EQU1 ## P = ρgh (1) where P: back pressure, ρ: density of liquid, g: acceleration of gravity,
h: represents the height from the tip of the purge pipe to the liquid surface. As a result, the back pressure P ₁ of the _first purge pipe 4 and the second purge pipe 5
Assuming that the back pressure is P ₂ , the following equations (2) and (3) are established.

[0004]

## EQU2 ## P ₁ = ρg (h + L) (2) P ₂ = ρgh (3) Therefore, the signal to the differential pressure detecting means 6 is P ₁ -P ₂ = ρg
It becomes L. Here, since the gravitational acceleration g and L: the difference between the tips of the first purge pipe 4 and the second purge pipe 5 are known, the density can be measured. However, this method can measure only the density of the places where both purge pipes 4 and 5 are installed.

[0005]

The density of the liquid stored in the liquid tank 3 is not always uniform. That is, the respective densities differ depending on the content, flow, temperature, etc. of the inflowing liquid, and it is difficult for the density distribution to be uniform. Therefore,
In the density measurement by the air purge method, both purge pipes 4, 5
If the density distribution is not uniform in the liquid tank 3 only at the place where is installed, it is not possible to represent the overall density.

As a countermeasure against this, a plurality of sets of purge pipes 4 and 5 are dispersedly arranged in the liquid tank 3 and the density data measured at the same time in each place are aggregated to calculate an average value.
Immediately before the measurement, the liquid in the liquid tank 3 is agitated to make the density distribution in the liquid tank 3 uniform, but in both cases, the device is complicated and the work is complicated, so that measurement results can be obtained. There was an obstacle that it took time.

The object of the present invention is to install an ultrasonic wave director and a receiver separately in a liquid, and to measure the uniformed density and liquid level of a liquid having an uneven density distribution. An object is to provide an ultrasonic liquid measuring device.

[0008]

In order to achieve the above object, an ultrasonic liquid measuring apparatus according to the present invention is installed in a liquid tank in which a liquid to be measured is stored, and a ultrasonic wave is emitted to the liquid to be measured. And an ultrasonic transceiver that sends ultrasonic waves to the waveguide and receives ultrasonic waves reflected from the boundary between the end of the waveguide and the liquid to be measured, and in the liquid to be measured. It is characterized by comprising an ultrasonic wave receiver for receiving the emitted ultrasonic wave and an arithmetic means for processing an output signal from each of the receivers.

[0009]

The ultrasonic waves emitted from the ultrasonic transmitter / receiver into the waveguide are reflected at the end of the waveguide and the boundary with the liquid to be measured. These reflected signals differ in the time received by the ultrasonic transceiver due to the difference in their respective distances,
The liquid level is calculated by the calculating means from the difference and a liquid level signal is output.

The ultrasonic waves radiated from the waveguide into the liquid to be measured propagate through the liquid to be measured having different densities and reach the ultrasonic wave receiver. Since the ultrasonic wave propagation velocity of the waveguide is slower than the propagation velocity of the liquid to be measured, the one radiated from the boundary portion of the liquid to be measured comes first. The output signal from the ultrasonic receiver is calculated by the calculation means from the propagation velocity thereof to obtain a uniform density, and a density signal is output.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. It should be noted that the same components as those in the above-described conventional technique are designated by the same reference numerals, and detailed description thereof will be omitted. As shown in the configuration diagram of FIG. 1, the ultrasonic oscillator 7 is connected to the ultrasonic transmitter / receiver 8 and sends out ultrasonic waves to the ultrasonic transmitter / receiver 8. The ultrasonic transmitter / receiver 8 is coupled with a director 9 which is partially installed in the liquid to be measured stored in the liquid tank 3.

The waveguide 9 is made of, for example, silicon rubber and has a medium whose ultrasonic wave propagation speed is slower than that of the liquid to be measured. The director 9 radiates the ultrasonic waves output from the ultrasonic transmitter / receiver 8 into the liquid and outputs a liquid level signal. Further, an ultrasonic wave receiver 11 is installed near the bottom of the liquid tank 3 so as to be isolated from the director 9 in the liquid, and receives an ultrasonic wave propagated in the liquid at the boundary with the liquid surface 10. , Liquid tank 3
The ultrasonic transmitter / receiver 8 and the ultrasonic receiver installed outside
It is composed of an arithmetic means for calculating the liquid level and density from the output signal from 11.

In addition to the ultrasonic oscillator 7, the arithmetic means includes a first amplified waveform shaper 12 for inputting an output signal of the ultrasonic receiver 11, a first flip-flop 13, a clock oscillator 14, and a first oscillator. AND circuit 15, a first counter 16, a second amplified waveform shaper 17 for inputting an output signal from the ultrasonic transceiver 8, a second flip-flop 18, a second
AND circuit 19, second counter 20, third amplified waveform shaper 21, third flip-flop 22, third AN
It is composed of a D circuit 23, a third counter 24 and a calculator 25 which outputs a density signal and a liquid level signal.

Next, the operation of the above configuration will be described. The ultrasonic waves sent from the ultrasonic oscillator 7 to the ultrasonic transmitter / receiver 8 pass through the director 9 and are radiated into the liquid to be measured in the liquid tank 3. This emitted ultrasonic wave is propagated in the liquid and received by the ultrasonic wave receiver 11.

Although the propagation time of this ultrasonic wave varies depending on the radiation position of the director 9 and the density in the liquid, the distance to the ultrasonic receiver 11, etc., the ultrasonic wave is radiated particularly from the terminal end of the director 9. Compared to the one radiated from the boundary with the liquid surface 10 near the base of the waveguide 9, the propagation time in the waveguide 9 is added and the propagation velocity is slower than that of the liquid to be measured. Therefore, a slight delay occurs.

Therefore, the ultrasonic wave receiver 11 first receives the ultrasonic wave radiated into the liquid at the boundary with the liquid surface 10. The output signal from the ultrasonic receiver 11 is amplified and shaped by the first amplified waveform shaper 12, and the first flip-flop
13 reset signal. Further, the output signal of the first flip-flop 13 together with the output signal of the clock oscillator 14
The time t ₁ is obtained as the output of the first counter 16 via the first AND circuit 15.

This time t ₁ contains the information on the time when the ultrasonic wave propagates in the liquid to be measured, but at the same time, it is necessary to clarify the information on the time when the ultrasonic wave propagates in a part of the waveguide 9. Further, in order to measure the density, it is necessary to measure the velocity of propagation in the liquid, and for that purpose, the velocity component of the ultrasonic wave propagating in the waveguide 9 is clarified.

Therefore, first, in order to measure the time of propagation in a part of the waveguide 9, the ultrasonic wave reflected at the boundary between the waveguide 9 and the liquid surface 10 is used. The reflected signal is received by the ultrasonic wave transmitter / receiver 8, is amplified and shaped by the second amplified waveform shaper 17, and becomes a reset signal for the second flip-flop 18.

The output signal of the second flip-flop 18 is combined with the output signal of the clock oscillator 14 into a second AND signal.
The time t is output as the output of the second counter 20 via the circuit 19.
_{Get 2}

Next, in order to clarify the velocity component of the ultrasonic wave propagating in the director 9, the ultrasonic wave reflected at the terminal end of the director 9 is used. The reflected signal from the terminal end of the director 9 is also received by the ultrasonic wave transmitter / receiver 8, and the amplified waveform is shaped by the third amplified waveform shaper 21 that has been masked (dead time) for a certain period of time. The reset signal of the flip-flop 22 is used.

The output signal of the third flip-flop 22 and the output signal of the clock oscillator 14 are combined with a third AND signal.
The time t is output as an output of the third counter 24 via the circuit 23.
_{Get three} .

The signals of these times t _{1 to} t ₃ are arithmetically processed by the arithmetic unit 25, and the liquid level signal is output together with the density signal. As shown in FIG. 1, the reference line 26 of the director 9 is set at the installation position of the ultrasonic receiver 11 in the liquid tank 3, and the distance from the ultrasonic transmitter / receiver 8 to the reference line 26 is H, and the reference line 26. To the end of the director 9 is Z, the distance from the reference line 26 to the liquid surface 10 is h, and the distance from the director 9 to the ultrasonic receiver 11 on the reference line 26 is L. Letting s be the propagation velocity of the ultrasonic wave in the wave vessel 9 and v be the propagation velocity of the ultrasonic wave in the liquid to be measured, the following equation (4),
(5) and (6) are satisfied.

[0023]

[Equation 3] When s is deleted from these equations (5) and (6), h corresponding to the liquid level signal is obtained by the following equation (7).

[0024]

[Equation 4] h = H (t ₃ −t ₂ ) / t ₃ −Z · t ₂ / t ₃ (7) Further, if s is deleted from the above equations (4) and (5), it corresponds to a density signal. v is obtained by the calculation of the following equation (8).

[0025]

[Equation 5] Note that h in the equation (8) is given by the equation (7), and all other numerical values are known.

On the other hand, since the density signal ρ is a function of v,
After all, the values of h and ρ can be measured. Also, in the director 9, ultrasonic waves are radiated from any part in the liquid,
In order for the ultrasonic wave radiated from the boundary with the liquid surface 10 to reach the ultrasonic wave receiver 11 first, the ultrasonic wave speed s in the director 9 should be lower than the ultrasonic wave speed v in the liquid. It is necessary to select the medium of the director 9 so that

There are cases where the density distribution is not uniform in the actual liquid, but in this case, refraction occurs at the interfaces having different densities, and the propagation path is not a straight line. However, as described above, the waveguide 9 is used. Since the ultrasonic velocity s> ultrasonic velocity v 1 is used for the medium, the measurement that reflects the density distribution of the entire stored liquid becomes possible.

If there is a change in the ultrasonic velocity due to the temperature of the liquid, it can be corrected from the change in the time t _{3 in} the above equation (6). As described above, according to the present invention, the whole object is measured instead of the fixed point monitoring, so that the density can be accurately equalized. Furthermore, because measurement can be performed without being affected by fluctuations in the liquid level 10, there is no need to provide a container or sample line to keep the ultrasonic wave transmission and reception intervals constant, and the structure, maintenance, and economy are simplified. it can.

[0029]

As described above, according to the present invention, the total density of all liquids in the liquid tank can be easily measured together with the liquid level. In addition, the density measurement is not affected by the liquid level fluctuation, and can be easily corrected even for temperature changes, which has the effect of obtaining high measurement accuracy.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an ultrasonic liquid measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a structural explanatory view of a conventional air purge type density meter.

[Explanation of symbols]

1, 2 ... Self-acting flow rate control valve, 3 ... Liquid tank, 4, 5 ... Purge pipe, 6 ... Differential pressure detecting means, 6a, 6b ... Differential pressure detector, 7 ...
Ultrasonic oscillator, 8 ... Ultrasonic transceiver, 9 ... Waveguide, 10 ...
Liquid level, 11 ... Ultrasonic receiver, 12 ... First amplified waveform shaper,
13 ... First flip-flop, 14 ... Clock oscillator, 15
... first AND circuit, 16 ... first counter, 17 ... second amplified waveform shaper, 18 ... second flip-flop, 19 ... second AND circuit, 20 ... second counter, 21 ... second 3 amplification waveform shaper, 22 ... third flip-flop, 23 ... third AND circuit, 24 ... third counter, 25 ... arithmetic unit, 26 ... reference line.

Claims (1)

[Claims] 1. A waveguide which is installed in a liquid tank in which a liquid to be measured is stored and radiates ultrasonic waves to the liquid to be measured; An ultrasonic wave transceiver for receiving ultrasonic waves reflected from the boundary with the liquid to be measured, an ultrasonic wave receiver for receiving the ultrasonic waves radiated in the liquid to be measured, and an output signal from each of the receivers. An ultrasonic liquid measuring device comprising a processing means for processing.