JPH0486525A - Ultrasonic level meter - Google Patents

Abstract

PURPOSE:To certainly measure the level of a liquid by utilizing the change of the propagation time of the ultrasonic wave propagating through an ultrasonic good conductor based on the change of the contact area of the ultrasonic good conductor and a liquid when a part of the ultrasonic good conductor is present in the liquid. CONSTITUTION:When a liquid 8 is received in a container 1, the surface wave excited by a transmitting and receiving ultrasonic vibrator 3 operated by the electric output pulse of a high frequency transmitter 4 propagates downwardly along the surface of a plate-shaped metal 2 and, when this surface wave reaches the surface of a liquid surface 9, said wave propagates at speed slower than the air propagation speed of the metal 2 by the resistance of the liquid 8 and is reflected at the lower end of the metal 2 to propagate upwardly. When the surface wave reaches the liquid surface 9, it again propagates at the air propagation speed of the metal 2 to be received by the vibrator 3. Therefore, as the contact range of the metal 2 with the liquid 8 increases, the propagation speed of the surface wave becomes slower than the air propagation speed of the metal 2. The acoustic energy received by the vibrator 3 is converted to an electric signal which is, in turn, amplified by a receiver 5 and a delay time is measured by an operation circuit 6 and the level of the liquid surface 9 is displayed on a display device 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic level meter that measures the level of a liquid using ultrasonic waves.

[Prior art]

A float-type type is well known as a conventional liquid level gauge, and is used in automobile fuel gauges and the like.

In this method, a float installed in a liquid tank moves up and down as the liquid increases and decreases, and a bar connected to the float changes the resistance value of the tilt potentiometer.
The resistance value indicates the liquid level on the meter.

In addition, an ultrasonic transducer is installed at the top of the liquid container, and the ultrasonic transducer emits ultrasonic pulses toward the liquid surface, and the distance to the liquid surface is determined by receiving the reflected echo from the liquid surface. Ultrasonic level meters that measure and display water levels are known.

[Problem to be solved by the invention]

However, with such conventional methods, measurement errors are extremely large due to vibrations of automobiles, shaking and tilting of the liquid level on slopes, etc.Especially with conventional ultrasonic level meters,
Due to fluctuations or inclinations of the liquid surface, ultrasonic echoes reflected from the liquid surface may not return to the ultrasonic transducer, resulting in cases where measurements cannot be made.

In addition, since piezoelectric vibrators are affected by liquids and gases, they have to be sealed or coated with rubber or the like, which reduces efficiency and increases the size and cost of the vibrator. Ta.

[Means to be solved by the invention]

In the present invention, an ultrasonic transducer is bonded to one end of a metal rod-shaped, cylindrical, or plate-shaped ultrasonic good conductor, and when an ultrasonic pulse is emitted from this ultrasonic vibrator, a longitudinal wave is generated in the ultrasonic good conductor. Transverse waves and surface waves are generated, of which the surface waves propagate on the surface of the ultrasonic good conductor. When a part of the ultrasonic good conductor is in a liquid, the propagation time of the surface wave of the ultrasonic wave propagating through the ultrasonic good conductor changes depending on the change in the contact area between the ultrasonic good conductor and the liquid. This is an ultrasonic level meter that measures levels.

[Effect]

According to the present invention, when a transmitting ultrasonic transducer is excited by the electric output of a high-frequency oscillator, an ultrasonic pulse is emitted from the ultrasonic transducer, and longitudinal waves, transverse waves, and surface waves are generated in the ultrasonic good conductor. . Among these, surface waves propagate at a constant speed on the surface of a good ultrasonic conductor in the air, and are received by a receiving ultrasonic transducer. However, on the surface of a good ultrasonic conductor submerged in liquid, the propagation speed of surface waves is slower than in air due to the resistance caused by the liquid. Therefore, the longer the distance that the ultrasonic good conductor is in contact with the liquid, the greater the influence of the surface wave on the sound velocity. In other words, if the part of the ultrasonic good conductor in the liquid is short, the resistance of the liquid will have little effect on the propagation speed of the surface wave, and the propagation time of the surface wave from when the ultrasonic wave is emitted until it is received is the same as in the air. The propagation time approaches and becomes shorter. On the other hand, when the part of the ultrasonic good conductor in the liquid is long, the propagation speed of the surface wave is greatly influenced by the resistance of the liquid, and the propagation time of the surface wave from when the ultrasonic wave is emitted to when it is received is shorter than that in the air. is longer than the propagation time of time. Therefore, by measuring the time during which this ultrasonic surface wave propagates on the surface of the ultrasonic good conductor, the water level of the liquid can be calculated. Third
The figure is a graph showing the relationship between water level and surface wave propagation speed when an experiment was conducted using a square pipe-shaped metal.

〔Example〕

Referring to FIG. 1, in the ultrasonic level meter according to one embodiment of the present invention, a metal plate 2 is fixed almost perpendicularly to the bottom of a liquid container 1, and the upper end of the metal plate 2 is used for transmitting and receiving ultrasonic vibrations. Child 3
is attached, and a high frequency oscillator 4 and a receiver 5 are connected to the ultrasonic transducer 3. An arithmetic circuit 6 and a display 7 are connected to the receiver 5 .

When the transmitting/receiving ultrasonic transducer 3 is excited by the electric pulse output of the high frequency oscillator 4, an ultrasonic pulse is emitted from the transmitting/receiving ultrasonic transducer 3, and an ultrasonic surface wave is generated on the sheet metal 2. The waves propagate downward on the surface of the metal plate 2 at a specific propagation speed, are reflected at the lower end of the metal plate 2, propagate upward again, and are received by the ultrasonic transducer 3 which serves both as a transmitter and receiver.

Now, when there is a liquid 8 in the container 1 as shown in FIG. Then, the liquid 8 propagates at a speed slower than the air propagation speed of the metal plate 2 due to the resistance of the liquid 8, is reflected at the lower end of the metal plate 2, and propagates upward.

Then, when the surface wave reaches the liquid surface 9, it propagates again at the air propagation velocity of the plate metal 2 and is received by the ultrasonic transducer 3 which serves as both transmitter and receiver.

Therefore, there are many areas where the plate metal 2 is in contact with the liquid 8.
That is, the closer the position of the liquid level 9 is to the transmitting/receiving ultrasonic transducer 3, the slower the surface wave propagation time becomes compared to the air propagation time of the plate metal 2.

The acoustic energy received by the transmitting/receiving ultrasonic transducer 3 is converted into an electrical signal, amplified by the receiver 5, and then sent to the arithmetic circuit 6.
The delay time is measured, and the water level of the liquid level 9 is displayed on the display 7.

Referring to FIG. 2, the ultrasonic level meter according to another embodiment of the present invention has a cylindrical metal 1 extending approximately perpendicularly from the bottom of the liquid container 1.
2 is fixed, a transmitting ultrasonic transducer 10 is attached below the cylindrical metal 12, and a receiving ultrasonic transducer 11 is attached above the cylindrical metal 12. The receiving ultrasonic transducer 11 is connected to the receiver 5 through the lead wire.
The receiver 5 is connected to a display 7 via an arithmetic circuit 6.

Now, when liquid 8 is contained in container 1, high frequency oscillator 4
When the transmitting ultrasonic transducer is excited by the output of It propagates upward at a speed slower than the air propagation speed of the metal 2, and when it reaches the liquid level 9, the cylindrical metal 2
The acoustic energy propagates on the surface at an air propagation velocity of , is received by the receiving ultrasonic transducer 11, and the acoustic energy is converted into an electrical signal. This electric signal is amplified by a receiver 5, and after a delay time is measured by an arithmetic circuit 6, a water level is displayed on a display 7.

In the above embodiment, the transmitting ultrasonic transducer 10 is attached below the cylindrical metal 2 and the receiving ultrasonic transducer 11 is attached above, but it is possible to obtain the same effect even if the transmitting ultrasonic transducer 10 is placed in the opposite position. Not even.

〔Effect of the invention〕

Since the present invention is configured as described above, the liquid level can be reliably measured even if the liquid level fluctuates or tilts. In addition, the structure is simple and mass production is easy and can be supplied at low cost. Because sound propagates easily through the metal material, the oscillation power can be low and the circuit is simple.

In addition, it is not easily affected by temperature changes, so the measurement accuracy is high. Fig. 1 is a configuration diagram of an ultrasonic level meter according to one embodiment of the present invention, and Fig. 2 is a configuration diagram of an ultrasonic level meter according to another embodiment of the present invention. Figure 3 is an experimental graph showing the relationship between water level and surface wave propagation time in a square pipe.

1...Liquid container 2...Plate metal 3...Ultrasonic transducer for transmitting and receiving 4...High frequency oscillator 5...
・Receiver 6... Arithmetic circuit 7... Display
8...Liquid 9...Liquid level lO...Ultrasonic transducer for wave transmission 11...Ultrasonic transducer for delivery 12...Cylindrical metal Fig. 1 Fig. 3 Fig. 2 (a畢)

Claims (1)

[Claims] When a part of the ultrasonic good conductor in a vacuum or gas is in a liquid, the propagation time of the surface wave of the ultrasonic wave propagating through the ultrasonic good conductor changes depending on the change in the contact area between the ultrasonic good conductor and the liquid. An ultrasonic level meter that measures the level of liquid using