JP2975804B2 - Sound velocity measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound velocity measuring device used for measuring sound velocity in various fluids required as basic data for various ultrasonic measurements.

[0002]

2. Description of the Related Art Many measuring devices using ultrasonic waves, such as ultrasonic flow meters, require that the speed of sound in a fluid such as a liquid or gas in a stationary state be known.
Even with one ultrasonic flow meter as an example, its application fields are extremely diverse, such as clean water / sewage treatment systems, petrochemical plants, brewing processes, and fuel gas transfer systems. For this reason, it is necessary to grasp the sound speed in a stationary state as basic data in advance for a very wide variety of fluids. Further, since the speed of sound depends on the temperature, it is necessary to know the temperature dependency over the expected temperature range for each application field.

[0003] The sound velocities of limited main fluids are described in various data books such as an ultrasonic handbook and a scientific chronological table, but data on most fluids, especially including temperature dependence, are also included. The data is almost unknown. Therefore, conventionally, prior to designing the ultrasonic measurement system, a user of the measurement system sends a fluid sample and assembles a measurement device as shown in FIG.

[0004] That is, a stainless steel cylinder 2 is fixed to a metal plate 1, a liquid is filled in the cylinder, and ultrasonic transmitters 3 and receivers 4 are placed on opposite sides of the cylinder with adapters 5 and 6 interposed therebetween. And the propagation time of the ultrasonic wave propagating between the transmitter 3 and the receiver 4 is measured by using a well-known sing-around method, and the propagation path length is divided by the measured propagation time. The speed of sound is calculated.

[0005]

The above-described conventional method of measuring the speed of sound has the following various problems. First, since the propagation time in the adapters 5 and 6 and the side wall surface of the pipe 2 is a significant proportion of the net propagation time in the fluid calculated by subtracting them, the propagation time to be subtracted is calculated. The inaccuracy of the value has a significant effect on the decrease in measurement accuracy.

In addition, since a cylindrical container is used, the shape of the wave front of the propagating ultrasonic wave becomes complicated, and the waveform of the received signal is disturbed, thereby lowering the measurement accuracy. Furthermore, since the heat capacity of the metal cylinder 2 and the metal plate 1 is large, it takes time until the liquid temperature is stabilized to obtain the high temperature data until it stabilizes at the target temperature, and diverges from the side of the upright cylinder by convection. Temperature control becomes difficult due to the large amount of heat to be applied.
Also, the metal cylinder 2 expands and contracts with a change in the liquid temperature, so that the propagation path changes, and the measurement accuracy decreases. Further, since the measuring apparatus is large and heavy, it is difficult to carry the measuring apparatus to a client such as a flow rate / flow rate measuring system and perform the measurement on the spot.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems in the prior art, a sound velocity measuring apparatus in liquid according to the present invention comprises a container for holding a liquid to be measured, and both sides held between opposing side surfaces of the container. It comprises a metal rod having a small coefficient of thermal expansion that determines the distance between the surfaces, and a pair of electric / acoustic transducers that are attached to the outside of the opposite sides of the container while facing each other. According to a preferred embodiment of the present invention, the opposing sides of the container are kept substantially flat and substantially parallel. According to a further preferred embodiment of the invention, the container comprises a thin-walled plastic container.

[0008]

The speed of sound in the liquid is measured from the propagation time of the ultrasonic wave propagating between the transmitter and the receiver mounted on the outside of the side surface of the container facing each other and facing each other. The length of the ultrasonic wave propagation path is kept constant over a wide temperature range by the length of the metal rod having a small coefficient of thermal expansion. By keeping the opposing sides of the container substantially flat and substantially parallel, the propagation path of the ultrasonic wave is straight and the shape of the wave front is simple. Hereinafter, the present invention will be described in more detail with examples.

[0009]

1 is a side view of an apparatus for measuring the speed of sound in liquid according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line BB 'in FIG. 1
Reference numeral 1 denotes a box-shaped thin-walled plastic container, and four metal rods 13a, 13b, 13c, and 13d having a circular cross section are provided between screws 14a, 14b, and 14c between opposed side surfaces 11a and 11b of the container. , 14d... Each of the metal rods 13a to 13d is made of an invar alloy, a super invar alloy, a stainless invar alloy, an Fe-Ni-based Elinvar alloy, or the like having a small coefficient of thermal expansion. The surfaces of the metal rods 13a to 13d are coated with a resin such as ethylene tetrafluoride in order to impart corrosion resistance to liquids such as acids and alkalis.

A disk-shaped ultrasonic transmitter 21 and an ultrasonic receiver 22 are fixed on a flat and parallel external surface of each of the opposed side surfaces 11a and 11b of the container 11 via a thin adhesive layer. Have been. The interval between the transmitter 21 and the receiver 22 is determined by the interval between the opposing side surfaces 11a and 11b.
The distance between the side surfaces 11a and 11b is maintained at a constant value by the length of the four metal rods 13a to 13d, which have much higher rigidity and a small temperature change as compared with the plastic material of the container 11.

An operation / display panel 2 is provided outside one side surface orthogonal to the side surface on which the transmitter 21 and the receiver 22 are fixed.
0 is fixed. The operation / display panel 20 includes a transmitter 21 and a receiver 2 by a well-known sing-around method.
It incorporates an electronic circuit that generates a signal related to the propagation time of a sound wave propagating between the two, and a conversion / output unit that converts the signal generated by the electronic circuit into a sound speed in liquid and outputs it to a liquid crystal display device or the like. . A lid plate 12 made of a thin plastic is detachably mounted on the upper part of the container 11. Bosses 15a, 15b, and 15c through which a power supply line to the heater, a thermometer, and a stirrer pass are implanted in the cover plate 12.

In order to operate the subsonic sound velocity measuring device,
The lid plate 12 is removed from the container 11, and the liquid to be measured is poured into the container 11 until the liquid level is at an appropriate height equal to or higher than the mounting height of the transmitter 21 and the receiver 22, and the lid plate 12 is attached. A key switch on the operation / display panel 20 is operated to start a measurement operation. An AC voltage in the ultrasonic band is supplied to the transmitter 21 from an electronic circuit in the operation / display panel 20, and the ultrasonic wave generated by the transmitter 21 propagates in the liquid, is received by the receiver 22, and is supplied to the electronic circuit. Is done. This electronic circuit measures a count value indicating a propagation time of an ultrasonic wave based on a known sing-around method. Operation / display panel 2
The conversion / output unit within 0 converts the count value measured by the electronic circuit into a sound speed in the liquid, and digitally displays it on a display surface 24 composed of a liquid crystal panel or the like.

In order to obtain data on the temperature dependence of sound speed,
A throw-in type electric heater is put into the container 11, and the boss 15a
15c. In addition, a stirrer is inserted into the liquid through another boss, and stirring is performed so that the liquid temperature becomes uniform. Further, a thermometer is inserted into the liquid through another boss to measure the temperature of the liquid. Since the container 11 is small, lightweight and has a small heat capacity, it reaches a desired temperature in a short time. Further, since the container 11 is made of plastic having good heat insulating properties, the amount of heat radiated by convection or the like is small, and the temperature control is easy. It should be noted that the electric heater may be fixed to the bottom of the container 11 instead of being a throw-in type. Further, by providing a Peltier cooling element in the container in addition to the electric heater, the liquid temperature can be controlled to a lower temperature side.

As described above, an example has been described in which a transmitter and a receiver are attached to each of the opposed side surfaces of the container, and the speed of sound in the liquid is measured from the propagation time of the ultrasonic wave propagating between the transmitter and the receiver. However, a transmitter / receiver for both transmission and reception is installed on one side,
A configuration may be adopted in which a reflected wave radiated from the transceiver and reflected on the other side is received by the transceiver, and the speed of sound in the liquid is measured from the propagation time of the ultrasonic wave reciprocating between the sides.
In this case, a curved surface body for converging the reflected wave is added inside the other side surface for reflecting the ultrasonic wave, or the inside of the container or the cover plate is covered with a sound absorbing material for preventing unnecessary reflection. If so, it is more preferable. As described above, if the reciprocating structure is employed, the size and weight of the container can be further reduced, and the manufacturing cost can be reduced due to the reduction in the number of elements.

Although the present invention has been described by taking the case where the fluid to be measured is a liquid as an example, the airtightness between the container 11 and the cover plate 12 and the boss portion is improved, and the container 11 and the cover plate 1 are improved.
By adding a gas filling port and an exhaust port to 2, the sound velocity measuring device can be extended to an aerial sound velocity measuring device.

Although the operation / display panel 20 is fixed to the side surface of the container 11, the operation / display panel may be fixed on the cover plate. Further, in order to further improve the convenience of carrying, a handle may be attached in which both ends are rotatably supported on the upper portions of the side surfaces 11a and 11b. Alternatively, the operation / display portion may be provided separately from the container.

[0017]

As described above in detail, in the sound velocity measuring device of the present invention, since the propagation path length of the ultrasonic wave is fixed by the length of the metal rod, the propagation path length which directly affects the measurement accuracy is determined. It can be calculated accurately.

In addition, since the propagation time in the side of the thin-walled container is very small relative to the propagation time in the fluid calculated by subtracting them, the calculated value of the propagation delay time to be subtracted is somewhat inaccurate. Even so, the effect on the measurement accuracy is small.

Furthermore, since the transmitter and the receiver are fixed on the flat sides facing each other substantially in parallel, the shape of the wave front of the ultrasonic wave propagating in the liquid is simplified, the waveform of the received signal is adjusted, and the measurement accuracy is improved. Is improved.

The width of the container is extremely small, at most about 10 cm. In addition, a metal rod having a large density has a small volume, and a container and a cover plate having a large volume are both made of a thin plastic material. Therefore, the in-liquid sound velocity measuring device is carried by a client such as a flow / velocity measuring system, and the sample fluid is transferred to the container 1.
It is easy to pour into and measure the speed of sound.

Since the container is small, lightweight and has a small heat capacity,
Since the desired temperature can be reached in a short time and the container is made of plastic having good heat insulating properties, the amount of heat radiated from the upright side surface by convection or the like is small, and the temperature can be easily controlled. In this way, even if the container has a thin flexible structure, the opposing side surfaces are restrained by a large rigid metal rod, so that the side of the container is bent by the weight of the injected liquid, and the distance between the transmitter and the receiver is reduced. Change,
The measurement accuracy does not decrease due to the deterioration of the parallelism between them.

Further, since the metal rod for keeping the propagation path length of the ultrasonic wave in the liquid constant is made of Invar alloy or the like having a small coefficient of thermal expansion, the propagation path is constant over a wide temperature range even if the liquid temperature changes. , The measurement accuracy is reduced, and there is no need to perform complicated correction.

[Brief description of the drawings]

FIG. 1 is a side view showing a configuration of an in-liquid sound velocity measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line B-B 'of FIG.

FIG. 3 is a perspective view showing a configuration of a conventional sound velocity measuring device in liquid.

[Explanation of symbols]

 11 Box-shaped thin plastic container 12 Cover plate 13a to 13d Metal rod 14a to 14d Screw 15a to 15d Boss 20 Operation / display panel 21 Ultrasonic transmitter 22 Ultrasonic receiver 24 Display to display sound velocity value of measurement result surface

Claims (7)

(57) [Claims] 1. A container for holding a liquid to be measured, a metal rod held between opposing side surfaces of the container and having a small coefficient of thermal expansion defining an interval between both side surfaces; A transmitter and a receiver mounted on the outside of the side face facing each other, and an electronic circuit for generating a signal relating to a propagation delay time of a sound wave propagating between the transmitter and the receiver; and a signal generated by the electronic circuit. And a conversion / output unit for converting and outputting the sound velocity to the sound velocity propagating in the liquid. 2. The in-liquid sound velocity measuring apparatus according to claim 1, wherein the mutually facing side surfaces of the container are kept substantially flat and substantially parallel to each other. 3. The metal according to claim 1, wherein the metal having a small coefficient of thermal expansion is an invar alloy, a super invar alloy, a stainless invar alloy, or Fe—Ni.
An apparatus for measuring the speed of sound in liquid, wherein one of the base Elinvar alloys is used as a material, and the container is a thin-walled container made of plastic. 4. The one of claims 1 to 3, the upper portion of said container, a thermometer, heater power, the boss passing the agitator is detachably covered by a cover plate planted A sound velocity measuring device in liquid characterized by the above-mentioned. 5. The one of claims 1 to 4, said electronic circuit, said conversion and output section in a liquid sound speed measurement, characterized in that mounted on the side surface or the cover plate of the container apparatus. 6. A container for holding a liquid to be measured, a metal rod held between the opposing sides of the container and having a small coefficient of thermal expansion for defining a distance between the two side surfaces; A transceiver mounted externally on one of the side surfaces to be radiated, and an electronic circuit for generating a signal related to the propagation delay time of the ultrasonic wave radiated from the transceiver and reflected by the other of the opposite side surfaces and received by the transceiver. And a conversion / output unit that converts a signal generated by the electronic circuit into a sound speed propagating in the liquid and outputs the converted sound speed. 7. A container for holding a gas to be measured in a sealed state, a metal rod having a small thermal expansion coefficient held between opposing side surfaces of the container and defining an interval between both side surfaces; A transmitter and a receiver that are mounted facing each other outside the side surfaces facing each other, an electronic circuit that generates a signal relating to a propagation delay time of a sound wave propagating between the transmitter and the receiver, and an electronic circuit that generates the electronic circuit. And a conversion / output unit for converting the converted signal into a sound speed propagating in the liquid and outputting the converted signal.