JPH0375809B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method and device for measuring the speed of sound, and in particular to a method for measuring the speed of sound that makes it possible to remotely measure the speed of sound in a fluid, etc. using leaky waves. and regarding its equipment.

[Conventional technology]

When measuring the speed of sound or the temperature of an object using ultrasonic waves, a configuration is adopted in which longitudinal ultrasonic waves output from one ultrasonic sensor are directly propagated through the object to be measured to the other ultrasonic sensor. There is. The majority of methods attempt to measure the sound velocity or temperature and changes thereof based on the propagation time and changes thereof of the ultrasonic waves that are repeatedly transmitted and received during this period.

[Problem that the invention seeks to solve]

Ultrasonic sensors used for monitoring high-temperature fluids or fluids under dangerous conditions, or for monitoring temperature changes in liquid hazardous materials, are required to withstand sufficiently even under these harsh environments.

However, general ultrasonic sensors consist of a composite body of a vibrator and a protector, and these are integrated with a bonding material, so there is an upper limit to the operating temperature (approximately
400 [°C]), making it nearly impossible to regularly and continuously measure temperatures between 500 and 800 [°C]. In addition, many vibrators and protectors are easily contaminated chemically, and there is a disadvantage that their deterioration progresses extremely quickly, especially in environments with rapid temperature changes.

[Purpose of the invention]

The present invention improves the disadvantages of the conventional examples, and in particular, even if the objects to be measured, such as fluids, are hazardous substances or are placed under high temperatures, the sound velocity and To provide a high-speed measurement method and device that can remotely measure the change with high precision, thereby making it possible to measure the temperature and viscosity of the object to be measured and their changes with high precision. That is its purpose.

[Means for solving problems]

Therefore, in the present invention, the ultrasonic waveguide and the ultrasonic reflecting member are made to face each other at a certain distance, and a medium to be measured is interposed between the other ends of these members, and then the ultrasonic wave Use of a waveguide Measure the phase velocity V _p and group velocity V _g of the ultrasonic wave, and propagate the ultrasonic wave from one end of the ultrasonic waveguide to the other end before and after these measurements. , the time it takes for the reflected wave from the other end to be received at one end, and the time it takes for the ultrasound leaking from the ultrasound waveguide to propagate back and forth between the ultrasound reflecting member and be received. Find the difference Δt between
Based on each of these measured values, the following formula, ie, F ₁ (V _P , V _g , Δt, V) = 0, is calculated to specify the sound velocity V of the medium to be measured. It is an attempt to achieve a goal.

[One embodiment of the invention]

Hereinafter, the first embodiment of the present invention will be explained with reference to FIGS. 1 to 3.
This will be explained based on the diagram.

In Fig. 1, the sound velocity measuring devices are plate-shaped (strip-shaped) arranged at a certain distance D from each other.
Ultrasonic waveguide (hereinafter simply referred to as "waveguide")
1, an ultrasonic reflecting member (hereinafter simply referred to as "reflecting member") 2 formed in the same shape as the ultrasonic waveguide 1, and an ultrasonic transducer attached to one end of the ultrasonic waveguide 1. 3.

A waveguide 1 and a reflecting member 2 provided opposite thereto
are made of stainless steel and have the same length in this embodiment. This waveguide 1 and reflecting member 2
The other end is arranged within the medium 5 to be measured as shown in the figure.

The ultrasonic transducer 3 is installed on the side surface of one end of the waveguide 1. Then, ultrasonic waves (longitudinal waves) are obliquely incident on the waveguide 1 from the ultrasonic transducer 3, and after a predetermined period of time, the waveguide 1
It is now possible to receive reflected propagation waves containing various information from within.

Reference numerals 1A, 2A, 1B, and 2B respectively indicate end faces of the waveguide 1 and the reflecting member 2 as ultrasonic wave reflecting means.

Here, the wave propagating in the waveguide 1 and the propagation situation in the medium to be measured 5 will be explained.

When the waveguide 1 comes into contact with a liquid or solid, the waveguide 1
A portion of the sound wave energy propagating inside has the property of leaking into a contact medium such as a liquid. Taking advantage of this property,
For example, if a pair of waveguides (in this example, the other waveguide constitutes the ultrasonic reflecting member 2) is placed in the contact medium, part of the energy of the sound wave propagating through one of the waveguides is transferred to the contact medium. The sound wave propagates to the other waveguide via the waveguide. At this time, the speed of sound in the contact medium can be detected by measuring the time required for the sound to propagate through the contact medium.

When an ultrasonic wave is incident on the waveguide 1 from the ultrasonic transducer 3, this wave propagates within the waveguide 1 toward the medium 5 to be measured. In this case, of the speed at which the ultrasonic wave propagates through the waveguide 1, the phase speed is
Let V _p be the group velocity, and V _g be the group velocity. When the waveguide 1 is in contact with the medium 5 to be measured and the sound velocity V of the medium 5 to be measured at this time is smaller than the phase velocity V _p of the waveguide 1, the waveguide 1
A portion of the ultrasonic energy propagating therein is radiated into the medium 5 to be measured. The radiation angle θ at this time is determined by the following equation.

θ=sin ^-1 (V/V _p ) ... The ultrasonic wave emitted to the medium 5 to be measured reaches the reflecting member 2, and is divided into a wave propagating along the reflecting member 2 and a wave reflected here and guided. There is a wave that returns to the wave path 1 side.

Now, if the length of the waveguide 1 and the reflecting member 2 are equal, and if the interval between the waveguides is D, then if the round trip is 2 steps, the path in the medium to be measured will take N steps (N=
The arrival time of the received waves of 1, 2, 3, ...) is t _N = [(2L-ND tanθ)/V _g ] + [ND/V cosθ] + τ ₁ + τ ₂ ... Here, τ ₁ , τ ₂ is a fixed delay amount during transmission and reception.

Next, when calculating the difference between N=2 and 4, Δt=2D [(1/V cosθ) − (tanθ/V _g )]... Based on this equation and the above-mentioned equation, the sound velocity V of the medium to be measured is The following equation is obtained as the equation for finding .

(4D ² +V _g ² Δt ² )V ⁴ −(8D ² V _p V _g +V _p ² V _g ² Δt ² )V ² +4D ² V _p ² V _g ² =0... Therefore, if we measure Δt, , the known speed of sound V in the medium 5 to be measured can be found from the formula using D and V _g and V _p which are measured separately.

These series of calculations are performed in a signal processing system of the main body equipped with a display function, as will be described later.

Here, the operating principle when determining the phase velocity V _p and group velocity V _g of the ultrasonic wave propagating in the waveguide 1 will be explained.

First, FIG. 3 shows the wedge member 3A and the ultrasonic transducer 3B of the ultrasonic transducer 3. This wedge member 3A has a trapezoidal cross section, and an ultrasonic transducer 3B is fixed to one slope 3a. Further, the other slope 3c constitutes a surface perpendicular to the propagation path when the ultrasonic waves emitted from the ultrasonic transducer 3B are reflected by the incident surface 3b and propagated within the wedge member 3A. There is. Therefore, the reflected wave from the slope 3C returns to the ultrasonic transducer 3B. l ₁ and l ₁ ' indicate the propagation path and distance in that case.

Therefore, by measuring the total propagation time T ₀ of the ultrasonic waves within the wedge member 3A at this time, the sound speed C _p within the wedge member 3A can be calculated using the following equation.

C _p = 2 (l ₁ + l ₁ ′) / T ₀ ... In addition, the relationship between the sound speed C _P of the wedge member 3A and the phase velocity V _p of the ultrasonic wave propagating in the waveguide 1 is expressed by the following equation. be.

V _p = C _p /sin θ _i ... However, θ _i : Incident angle (see Figure 3) Furthermore, as shown in Figure 1, the length of the waveguide 1 is L, and the wave emitted from the ultrasonic transducer 3B is The propagation time required for the ultrasonic wave to make one round trip through the waveguide 1 is T
Then, the group velocity of the ultrasonic wave propagating in waveguide 1 is
V _g is expressed by the following formula.

V _g = 2L/T... Here, since L is a fixed value, the required group velocity of the waveguide 1 can be calculated very easily by measuring the total propagation time T in the formula and calculating the formula. . The group velocity and phase velocity are calculated by a first calculation means 13B of the processing system, which will be described later.

Here, to explain the signal processing system in more detail, the signal received by the transmitter/receiver circuit section 10A is sent to the timer means 13 via the signal selection means 13A, where the propagation time is measured. Predetermined processing is performed in the processing unit 20.

As shown in FIG. 1, this signal processing section 20 includes a first memory 14, a time difference calculation means 15, a second memory 16 as a storage means, and a second calculation section 1.
7, and further includes a first calculation section 13B between the clock means 13 and the second memory 16. In this signal processing section 20, the waveguide 1
The phase velocity V _p , group velocity V _g and sound velocity C of the fluid are calculated. The calculation results in the signal processing section 20 are displayed on the display means 18.

Each electrical system, such as the signal processing section 20 and the above-mentioned time measuring means 13, is driven and controlled by a main control section 30, respectively.

This main control section 30 outputs an overall drive control signal for synchronizing the timing of the operation of the entire circuit, and also has a first control function for determining the ultrasonic phase velocity in the waveguide 1 during measurement. It has a second control function for determining the ultrasonic group velocity of wave path 1 or 2, and a third control function for determining the sound velocity of the fluid to be measured. In this embodiment, these control functions of the main control section 30 can be switched by an external command from an operator from the measurement condition setting section 30A.

Next, the overall operation of the above embodiment will be explained.

First, a waveguide 1, a reflecting member 2, and an ultrasonic transducer 3 are arranged in the fluid to be measured as shown in FIG. Subsequently, when the entire device is operated, the received wave RE shown in FIG. 2 is obtained on the receiving side. Here, among the received waves RE, W ₁ is the received wave reflected by the reflecting surface 3C in the ultrasonic transducer 3, and W ₂ is the received wave reflected twice by the reflecting surface 3C in the ultrasonic transducer 3. This shows the received waves. In addition, N=0 means the received wave without passing through the path in the medium to be measured, and N=2 means the received wave that has passed through the path in the medium to be measured two times.
=4 similarly indicates the received waves that have passed through four paths.
The mark * indicates a received wave that is delayed by the time required to make one round trip through the waveguide 1 after the wave of N=0 is received.

Next, the first control function of the main control unit 30 is activated, and the entire circuit is set to a measurement state (phase velocity measurement mode) of the phase velocity V _p using ultrasonic waves when measuring the first part of the waveguide. When the entire circuit is set to this phase velocity measurement mode, the signal selection means 13A
is operated in accordance with instructions from the main controller 30 to allow only the received signals W ₁ and W ₂ of the received waves shown in FIG. 2 to pass through. These signals W ₁ , W ₂ and the transmission signal TR inputted in advance are sent to the timer means 13 through the signal selection means 13A, where the above-mentioned time T ₀ (however, T ₀ = t ₁ = t ₂ ) is timed and the time data is sent to the first calculation section 13B. In the first calculation unit 13B, calculations are performed based on the measurement time _T0 , and the results are stored in the second memory 1.
6 and displayed on the display means 18.

Next, when the second control function of the main control section 30 is activated in accordance with an operator's instruction, the entire circuit is set to the group velocity measurement mode of the waveguide 1.

In this case, the signal selection means 13A
Of the received signals in FIG.
=2 and the signal marked with * are selected and clocked by the clocking means 13.
It operates to send it to A. Here, the above-mentioned time T (T=t ₃ ) is measured as the difference between N=1 and the received signal marked with *, and the time data is sent to the first calculation section 13B. In the first calculation section 13B, the calculation of the equation is performed based on the measurement time T, and the result is stored in the same way as for the phase velocity V _p and displayed on the display means 18 in the same way.

Subsequently, when the third control function of the main control unit 30 is activated by an input command from the operator, the entire circuit is set to the liquid sound velocity measurement mode. In this fluid sound velocity measurement mode, the signal selection means 13A allows N=0 and N=0 in FIG.
=2 received waves are allowed to pass through, and the propagation time thereof is specifically measured by the clock means 13.

The timer 13 measures the propagation time of the two input signals and then stores the time data in the first memory 14.
Sequentially send to. This first memory 14 has N=
When the time data of 2 is input, it is output to the time difference calculation means 15 together with the time data of N=0.
This time difference calculating means 15 immediately calculates the time difference Δt.
(However, Δt=t ₄ ) is calculated and stored in the second memory 16.

In the second memory 16, when this Δt is input, the waveguide 1 stored in advance along with these Δt
The phase velocity V _p and group velocity V _g of the ultrasonic wave are outputted to the second calculation unit 17 . In this second calculation section 17,
A formula is calculated based on these input information, and the resulting sound velocity V of the fluid is outputted and displayed on the display means 18 in real time.

According to this embodiment, the waveguide 1 and the reflective member 2
The sound velocity V of the medium to be measured can be effectively determined regardless of the length of the wave, and N=2 and N=4 of the received waves.
It is possible to detect the reception time difference of , and simultaneously measure the phase velocity V _p and group velocity V _g of the waveguide 1 before and after this detection. Since the sound velocity V of the medium to be measured can be immediately determined without causing any interference, and is independent of the length of the waveguide 1 and the reflecting member 2, it is possible to remotely measure high-temperature fluids or highly dangerous fluids from a distance. Therefore, even if a normal ultrasonic transducer 3 is used,
This has the advantage that sufficient durability can be ensured. Furthermore, if the insertion dimensions of the waveguide 1 and the reflecting member 2 into the medium 5 to be measured are set large, the receiving sensitivity will increase, but this has no direct relationship with the measurement accuracy. The dimensions of the medium 5 to be introduced into the medium to be measured 5 are not particularly required to be exact, and therefore handling is easy, which is an excellent advantage as a remote measurement.

On the other hand, since the insertion dimensions into the medium 5 to be measured are directly related to the level of the ultrasonic waves received by the ultrasonic transducer 3, the liquid level of the medium 5 to be measured can be detected at the same time. There are also advantages.

Further, in the above embodiments, the waveguide is formed of a plate-shaped member, but the waveguide may be formed of other members, such as a round bar member, a suitable wire member, a pipe-shaped member, etc. good.

〔Effect of the invention〕

Since the present invention is configured and functions as described above,
According to this method, it is possible to measure the sound speed of a medium to be measured with high accuracy regardless of the length of the waveguide, and therefore even if the medium to be measured is a high-temperature fluid or a highly dangerous fluid, it can be measured from a distance. Remote measurement has become fully possible, and even if the phase velocity and group velocity of the waveguide are unknown, they can be measured simultaneously. Therefore, it is possible to calculate the speed of sound after measuring all the variables necessary for calculation in real time. This is an unprecedented method for measuring the speed of sound, as it enables high-precision sound speed measurements that do not require temperature correction at all, and also has a simple configuration and is easy to handle because it functions sufficiently with a single ultrasonic transducer. and the equipment thereof.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram showing an embodiment of the present invention, Fig. 2 is an explanatory diagram showing an example of the received waveform in Fig. 1, and Fig. 3 is an ultrasonic transducer used in Fig. 1. FIG. 2 is a partially omitted cross-sectional view showing. 1... Ultrasonic waveguide, 1A, 2A, 1B, 2B
...Ultrasonic reflecting means, 2... Ultrasonic reflecting member, 3
...Ultrasonic transducer, 13... Timing means, 15...
. . . Time difference calculation means, 16 . . . second memory as storage means, 17 . . . second calculation unit.

Claims (1)

[Claims] 1. An ultrasonic waveguide and an ultrasonic reflecting member are opposed to each other at a certain distance, and a medium to be measured is interposed between the other ends of these members, and then the ultrasonic Use of an ultrasound waveguide Measure the phase velocity V _p and group velocity V _g of ultrasound, and propagate the ultrasound from one end of the ultrasound waveguide to the other end before and after these measurements. In addition, the time it takes for the reflected wave from the other end to be received at one end, and the time it takes for the ultrasound leaking from the ultrasound waveguide to propagate back and forth between the ultrasound reflecting member and be received. _The difference Δt between _{the two} and Featured sound speed measurement method. 2. An ultrasonic waveguide equipped with an ultrasonic transducer at one end and an ultrasonic reflecting means at the other end disposed within the medium to be measured, and a predetermined distance apart from this ultrasonic waveguide. An ultrasonic reflecting member disposed at a transmitting/receiving circuit, the signal processing system is configured to control the time until the reflected wave from the other end of the ultrasonic waveguide is received and the ultrasonic wave leaking from the ultrasonic waveguide toward the reflecting member. a time-measuring means for measuring the time it takes to propagate back and forth in a medium to be measured until it is received; a time-difference calculating means for calculating the difference in arrival time of two received waves measured by the time-measuring means; A storage means for storing the output of the means is provided, and the storage means measures and stores the phase velocity and group velocity of the ultrasonic wave used at the time of measuring the sound velocity of the ultrasonic waveguide, and the output information of the storage means. A sound speed measuring device comprising: a sound speed calculation means for performing a predetermined calculation based on the above-mentioned sound speed to determine the sound speed of the fluid.