JPH052250B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a sound speed measuring device, and more particularly to a sound speed measuring device that can remotely measure the sound speed of a fluid or the like using leaky waves.

[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 inconveniences of the conventional examples, and in particular, even if the object to be measured, such as a fluid or a soft member, is a harmful substance or is constantly kept under high temperature, ultrasonic transmission and reception is possible. It is an object of the present invention to provide a sound speed measuring device that enables quick and highly accurate remote measurement of the sound speed of an object to be measured and its changes through a contact member for a wave instrument.

[Means for solving problems]

The present invention includes a pair of ultrasonic waveguides each equipped with an ultrasonic transducer at one end and an ultrasonic reflecting means at the other end disposed within the medium to be measured. Each of the devices has a transmitting/receiving switching section that alternately switches and connects the transmitting circuit section and the receiving circuit section as necessary. The receiving circuit section includes information on the time it takes for the ultrasonic waves leaking from one side of each ultrasonic waveguide to the other to propagate within the medium to be measured and to be received by the ultrasonic transducer of the other ultrasonic waveguide; A timer is provided for measuring the time it takes for the ultrasonic waves leaking from the other ultrasonic waveguide into the medium to be measured to propagate back and forth between the two ultrasonic waveguides and to be received. There is. In addition, based on the output data from this timer and the time difference data, etc., the phase velocity and group velocity of the ultrasonic waves used at the time of measuring the sound velocity of the ultrasonic waveguide are calculated based on a preset method, and these A signal processing unit is provided to calculate the sound speed of the medium to be measured based on the calculation data. A main control section that regulates the operation of this signal processing section and each circuit configuration is provided. This main control section has a first control function that switches and sets the entire signal processing section and each circuit configuration to the phase velocity calculation mode of the used ultrasonic wave, and a first control function that switches and sets the entire signal processing section and each circuit configuration to the phase velocity calculation mode of the ultrasonic wave used. A second control function that switches to and sets the velocity calculation mode, and signal processing with the intention of calculating the sound velocity of the medium to be measured based on the calculated phase velocity and group velocity of the ultrasonic wave used, output data from the timer, etc. and a third control function for switching and setting the entire section and each circuit configuration to the sound speed calculation mode. This aims to achieve the above-mentioned purpose.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 7.

In Fig. 1, the sound velocity measuring device is connected to
A pair of plate-shaped (or band-shaped) ultrasonic waveguides (hereinafter simply referred to as "waveguides") 1 and 2 as abutted members placed apart from each other, and one end of each of the waveguides 1 and 2. Ultrasonic transducers 3 and 4 installed separately in each section
It is equipped with

In this embodiment, the waveguides 1 and 2 are made of stainless steel and have the same length. This waveguide 1,
The other end of the probe 2 is disposed within the medium 5 to be measured, as shown in the figure.

In this embodiment, one of the ultrasonic transducers 3 and 4 is used as a transmitter, and the other ultrasonic transducer 4 is used as a receiver. Each of the wave transmitter 3 and the wave receiver 4 is attached to the side surface of one end of the waveguides 1 and 2. Ultrasonic waves are obliquely incident on the waveguide 1 from the transmitter 3. Receiver 4 is transmitter 3
Ultrasonic waves can be received from the waveguide 2 under almost the same conditions as the transmission operation of the waveguide 2.

Reference numerals 1A, 2A, 1B, and 2B indicate end faces of waveguides 1 and 2 as ultrasonic reflecting means, respectively.

Here, the waves propagating in the waveguides 1 and 2 and the propagation situation in the medium to be measured 5 will be explained.

When a waveguide is brought into contact with a liquid or a solid, part of the sonic energy propagating in the waveguide tends to leak into the liquid and solid contact medium. By utilizing this property, when a pair of waveguides is arranged within the contacted medium, a portion of the sonic energy propagating in one waveguide propagates to the other waveguide via the contacted medium. At this time, the speed of sound in the contacted medium can be calculated by measuring the time required for the sound to propagate through the contacting medium.

When ultrasonic waves are transmitted from the wave transmitter 3 to the waveguide 1, the waves propagate within the waveguide 1 toward the medium 5 to be measured. In this case, let the phase velocity of the ultrasonic wave in the waveguide 1 be V _p and the group velocity be V _g . The waveguide 1 is in contact with the medium 5 to be measured, and the medium 5 to be measured at this time
When the sound velocity V is smaller than the phase velocity V _p of the waveguide 1 , a part of the ultrasonic energy propagating in the waveguide 1 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 that entered the medium 5 to be measured reaches the waveguide 2, and the wave that propagates along the waveguide 2 and the wave that is reflected here and enter the medium 5. There is a wave that returns to the side. Waveguide 2
The wave traveling along is reflected at its tip 2A,
It reaches the receiver 4.

Now, if the lengths of the two waveguides 1 and 2 are equal,
When the distance between the waveguides is D, the arrival time of each received wave whose path in the medium to be measured is N journeys is t _N = [(2L−NDtanθ)/V _g ] + [ND/Vcosθ] + τ ₁ + τ ₂ ... Here, τ ₁ and τ ₂ are fixed delay amounts during transmission and reception.

Next, when calculating the difference in the case of N=1 and 3, Δt=2D [(1/Vcosθ)−(tanθ/V _g )]... From this equation and the above-mentioned equation, the measured medium 5
The following equation is obtained as the equation for determining the sound velocity V.

(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, , known D and separately measured V _g and V _p , the sound velocity V of the medium to be measured 5 can be found from the equation.

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

First, FIG. 4 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 internally reflected waves propagating within the wedge member 3A return to the ultrasonic transducer 3B. l ₁ , l ₁ ′ are
The propagation route and distance in that case are shown.

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

C _p = 2 (l ₁ + l ₁ ') / T ₀ ... Also, the following equation exists 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. .

V _p = C _p /sin θ _i ...where θ _i is the angle of incidence (see Figure 4) Furthermore, as shown in Figure 1, the length of the waveguide 1 is L, and the waveform emitted from the ultrasonic transducer 3B is Let T be the propagation time when the ultrasonic wave propagates through the waveguide 1, reflects at its tip, and reaches the ultrasonic transducer 3B, then the group velocity V _g of the ultrasonic wave propagating through the waveguide 1 is:
It is expressed by the following formula.

V _g = 2L/T... Here, since L is a fixed value, it is possible to calculate the required group velocity of the waveguide 1 very easily by measuring the propagation time T in the formula and calculating the formula. can.

This calculation of the group velocity and phase velocity is performed by a first calculation section 13B of the signal processing section 20, which will be described later.

Here, to explain the signal processing system in more detail,
The signal received by the receiving circuit section 12 is sent to the timer means 13 via the signal selection means 13A, where the propagation time is timed, and then predetermined signal processing is performed at the signal processing section 20. This signal processing section 2
0 includes a first memory 14 as shown in FIG.
It has a time difference calculation means 15, a second memory 16 as a storage means, and a second calculation section 17, and furthermore, a first
The configuration includes a calculation section 13B. This signal processing section 20 calculates the phase velocity V _p of the waveguide 1, the group velocity V _g , and the sound velocity V of the medium to be measured 5.
The calculation results in the signal processing section 20 are displayed on the display means 18.

Each signal processing system, such as the signal processing section 20 and the above-mentioned time measurement 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 sets the signal processing section 20 and the entire circuit configuration to a phase velocity calculation mode of the ultrasonic wave used. a first control function for switching and setting, a second control function for switching and setting the entire signal processing unit 20 and each circuit configuration to a group velocity calculation mode of the ultrasonic wave to be used, and a calculated phase velocity of the ultrasonic wave to be used; and a third control function that switches and sets the signal processing unit 20 and the entire circuit configuration to a sound speed calculation mode with the intention of calculating the sound speed of the medium to be measured based on the group velocity and output data from the timing means, etc. ing.

In this embodiment, these control functions of the main control section 30 can be switched by an external command from the operator from the measurement condition setting section 30A.

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

First, waveguides 1 and 2 are connected to the medium to be measured.
and ultrasonic transducers 3 and 4 are arranged as shown in FIG. Subsequently, when the entire apparatus is operated, a received waveform shown in FIG. 2 or 3 is obtained on the receiving side.

Among these, the received waveform in FIG. 2 is obtained by electrically separating the ultrasonic transducer 4 and
The waveform obtained when the transmitting operation and the receiving operation are performed using only the waveguide 2, that is, the waveform obtained when the waveguide 2 is used as a reflecting member is shown. here,
TR indicates a transmitted wave and RE indicates a received wave. Received wave RE
Among them, W ₁ is the reflective surface 3C in the ultrasonic transducer 3
_W2 indicates the received wave that has been reflected twice by the reflecting surface 3C in the ultrasonic transducer 3. Further, N=0 indicates a received wave that propagated through the waveguide 1, was reflected at the end face 1A, and returned to the ultrasonic transducer 3 without leaking into the medium 5 to be measured. N=2 indicates a received wave that has passed through the medium to be measured two times. Further, N=4 similarly indicates each received wave that has 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.

3 shows a waveform obtained when the ultrasonic transducer 4 is used as a transmitter and the ultrasonic transducer 3 is used as a receiver. Here, N=1 is the received wave that has passed through the medium to be measured for only one step.
Similarly, numerals 3 and 3 indicate the received waves that have passed through three paths.
Further, the mark * indicates a received wave that is delayed by the time required to make one round trip through the waveguide 2 after the wave of N=1 is received.

Next, the first control function of the main control unit 30 is activated, and the entire circuit is set to the measurement state (phase velocity measurement mode) of the ultrasonic phase velocity V _p of the waveguide 1 portion at the time of measurement. When the entire circuit is set to this phase velocity measurement mode, the other ultrasonic transducer 4 is electrically disconnected from the transmission/reception switching section 10, and only one ultrasonic transducer 3 operates as a transducer. (The ultrasonic transducer 4 may be used instead of the ultrasonic transducer 3). FIG. 5 shows the transmission state of the transmitted and received signals in this case. The transmitted signal TR transmitted from the transmitting circuit section 11 is simultaneously sent to the ultrasonic transducer 3 and the receiving circuit section 12.
Further, the internally reflected wave RE from the ultrasonic transducer 3 is also sent to the receiving circuit section 12. Each of these signals TR and
The RE passes through the signal selection means 13A and is sent to the timer 13, where it is sent to the timer 13 for the aforementioned time T ₀ (however, T ₀
=t ₁ =t ₂ ) is measured, and the time data is sent to the first calculation unit 13B. In the first calculation unit 13B,
Equations and equations are calculated based on the measurement time T ₀ , and the results are stored in the second memory 16 and displayed on the display means 18 .

Next, when the operator activates the second control function of the main control section 30, the entire circuit is set to the group velocity measurement mode of the waveguide 1.

In this case, in this embodiment, one ultrasonic transducer 3 performs a transmitting operation, and the other ultrasonic transducer 4 performs a receiving operation. That is, the transmission signal TR and the reception signal RE are transmitted as shown in FIG. Each of these signals
TR and RE pass through the signal selection means 13A (the signal selection means selects N=0 and the signal marked *) and are sent to the timer means 13, where they are sent to the timer means 13 for the above-mentioned time T (however,
T=t ₃ ) is measured as the arrival time difference between N=0 and the received signal marked with *, and the time data is sent to the first calculation unit 1.
Sent to 3B. 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 section 30 is activated in response to an input command from the operator, the entire circuit is set to the sound velocity measurement mode of the medium to be measured. In this sound velocity measurement mode of the medium to be measured, the signal selection means 13A allows the received waves of N=1 and N=3 in FIG.

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 3 is inputted, it is outputted to the time difference calculation means 15 together with the time data of N=1. The time difference calculation means 15 immediately calculates the time difference Δt (where Δt=t ₄ ) and stores it 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,
An equation is calculated based on these input information, and the resulting sound velocity V of the medium to be measured is output to the display means 18 and displayed in real time.

Next, specific experimental results in the above embodiment will be explained based on FIGS. 8 to 11.

In the experimental model shown in FIG. 8, steel plates with a thickness of 0.95 mm are used as waveguides 1 and 2, and a variable angle probe 33 with a frequency of 1 MHz is used as an ultrasonic transducer. I used 34. The wedge of the variable angle probe is made of acrylic resin, and the incident angle is 31.5.
The waveguide was fixed at a certain angle so that the S ₀ mode plate wave was guided. Tap water (21 [°C]) was used as the measurement medium. Therefore, in this case, the group velocity V _g and phase velocity V _p of the guided wave can be considered to be approximately equal to the S ₀ mode even within the medium 5 to be measured (IAViktrov.
"Rayleigh and Lamb Waves" P.117).

The applied electric pulse was a two-sine wave of 200 [V _pp ). FIG. 9 shows an example of the observed received waveform. In the figure, T indicates the waveform of the transmitted wave, and R indicates the waveform of the received wave. N=1 and 3 indicate waves whose underwater paths are one stroke and three strokes, respectively. The * mark indicates the received waveform of a wave in which the N=1 wave further made one round trip through the waveguide 1. In this example, Δt=75.1 [μs]. From the arrival time difference between the wave marked * and the wave with N=1, the group velocity of the waveguide 1 in the ultrasonic wave used is experimentally determined,
V _g ≒5200 [m/s]. In addition, the acoustic velocity of acrylic is 2720 [m/s] and the set incidence angle of the variable angle probe.
The phase velocity can be calculated from 31.5℃, and V _p ≒ 5300
[m/s].

On the other hand, FIG. 10 shows the results of confirming the relationship in the equation through actual measurements while changing the distance D between the waveguides 1 and 2. From this, it was possible to obtain Δt/D=1.26 [μs/mm]. The sound velocity V of water can be calculated from the formula using V _g and V _p obtained previously. The results are shown in FIG. The temperature was measured at three points. Result is,
This agrees very well with generally published values.

As described above, according to this embodiment, the sound velocity V of the medium to be measured 5 can be effectively determined regardless of the lengths of the waveguides 1 and 2.
In addition to detecting the reception time difference between and “N=3”,
Before and after this, the phase velocity V _p and group velocity of waveguide 1
Therefore, the sound velocity V of _the medium to be measured can be immediately determined without immersing the ultrasonic transducers 3 and 4 into the medium to be measured. Since the length of 2 is irrelevant, it is possible to remotely measure high-temperature fluids or highly dangerous fluids, for example. Therefore, even if a normal ultrasonic transducer 3 is used, it is sufficient. It has the advantage of ensuring durability. Furthermore, if the insertion dimensions of the waveguides 1 and 2 into the medium to be measured 5 are set large, the receiving sensitivity will increase, but this has no direct relation to the measurement accuracy. The dimensions of the ultrasonic sensor device to be inserted into the ultrasonic sensor device are not particularly required to be exact, and therefore, it is possible to obtain an ultrasonic sensor device having excellent properties as a remote measurement device, which is easy to handle.

In addition, 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, it is possible to simultaneously detect the liquid level of the medium 5 to be measured. There are also advantages.

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.

Furthermore, in the above embodiment, when measuring the group velocity V _g of the waveguide 1, t ₃ measured in FIG. 3 was used as an example, but t ₃ measured in FIG. It's okay. In addition, when measuring Δt, the case shown in FIG. 3 was illustrated in the above embodiment, but
After obtaining the received signal shown in Fig. 2 under the configuration shown in Fig. 12, t ₄ obtained based on this (however, t ₄
=Δt) may also be used. In addition, in the above embodiment, especially the phase velocity V _p of the ultrasonic wave in the waveguide 1
Although the case where the group velocity V g and the group velocity V _g are obtained prior to the measurement of Δt has been exemplified, they may be obtained in the reverse order. Further, in the above embodiment, the first, second, and third control functions are operated in accordance with an input command from the operator, but these control functions are operated automatically in sequence. It's okay. Furthermore, since the sound velocity of the liquid can be measured with high precision, the corresponding temperature change of the liquid can also be measured with high precision.

Further, the present invention can also be applied to the measurement of the sound velocity of a fluid in a pipe shown in FIG. 13 by modifying its technical idea.

〔Effect of the invention〕

Since the present invention is configured and functions as described above,
According to this, the sound speed of the medium to be measured can be measured regardless of the length of the ultrasonic waveguide, and this allows remote measurement from a distance even if the medium to be measured is, for example, a high-temperature fluid or a highly dangerous fluid. It has become possible to calculate the phase velocity, group velocity, etc. of the ultrasonic waves used in the ultrasonic waveguide in real time according to commands from the main control unit, and based on this, the speed of sound can be calculated. It is now possible to perform high-accuracy sound velocity calculations without the need for temperature correction for the Since the calculation of the phase velocity, group velocity, or sound velocity described above can be performed sequentially by simply switching the operation command of the main control unit while maintaining the sound velocity measurement state using the processing unit, the entire device To provide an excellent sound speed measuring device which is unprecedented and capable of reducing malfunctions, stabilizing the operation of the entire device, and thus measuring the sound speed of a medium to be measured quickly and with high accuracy. I can do it.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention, FIGS. 2 and 3 are explanatory diagrams showing an example of the transmitted waveform and received waveform in FIG. 1, and FIG.
The figure is a partially omitted cross-sectional view showing the ultrasonic transducer used in Figure 1, Figures 5 to 7 are explanatory diagrams of the operation of Figure 1, and Figures 8 to 11 are each a cross-sectional view of the ultrasonic transducer used in Figure 1. The explanatory drawings showing the embodiment, FIGS. 12 and 13 are overall configuration diagrams showing other embodiments, respectively. 1, 2... Ultrasonic waveguide as a contact member, 3,
4... Ultrasonic transducer, 10... Transmission/reception switching unit, 11
... Transmitting circuit section, 12... Receiving circuit section, 13... Time counting means, 13A... Signal selection means, 15... Time difference calculation means, 16... Second memory as storage means, 17
...Second calculation section, 30...Main control section.

Claims (1)

[Scope of Claims] 1. A pair of ultrasonic waveguides each equipped with an ultrasonic transducer at one end and an ultrasonic reflecting means at the other end disposed within the medium to be measured; Each of the acoustic wave transducers has a transmitting/receiving switching unit that alternately switches and connects the transmitting circuit unit and the receiving circuit unit as necessary, and the receiving circuit unit has a transmitting/receiving switching unit that connects the transmitting circuit unit and the receiving circuit unit alternately as necessary, The time it takes for the leaked ultrasound to propagate within the medium to be measured and be received by the ultrasound transducer of the other ultrasonic waveguide, and the time it takes for the leaked ultrasound to propagate within the medium to be measured, and the time it takes for the leaked ultrasound to propagate within the medium to be measured and the time it takes for the leaked ultrasound to propagate within the medium to be measured A clock means is provided for measuring the time it takes for the ultrasonic wave to propagate back and forth between the ultrasonic waveguide and the one ultrasonic waveguide until it is received, and based on the output data from the clock means and the time difference data, etc. calculate the phase velocity and group velocity of the ultrasonic wave used when measuring the sound velocity of the ultrasonic waveguide based on a preset method, and calculate the sound velocity of the medium to be measured based on these calculation data. A signal processing section is provided, and a main control section that regulates the operation of the signal processing section and each of the circuit configurations is provided, and this main control section controls the entire signal processing section and each of the circuit configurations using the ultrasonic waves used. a first control function that switches and sets the phase velocity calculation mode of the ultrasonic wave to be used; a second control function that switches and sets the entire signal processing section and each of the circuit configurations to the group velocity calculation mode of the ultrasonic wave used; In order to calculate the sound speed of the medium to be measured based on the phase velocity and group velocity of the ultrasonic waves used and the output data from the time measurement means, the signal processing section and the entire circuit configuration are switched to the sound speed calculation mode. A sound speed measuring device comprising: a third control function for setting.