JP4558114B2 - Non-contact fluid temperature measurement method using electromagnetic ultrasonic waves - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for measuring the temperature of a fluid flowing in a pipe, and more specifically, by using electromagnetic ultrasonic waves, an ultrasonic transmitter and an ultrasonic detector are arranged in a non-contact state outside the pipe. The present invention relates to a non-contact type fluid temperature measurement method using electromagnetic ultrasonic waves that can measure a fluid temperature.
[0002]
[Prior art]
An ultrasonic thermometer that measures the temperature of an object using ultrasonic waves is disclosed in Japanese Patent Laid-Open No. 7-243922. In this publication, an object such as a human body or a tuna meat is placed in a plastic container, and an ultrasonic oscillation element and an ultrasonic receiving element are arranged opposite to each other with the container in contact with the outside of the plastic container. The speed of sound in the object is measured from the transmission time, and the temperature of the object is determined by utilizing the fact that the speed of sound in the object changes according to the object temperature.
[0003]
This method has no problem when the object temperature inside the plastic container is about room temperature, but it causes many problems when the object temperature is a high temperature of several hundred degrees Celsius or the plastic container vibrates.
Generally, a piezoelectric element is used for an ultrasonic oscillation element and an ultrasonic reception element. This piezoelectric element has a property that ultrasonic waves are not transmitted to the inside unless it is in close contact with the plastic surface. Therefore, it is indispensable to interpose a contact medium on the plastic surface. In JP-A-9-138149 and the like, this contact medium is called an ultrasonic transmitter.
[0004]
If the object being measured is hot, the plastic surface will also be hot. As a result, the piezoelectric element is liable to malfunction and the temperature cannot be measured normally. Even when the object temperature is very low or extremely low, the piezoelectric element malfunctions, making accurate temperature measurement difficult.
[0005]
[Problems to be solved by the invention]
By the way, it is requested from many industrial fields to accurately measure the temperature of the fluid from outside the pipe. For example, in a breeding reactor in nuclear engineering, liquid sodium at about 400 ° C. is used as a working fluid. However, it is essential to measure the temperature of liquid sodium safely and reliably from outside the pipe.
[0006]
However, since the conventional ultrasonic thermometer is actually the generation and detection of ultrasonic waves by a piezoelectric element, a contact medium is required as an adhesive to the outer surface of the pipe. Not suitable. Even if the piezoelectric element is bonded, there is no actual example of stable measurement under severe environments such as high temperature and vibration. Further, in the replacement of the piezoelectric element, it is difficult to replace the piezoelectric element itself under such an extreme environment, and the repair cannot be easily performed.
[0007]
The present invention is intended to solve the above-described problems in temperature measurement using a conventional ultrasonic thermometer, and the ultrasonic transmitter and the ultrasonic detector are not in contact with the outer peripheral surface of the pipe. It is a first object of the present invention to provide a non-contact type fluid temperature measuring method that is arranged in the above-described manner so that the temperature of the fluid in the pipe can be measured stably and with high accuracy.
In addition, the present invention provides an ultrasonic oscillator and an ultrasonic detector that are not in contact with piping so that extreme adverse conditions such as mechanical vibrations and high temperatures are not directly transmitted to the oscillator and detector. It is a second object of the present invention to provide a non-contact type fluid temperature measurement method capable of performing temperature measurement, maintenance inspection, and part replacement.
Furthermore, in the detection of the ultrasonic wave, the third object of the invention is that if the high resolution ultrasonic sensor already filed by the present inventor is used, the speed of sound can be measured with high accuracy and the fluid temperature can be accurately derived. It is what.
[0008]
[Means for Solving the Problems]
According to the invention of claim 1, an electromagnetic ultrasonic transmitter is arranged in a non-contact manner on the outer peripheral surface of a pipe through which a fluid flows, and the electromagnetic ultrasonic transmission on the upstream side and the downstream side of the electromagnetic ultrasonic transmitter is arranged. An ultrasonic detector is arranged in a non-contact manner on the outer peripheral surface of the pipe at a position where the primary interference ultrasonic wave reaches from the vessel, and an ultrasonic wave is generated in the pipe or the fluid by the electromagnetic ultrasonic transmitter. The fluid and the pipe are vibrated by the ultrasonic energy propagated through the pipe, the magnetic field in the pipe or the fluid is fluctuated by the vibration of the ultrasonic wave, and the fluctuating magnetic field is detected by the ultrasonic detector and the ultrasonic transmission time τ is obtained. detecting the upstream ultrasonic arrival point and the downstream ultrasonic arrival point, a distance until said both arrival point electromagnetic ultrasonic transmitter as a reference point, i.e., to calculate the upstream distance L _u and the downstream distance L _d Deriving the sound velocity c of the fluid from these parameters, It is an basic configuration of the invention to measure the fluid temperature T from the sound velocity c in.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The present inventor has come up with the idea that in order to avoid the influence of high temperature, vibration, etc., it is desirable to dispose the ultrasonic transmitter and the ultrasonic detector in a non-contact state in the vicinity of the outer peripheral surface of the pipe. And as a result of earnest research to realize this non-contact condition, an ultrasonic detector that uses an electromagnetic ultrasonic transmitter as an ultrasonic transmitter and an ultrasonic detector that detects magnetic field fluctuations are optimal as an ultrasonic detector. The conclusion was reached.
[0013]
In order to measure the fluid temperature, first, the sound velocity c of the ultrasonic wave propagating in the fluid is measured. If the fluid that is the ultrasonic transmission medium is determined, a functional relationship T = g (c) is established between the fluid temperature T and the sound velocity c. For example, considering air, a linear relationship of c = 331 + 0.6T is established between the sound velocity c (m / s) and the temperature T (° C.). Therefore, T = (c-331) /0.6=g (c) is established. Such a relational expression holds for all gases and liquids. That is, the fluid temperature T is uniquely determined from the sound velocity c, and only the relational expression of T = g (c) is different for each fluid.
[0014]
Therefore, in order to determine the fluid temperature T, it is premised that the flow velocity c in the fluid piping is determined. The flow velocity c can be easily determined even under extreme conditions such as high temperature and vibration by the above-described electromagnetic ultrasonic transmitter and the variable magnetic field detection type ultrasonic detector.
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0015]
FIG. 1 is a schematic explanatory view of a first embodiment of a non-contact type fluid temperature measuring method according to the present invention. A fluid 8 is flowing in the direction of the arrow at a flow velocity u in the pipe 6 having a diameter D. Near the outer peripheral surface of the pipe 6, the electromagnetic ultrasonic transmitter 2 and the ultrasonic detector 4 are arranged in a non-contact state in the diameter direction of the pipe.
[0016]
The measurement method of the sound velocity c and the flow velocity u will be briefly described. It is assumed that the ultrasonic detector 4 detects the ultrasonic wave after a time τ after the electromagnetic ultrasonic transmitter 2 transmits the ultrasonic wave. If the fluid 8 is stationary, it reaches a stationary arrival point O indicated by a dotted line. However, since the fluid 8 that is a medium is flowing at a flow velocity u, the fluid 8 reaches a flow arrival point P indicated by a solid line.
[0017]
If the fluid 8 is stationary, the stationary transmission distance PT becomes the diameter D as indicated by the dotted line. The ultrasonic wave takes time τ to travel the stationary transmission distance PT at the speed of sound c, and PT = cτ is established. Therefore, the speed of sound c is obtained by c = PT / τ = D / τ. On the other hand, if the interval OP is expressed by ΔL, ΔL should be equal to uτ, and the flow velocity u can be calculated from u = ΔL / τ.
[0018]
FIG. 2 is a perspective view of the electromagnetic ultrasonic transmitter 2, which is configured by combining a plurality of permanent magnets 2a while reversing the magnetic poles, and meandering a coil 2b on the upper surface thereof. The distance d gives a repetitive unit of magnetic poles and is a distance between two homopolar magnets. The number of magnets can be selected arbitrarily, and is finally configured in a size of horizontal W, vertical K, and height H.
[0019]
FIG. 3 is an explanatory diagram of a transmission mechanism of the electromagnetic ultrasonic transmitter 2. In this figure, the electromagnetic ultrasonic transmitter 2 shown in FIG. 2 is reversely disposed in the vicinity of the pipe 6 in a non-contact manner.
When a high-frequency current (for example, 700 to 200 KHZ) is passed through the coil 2b in the symbol direction, an eddy current flows in the pipe 6 in the illustrated direction. This eddy current interacts with the magnetic force line M of the magnet 2a, and the Lorentz force F acts in the direction of the solid line arrow. This Lorentz force F generates longitudinal ultrasonic waves on the metal in the pipe, and ultrasonic waves having the same frequency as the frequency of the high-frequency current are generated.
[0020]
The ultrasonic wave thus generated is an L wave (Longitudinal Wave), but the electromagnetic ultrasonic wave transmitter used in the present invention may have any configuration, but the generated ultrasonic wave propagates through the fluid 8. Longitudinal waves are chosen because of the need to do. In addition, even if the electromagnetic ultrasonic transmitter is not in contact with the pipe 6, it can transmit ultrasonic waves to the fluid 8 as long as it is in close proximity.
[0021]
Although FIG. 3 shows the case where the ultrasonic wave is induced in the metal part of the pipe 6, the ultrasonic wave can also be directly induced in the fluid. When the fluid 8 is a liquid metal, an eddy current can be generated in the fluid. For example, liquid sodium used in breeding reactors of nuclear engineering has high electrical conductivity, so that eddy currents are generated in the fluid and ultrasonic waves can be directly induced in the fluid.
[0022]
FIG. 4 is an explanatory diagram of the propagation direction of ultrasonic waves. If it is considered that an ultrasonic wave is generated from each of the magnets 2a of the electromagnetic ultrasonic transmitter 2, the ultrasonic wave is emitted only in a specific direction due to the interference of the ultrasonic wave. The phase difference Δ between the two ultrasonic waves emitted in the direction of the angle θ is given by Δ = d sin θ, and is strengthened when this is an integral multiple of the wavelength λ, and the ultrasonic wave is only in the direction of the angle θ where d sin θ = nλ is established. Propagating.
[0023]
Therefore, when n = 0, θ = 0, and the 0th-order interference ultrasonic wave propagates in the diameter direction of the pipe 6. When n = 1, the primary interference ultrasonic wave propagates in the angle direction of dsin θ = λ, that is, θ = sin ⁻¹ (λ / d). Furthermore, the n-th order interference ultrasonic waves propagate in the angle direction given by θ = sin ⁻¹ (nλ / d), and the ultrasonic waves weaken and do not propagate in other directions. However, the ultrasonic intensity decreases as the order n increases. That is, low-order interference ultrasonic waves such as 0th order and 1st order are effective for ultrasonic measurement.
[0024]
FIG. 5 is an enlarged view of a main part of FIG. 1, and is a detection state diagram of the 0th-order interference ultrasonic wave. The ultrasonic detector 4 is an array type detector configured by arranging a plurality of detector units 4a. In this array type detector, the arrival point is detected digitally. For example, since the ultrasonic wave has spread a little, the stationary arrival point O is detected by the plurality of detector units 4a, but the position of the detector unit 4a that gives the peak value of the detection output gives the stationary arrival point O. The flow arrival point P is similarly determined, and the interval OP = ΔL is determined as an interval corresponding to how many detector units. Further, the ultrasonic transmission time τ can be measured with high accuracy.
[0025]
In general, since the speed of sound is much faster than the flow velocity, ΔL is a small value. Since the conventional detection element has a large detection area, it is difficult to decompose and receive ΔL. The present inventor has already developed and applied for a non-contact and ultra-high resolution detection element. This detection element is an ultra-thin detector unit 4a, and by using this, ΔL can be measured with high accuracy.
[0026]
The ultrasonic detector 4 may be the above-described array type detector, but one detector unit 4a may be movable in the pipe axis direction. That is, the detector unit 4a is swept and the maximum point of the detected intensity is set as the flow arrival point P.
In addition, various types of ultrasonic detectors 4 can be used.
[0027]
FIG. 6 is a configuration diagram of an example of the detector unit 4a. Magnets 4c and 4c are provided at the tip of the U-shaped core 4b, and a detection coil 4d is wound around the core at the center. If the pipe 6 is moved in the direction of the vertical arrow by the ultrasonic wave, an eddy current is generated in the pipe by the action of the magnet 4c. The lines of magnetic force due to this eddy current enter the core 4b, and ultrasonic waves are detected by the detection coil 4d. The size of the core gap 4e provides the ultrasonic detection resolution.
Since this detector unit 4a detects a variable magnetic field, it can be arranged in a non-contact manner with respect to the pipe 6. Even if there is no magnet 4c, if there is residual magnetism in the pipe 6 or if there is magnetism in the fluid 8, eddy currents are generated by these magnetisms, and ultrasonic waves can be detected.
[0028]
The detector unit 4a is not limited to the configuration shown in the figure, and the units described in Japanese Patent Application Nos. 10-363453, 10-363454, and 11-202443, which have already been disclosed by the present inventors. Can also be used. Of course, other known ultrasonic detectors can also be used. However, any ultrasonic detector that can be detected in a non-contact manner with respect to the pipe 6 can be used in the present invention.
[0029]
The important point of the present invention is that the electromagnetic ultrasonic transmitter 2 and the ultrasonic detector 4 can be arranged in a non-contact manner with respect to the outer peripheral surface of the pipe. Even if the piping is in extreme conditions such as high temperature, it is not contacted and is not directly affected. Moreover, since it is non-contact, the electromagnetic ultrasonic transmitter and the ultrasonic detector can be cooled, and the durability of these devices can be guaranteed. At the same time, the replacement work can be easily performed.
[0030]
FIG. 7 is a schematic explanatory diagram of the second embodiment of the present invention. While FIG. 1 uses the 0th order interference ultrasonic wave, FIG. 7 is characterized in that the 1st order interference ultrasonic wave is used. For example, when there is no room to physically place the ultrasonic detector 4 in the diameter direction of the electromagnetic ultrasonic transmitter 2, or when the pipe diameter D is smaller than the ultrasonic pulse width, the detection accuracy is deteriorated. Therefore, a primary interference ultrasonic wave having a long path is used.
[0031]
FIG. 8 is a schematic explanatory diagram of a third embodiment of the present invention. The ultrasonic detector 4 is provided on the same side as the electromagnetic ultrasonic transmitter 2. For example, when there is no space on the back side of the pipe 6, it is necessary to place both devices 2 and 4 on the same side. In this case, since the reflected wave is detected, the primary interference ultrasonic wave is used. Higher order interfering ultrasonic waves may be used, but care must be taken because the signal strength decreases as the order increases.
[0032]
7 and 8 are exactly the same as those in FIG. If the angle θ is determined, the stationary transmission distance PT, which is the entire length of the dotted line, is determined from PT = D / cos θ in FIG. 7 and PT = 2D / cos θ in FIG. Since the ultrasonic transmission time τ can be determined as the difference between the ultrasonic emission time and the ultrasonic detection time, the sound speed c can be calculated through c = PT / τ.
[0033]
On the other hand, the distance OP between the stationary arrival point O and the flow arrival point P is ΔL, and the relational expression ΔL = uτ holds. Therefore, the flow velocity u is measured by u = ΔL / τ by measuring the ultrasonic arrival time τ.
[0034]
FIG. 9 is a flow chart for measuring the flow rate and flow rate of the fluid. In step n1, electromagnetic ultrasonic waves are emitted at time t = 0, and ultrasonic waves are detected at time t = τ (n2). This time interval τ becomes the ultrasonic wave arrival time. Since the static transmission distance PT is geometrically determined once the system is determined, the speed of sound c is obtained from c = PT / τ (n3). Next, the fluid temperature T is finally derived from the temperature sound velocity relational expression (n4) of T = g (c).
[0035]
FIG. 10 is a schematic explanatory diagram of the fourth embodiment of the present invention. A fluid 8 flows in the pipe 6 at a flow velocity u in the direction of the arrow. The electromagnetic ultrasonic transmitter 2 is disposed on the upper side of the pipe 6, and the upstream ultrasonic detector 4 u and the downstream ultrasonic detector 4 d are disposed on the opposite side. Both the detectors 4u and 4d are an aggregate of a plurality of detector units, as in the ultrasonic detector 4.
[0036]
In the present embodiment, the primary interference ultrasonic wave (n = 1) is used because the oblique path is used to make the transmission path longer than the interval between the ultrasonic pulses, and the ultrasonic pulse is accurately detected. This is to detect and increase measurement accuracy. The dotted line represents the path in the stationary fluid, and the angle θ is given by θ = sin ⁻¹ (λ / d). If the fluid is stationary, the ultrasonic waves will reach the stationary arrival points O ₁ and O ₂ on both the upstream and downstream sides. However, since the fluid flows at the flow velocity u, the ultrasonic waves reach the upstream ultrasonic wave arrival point P ₁ and the downstream ultrasonic wave arrival point P ₂ . If the ultrasonic transmission time is τ, O ₁ P ₁ = uτ and O ₂ P ₂ = uτ.
[0037]
First, a general formula in the case of using nth-order interference ultrasonic waves is derived. If the center point is O, OP ₁ = L _u , OP ₂ = L _d , OO ₁ = L, OO ₂ = L, then L _u = L−uτ and L _d = L + uτ.
From this, L _u + L _d = 2L. On the other hand, L = cτ · sin θ from the length of the hypotenuse represented by the dotted line, that is, the static transmission distance cτ, and L _u + L _d = 2cτ · sin θ. Further, since dsin θ = nλ, sin θ = nλ / d. From the ultrasonic frequency f, λ = c / f and sin θ = nc / df. Therefore, from L _d + L _u = 2nc ² τ / df, c = {df (L _d + L _u ) / 2nτ} ^1/2 .
[0038]
Therefore, the sound speed c can be calculated by detecting three parameters, the upstream distance L _u , the downstream distance L _d, and the ultrasonic transmission time τ. The interference order n, interval d, and frequency f are given in advance. Since the primary interference ultrasonic wave (n = 1) is usually used, the speed of sound can be obtained by c = {df (L _d + L _u ) / 2τ} ^1/2 .
[0039]
It can also be seen that the flow velocity u is calculated by u = (L _d −L _u ) / 2τ. That is, it can be seen that the flow velocity u can also be calculated by three types of parameters, the upstream distance L _u , the downstream distance L _d, and the ultrasonic transmission time τ. Since the ultrasonic arrival points P ₁ and P ₂ on the upstream side and the downstream side are accurately obtained by the ultrasonic detectors 4u and 4d, the sound velocity c and the flow velocity u can be accurately derived from the above equations.
[0040]
FIG. 11 is a schematic explanatory diagram of a fifth embodiment of the present invention. The difference from FIG. 10 is that the upstream ultrasonic detector 4 u and the downstream ultrasonic detector 4 d are arranged on the same side as the electromagnetic ultrasonic transmitter 2. This is effective when there is no space for arranging these devices on the opposite side of the pipe 6. Therefore, in the present embodiment, the first interference ultrasonic wave is reflected and measured.
[0041]
FIG. 12 is a development view of FIG. Therefore, the vertical distance is twice the pipe diameter D. Considering the detection of ultrasonic waves in this developed view, it is exactly the same as FIG. The flow velocity u is calculated by u = (L _d −L _u ) / 2τ, and the sound velocity c is calculated by c = {df (L _d + L _u ) / 2τ} ^1/2 . The τ ultrasonic transmission time is the time reaching reflected once, the upstream distance L _u and the downstream distance L _d is as shown.
[0042]
FIG. 13 is a flow chart for measuring the temperature of the fluid with respect to FIGS. In step n11, electromagnetic ultrasonic waves are emitted at time t = 0, and ultrasonic waves are detected at time t = τ (n12). At the same time, the upstream distance L _u and the downstream distance L _d are calculated (n13), and the sound speed c is derived (n15) using the interference order n (n14). Finally, the fluid temperature T is determined through the temperature / sound velocity relational expression (n16).
[0043]
14 to 16 show an embodiment of the transmitter unit 2 c of the electromagnetic ultrasonic transmitter 2. If the transmitter unit 2c of FIG. 14 is connected, the electromagnetic ultrasonic transmitter 2 described above can be configured. The transmitter unit 2c in FIGS. 15 and 16 is different in shape, but is similar in that it is a unit of the transmitter 2.
[0044]
The coil 2b of each transmitter unit 2c may be connected, or each coil 2b may be individually separated. When separated, it is necessary to control the phase of the current flowing through each coil 2b. When connected to a single line, phase control is not necessary as shown in FIG. In any case, a known technique can be applied.
[0045]
The present invention is not limited to the above-described embodiments, and includes various modifications, design changes, and the like within the technical scope without departing from the technical idea of the present invention.
[0046]
【The invention's effect】
According to the present invention , the electromagnetic ultrasonic transmitter and the ultrasonic detector are arranged in a non-contact state on the outer peripheral surface of the pipe so as to measure the fluid temperature. Measurement under extreme adverse conditions is possible without being affected by vibration. As a result, it is possible to extend the life of the measurement system and facilitate work such as maintenance and inspection and part replacement.
[0047]
Further, according to the present invention, even when the pipe diameter is short, it is possible to improve the accuracy of temperature measurement by lengthening the traveling path of the ultrasonic wave by using the primary interference ultrasonic wave, and to improve the accuracy of the electromagnetic ultrasonic wave. This can be utilized even when the space on the facing surface of the transmitter is not sufficient, and the arrangement of the measurement system can be diversified.
[0049]
Furthermore, according to the present invention, since the first interference ultrasonic wave having a high ultrasonic intensity is used, the accuracy of fluid temperature measurement can be expected.
[Brief description of the drawings]
FIG. 1 is a schematic explanatory diagram of a first embodiment of a non-contact type fluid temperature measuring method according to the present invention.
FIG. 2 is a perspective view of an electromagnetic ultrasonic transmitter.
FIG. 3 is an explanatory diagram of a transmission mechanism of an electromagnetic ultrasonic transmitter.
FIG. 4 is an explanatory diagram of a propagation direction of ultrasonic waves.
FIG. 5 is a detection state diagram of the 0th-order interference ultrasound in which the main part of FIG. 1 is enlarged.
FIG. 6 is a configuration diagram of an example of a detector unit.
FIG. 7 is a schematic explanatory diagram of a second embodiment of the present invention.
FIG. 8 is a schematic explanatory diagram of a third embodiment of the present invention.
FIG. 9 is a flow chart for measuring a fluid temperature.
FIG. 10 is a schematic explanatory diagram of a fourth embodiment of the present invention.
FIG. 11 is a schematic explanatory diagram of a fifth embodiment of the present invention.
12 is a development view of FIG. 11. FIG.
13 is a fluid temperature measurement flowchart for FIGS. 10 and 11. FIG.
FIG. 14 is a first embodiment of a transmitter unit of an electromagnetic ultrasonic transmitter.
FIG. 15 is a second embodiment of a transmitter unit of an electromagnetic ultrasonic transmitter.
FIG. 16 is a third embodiment of a transmitter unit of an electromagnetic ultrasonic transmitter.
[Explanation of symbols]
2 is an electromagnetic ultrasonic transmitter, 2a is a magnet, 2b is a coil, 2c is a transmitter unit, 4 is an ultrasonic detector, 4a is a detector unit, 4b is a core, 4c is a magnet, 4d is a detection coil, 4e is Core gap, 4u is upstream ultrasonic detector, 4d is downstream ultrasonic detector, 6 is piping, 8 is fluid, c is sound velocity, D is pipe diameter, d is interval, f is ultrasonic frequency, F Lorentz force, H is height, K is vertical, L _u upstream distance, L _d downstream distance, M is the magnetic field lines, n represents the order of interference, PT is stationary transmission distance, W is horizontal, delta phase difference .

Claims (1)

An electromagnetic ultrasonic transmitter is disposed close to the outer peripheral surface of the pipe through which the fluid flows in a non-contact manner. From the electromagnetic ultrasonic transmitters on the upstream side and the downstream side of the electromagnetic ultrasonic transmitter, the primary interference ultrasonic wave is transmitted. Ultrasonic energy that has been propagated in the fluid by placing an ultrasonic detector on the outer peripheral surface of the pipe in a non-contact manner at the position where the sound wave reaches, generating ultrasonic waves in the pipe or fluid by the electromagnetic ultrasonic transmitter The fluid and the pipe are vibrated by, the magnetic field in the pipe or the fluid is fluctuated by the vibration of the ultrasonic wave, the fluctuating magnetic field is detected by the ultrasonic detector, and the ultrasonic transmission time τ and the upstream ultrasonic wave arrival point are detecting the downstream ultrasonic arrival point, a distance until said both arrival point electromagnetic ultrasonic transmitter as a reference point, i.e., to calculate the upstream distance L _u and the downstream distance L _d, of the fluid from these parameters The sound speed c is derived, and the fluid is derived from the sound speed c. A non-contact type fluid temperature measuring method using electromagnetic ultrasonic waves, characterized by measuring a temperature T.

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