JP2019144007A - Measurement device - Google Patents

Abstract

To safely measure the density of fluid only by installing an ultrasonic probe onto an outer surface of a pipe.SOLUTION: A measurement device (1) measures, with an ultrasonic probe (20) disposed on an outer surface of a pipe (10), a density of fluid (15) in the pipe. The measurement device is configured to detect signal amplitudes of a plurality of ultrasonic waves (Sc, Sd) having different numbers of reflections in the pipe and detect propagation time of the ultrasonic waves propagating through the fluid in the pipe. The measurement device calculates acoustic impedance in which attenuation of the ultrasonic wave is corrected by using the plurality of signal amplitudes, calculates a sound speed of the ultrasonic wave propagating in the fluid from the propagation time of the ultrasonic wave, and calculates the density of the fluid in the pipe from the acoustic impedance and the sound speed.SELECTED DRAWING: Figure 4

Description

  The present disclosure relates to a measurement device.

  Conventionally, when performing piping work or maintenance, it may be necessary to confirm whether the contents are being sent out to the pipe according to the design drawing or sketch. In some cases, the contents can be confirmed from piping valves and plugs, but there are dangers when the internal pressure of the piping is high or the contents are highly toxic and flammable. The contents are confirmed by the sound of hitting the pipe, but sufficient experience is required for the worker, and it is difficult for a worker with little experience to judge. For this reason, a method has been proposed in which a dedicated pipe with an ultrasonic transducer is interposed in the middle of the pipe, and the density of the contents sent out through the pipe is measured by the signal amplitude of the ultrasonic wave (for example, Patent Document 1). reference).

JP 2008-304283 A

  However, in the method described in Patent Document 1, an ultrasonic vibrator is attached to the dedicated pipe, and piping work must be performed in order to interpose the dedicated pipe in the existing pipe.

  This indication is made in view of this point, and it aims at providing the measuring device which can measure the density of fluid safely only by installing an ultrasonic probe in the outer surface of piping. .

  A measurement device according to an aspect of the present disclosure is a measurement device that installs an ultrasonic probe on an outer surface of a pipe and measures the density of fluid in the pipe, and includes a plurality of ultrasonic waves having different numbers of reflections in the pipe An amplitude detector that detects the signal amplitude of the signal, a propagation time detector that detects the propagation time of the ultrasonic wave that propagates through the fluid in the pipe, an impedance calculator that calculates the acoustic impedance of the fluid from a plurality of signal amplitudes, A sound speed calculation unit that calculates the sound speed of the ultrasonic wave that propagates the fluid from the propagation time of the ultrasonic wave, and a density calculation unit that calculates the density of the fluid in the pipe from the acoustic impedance and the sound speed, the impedance calculation unit, An acoustic impedance obtained by correcting attenuation of ultrasonic waves using a plurality of signal amplitudes is calculated.

  A measuring device according to another aspect of the present disclosure is a measuring device that measures the density of fluid in the pipe by installing an ultrasonic probe on the outer surface of the pipe, and includes a plurality of ultrasonic waves having different numbers of reflections in the pipe An amplitude detection unit for detecting the signal amplitude of the signal, a propagation time detection unit for detecting the propagation time of the ultrasonic wave propagating through the fluid in the pipe, and an attenuation constant calculation unit for calculating the attenuation constant of the fluid from a plurality of signal amplitudes And a sound speed calculation unit that calculates the sound speed of the ultrasonic wave that propagates the fluid from the propagation time of the ultrasonic wave, and a density calculation unit that calculates the density of the fluid in the pipe from the attenuation constant and the sound speed.

  According to the present disclosure, the density of the fluid considering the attenuation is calculated from the signal amplitudes of the plurality of ultrasonic waves having different propagation distances by creating a difference in the propagation distance of the plurality of ultrasonic waves by reflecting the ultrasonic waves in the pipe. doing. Therefore, the density of the fluid in the pipe can be measured safely and accurately by a simple operation of installing the ultrasonic probe on the outer surface of the pipe. Moreover, since the sound speed of the ultrasonic wave propagating through the fluid is calculated, an error due to a change in sound speed can be suppressed.

It is a schematic block diagram of the measuring device of 1st Embodiment. It is a figure which shows an example of the measurement process of a comparative example. It is a block diagram of the measurement process part and data storage part of 1st Embodiment. It is a figure which shows an example of the measurement process of 1st Embodiment. It is a figure which shows another example of the measurement process of 1st Embodiment. It is a block diagram of the measurement process part and data storage part of 2nd Embodiment. It is a figure which shows the measuring device of 3rd Embodiment. It is a figure which shows the relationship between the wedge of 3rd Embodiment, piping, and the incident angle of a fluid. It is a block diagram of the measurement process part and data storage part of 4th Embodiment. It is a schematic block diagram of the measuring device of a modification. It is a schematic block diagram of the measuring device of another modification.

  Hereinafter, the measuring apparatus according to the first embodiment will be described. FIG. 1 is a schematic configuration diagram of a measurement apparatus according to the first embodiment. FIG. 2 is a diagram illustrating an example of the measurement process of the comparative example. In addition, the measuring apparatus of FIG. 1 shows an example, and is not limited to the structure shown in the figure.

  As shown in FIG. 1, the measuring apparatus 1 is configured to install an ultrasonic probe 20 on the outer surface 11 of the pipe 10 and measure the density of the fluid 15 in the pipe 10 by transmitting and receiving ultrasonic waves by the ultrasonic probe 20. It is configured. The pipe 10 is formed in a cylindrical shape having a predetermined thickness, for example, and the pipe 10 is filled with a fluid 15 as a measurement target. The ultrasonic probe 20 is a so-called two-vibrator vertical probe, and includes a pair of ultrasonic transducers 21a and 21b and a pair of wedges 22a and 22b arranged in parallel with an acoustic insulating plate (not shown) interposed therebetween. It is configured. The ultrasonic probe 20 applies ultrasonic waves from the ultrasonic transducers 21 a and 21 b to the wedges 22 a and 22 b to make the ultrasonic waves enter the pipe 10.

  At this time, in the ultrasonic probe 20, the slightly inclined incident angles of the ultrasonic transducers 21 a and 21 b are targeted with respect to the perpendicular of the outer surface 11 of the pipe 10. For this reason, the ultrasonic wave emitted from one of the pair of ultrasonic transducers 21a and 21b passes through the fluid 15 and is reflected by the inner surface 12 of the pipe 10, and either of the pair of ultrasonic transducers 21a and 21b. Incident on the other side. On the outer surface 11 of the pipe 10, a noise absorber 16 that absorbs a noise component propagating through the pipe wall is installed. The noise absorber 16 is for absorbing and attenuating ultrasonic noise, and functions effectively when the ultrasonic signal amplitude is small, for example, when the fluid 15 is a gas.

  A transmitter 25 and a receiver 26 are connected to the ultrasonic transducer 21a via a switch 24a, and a transmitter 25 and a receiver 26 are connected to the ultrasonic transducer 21b via a switch 24b. The transmission unit 25 inputs a transmission signal to one of the ultrasonic transducers 21a and 21b to generate an ultrasonic signal, and the reception unit 26 receives the ultrasonic signal from either one of the ultrasonic transducers 21a and 21b. Receive the received signal. The switch units 24a and 24b alternately switch the connection destination of the ultrasonic transducers 21a and 21b to the transmission unit 25 or the reception unit 26, so that the set of ultrasonic transducers 21a and 21b functions as a reception sensor or a transmission sensor. To do.

  When the reception signal is received by the reception unit 26, the reception signal is amplified and filtered and output to the measurement processing unit 30. The measurement processing unit 30 refers to the parameter stored in the data storage unit 40 and calculates the density of the fluid 15 based on the received signal from the receiving unit 26. A control unit 27 is connected to the measurement processing unit 30, the data storage unit 40, the transmission unit 25, the reception unit 26, and the switch units 24a and 24b. The control unit 27 performs overall control of each unit of the measurement device 1. For example, the control unit 27 outputs the density of the fluid 15 calculated by the measurement processing unit 30 to an external device (not shown), and inputs a known parameter to the data storage unit 40 from the external device.

  The control unit 27, the measurement processing unit 30, and the data storage unit 40 are configured by a processor, a memory, and the like that execute various processes. The memory is composed of one or a plurality of storage media such as a ROM (Read Only Memory) and a RAM (Random Access Memory) depending on the application. The memory stores a program that causes the measurement device 1 to execute various processes such as a calculation process of the density of the fluid 15. The transmission unit 25 includes various circuits such as an amplifier circuit, and the reception unit 26 includes various circuits such as an amplifier circuit and a filter circuit. Detailed configurations of the measurement processing unit 30 and the data storage unit 40 will be described later.

  Generally, in order to check the density of the fluid in the pipe, it is necessary to open the valve or the like to take out the fluid. However, when the internal pressure of the pipe is high, the fluid cannot be easily taken out. A highly skilled worker can check the density of fluid from the outside of the pipe by hitting the pipe, but it is difficult for an inexperienced worker to check the density of the fluid. Therefore, paying attention to the fact that the acoustic impedance and sound velocity of the fluid can be obtained even for an unknown fluid, a method for calculating the density from the acoustic impedance and sound velocity of the fluid obtained using ultrasonic waves from the outside of the pipe Is being considered.

The acoustic impedance is expressed by the product of the material density and the speed of sound. The acoustic impedance Zw of the wedge is expressed by the following equation (1) where ρw is the density of the wedge and Cw is the velocity of the ultrasonic waves in the wedge. Similarly, the acoustic impedance Zp of the pipe is expressed by the following equation (2) where ρp is the density of the pipe and Cp is the velocity of ultrasonic waves in the pipe. The acoustic impedance Zf of the fluid is expressed by the following equation (3) where ρf is the density of the fluid and Cf is the speed of sound of the ultrasonic waves in the fluid. Since ρw, Cw, ρp, and Cp are known parameters, Zw and Zp can be obtained. These known parameters are stored in advance so that they can be referred to when calculating the density.
(1)
Zw = ρw · Cw
(2)
Zp = ρp · Cp
(3)
Zf = ρf · Cf

The signal amplitude B of the ultrasonic wave from the ultrasonic transducer toward the wedge is measured in advance and stored as a known parameter. The transmittance Qwp of the ultrasonic wave from the wedge toward the pipe is expressed by the following equation (4). The transmittance Qpf of ultrasonic waves from the pipe toward the fluid is expressed by the following equation (5). The reflectance Rfp of the ultrasonic wave reflected from the inner surface of the pipe is expressed by the following formula (6). The transmittance Qfp of ultrasonic waves from the fluid to the pipe is expressed by the following equation (7). Finally, the transmittance Qpw of the ultrasonic wave from the pipe toward the wedge is expressed by the following equation (8). The transmittance Qwv from the wedge toward the ultrasonic transducer is measured in advance and stored in advance as a known parameter.
(4)
Qwp = 2 · Zp / (Zp + Zw)
(5)
Qpf = 2 · Zf / (Zf + Zp)
(6)
Rfp = (Zp−Zf) / (Zp + Zf)
(7)
Qfp = 2 · Zp / (Zp + Zf)
(8)
Qpw = 2 · Zw / (Zw + Zp)

At this time, since Zp and Zw included in Qwp are known parameters, Qwp can be obtained. Qpf, Rfp, and Qfp include an unknown parameter Zf. Since Zp and Zw included in Qpw are known parameters, Qpw can be obtained as a known parameter. Then, the signal amplitude A of the ultrasonic wave propagated through the ultrasonic transducer, wedge, pipe, and fluid, reflected from the inner surface of the pipe, and propagated through the fluid, pipe, wedge, and ultrasonic transducer is expressed by the following equation (9). Is done. Since Zf is the only unknown parameter in equation (9), Zf can be calculated by detecting the signal amplitude A of the received signal.
(9)
A = B, Qwp, Qpf, Rfp, Qfp, Qpw, Qwv

Further, the total propagation time T of the ultrasonic wave is detected by measuring the time from the output of the transmission signal to the input of the reception signal. The total ultrasonic propagation time T is expressed by the following equation (10), where Tw is the propagation time in the wedge, Tp is the propagation time in the pipe, Tf is the propagation time in the fluid, and Tl is the signal delay time. Tl is a delay time generated in various circuits and ultrasonic transducers in the apparatus, and can be obtained as a known parameter.
(10)
T = 2 (Tw + Tp + Tf) + Tl

Tw is expressed by the following equation (11), where Cw is the velocity of ultrasonic waves in the wedge and Lw is the propagation distance in the wedge. Since Cw and Lw are known parameters, Tw can be obtained in advance. Tp is expressed by the following equation (12), where Do is the outer diameter of the pipe, Di is the inner diameter of the pipe, and Cp is the velocity of ultrasonic waves in the pipe. Do can be measured, but Di is difficult to measure directly. In this case, the nominal value determined by the standard may be used as Di, or the pipe thickness THp may be measured using an ultrasonic thickness meter or the like, and obtained from the following equation (13). Therefore, since Do, Di, and Cp are known parameters, Tp can be obtained. Since Tf is the only unknown parameter in the above equation (10), it is possible to calculate Tf by detecting the total propagation time T.
(11)
Tw = Lw / Cw
(12)
Tp = (Do−Di) / (2 · Cp)
(13)
Di = Do-2 · THp

Further, the sound velocity Cf of the ultrasonic wave in the fluid is expressed by the following equation (14), where Di is the inner diameter of the pipe and Tf is the propagation time in the fluid. As described above, Zf and Cf, which are unknown parameters, are obtained, so that the fluid density ρf is obtained by Expression (15) obtained by modifying Expression (3).
(14)
Cf = Di / Tf
(15)
ρf = Zf / Cf

  By the way, in the above calculation method, although the density of the fluid can be calculated, the attenuation of ultrasonic waves is not taken into consideration. Since the ultrasonic wave is attenuated while propagating through the fluid, and the signal amplitude A decreases due to the attenuation of the ultrasonic wave, the density of the fluid cannot be calculated with sufficient accuracy. Further, as shown in Expression (10), when calculating Tf, it is affected by errors included in known parameters such as Tw, Tp, and Tl. As described above, in the method using the signal amplitude of a single ultrasonic wave, there is a limit to the measurement accuracy of the fluid density due to the attenuation and the error of a known parameter.

  In this case, as shown in the comparative example of FIG. 2, the measurement accuracy of the density of the fluid 15 can be improved by using the dedicated pipe 101 integrated with the ultrasonic probes 100a and 100b. A dedicated pipe 101 is formed by connecting a large diameter portion 102 and a small diameter portion 103, and ultrasonic probes 100 a and 100 b are attached to the large diameter portion 102 and the small diameter portion 103, respectively. The ultrasonic wave from the ultrasonic probe 100a propagates through the fluid 15 and is reflected by the inner surface of the large-diameter portion 102 and received by the ultrasonic probe 100a, and the ultrasonic wave from the ultrasonic probe 100b propagates through the fluid 15 and passes through the small-diameter portion. It is reflected by the inner surface of 103 and received by the ultrasonic probe 100a. By using the signal amplitude and propagation time difference between two ultrasonic waves having different propagation distances, the influence of ultrasonic attenuation and the influence of errors included in known parameters are eliminated.

  The dedicated pipe 101 shown in the comparative example creates a difference between the propagation distances of two ultrasonic waves depending on the pipe diameter difference between the large diameter portion 102 and the small diameter portion 103. For this reason, in order to measure the density of the fluid 15 in the existing piping, it is necessary to carry out piping work and attach the dedicated piping 101 in the middle of the existing piping. Further, since the flow of the fluid 15 is disturbed at the change of the pipe diameter of the dedicated pipe 101, it is necessary to attach the ultrasonic probes 100a and 100b sufficiently apart in the extending direction of the dedicated pipe 101. For this reason, there exists a malfunction that the exclusive piping 101 becomes large. Thus, it has been difficult to measure the density of the fluid 15 by applying the dedicated pipe 101 of the ultrasonic probes 100a and 100b to the existing pipe.

  Therefore, in the measurement apparatus 1 (see FIG. 1) of the present embodiment, paying attention to the fact that the difference in the propagation distance of the ultrasonic wave can be obtained depending on the number of reflections in the pipe 10, using a plurality of ultrasonic waves having different reflection times. A measurement processing unit 30 capable of measuring the density in consideration of the attenuation of the fluid 15 is provided. Since there is no need to change the diameter of the pipe 10, the ultrasonic probe 20 is simply installed on the outer surface of the existing pipe without using the dedicated pipe 101 as shown in the comparative example. It is possible to accurately measure the density.

  Hereinafter, density measurement by the measurement device will be described in detail with reference to FIGS. 3 to 5. FIG. 3 is a block diagram of the measurement processing unit and the data storage unit according to the first embodiment. FIG. 4 is a diagram illustrating an example of a measurement process according to the first embodiment. FIG. 5 is a diagram illustrating another example of the measurement process according to the first embodiment. Note that the measurement processing unit and the data storage unit in FIG. 3 are examples, and are not limited to the configuration shown in the figure.

  As shown in FIGS. 3 and 4, the measurement processing unit 30 includes an amplitude detection unit 31 that detects signal amplitudes of a plurality of ultrasonic waves having different numbers of reflections in the pipe 10, and an acoustic of the fluid 15 from the plurality of signal amplitudes. An impedance calculation unit 32 that calculates impedance is provided. Further, the measurement processing unit 30 calculates a propagation time detection unit 33 that detects the propagation time of the ultrasonic wave that propagates through the fluid 15 in the pipe 10, and calculates the sound velocity of the ultrasonic wave that propagates through the fluid 15 from the propagation time of the ultrasonic wave. And a sound speed calculation unit 34 is provided. Further, the measurement processing unit 30 is provided with a density calculation unit 35 that calculates the density of the fluid 15 in the pipe 10 based on acoustic impedance and sound speed.

  The data storage unit 40 is provided with a parameter storage unit 41. The parameter storage unit 41 stores known parameters that are appropriately read by the measurement processing unit 30. Known parameters include known density ρw, ρp, known sound speed Cw, Cp, known acoustic impedance Zw, Zp, known transmittance Qwp, Qpw, Qwv, known ultrasonic signal amplitude B, pipe 10 The outer diameter Do, the inner diameter Di, the known times Tw, Tp, Tl, etc. are stored as necessary. The data storage unit 40 may be provided with a correction coefficient storage unit 42 and a temperature correction data storage unit 43 described later.

  The amplitude detection unit 31 receives a plurality of ultrasonic waves at the reception unit 26 and detects the signal amplitudes of the plurality of ultrasonic waves according to the reception signal input from the reception unit 26. In this case, when an ultrasonic wave is output from the ultrasonic transducer 21a to the pipe 10, the reflection of the ultrasonic wave is repeated on the inner surface 12 of the pipe 10, and ultrasonic waves having different numbers of reflections are transmitted via the ultrasonic vibrator 21b. Received by the receiver 26. By receiving a plurality of ultrasonic waves at different timings by the receiving unit 26, signal amplitudes of a plurality of ultrasonic waves having different propagation distances are output from the receiving unit 26 to the amplitude detecting unit 31. The amplitude detector 31 detects the signal amplitudes Ac and Ad of the ultrasonic wave Sc reflected once in the pipe 10 and the ultrasonic wave Sd reflected three times in the pipe 10.

In the impedance calculation unit 32, the acoustic impedance corrected for attenuation in the fluid 15 is calculated using the signal amplitudes Ac and Ad of the plurality of ultrasonic waves Sc and Sd. In this case, the attenuation of the ultrasonic wave is expressed by the following equation (16), where A is the signal amplitude, α is the attenuation constant, d is the propagation distance, and A ₀ is the signal amplitude without attenuation. The ultrasonic wave Sc propagates through the ultrasonic vibrator 21a, the wedge 22a, the pipe 10, and the fluid 15, is reflected by the inner surface 12 of the pipe 10, and enters the fluid 15, the pipe 10, the wedge 22b, and the ultrasonic vibrator 21b. The signal amplitude Ac damping the absence represented by the above formula (9), the use of A ₀ is expressed by the following equation (17). In consideration of attenuation, the signal amplitude Ac reciprocates the inner diameter of the pipe 10 once, and therefore the propagation distance d becomes 2Di and is expressed by the following equation (18).
(16)
A = A ₀ · e ^-2αd
(17)
A ₀ = B, Qwp, Qpf, Rfp, Qfp, Qpw, Qwv
(18)
Ac = A ₀ · e ^-4αDi

The ultrasonic wave Sd is a part of the ultrasonic wave Sc that is further reciprocated once in the pipe 10 and reflected by the inner surface 12 of the pipe 10 three times. That is, the ultrasonic wave Sd propagates through the ultrasonic vibrator 21a, the wedge 22a, the pipe 10, and the fluid 15 and is reflected three times by the inner surface 12 of the pipe 10, and the fluid 15, the pipe 10, the wedge 22b, and the ultrasonic vibrator 21b. Is incident on. For this reason, when the signal amplitude in a state without attenuation is Ad ₀ , it is expressed by the following equation (19). In consideration of attenuation, the signal amplitude Ad is expressed by the following equation (20) as the propagation distance d is 4 Di because the ultrasonic wave Sd reciprocates the inner diameter of the pipe 10 twice.
(19)
Ad ₀ = B · Qwp · Qpf · Rfp ³ · Qfp · Qpw · Qwv
= A ₀・ Rfp ²
(20)
Ad = Ad ₀ · e ^−8αDi
= A ₀ · Rfp ² · e ^-8αDi

Unknown parameters of simultaneous equations of formula (18) and (20) are two of Zf and alpha, for unknown parameters of A ₀ is Zf, the influence of the attenuation of ultrasonic waves by solving this Zf is obtained in a corrected form. As described above, the impedance calculation unit 32 calculates the acoustic impedance in which the attenuation in the fluid 15 is corrected using a plurality of signal amplitudes of ultrasonic waves having different numbers of reflections. Here, although the ultrasonic wave Sc reflected once and the ultrasonic wave Sd reflected three times have been described as an example, it is possible to similarly correct the influence of attenuation by using ultrasonic waves having different numbers of reflections.

The propagation time detector 33 detects the total propagation time of a plurality of ultrasonic waves Sc and Sd having different propagation distances. In this case, the transmission timing is controlled by the transmission unit 25 by the control unit 27 (see FIG. 1), but the detection of the propagation time is started by the propagation time detection unit 33 in accordance with the transmission timing of the transmission unit 25. Based on the transmission timing of the ultrasonic waves, the total propagation time until the reception signals of the ultrasonic waves Sc and Sd are input from the receiving unit 26 is measured. The in-fluid propagation time Tf is expressed by the following equation (21), where Tc is the total propagation time of the ultrasonic wave Sc and Td is the total propagation time of the ultrasonic wave Sd. Since known parameters such as Tw, Tp, and Tl are not used as in equation (10), they are not affected by errors included in these parameters.
(21)
Tf = (Td−Tc) / 2

  The sound speed calculation unit 34 calculates the sound speed Cf of the ultrasonic wave in the fluid 15 from the inner diameter Di of the pipe 10 and the propagation time Tf in the fluid by the above equation (14). Further, the density calculation unit 35 calculates the density ρf of the fluid 15 from the acoustic impedance Zf and the sound velocity Cf of the ultrasonic wave in the fluid 15 by the above equation (15). In the measuring device 1, a propagation distance difference is created from the difference in the number of reflections of the two ultrasonic waves Sc and Sd, and the density of the fluid 15 is accurately measured from the signal amplitudes Ac and Ad of the ultrasonic waves Sc and Sd. The ultrasonic probe 20 may be installed on the outer surface of the existing pipe, and it is not necessary to prepare the dedicated pipe 101 (see FIG. 2) shown in the comparative example and perform the piping work.

  In the measuring apparatus 1 configured as described above (see FIG. 1), the ultrasonic probe 20 is installed on the outer surface 11 of the pipe 10, and ultrasonic waves are output from one ultrasonic transducer 21 a of the ultrasonic probe 20. The ultrasonic wave output from the ultrasonic transducer 21 a propagates to the wedge 22 a and the pipe 10, further passes through the fluid 15 from the pipe 10 and is reflected by the inner surface 12 of the pipe 10. The ultrasonic wave reflected by the inner surface 12 of the pipe 10 passes through the fluid 15, propagates to the pipe 10 and the wedge 22b, and is input to the ultrasonic vibrator 21b as the ultrasonic wave Sc. A part of the ultrasonic wave Sc is repeatedly reflected in the pipe 10 and reciprocated once, and then propagates to the pipe 10 and the wedge 22b and is input to the ultrasonic vibrator 21b as the ultrasonic wave Sd.

  When the ultrasonic wave Sc is received by the ultrasonic vibrator 21b, the amplitude detector 31 detects the signal amplitude of the received signal. After that, when the ultrasonic wave Sd is received by the ultrasonic transducer 21b, the amplitude detector 31 detects the signal amplitude of the received signal. The impedance calculation unit 32 calculates the acoustic impedance of the fluid 15 in consideration of attenuation from the signal amplitudes of the ultrasonic waves Sc and Sd while reading a known parameter from the parameter storage unit 41. On the other hand, the propagation time detection unit 33 calculates the propagation time in the fluid from the time difference between the total propagation times of the ultrasonic waves Sc and Sd, and the sound speed calculation unit 34 calculates the sound velocity of the ultrasonic waves in the fluid 15 from the propagation time in the fluid. The

  The density calculator 35 calculates the density of the fluid 15 from the acoustic impedance and the sound speed. In this case, since the pair of ultrasonic transducers 21 a and 21 b are included in the single ultrasonic probe 20, the installation work for the pipe 10 can be simplified. In addition, when one ultrasonic transducer 21a in the ultrasonic probe 20 functions as a transmission sensor, the other ultrasonic transducer 21b functions as a reception sensor. Since the ultrasonic probe 20 also includes an acoustic insulating plate between the transmission sensor and the reception sensor, the accuracy is improved without the reverberation of the transmission sensor affecting the reception sensor.

  Further, when the ultrasonic probe 20 is installed on the outer surface 11 of the pipe 10, an error may occur in the signal amplitudes of the ultrasonic waves Sc and Sd depending on the shape and surface state of the pipe 10. For this reason, in this embodiment, the signal amplitudes of the plurality of ultrasonic waves Sc and Sd may be corrected using a correction coefficient calculated with a known fluid whose density is known in advance. In this case, the measured value of the ultrasonic signal amplitude and the propagation time in the fluid are detected with a known fluid. The speed of sound in the fluid is calculated from the propagation time in the fluid by Expression (14), and the acoustic impedance is calculated from the speed of sound and the known density by Expression (15). And the theoretical value of the signal amplitude of an ultrasonic wave is calculated | required by Formula (9).

Although the theoretical value of the ultrasonic signal amplitude is the original amplitude, actually measured values different from the theoretical values are detected. This shows that the signal amplitude of the ultrasonic wave has changed from the theoretical value to the actually measured value due to the shape of the pipe 10 and the like. The rate of this change is constant, and changes so that the ultrasonic signal amplitude is multiplied by As / At, where At is the theoretical value of the signal amplitude of the sound wave and As is the actual measurement value. In order to correct this error, the equation (17) is replaced by the following equation (22) using the correction coefficient At / As. Note that the fluid used for correction needs to be known, but the correction coefficient can be used regardless of the type of fluid. The correction coefficient is stored in the correction coefficient storage unit 42 and is referred to by the impedance calculation unit 32. In the impedance calculation unit 32, the acoustic impedance of the fluid 15 is calculated from a plurality of signal amplitudes corrected by the correction coefficient.
(22)
A ₀ · At / As = B · Qwp · Qpf · Rfp · Qfp · Qpw · Qwv

  Further, in the calculation method described above, parameters indicating the performance of the ultrasonic probe 20 such as B and Qwv are required as shown in Expression (17) and Expression (22), and the ultrasonic probe 20 is calibrated in advance. B, Qwv must be obtained. Further, when the ultrasonic probe 20 is installed on the outer surface 11 of the pipe 10, the influence of errors included in the known parameters of the transmittances Qwp and Qpw between the wedges 22 a and 22 b and the pipe 10 due to the shape of the pipe 10 and the like. There is a risk of receiving. For this reason, in this embodiment, the error may be further reduced by using the signal amplitude of the ultrasonic wave Sb reflected from the inner surface of the pipe 10 before the fluid 15.

As shown in FIG. 5, the ultrasonic wave Sb propagates through the ultrasonic transducer 21a, the wedge 22a, and the pipe 10, reflects off the inner surface of the pipe 10, and enters the pipe 10, the wedge 22b, and the ultrasonic transducer 21b. The reflectance Rpf of the ultrasonic wave reflected from the inner surface of the pipe 10 is expressed by the following equation (23), and the signal amplitude Ab of the ultrasonic wave Sb is expressed by the following equation (24). Substituting equation (24) into equation (17) transforms into equation (25), and equation (25) can be used instead of equation (17). Expression (25) does not include B and Qwv, and it is not necessary to calibrate the ultrasonic probe 20 to obtain B and Qwv. Errors of known parameters such as Qwp, Qpw, B, and Qwv can be eliminated, and the calculation accuracy of acoustic impedance can be improved.
(23)
Rpf = (Zf−Zp) / (Zf + Zp)
(24)
Ab = B, Qwp, Rpf, Qpw, Qwv
(25)
A ₀ = Qpf · Rfp · Qfp · Ab / Rpf

In this embodiment, the configuration is such that two ultrasonic signal amplitudes having different numbers of reflections are used. However, the measurement accuracy can be further improved by using three or more ultrasonic signal amplitudes. Can do. When the number of times of reflection of the ultrasonic wave on the inner surface of the pipe is k, the equations (18) and (20) are generalized by the following equation (26). Applying equation (26) to three or more k results in k simultaneous equations, but since there are two unknown parameters, Zf and α, there are more equations than the unknown parameters and an exact solution is obtained. I can't.
(26)
Ak = A ₀ · Rfp ^(k−1) · e ^{−2 (k + 1) αDi}

In this case, a solution with the smallest error can be obtained by applying the method of least squares, and the error εk when the number of reflections is k is defined by the following equation (27). At this time, the solution for minimizing the total Σεk of the errors εk for three or more k is the simultaneous equations of the following equations (28) and (29) that are different from each other by unknown parameters Zf and α being zero. Is the solution. As described above, when the least square method is applied, the calculation accuracy of Zf can generally be improved as the value of k increases.
(27)
εk = (Ak−A ₀ · Rfp ^(k−1) · e ^{−2 (k + 1) αDi} ) ²
(28)
δ (Σεk) / δZf = 0
(29)
δ (Σεk) / δα = 0

  As described above, in the first embodiment, the ultrasonic waves are reflected in the pipe 10 to create a difference in the propagation distances of the plural ultrasonic waves, and are attenuated from the signal amplitudes of the plural ultrasonic waves having different propagation distances. The density of the fluid 15 is calculated in consideration of the above. Therefore, the density of the fluid 15 in the pipe 10 can be measured safely and accurately by a simple operation of installing the ultrasonic probe 20 on the outer surface 11 of the pipe 10. Moreover, since the sound speed of the ultrasonic wave propagating through the fluid 15 is calculated, an error due to a change in sound speed can be suppressed.

  In the first embodiment, the density is calculated from the acoustic impedance and sound speed of the fluid, but the present invention is not limited to this configuration. The density may be calculated from the fluid attenuation constant and sound velocity. Hereinafter, the measuring apparatus according to the second embodiment will be described with reference to FIG. FIG. 6 is a block diagram of a measurement processing unit and a data storage unit according to the second embodiment. The second embodiment is different from the first embodiment in the measurement processing unit. Therefore, the difference will be described in detail. Further, the measurement processing unit and the data storage unit in FIG. 6 are examples, and are not limited to the illustrated configuration. In the second embodiment, it is assumed that the type of fluid is known in advance.

  The measurement processing unit 50 includes an amplitude detection unit 51 that detects signal amplitudes of a plurality of ultrasonic waves having different numbers of reflections in the pipe 10, and an attenuation constant calculation unit 52 that calculates an attenuation constant of the fluid 15 from the plurality of signal amplitudes. Is provided. The measurement processing unit 50 also calculates a propagation time detection unit 53 that detects the propagation time of the ultrasonic wave that propagates through the fluid 15 in the pipe 10, and calculates the sound velocity of the ultrasonic wave that propagates through the fluid 15 from the propagation time of the ultrasonic wave. And a sound speed calculation unit 54 is provided. Further, the measurement processing unit 50 is provided with a density calculation unit 55 that calculates the density of the fluid 15 in the pipe 10 based on the attenuation constant and the speed of sound.

  The data storage unit 60 is provided with a parameter storage unit 61. The parameter storage unit 61 stores known parameters that are appropriately read out by the measurement processing unit 50. Known parameters include known density ρw, ρp, known sound speed Cw, Cp, known acoustic impedance Zw, Zp, known transmittance Qwp, Qpw, Qwv, known ultrasonic signal amplitude B, pipe 10 The outer diameter Do, the inner diameter Di, the known times Tw, Tp, Td, the viscosity coefficient η, the ultrasonic angular frequency ω, and the like are stored as necessary. The data storage unit 60 may include a correction coefficient storage unit 62 and a temperature correction data storage unit 63.

In the attenuation constant calculation unit 52, there are two unknown parameters of the simultaneous equations of Equation (18) and Equation (20) or Equation (28) and Equation (29), Zf and α. α can be obtained. The attenuation constant α is expressed by the following equation (30), where η is the viscosity coefficient, ω is the angular frequency of the ultrasonic wave, Cf is the sound velocity of the ultrasonic wave in the fluid 15, and ρf is the density of the fluid 15. The density calculation unit 55 calculates the density of the fluid 15 from the attenuation constant α and the sound velocity Cf by the following equation (31) obtained by modifying the equation (30). Each process of the amplitude detection unit 51, the propagation time detection unit 53, and the sound speed calculation unit 54 is the same as that of the first embodiment.
(30)
α = η · ω ² / (2 · Cf ³ · ρf)
(31)
ρf = η · ω ² / (2 · Cf ³ · α)

  Also in the measurement apparatus of the second embodiment, the correction coefficient is stored in the correction coefficient storage unit 62, and the attenuation constant of the fluid 15 may be calculated from a plurality of signal amplitudes corrected by the correction coefficient by the attenuation constant calculation unit 52. . Further, by using the ultrasonic wave Sb reflected from the inner surface of the pipe 10 in front of the fluid 15, the attenuation constant calculation unit 52 eliminates the influence of errors of known parameters of Qwp, Qpw, B, and Qwv, and calculates the attenuation constant calculation accuracy. May be improved. Further, the attenuation constant calculation accuracy may be improved by using the amplitudes of three or more ultrasonic waves having different numbers of reflections.

  As described above, in the second embodiment, as in the first embodiment, the density of the fluid 15 in the pipe 10 is reduced by a simple operation of installing the ultrasonic probe 20 on the outer surface of the pipe 10. Safe and accurate measurement is possible.

  In the first and second embodiments, a single ultrasonic probe is used. However, the present invention is not limited to this configuration. A plurality of ultrasonic probes may be installed at intervals with respect to the piping so that the ultrasonic wave crosses the fluid obliquely. Hereinafter, the measuring apparatus according to the third embodiment will be described with reference to FIGS. FIG. 7 is a diagram illustrating a measurement apparatus according to the third embodiment. FIG. 8 is a diagram illustrating the relationship between the wedge, the pipe, and the incident angle of the fluid according to the third embodiment. In the third embodiment, the installation configuration of the ultrasonic probe is different from the first and second embodiments. Therefore, the difference will be described in detail.

  As shown in FIG. 7, a pair of ultrasonic probes 70 a and 70 b are installed on the outer surface 11 of the pipe 10 so as to face each other diagonally. Each of the ultrasonic probes 70a and 70b is configured to be attached to the wedges 72a and 72b so that the incident angles of the ultrasonic transducers 71a and 71b face each other. One ultrasonic probe 70 a is installed on the upstream side with respect to the flow of the fluid 15 in the pipe 10, and the other ultrasonic probe 70 b is installed on the downstream side with respect to the flow of the fluid 15 in the pipe 10. Ultrasonic waves are obliquely incident on the wedge 72a and the pipe 10 from the ultrasonic vibrator 71a, and the ultrasonic waves are obliquely traversed in the fluid 15 and received by the ultrasonic vibrator 71b via the pipe 10 and the wedge 72b.

  Transmission and reception of the ultrasonic probes 70a and 70b are switched by the switch unit. Since the ultrasonic wave obliquely crosses the fluid 15, the propagation time of the ultrasonic wave from the upstream ultrasonic probe 70a to the downstream ultrasonic probe 70b of the fluid 15 is shortened. On the contrary, the propagation time of the ultrasonic wave from the ultrasonic probe 70b on the downstream side of the fluid 15 to the ultrasonic probe 70a on the upstream side becomes longer. Since the propagation time difference of these ultrasonic waves changes depending on the flow velocity of the fluid 15, the volume flow rate can be obtained from the velocity of the fluid 15 by measuring the propagation time difference by a propagation time difference measurement unit (not shown). .

The density of the fluid 15 can also be measured by the measuring device according to the third embodiment. By measuring the density of the fluid 15, the mass flow rate can be obtained from the volume flow rate and the density. Therefore, in the third embodiment, in addition to the density of the fluid 15, the volume flow rate and the mass flow rate can be measured. Here, the measurement of density will be described. As shown in FIG. 8, when the incident angles of the wedges 72a and 72b are θw, the incident angle of the pipe 10 is θp, and the incident angle of the fluid 15 is θf, the incident angles θw, θp, and θf are expressed by the following formula (32 ) When the equation (32) is transformed, it is expressed by the following equations (33) and (34). Note that θw is a known parameter.
(32)
Cw / sin θw = Cp / sin θp = Cf / sin θf
(33)
θp = sin ⁻¹ (Cp · sin θw / Cw)
(34)
θf = sin ⁻¹ (Cf · sin θw / Cw)

Next, Qwp is the following equation (35), Qpf is the following equation (36), Rfp is the following equation (37), Qfp is the following equation (38), Qpw is the following equation (39), and Tp is the following equation (40). , Cf are represented by the following equations (41), respectively. When the formula (34) is substituted into the formula (41), the following formula (42) is obtained. Since Cf is the only unknown parameter in equation (42), Cf can be obtained. By replacing the equations (4) to (8) with the equations (35) to (39), the equation (12) with the equation (40), and the equation (14) with the equation (42), the density of the fluid 15 is changed. It is possible to ask.
(35)
Qwp = 2 · Zp · cos θw / (Zp · cos θw + Zw · cos θp)
(36)
Qpf = 2 · Zf · cos θp / (Zf · cos θp + Zp · cos θf)
(37)
Rfp = (Zp · cos θf−Zf · cos θp) / (Zp · cos θf + Zf · cos θp)
(38)
Qfp = 2 · Zp · cos θf / (Zp · cos θf + Zf · cos θp)
(39)
Qpw = 2 · Zw · cos θp / (Zw · cos θp + Zp · cos θw)
(40)
Tp = (Do−Di) / (2 · Cp · cos θf)
(41)
Cf = Di / cos θf / Tf
(42)
Cf = Di / cos (sin ⁻¹ (Cf · sin θw / Cw)) / Tf

Further, by replacing the equation (23) with the equation (43), the influence of the error of the known parameters of Qwp, Qpw, B, and Qwv using the ultrasonic wave Sb reflected on the inner surface of the pipe 10 before the fluid 15 is achieved. Can improve the calculation accuracy.
(43)
Rpf = (Zf · cos θp−Zp · cos θf) / (Zf · cos θp + Zp · cos θf)

The ultrasonic wave Sg propagates through the ultrasonic vibrator 71a, the wedge 72a, the pipe 10, and the fluid 15, and enters the pipe 10, the wedge 72b, and the ultrasonic vibrator 71b. The signal amplitude A _{0 of the} ultrasonic wave without attenuation is expressed by the following equation (44). Qwp, Qpf, Qfp, and Qpw are expressed by Expression (35), Expression (36), Expression (38), and Expression (39), respectively. Next, the signal amplitude Ag of the ultrasonic wave Sg not reflected by the pipe 10 is expressed by the following expression (45), and the signal amplitude Ag of the ultrasonic wave Sh reflected once by the pipe 10 and reciprocated is expressed by the following expression (46). The Since the ultrasonic wave Sh crosses the fluid 15 obliquely three times, the propagation distance d is 3 · Di / cos θf. Since there are two unknown parameters Zf and α in the simultaneous equations of Equation (45) and Equation (46), Zf or α can be obtained by solving them.
(44)
A ₀ = B, Qwp, Qpf, Qfp, Qpw, Qwv
(45)
Ag = A ₀ · e ^{−2αDi / cos θf}
(46)
Ah = A ₀ · Rfp ² · e ^{−6αDi / cos θf}

In the third embodiment, the measurement accuracy can be further improved by using the signal amplitudes of three or more ultrasonic waves. When the number of reflections in the equations (45) and (46) is generalized as k, it is expressed by the following equation (47). 7A shows an example in which k = 0, FIG. 7B shows an example in which k = 2, and FIG. 7C shows an example in which k = 4. Further, when the least square method is applied, a solution with the smallest error can be obtained, and the error εk when the number of reflections is k is defined by the following equation (48). And the calculation precision of (alpha) and Zf can be improved by calculating | requiring the solution of simultaneous equations of above-mentioned Formula (28) and Formula (29).
(47)
Ak = A ₀ · Rfp ^k−1 · e ^{−2 (k + 1) αDi / cos θf}
(48)
εk = (Ak−A ₀ · Rfp ^k · e ^{−2 (k + 1) αDi / cos θf} ) ²

  Also in the measurement apparatus of the third embodiment, the acoustic impedance or attenuation constant of the fluid 15 may be calculated from a plurality of signal amplitudes corrected with the correction coefficient. In addition, by using the ultrasonic wave Sb reflected from the inner surface of the pipe 10 before the fluid 15, the calculation accuracy of the acoustic impedance or attenuation constant is improved without the influence of the error of the known parameters of Qwp, Qpw, B, Qwv. May be.

As described above, in the third embodiment, as in the first and second embodiments, the fluid in the pipe 10 can be obtained by a simple operation of installing the ultrasonic probe 20 on the outer surface 11 of the pipe 10. The density of 15 can be measured safely and accurately. In addition to the density of the fluid 15, the volume flow rate and mass flow rate of the fluid 15 can be calculated. In addition, there is a case where the ultrasonic signal amplitude is increased to improve the measurement accuracy of the propagation time and the density calculation accuracy. Actually, when the inventor calculated the signal amplitude of the ultrasonic wave with the following parameters, the result was that the signal amplitude was twice the normal incidence.
(Common parameters)
Wedge sound speed: 2730 [m / s] (material PVC, longitudinal wave)
Wedge density: 1188 [kg / m ³ ] (Material PVC)
Piping density: 7910 [kg / m ³ ] (material SUS)
Fluid sound velocity: 340 [m / s] (air)
Fluid density: 1.2 [kg / m ³ ] (air)
(Normal incidence)
Wedge incident angle: 0 [°]
Pipe sound speed: 6000 [m / s] (Material: SUS, longitudinal wave)
(Oblique incidence)
Wedge incident angle: 45 [°]
Pipe sound speed: 3075 [m / s] (Material: SUS, shear wave)

  In the first to third embodiments, the fluid density is measured by the measurement device, but the configuration is not limited to this. In the measuring device, the pressure may be measured in addition to the density of the fluid. Hereinafter, the measurement apparatus according to the fourth embodiment will be described with reference to FIG. FIG. 9 is a block diagram of a measurement processing unit and a data storage unit according to the fourth embodiment. The fourth embodiment is different from the first and second embodiments in that a temperature calculation unit and a pressure calculation unit are provided. Therefore, the difference will be described in detail. Further, the measurement processing unit and the data storage unit in FIG. 9 are examples, and are not limited to the illustrated configuration. In the fourth embodiment, it is assumed that the type of fluid is known in advance.

  The measurement processing unit 80 includes an amplitude detection unit 81 that detects signal amplitudes of a plurality of ultrasonic waves having different numbers of reflections in the pipe 10, and an impedance calculation unit 82 that calculates the acoustic impedance of the fluid 15 from the plurality of signal amplitudes. Is provided. The measurement processing unit 80 includes a propagation time detection unit 83 that detects the propagation time of the ultrasonic wave that propagates through the fluid 15 in the pipe 10, and calculates the sound velocity of the ultrasonic wave that propagates through the fluid 15 from the propagation time of the ultrasonic wave. And a sound speed calculation unit 84 is provided. Furthermore, the measurement processing unit 80 includes a density calculation unit 85 that calculates the density of the fluid 15 in the pipe 10 based on acoustic impedance and sound speed, a temperature calculation unit 86 that calculates the temperature of the fluid 15 in the pipe 10 based on sound speed, A pressure calculation unit 87 that calculates pressure from the density and temperature of the fluid 15 is provided. The measurement processing unit 80 may be provided with an attenuation constant calculation unit instead of the impedance calculation unit 82.

  The data storage unit 90 is provided with a parameter storage unit 91. The parameter storage unit 91 stores known parameters that are appropriately read by the measurement processing unit 80. Known parameters include known density ρw, ρp, known sound speed Cw, Cp, known acoustic impedance Zw, Zp, known transmittance Qwp, Qpw, Qwv, known ultrasonic signal amplitude B, pipe 10 The outer diameter Do, inner diameter Di, known times Tw, Tp, Td, viscosity coefficient η, ultrasonic angular frequency ω, specific heat ratio κ, molar gas constant R, molar mass M, and the like are stored as necessary. The data storage unit 90 may include a correction coefficient storage unit 92 and a temperature correction data storage unit 93.

  Further, the data storage unit 90 is provided with a temperature conversion data storage unit 94 and a pressure conversion data storage unit 95. The temperature conversion data storage unit 94 stores temperature conversion data indicating the correspondence between the speed of sound of the ultrasonic waves in the fluid 15 and the temperature, and the pressure conversion data storage unit 95 corresponds to the density, temperature, and pressure of the fluid 15. Pressure conversion data indicating the relationship is stored. The temperature conversion data is not particularly limited as long as it indicates the correspondence between the ultrasonic sound speed and the temperature, and may be stored in a table format or a map format. Similarly, the pressure conversion data only needs to indicate the correspondence relationship between the density, temperature, and pressure of the fluid 15, and may be stored in a table format or a map format.

The temperature calculation unit 86 calculates the temperature of the fluid 15 by comparing the sound speed calculated by the sound speed calculation unit 84 with the correspondence relationship between the sound speed and the temperature of the temperature conversion data. In general, it is known that the sound velocity of ultrasonic waves in the fluid 15 has a large temperature change and a small pressure change. In particular, when the fluid 15 is a gas, the temperature of the fluid 15 can be calculated using an equation instead of referring to the temperature conversion data. The ultrasonic sound velocity Cf in the fluid 15 is expressed by the following equation (49), where the specific heat ratio is κ, the molar gas constant is R, the molar mass is M, and the temperature of the fluid 15 is tf. The temperature tf of the fluid 15 can be calculated using the following equation (50) obtained by modifying the equation (49).
(49)
Cf = √ (κ · R · tf / M)
(50)
tf = Cf ² · M / (κ · R)

In the pressure calculation unit 87, the density of the fluid 15 calculated by the density calculation unit 85 and the temperature of the fluid 15 calculated by the temperature calculation unit 86 are compared with the correspondence relationship between the density, temperature, and pressure of the pressure conversion data. The pressure of the fluid 15 is calculated. In particular, when the fluid 15 is a gas, the pressure of the fluid 15 can be calculated using an equation instead of referring to the pressure conversion data. The pressure P of the fluid 15 is expressed by the following equation (51), where V is the volume of the fluid 15, n is the amount of substance, R is the molar gas constant, and tf is the temperature of the fluid 15.
(51)
P ・ V = n ・ R ・ tf

The density ρf is represented by the following formula (52) when the volume is V and the mass is m, and the mass m is represented by the following formula (53) when the substance amount is n and the molar mass is M. From the equations (52) and (53), the density ρf is expressed by the following equation (54), and the volume V is expressed by the following equation (55) obtained by modifying the equation (54). Then, by substituting the equation (55) into the equation (51) and arranging the pressure P, the following equation (56) is obtained, and the pressure P can be calculated from the temperature tf and the density ρf of the fluid 15.
(52)
ρf = m / V
(53)
m = n · M
(54)
ρf = n · M / V
(55)
V = n · M / ρf
(56)
P = R · tf · ρf / M

  Also in the fourth embodiment, the acoustic impedance or the attenuation constant of the fluid 15 may be calculated from a plurality of signal amplitudes corrected by the correction coefficient. In this case, the measured value of the ultrasonic signal amplitude and the propagation time in the fluid are detected with a known fluid. The speed of sound of the ultrasonic wave in the fluid 15 is calculated from the propagation time in the fluid by Expression (14). Next, the temperature of the fluid 15 is calculated from the sound speed using the temperature conversion data or the equation (50). Further, the density of the fluid 15 is calculated from the pressure and temperature of the known fluid 15 using pressure conversion data or Expression (56), and the acoustic impedance is calculated from the sound speed and the known density using Expression (15). Then, the theoretical value of the signal amplitude of the ultrasonic wave is obtained by the equation (9), and the correction coefficient obtained from the theoretical value of the signal amplitude and the actually measured value is stored in the correction coefficient storage unit 92.

  Further, by using the ultrasonic wave Sb reflected from the inner surface of the pipe 10 in front of the fluid 15, it is possible to improve the calculation accuracy of the acoustic impedance or attenuation constant by eliminating the influence of known parameter errors of Qwp, Qpw, B, and Qwv. May be. Furthermore, the calculation accuracy of the acoustic impedance or attenuation constant may be improved by using the amplitudes of three or more ultrasonic waves having different numbers of reflections. Further, as in the third embodiment, a pair of ultrasonic probes are made to face each other so that the incident angle is inclined, and in addition to the pressure of the fluid 15, the density, volume flow rate, and mass flow rate are measured. May be.

  As described above, in the fourth embodiment, similarly to the first to third embodiments, the fluid 15 in the pipe 10 is a simple operation of installing the ultrasonic probe 20 on the outer surface of the pipe 10. Can be measured safely and accurately.

  In the first to fourth embodiments described above, the physical property values having temperature characteristics may be corrected by the measurement processing units 30, 50, and 80. In this case, in the first to third embodiments, a temperature measuring unit 99 for measuring the outer surface temperature is installed on the outer surface of the pipe, and a physical property value having temperature characteristics based on the temperature measured by the temperature measuring unit 99. Is corrected. In the fourth embodiment, since the temperature of the fluid 15 is calculated in the process of calculating the pressure, the physical property value having temperature characteristics is corrected based on the temperature calculated by the temperature calculation unit 86. Therefore, the temperature measuring unit 99 is not necessary in the fourth embodiment. The physical property values are parameters such as ρw, Cw, ρP, Cp, Td, Lw, Do, Di, and η used to calculate the density. The temperature characteristics of each parameter are stored as temperature correction data in the temperature correction data storage units 43, 63, and 93 of the data storage units 40, 60, and 90, and are appropriately referred to by the measurement processing units 30, 50, and 80. The temperature correction data only needs to indicate the correspondence relationship between the temperature and the correction value, and may be stored in a table format or a map format.

  In each of the above-described embodiments, the dual transducer vertical probe and the oblique probe are exemplified as the ultrasonic probe, but the present invention is not limited to this configuration. The ultrasonic probe may be composed of a vertical probe. In this case, a single ultrasonic probe 97 may be installed on the outer surface 11 of the pipe 10 as shown in the modification of FIG. 10, or on the outer surface 11 of the pipe 10 as shown in the modification of FIG. A pair of ultrasonic probes 98a and 98b may be installed so as to face each other. Even with these configurations, the density of the fluid 15 can be accurately measured using the signal amplitudes of a plurality of ultrasonic waves having different numbers of reflections. Therefore, the configuration of the ultrasonic probe is not particularly limited, and one of the ultrasonic probes may function as a transmission sensor, and either of the other may function as a reception sensor. A configuration having a single ultrasonic transducer functioning as a reception sensor may be used.

  In each of the above embodiments, the data storage unit is provided with the correction coefficient storage unit and the temperature correction data storage unit. However, the present invention is not limited to this configuration. The data storage unit may not include the correction coefficient storage unit and the temperature correction data storage unit. That is, the instrumentation device does not have to perform amplitude correction using the correction coefficient and temperature correction using the temperature correction data.

  Moreover, in each above-mentioned embodiment, the calculation process of each part is not limited to the structure implemented with the said numerical formula. For example, the propagation time detection unit may detect the propagation time by any method as long as the propagation time of the ultrasonic wave propagating through the fluid can be detected. The impedance calculation unit may calculate the acoustic impedance by any method as long as the acoustic impedance of the fluid can be calculated. The attenuation constant calculation unit may calculate the attenuation constant by any method as long as the attenuation constant can be calculated. The sound speed calculation unit may calculate the sound speed by any method as long as the sound speed of the ultrasonic wave propagating through the fluid can be calculated. The density calculation unit may calculate the density by any method as long as the density of the fluid can be calculated. The temperature calculation unit may calculate the temperature by any method as long as the temperature of the fluid can be calculated. The pressure calculation unit may calculate the pressure by any method as long as the pressure of the fluid can be calculated.

  Moreover, although each embodiment and the modified example were demonstrated, what combined the said embodiment and modified example entirely or partially as another embodiment may be sufficient.

  Further, the present embodiment is not limited to the above-described embodiments and modifications, and various changes, substitutions, and modifications may be made without departing from the spirit of the technical idea. Further, if the technical idea can be realized in another way by the advancement of technology or another technique derived therefrom, the method may be implemented using the method. Accordingly, the claims cover all embodiments that can be included within the scope of the technical idea.

  Further, in the present embodiment, the configuration in which the technology of the present disclosure is applied to the density measurement of the fluid in the pipe has been described, but the present disclosure can also be applied to other flow paths that require flow rate measurement.

The feature points in the above embodiment are organized below.
The measurement device described in the above embodiment is a measurement device that installs an ultrasonic probe on the outer surface of a pipe and measures the density of the fluid in the pipe, and includes a plurality of ultrasonic waves having different numbers of reflections in the pipe. An amplitude detection unit that detects a signal amplitude, a propagation time detection unit that detects a propagation time of an ultrasonic wave that propagates through a fluid in a pipe, an impedance calculation unit that calculates an acoustic impedance of the fluid from a plurality of signal amplitudes, and an ultrasonic wave A sound speed calculation unit that calculates the sound speed of the ultrasonic wave that propagates the fluid from the propagation time of the sound, and a density calculation unit that calculates the density of the fluid in the pipe from the acoustic impedance and the sound speed, and the impedance calculation unit includes a plurality of signal amplitudes. Is used to calculate the acoustic impedance corrected for the attenuation of the ultrasonic wave.

  Another measurement device described in the above embodiment is a measurement device that measures the density of fluid in a pipe by installing an ultrasonic probe on the outer surface of the pipe, and includes a plurality of super An amplitude detector for detecting the signal amplitude of the sound wave, a propagation time detector for detecting the propagation time of the ultrasonic wave propagating through the fluid in the pipe, and an attenuation constant calculator for calculating the attenuation constant of the fluid from a plurality of signal amplitudes And a sound speed calculation unit that calculates the sound speed of the ultrasonic wave that propagates the fluid from the propagation time of the ultrasonic wave, and a density calculation unit that calculates the density of the fluid in the pipe from the attenuation constant and the sound speed.

  According to these configurations, the ultrasonic wave is reflected in the pipe to create a difference in the propagation distance of the plurality of ultrasonic waves, and the density of the fluid in consideration of attenuation is determined from the signal amplitudes of the plurality of ultrasonic waves having different propagation distances. Calculated. Therefore, the density of the fluid in the pipe can be measured safely and accurately by a simple operation of installing the ultrasonic probe on the outer surface of the pipe. Moreover, since the sound speed of the ultrasonic wave propagating through the fluid is calculated, an error due to a change in sound speed can be suppressed.

  In the measurement apparatus described in the above embodiment, the impedance calculation unit calculates the acoustic impedance from the signal amplitudes of three or more ultrasonic waves having different numbers of reflections in the pipe, and the three or more ultrasonic waves are reflected. The acoustic impedance is calculated so that the total error is minimized. According to this configuration, the calculation accuracy of the acoustic impedance can be improved by using the signal amplitude of three or more ultrasonic waves.

  In the measurement device described in the above embodiment, the impedance calculation unit includes a correction coefficient storage unit that stores a correction coefficient obtained from a theoretical value and a measured value of an ultrasonic signal amplitude that propagates a fluid having a known density. The acoustic impedance of the fluid is calculated from a plurality of signal amplitudes corrected with the correction coefficient. According to this configuration, it is possible to suppress the signal amplitude error due to the shape of the pipe and the like and improve the calculation accuracy of the acoustic impedance.

  In another measurement apparatus described in the above embodiment, the attenuation constant calculation unit calculates an attenuation constant from the signal amplitudes of three or more ultrasonic waves having different numbers of reflections in the pipe, and the three or more An attenuation constant is calculated such that the total error when the sound wave is reflected is minimized. According to this configuration, it is possible to improve the calculation accuracy of the attenuation constant by using the signal amplitude of three or more ultrasonic waves.

  In the other measurement device described in the above embodiment, a correction coefficient storage unit that stores a correction coefficient obtained from a theoretical value and a measured value of an ultrasonic signal amplitude that propagates a fluid having a known density is provided, and an attenuation constant is calculated. The unit calculates a fluid attenuation constant from a plurality of signal amplitudes corrected by the correction coefficient. According to this configuration, it is possible to improve the calculation accuracy of the attenuation constant by suppressing an error in the signal amplitude caused by the shape of the piping.

  In the measurement device described in the above embodiment and other measurement devices, a temperature calculation unit that calculates the temperature of the fluid in the pipe from the sound velocity, and a pressure calculation unit that calculates the pressure from the density and temperature of the fluid in the pipe. I have. According to this configuration, the density and pressure of the fluid in the pipe can be measured safely and accurately by a simple operation of installing the ultrasonic probe on the outer surface of the pipe.

  In the measurement apparatus described in the above embodiment and other measurement apparatuses, the physical property value having temperature characteristics is corrected from the temperature of the fluid in the pipe calculated by the temperature calculation unit. According to this configuration, it is possible to improve the calculation accuracy of the density of the fluid by correcting the error due to the temperature change of the physical property values of the pipe and the ultrasonic probe.

  In the measurement apparatus described in the above embodiment and other measurement apparatuses, a physical property value having a temperature characteristic from the outer surface temperature measured by the temperature measurement unit is provided with a temperature measurement unit that is installed on the outer surface of the pipe and measures the outer surface temperature. Correct. According to this configuration, it is possible to improve the calculation accuracy of the density of the fluid by correcting the error due to the temperature change of the physical property values of the pipe and the ultrasonic probe.

  In the measurement apparatus and other measurement apparatuses described in the above embodiments, the propagation time detection unit detects the propagation time of the ultrasonic wave that propagates the fluid in the pipe from the total propagation time of the plurality of ultrasonic waves. According to this configuration, it is possible to improve the calculation accuracy of the propagation time of the ultrasonic wave propagating through the fluid while suppressing an error that occurs when the ultrasonic wave crosses other than the fluid.

  In the measurement apparatus and other measurement apparatuses described in the above embodiments, the ultrasonic probe has a single ultrasonic transducer that functions as a transmission sensor and a reception sensor. According to this configuration, the calculation accuracy of the fluid density can be improved with a simple configuration.

  In the measurement apparatus and other measurement apparatuses described in the above embodiments, the ultrasonic probe has a pair of ultrasonic transducers, one of which functions as a transmission sensor and the other of which functions as a reception sensor. According to this configuration, since transmission and reception of ultrasonic waves are performed by separate ultrasonic transducers, reverberation noise when transmitting ultrasonic waves does not overlap with the received signal, and the calculation accuracy of fluid density is improved. Can be improved.

1: Measuring device 10: Piping 11: Outer surface 12 of piping: Inner surface 15 of piping: Fluid 20: Ultrasonic probe 31: Amplitude detecting unit 32: Impedance calculating unit 33: Propagation time detecting unit 34: Sound velocity calculating unit 35: Density calculation Unit 42: Correction coefficient storage unit 51: Amplitude detection unit 52: Attenuation constant calculation unit 53: Propagation time detection unit 54: Sound speed calculation unit 55: Density calculation unit 62: Correction coefficient storage unit 70a: Ultrasonic probe 70b: Ultrasonic probe 81: Amplitude detection unit 82: Impedance calculation unit 83: Propagation time detection unit 84: Sound speed calculation unit 85: Density calculation unit 86: Temperature calculation unit 87: Pressure calculation unit 92: Correction coefficient storage unit 97: Ultrasonic probe 98a: Ultra Acoustic probe 98b: Ultrasonic probe 99: Temperature measurement unit

Claims (12)

An ultrasonic probe is installed on the outer surface of a pipe to measure the density of fluid in the pipe,
An amplitude detector that detects the signal amplitude of a plurality of ultrasonic waves having different numbers of reflections in the pipe;
A propagation time detector for detecting the propagation time of the ultrasonic wave propagating through the fluid in the pipe;
An impedance calculator that calculates the acoustic impedance of the fluid from a plurality of signal amplitudes;
A sound velocity calculation unit for calculating the sound velocity of the ultrasonic wave propagating through the fluid from the propagation time of the ultrasonic wave,
A density calculator that calculates the density of the fluid in the pipe from the acoustic impedance and the speed of sound;
The impedance calculation unit calculates an acoustic impedance obtained by correcting attenuation of ultrasonic waves using a plurality of signal amplitudes. The impedance calculator calculates an acoustic impedance from signal amplitudes of three or more ultrasonic waves having different numbers of reflections in the pipe,
The measurement apparatus according to claim 1, wherein the acoustic impedance is calculated such that a total error is minimized when three or more ultrasonic waves are reflected. A correction coefficient storage unit that stores a correction coefficient obtained from a theoretical value and an actual measurement value of the signal amplitude of an ultrasonic wave propagating through a fluid having a known density;
The measurement apparatus according to claim 1, wherein the impedance calculation unit calculates an acoustic impedance of the fluid from a plurality of signal amplitudes corrected with a correction coefficient. An ultrasonic probe is installed on the outer surface of a pipe to measure the density of fluid in the pipe,
An amplitude detector that detects the signal amplitude of a plurality of ultrasonic waves having different numbers of reflections in the pipe;
A propagation time detector for detecting the propagation time of the ultrasonic wave propagating through the fluid in the pipe;
An attenuation constant calculation unit for calculating an attenuation constant of the fluid from a plurality of signal amplitudes;
A sound velocity calculation unit for calculating the sound velocity of the ultrasonic wave propagating through the fluid from the propagation time of the ultrasonic wave,
A measurement apparatus comprising: a density calculation unit that calculates a density of fluid in the pipe from an attenuation constant and sound velocity. The attenuation constant calculator calculates an attenuation constant from the signal amplitudes of three or more ultrasonic waves having different numbers of reflections in the pipe,
The measurement apparatus according to claim 4, wherein an attenuation constant is calculated such that the sum of errors when three or more ultrasonic waves are reflected is minimized. A correction coefficient storage unit that stores a correction coefficient obtained from a theoretical value and an actual measurement value of the signal amplitude of an ultrasonic wave propagating through a fluid having a known density;
The measurement apparatus according to claim 4, wherein the attenuation constant calculation unit calculates a fluid attenuation constant from a plurality of signal amplitudes corrected by a correction coefficient. A temperature calculation unit for calculating the temperature of the fluid in the pipe from the speed of sound;
The measurement apparatus according to claim 1, further comprising a pressure calculation unit that calculates pressure from the density and temperature of the fluid in the pipe.   The measuring apparatus according to claim 7, wherein a physical property value having a temperature characteristic is corrected from the temperature of the fluid in the pipe calculated by the temperature calculation unit. A temperature measurement unit is installed on the outer surface of the pipe to measure the outer surface temperature.
The measuring apparatus according to claim 1, wherein a physical property value having a temperature characteristic is corrected from an outer surface temperature measured by the temperature measuring unit.   The said propagation time detection part detects the propagation time of the ultrasonic wave which propagates the fluid in the said piping from the total propagation time of several ultrasonic waves, The Claim 1 characterized by the above-mentioned. Measuring device.   The measurement apparatus according to claim 1, wherein the ultrasonic probe has a single ultrasonic transducer that functions as a transmission sensor and a reception sensor.   The ultrasonic probe includes a pair of ultrasonic transducers, one of which functions as a transmission sensor and the other of which functions as a reception sensor. Measuring device.

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