Piezoelectric device and ultrasonic wave flow rate meter

Abstract

To provide a piezoelectric device in which the load of attaching an attachment plate to a packing can be reduced and attenuation of vibrations from a piezoelectric element in the packing is suppressed at the same time.SOLUTION: A piezoelectric device 40 includes: a metal plate 41 with an upper surface 41a to be attached to a piezoelectric element 42 and a lower surface 41b on the opposite side to the upper surface 41a; and a packing 45 with a first supporting part 55b supporting the upper surface 41a and a second supporting part 55d supporting the lower surface 41b. A first supporting region for the first supporting part 55b to support an upper surface 41 and a second supporting region for the second supporting part 55d to support the lower surface 41b are not overlapped with each other in the thickness direction of the metal plate 41.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present disclosure relates to a piezoelectric device and an ultrasonic flowmeter.

Background Art

[0002] Patent Document 1 discloses a piezoelectric device having a piezoelectric element. The piezoelectric device disclosed in Patent Document 1 generates vibrations by expanding and contracting the piezoelectric element. Further, in the piezoelectric device disclosed in Patent Document 1, a mounting plate to which the piezoelectric element is attached is fixed to a housing via a packing. Thus, the piezoelectric device disclosed in Patent Document 1 is configured to achieve both fixation to the housing and suppression of attenuation of vibrations generated by the piezoelectric element by providing the packing.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the piezoelectric device disclosed in Patent Document 1, the entire outer peripheral portion of the mounting plate is uniformly inserted into the inner peripheral groove of the annular packing. Thus, if the insertion of the mounting plate into the packing is made tight, it becomes difficult for the mounting plate to bend. Therefore, in the piezoelectric device disclosed in Patent Document 1, when vibrations generated by the piezoelectric element are transmitted to the mounting plate, there is a risk of attenuating the vibrations.

[0005] Further, when inserting the mounting plate into the packing, after spreading the packing outward, the entire outer peripheral portion of the mounting plate is inserted into the inner peripheral groove of the packing. Therefore, a large mounting load is applied to the mounting plate. As a result, the mounting plate may be deformed or damaged.

[0006] The present disclosure has been made to solve the above problems, and an object thereof is to provide a piezoelectric device capable of reducing the mounting load of a mounting plate on a packing while suppressing the attenuation of vibration from a piezoelectric element in the packing.

Means for Solving the Problems

[0007] The piezoelectric device according to the present disclosure includes a mounting plate having a first surface to which a piezoelectric element is attached and a second surface located on the opposite side of the first surface, a first support portion that supports the first surface, and a second support portion that supports the second surface. The packing has a first support region where the first support portion supports the first surface and a second support region where the second support portion supports the second surface, and the first support region and the second support region do not overlap in the thickness direction of the mounting plate.

Effects of the Invention

[0008] According to the present disclosure, it is possible to reduce the mounting load of the mounting plate on the packing while suppressing the attenuation of vibration from the piezoelectric element in the packing.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings.

[0011] Embodiment 1. The piezoelectric devices 40a and 40b according to Embodiment 1 will be described with reference to FIGS. 1 to 8.

[0012] First, the configuration of the ultrasonic flowmeter 100 according to Embodiment 1 will be described with reference to FIGS. 1 to 3. FIG. 1 is an external perspective view of the ultrasonic flowmeter 100 to which the piezoelectric devices 40a and 40b according to Embodiment 1 are applied. FIG. 2 is a diagram showing a state where the piezoelectric device 40b according to Embodiment 1 is attached to the case member 20b. FIG. 3 is a plan view of the case members 20a and 20b. In FIG. 1, the upstream wiring 44 and the downstream cap 30b are removed.

[0013] The ultrasonic flowmeter 100 shown in FIG. 1 measures the flow rate or flow velocity of a fluid using ultrasonic waves. The fluid to be measured is a gas such as air or gas, or a liquid such as water. The ultrasonic flowmeter 100 is mounted on, for example, a gas meter or a water meter. The arrow shown in FIG. 1 indicates the flow direction of the fluid passing through the inside of the ultrasonic flowmeter 100.

[0014] As shown in FIG. 1, the ultrasonic flowmeter 100 includes a measurement pipe 10, a pair of case members 20a and 20b, a pair of caps 30a and 30b, and a pair of piezoelectric devices 40a and 40b. The measurement pipe 10 and the case members 20a and 20b constitute the housing of the ultrasonic flowmeter 100.

[0015] The measurement pipe 10 has a cylindrical shape. The measurement pipe 10 has a measurement flow path 11, an inlet 12, and an outlet 13. The measurement pipe 10 is formed of, for example, a resin material. The measurement flow path 11, the inlet 12, and the outlet 13 are integrally formed.

[0016] The measurement flow path 11 is constituted by the inner peripheral surface of the measurement pipe 10 and is formed along the axial direction of the measurement pipe 10. The fluid flows along the axial direction of the measurement flow path 11. The upstream opening end of the measurement flow path 11 constitutes the inlet 12 through which the fluid flows in. On the other hand, the downstream opening end of the measurement flow path 11 constitutes the outlet 13 through which the fluid flows out. That is, the measurement pipe 10 passes the fluid supplied into the measurement flow path 11 from the inlet 12 through the measurement flow path 11 and then discharges it from the outlet 13. Although details will be described later, the ultrasonic flowmeter 100 measures the flow rate or flow velocity of the fluid when the fluid passes through the measurement flow path 11.

[0017] As shown in FIGS. 1 to 3, the case members 20a and 20b are members for attaching the piezoelectric devices 40a and 40b to the measurement pipe 10. The case members 20a and 20b are provided along the axial direction (fluid flow direction) of the measurement flow path 11 on the upper surface that is the same surface of the measurement pipe 10. One case member 20a is arranged on the upstream side of the measurement flow path 11. The other case member 20b is arranged on the downstream side of the measurement flow path 11.

[0018] The case members 20a and 20b are formed of, for example, a resin material. The case members 20a and 20b may be integrally formed with the measurement pipe 10 or may be separate from the measurement pipe 10.

[0019] The case members 20a and 20b have an annular bottom plate 21 and a vertical wall 22 provided at the outer peripheral portion of the bottom plate 21. Thus, the case members 20a and 20b form a box shape with an open upper side. Therefore, the case members 20a and 20b can accommodate and attach the piezoelectric devices 40a and 40b inside them. The case members 20a and 20b are arranged such that their central axes are inclined with respect to the axial direction of the measurement flow path 11. Note that the vertical wall 22 has a through hole 22a for wiring in a notch shape.

[0020] As shown in FIGS. 1 and 2, the caps 30a and 30b can be respectively attached to the vertical walls 22 of the case members 20a and 20b as covers for protecting the piezoelectric devices 40a and 40b. The caps 30a and 30b are formed of, for example, a resin material.

[0021] As shown in FIGS. 1 to 3, the piezoelectric devices 40a and 40b are, for example, ultrasonic sensors or ultrasonic vibration elements that generate ultrasonic waves. The piezoelectric devices 40a and 40b can transmit and receive ultrasonic waves to and from each other. One piezoelectric device 40a functions as an oscillator and a receiver of ultrasonic waves. The other piezoelectric device 40b functions as a receiver and a transmitter of ultrasonic waves.

[0022] The piezoelectric devices 40a and 40b are provided along the axial direction of the measurement flow path 11. The piezoelectric devices 40a and 40b are attached inside the case members 20a and 20b. That is, one piezoelectric device 40a arranged on the upstream side of the measurement flow path 11 is attached inside the case member 20a. The other piezoelectric device 40b arranged on the downstream side of the measurement flow path 11 is attached inside the case member 20b.

[0023] In this way, the piezoelectric devices 40a and 40b are attached inside the case members 20a and 20b, so that their central axes are inclined with respect to the axial direction of the measurement flow path 11 and are arranged to face the measurement flow path 11. Specifically, the piezoelectric device 40a is arranged obliquely such that its transmission / reception surface faces the downstream side. Also, the piezoelectric device 40b is arranged obliquely such that its transmission / reception surface faces the upstream side. Furthermore, when the piezoelectric devices 40a and 40b are attached inside the case members 20a and 20b, their peripheries will be surrounded by the vertical walls 22, but they do not protrude above the upper ends of the vertical walls 22.

[0024] Here, the ultrasonic flowmeter 100 propagates the ultrasonic waves transmitted from the piezoelectric devices 40a and 40b into the fluid flowing through the measurement flow path 11. Then, the ultrasonic flowmeter 100 measures the flow rate or flow velocity of the fluid flowing through the measurement flow path 11 based on the propagation time difference of the ultrasonic waves between the piezoelectric devices 40a and 40b.

[0025] Specifically, the ultrasonic wave transmitted from the piezoelectric device 40a obliquely propagates from the upstream side to the downstream side in the fluid flowing through the measurement flow path 11, reflects off the bottom surface of the measurement flow path 11, and is then received by the piezoelectric device 40b. On the other hand, the ultrasonic wave transmitted from the piezoelectric device 40b obliquely propagates from the downstream side to the upstream side in the fluid flowing through the measurement flow path 11, reflects off the bottom surface of the measurement flow path 11, and is then received by the piezoelectric device 40a. That is, the propagation paths of both ultrasonic waves are respectively formed in a V shape. Then, the ultrasonic flowmeter 100 obtains the propagation times of the two-direction ultrasonic waves by the piezoelectric devices 40a and 40b transmitting and receiving the ultrasonic waves, and then measures the flow rate or flow velocity of the fluid flowing through the measurement flow path 11 based on the propagation time difference between them.

[0026] Next, the configurations of the piezoelectric devices 40a and 40b will be described with reference to FIGS. 4 to 8. FIG. 4 is an external perspective view of the piezoelectric device 40 according to Embodiment 1. FIG. 5 is a cross-sectional view taken along the line V-V in FIG. 4A. FIG. 6 is an external perspective view of the packing 45 as seen from the front side. FIG. 7 is an external perspective view of the packing 45 as seen from the back side. FIG. 8 is a diagram showing a state in which the packing 45 is elastically deformed to attach the metal plate 41. Note that since the piezoelectric devices 40a and 40b have the same configuration and the same functions, in the following description, the piezoelectric devices 40a and 40b are described as the piezoelectric device 40.

[0027] As shown in FIGS. 4 and 5, the piezoelectric device 40 is generally circular in shape. The piezoelectric device 40 includes a metal plate 41, a piezoelectric element 42, an acoustic matching layer 43, wiring 44, and a packing 45.

[0028] The metal plate 41 is flat and circular in shape. This metal plate 41 serves as a diaphragm. The metal plate 41 has an upper surface 41a and a lower surface 41b. The upper surface 41a and the lower surface 41b are arranged on opposite sides in the thickness direction of the metal plate 41. The metal plate 41 is formed of a metal material such as stainless steel, aluminum, or copper, for example.

[0029] When the piezoelectric device 40 is attached to the case members 20a and 20b, the upper surface 41a is disposed on the opening side of the case members 20a and 20b. This upper surface 41a is a surface for attaching the piezoelectric element 42. When the piezoelectric device 40 is attached to the case members 20a and 20b, the lower surface 41b faces the bottom plate 21 of the case members 20a and 20b. This lower surface 41b is a surface for attaching the acoustic matching layer 43.

[0030] Note that the metal plate 41 constitutes a mounting plate. The upper surface 41a constitutes a first surface. The lower surface 41b constitutes a second surface.

[0031] The piezoelectric element 42 can mutually convert an ultrasonic signal, which is an electrical signal, and ultrasonic waves. Also, the piezoelectric element 42 can transmit and receive ultrasonic waves. Specifically, when a voltage is applied to the piezoelectric element 42, it expands and contracts (vibrates) in the thickness direction of the metal plate 41 to generate ultrasonic waves. Further, when ultrasonic waves (vibrations) are applied from the outside to the piezoelectric element 42, it generates a voltage. The piezoelectric element 42 is attached to the upper surface 41a of the metal plate 41 via, for example, an adhesive.

[0032] The acoustic matching layer 43 improves the efficiency of transmitting and receiving ultrasonic waves in the piezoelectric element 42. This acoustic matching layer 43 matches the acoustic impedance of the piezoelectric element 42 and the acoustic impedance of the fluid to suppress reflection of ultrasonic waves therebetween. For this reason, the acoustic matching layer 43 is attached to the lower surface 41b facing the measurement flow path 11.

[0033] Therefore, the ultrasonic waves generated by the piezoelectric element 42 are emitted from the acoustic matching layer 43 to the measurement flow path 11 through the metal plate 41. On the other hand, the ultrasonic waves incident on the acoustic matching layer 43 from the measurement flow path 11 are propagated to the piezoelectric element 42 through the metal plate 41.

[0034] The two wirings 44 are respectively connected to the upper surface 41a of the metal plate 41 and the surface of the piezoelectric element 42. These wirings 44 are drawn out from the piezoelectric device 40 attached inside the case members 20a and 20b to a control device (not shown) provided in the ultrasonic flowmeter 100 through the passage port 22a of the vertical wall 22 thereof.

[0035] Specifically, one end of one wiring 44 is connected to the upper surface 41a of the metal plate 41, and the other end of the wiring 44 is connected to a control device (not shown) provided in the ultrasonic flowmeter 100. Also, one end of the other wiring 44 is connected to the surface of the piezoelectric element 42, and the other end of the wiring 44 is connected to the above control device.

[0036] The packing 45 is designed to achieve both the fixation to the case members 20a and 20b of the piezoelectric device 40 and the suppression of the attenuation of the ultrasonic vibration generated by the piezoelectric element 42. In this way, the ultrasonic flowmeter 100 can suppress the vibration transmitted from the piezoelectric device 40 to the measurement pipe 10 through the case members 20a and 20b by fixing the piezoelectric device 40 to the case members 20a and 20b via the packing 45. Therefore, the ultrasonic flowmeter 100 can suppress the decrease in measurement accuracy.

[0037] As shown in FIGS. 4 to 7, the packing 45 has a main body 51, an outer peripheral wall portion 52, a notch portion 53, a wiring holding portion 54, and an insertion groove 55. The packing 45 is formed of, for example, an elastic resin material. The main body 51, the outer peripheral wall portion 52, the notch portion 53, the wiring holding portion 54, and the insertion groove 55 are integrally formed.

[0038] The main body 51 is annular. The outer peripheral wall portion 52 is provided along the circumferential direction at the outer peripheral portion of the upper surface of the main body 51. The notch portions 53 are respectively formed at a plurality of positions on the outer peripheral wall portion 52 so as to notch the outer peripheral wall portion 52. FIGS. 6 and 7 show an example in which three notch portions 53 are formed for one outer peripheral wall portion 52. One or more notch portions 53 may be formed. Of the three notch portions 53, two notch portions 53 are formed at positions facing each other on the outer peripheral wall portion 52.

[0039] The wiring holding portion 54 holds the two wirings 44. A groove for holding the wiring 44 is formed in the wiring holding portion 54. The wiring holding portion 54 is formed so as to project radially outward from one notch portion 53 toward the main body 51. Further, the wiring holding portion 54 is formed so as to be continuous with the outer peripheral wall portions 52 on both sides in the radial direction.

[0040] The insertion groove 55 is a groove into which the outer peripheral portion of the metal plate 41 is inserted. A plurality of insertion grooves 55 are provided on the radially inner side of the outer peripheral wall portion 52. The insertion grooves 55 are arranged at a predetermined interval in the radial direction. FIGS. 6 and 7 show an example in which four insertion grooves 55 are formed.

[0041] Note that the insertion groove 55 according to the present embodiment is formed by using the upper surface of the main body 51 and the inner peripheral surface of the outer peripheral wall portion 52, but it may be formed without using the upper surface of the main body 51 and the inner peripheral surface of the outer peripheral wall portion 52. Hereinafter, the configuration of the insertion groove 55 will be described.

[0042] As shown in FIG. 5, the insertion groove 55 has a first opposing surface 55a, a first support portion 55b, a second opposing surface 55c, a second support portion 55d, and a bottom surface 55e. At this time, the first opposing surface 55a and the second opposing surface 55c face each other. The bottom surface 55e connects the first opposing surface 55a and the second opposing surface 55c.

[0043] The first opposing surface 55a is a surface that faces the upper surface 41a of the metal plate 41 inserted into the insertion groove 55.

[0044] The first support portion 55b is formed so as to protrude from the first opposing surface 55a toward the second opposing surface 55c. Further, the first support portion 55b is formed in an arc shape along the outer peripheral portion of the metal plate 41. Therefore, the support region of the first support portion 55b with respect to the upper surface 41a is formed in an arc shape. The first support portion 55b supports the upper surface 41a by contacting the upper surface 41a of the metal plate 41 inserted into the insertion groove 55.

[0045] In this way, since the first support portion 55b supports the upper surface 41a of the metal plate 41, the first opposing surface 55a does not contact the upper surface 41a of the metal plate 41. Specifically, the region of the first opposing surface 55a other than the portion where the first support portion 55b is provided does not contact the upper surface 41a of the metal plate 41. Therefore, a gap is formed between the first opposing surface 55a and the upper surface 41a.

[0046] The second opposing surface 55c is a surface that faces the lower surface 41b of the metal plate 41 inserted into the insertion groove 55.

[0047] The second opposing surface 55c constitutes the upper surface of the main body 51. The second support portion 55d is formed so as to protrude from the second opposing surface 55c toward the first opposing surface 55a. Further, the second support portion 55d is formed in an arc shape along the outer peripheral portion of the metal plate 41. For this reason, the support region of the upper surface 41a of the second support portion 55d is formed in an arc shape. The second support portion 55d supports the lower surface 41b by contacting the lower surface 41b of the metal plate 41 inserted into the insertion groove 55.

[0048] In this way, since the second support portion 55d supports the lower surface 41b of the metal plate 41, the second opposing surface 55c does not contact the lower surface 41b of the metal plate 41. Specifically, the region of the second opposing surface 55c other than the portion where the second support portion 55d is provided does not contact the lower surface 41b of the metal plate 41. For this reason, a gap is formed between the second opposing surface 55c and the lower surface 41b.

[0049] The first support portion 55b and the second support portion 55d are arranged so as not to overlap in the thickness direction of the metal plate 41 and the thickness direction of the packing 45. Specifically, the first support portion 55b and the second support portion 55d in one insertion groove 55 are displaced in the radial direction of the metal plate 41 and the radial direction of the packing 45. In the present embodiment, the first support portion 55b is arranged outside the metal plate 41 and outside the packing 45 in the radial direction with respect to the second support portion 55d, but the first support portion 55b may be arranged inside the metal plate 41 and inside the packing 45 in the radial direction with respect to the second support portion 55d.

[0050] That is, the first support region where the first support portion 55b supports the upper surface 41a of the metal plate 41 and the second support region where the second support portion 55d supports the lower surface 41b of the metal plate 41 do not overlap in the thickness direction of the metal plate 41 and the thickness direction of the packing 45. Specifically, the first support region and the second support region in one insertion groove 55 are displaced in the radial direction of the metal plate 41 and the radial direction of the packing 45. More specifically, the first support region is disposed outside the metal plate 41 and outside the packing 45 in the radial direction, compared with the second support region.

[0051] The bottom surface 55e does not contact the outer peripheral end surface of the metal plate 41 inserted into the insertion groove 55. Therefore, a gap is formed between the bottom surface 55e and the outer peripheral end surface of the metal plate 41. The bottom surface 55e constitutes the outer peripheral wall portion 52.

[0052] Therefore, when the metal plate 41 is inserted into the insertion groove 55, the outer peripheral portion of the metal plate 41 has three-directional gaps with the insertion groove 55 and is supported only by the first support portion 55b and the second support portion 55d. At this time, in each insertion groove 55, the first support region and the second support region are arranged so as not to overlap in the thickness direction of the metal plate 41 and the thickness direction of the packing 45. For this reason, the packing 45 can disperse and arrange the first support region and the second support region with respect to the upper surface 41a and the lower surface 41b of the metal plate 41. As a result, although the packing 45 supports the metal plate 41 only by the first support portion 55b and the second support portion 55d, it can secure the necessary support rigidity for the metal plate 41. Therefore, the packing 45 can suppress the attenuation of the vibration transmitted from the piezoelectric element 42 to the metal plate 41.

[0053] Also, as shown in FIG. 8, when inserting the metal plate 41 into the packing 45, first, the outer peripheral wall portion 52 of the packing 45 is pushed and expanded outward in the radial direction. For this reason, each insertion groove 55 of the packing 45 is elastically deformed and the groove width is widened. Next, the outer peripheral portion of the metal plate 41 is inserted into each insertion groove 55 with the widened groove width. Then, by removing the force acting on the outer peripheral wall portion 52 of the packing 45 in the radially outward direction, each insertion groove 55 returns to its original shape. For this reason, the outer peripheral portion of the metal plate 41 is inserted into each insertion groove 55. Note that the insertion of the metal plate 41 into each insertion groove 55 may be performed one by one, or may be performed all at once. In order to make it easier to bend the packing 45 and push and expand the outer peripheral wall portion 52 outward in the radial direction, the notch portions 53 are preferably formed at positions facing each other on the outer peripheral wall portion 52. In particular, the notch portions 53 are preferably formed so as to face each other at positions different from the positions where the wiring holding portions 54 are formed.

[0054] At this time, when the elastically deformed insertion groove 55 returns, the first support portion 55b and the second support portion 55d come into contact with the upper surface 41a and the lower surface 41b of the metal plate 41 in a dispersed manner. For this reason, small mounting loads are scattered on the metal plate 41, and no large mounting load is applied.

[0055] Also, since the packing 45 has the notch portions 53, the outer peripheral wall portion 52 can be formed in a divided manner. For this reason, the user can push and expand the outer peripheral wall portion 52 with a smaller force as compared with the non-divided annular outer peripheral wall portion. As a result, the piezoelectric device 40 can improve the workability of assembling the metal plate 41.

[0056] As described above, the piezoelectric device 40 according to Embodiment 1 can reduce the mounting load of the metal plate 41 on the packing 45 while suppressing the attenuation of vibration from the piezoelectric element 42 in the packing 45.

[0057] Note that within the scope of the present disclosure, it is possible to modify any component of the embodiment or omit any component of the embodiment.

Description of Reference Numerals

[0058] 10 Measuring tube, 11 Measuring flow path, 12 Inlet, 13 Outlet, 20a, 20b Case members, 21 Bottom plate, 22 Vertical wall, 22a Passing port, 30a, 30b Caps, 40, 40a, 40b Piezoelectric devices, 41 Metal plate, 41a Upper surface, 41b Lower surface, 42 Piezoelectric element, 43 Acoustic matching layer, 44 Wiring, 45 Packing, 51 Main body, 52 Outer peripheral wall portion, 53 Notch portion, 54 Wiring holding portion, 55 Insertion groove, 55a First opposing surface, 55b First support portion, 55c Second opposing surface, 55d Second support portion, 55e Bottom surface, 100 Ultrasonic flowmeter.

Claims

1. A mounting plate having a first surface to which a piezoelectric element is attached and a second surface located on the opposite side of the first surface, and a packing having a first support portion that supports the first surface and a second support portion that supports the second surface, wherein a first support region where the first support portion supports the first surface and a second support region where the second support portion supports the second surface do not overlap in the thickness direction of the mounting plate A piezoelectric device characterized by this.

2. The first support region and the second support region are displaced in the radial direction of the mounting plate The piezoelectric device according to claim 1, characterized by this.

3. The first support region is formed in an arc shape The piezoelectric device according to claim 1, characterized by this.

4. The second support region is formed in an arc shape The piezoelectric device according to claim 1, characterized by this.

5. The packing faces the first surface and has a first facing surface provided with the first support portion, The first facing surface does not contact the first surface The piezoelectric device according to claim 1, characterized by this.

6. The packing faces the second surface and has a second facing surface provided with the second support portion, The second facing surface does not contact the second surface The piezoelectric device according to claim 1, characterized by this.

7. The packing has an insertion groove into which the outer peripheral portion of the mounting plate is inserted, The bottom surface of the insertion groove does not contact the mounting plate The piezoelectric device according to claim 1, characterized by this.

8. The packing has an outer peripheral wall portion provided so as to surround the mounting plate, and a notch portion formed so as to notch the outer peripheral wall portion The piezoelectric device according to claim 1, characterized by this.

9. The notch portion is formed at positions facing each other in the outer peripheral wall portion The piezoelectric device according to claim 8, characterized by this.

10. Providing a pair of the piezoelectric devices according to any one of claims 1 to 9 An ultrasonic flowmeter characterized by this.

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