Piezoelectric sensor and liquid level measuring system

Abstract

A piezoelectric sensor includes: a first polarized piezoelectric member (12) having a first polarization direction; a second polarization piezoelectric member (14) having a second polarization direction opposite to the first polarization direction; a first electrical conductor (16); a second electrical conductor (18); and a central through hole (11) centrally positioned in the piezoelectric sensor (10) along a central axis and configured to receive a magnetostrictive wire (20) extending along the central axis. The structure of the piezoelectric sensor is simplified, so that the cost is reduced under the condition that the detection precision is not damaged. A liquid level measurement system comprising the piezoelectric sensor (10) is also provided.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to a liquid level measurement system using a magnetostrictive wire, and more particularly to a piezoelectric sensor configured to detect torsional waves in the magnetostrictive wire. Background Art

[0002] Many systems for measuring the liquid level in a storage tank, as well as systems for measuring linear displacement such as in a machine tool, utilize a movable permanent magnet float or position indicator around a linearly oriented magnetostrictive wire. Generally, the position of the permanent magnet represents the position of the monitored liquid volume or the position of the monitored object of interest.

[0003] Using such a magnetostrictive wire to detect the position of a permanent magnet is well known in the art. For example, U.S. Patent No. 5,473,245 discloses a piezoelectric sensor formed by a piezoelectric ring. The piezoelectric ring includes 8 segments that are circumferentially polarized and rejoined to a circle by an adhesive. U.S. Patent No. 10,048,291 B2 also discloses a piezoelectric sensor that includes a plurality of separate polarized piezoelectric elements that are also polarized in the circumferential direction. However, manufacturing and assembling these polarized piezoelectric elements are costly and time-consuming. There is a need to improve the piezoelectric sensor to simplify its structure. Summary of the Invention

[0004] Exemplary embodiments of the present disclosure provide a piezoelectric sensor and a liquid level measurement system with an improved structure.

[0005] In a first aspect of the present invention, a piezoelectric sensor is provided. The piezoelectric sensor includes: a first polarized piezoelectric member including a first circumferential end and a second circumferential end, with the first polarization direction of the first polarized piezoelectric member along the central axis; a second polarized piezoelectric member arranged adjacent to the first polarized piezoelectric member along the circumferential direction, the second polarized piezoelectric member including a first circumferential end adjacent to the first circumferential end of the first polarized piezoelectric member in the circumferential direction and a second circumferential end adjacent to the second circumferential end of the first polarized piezoelectric member in the circumferential direction, and the second polarization direction of the second polarized piezoelectric member being opposite to the first polarization direction; a first electrical conductor disposed between the first circumferential end of the first polarized piezoelectric member and the first circumferential end of the second polarized piezoelectric member and configured to connect to the first circumferential end of the first polarized piezoelectric member and the first circumferential end of the second polarized piezoelectric member; a second electrical conductor disposed between the second circumferential end of the first polarized piezoelectric member and the second circumferential end of the second polarized piezoelectric member and configured to connect to the second circumferential end of the first polarized piezoelectric member and the second circumferential end of the second polarized piezoelectric member; and a central through-hole centrally located in the piezoelectric sensor along the central axis and configured to receive a magnetostrictive wire extending along the central axis.

[0006] In the present disclosure, the structure of the piezoelectric sensor is simplified, thereby reducing the cost without compromising the detection accuracy.

[0007] In some embodiments, the first polarized piezoelectric member and the second polarized piezoelectric member may be symmetrically arranged with respect to the central axis. With this arrangement, the vibration mode caused by the torsional wave can be easily detected by the polarized piezoelectric members.

[0008] In some embodiments, the first polarized piezoelectric member and the second polarized piezoelectric member may be arranged in a substantially annular ring. With this arrangement, the polarized piezoelectric members can be easily manufactured in a cost-effective manner.

[0009] In some embodiments, the first polarized piezoelectric member and the second polarized piezoelectric member may be substantially in the shape of a semi-cylindrical ring, and the corresponding first circumferential end portion and second circumferential end portion may include a rectangular cross-sectional shape. With this arrangement, this shape helps to detect the vibration mode caused by the torsional wave.

[0010] In some embodiments, the piezoelectric sensor may further include an insulating intermediate member disposed radially inside the first polarized piezoelectric member and the second polarized piezoelectric member and configured to contact the radially inner surfaces of the first polarized piezoelectric member and the second polarized piezoelectric member, with the central through-hole formed in the insulating intermediate member. With this arrangement, the shear force caused by the torsional wave can be effectively transmitted to the polarized piezoelectric elements.

[0011] In some embodiments, the first polarized piezoelectric member and the second polarized piezoelectric member may include at least one of the following dimensions: the inner diameter of the first polarized piezoelectric member and the second polarized piezoelectric member is in the range of 4 mm ± 2 mm; the outer diameter of the first polarized piezoelectric member and the second polarized piezoelectric member is in the range of 9 mm ± 2 mm; or the thickness of the first polarized piezoelectric member and the second polarized piezoelectric member is in the range of 5 mm ± 2 mm. With this arrangement, the vibration mode caused by the torsional wave can be easily detected by the polarized piezoelectric members.

[0012] In some embodiments, the first electrical conductor may be attached to the first circumferential ends of the first polarized piezoelectric element and the second polarized piezoelectric element by a conductive adhesive. In some embodiments, the second electrical conductor may be attached to the second circumferential ends of the first polarized piezoelectric element and the second polarized piezoelectric element by a conductive adhesive. With these arrangements, the electrical conductors can be easily attached to the polarized piezoelectric elements.

[0013] In some embodiments, both the first electrical conductor and the second electrical conductor include a portion protruding above the first polarized piezoelectric member and the second polarized piezoelectric member on the central axis.

[0014] In some embodiments, the piezoelectric sensor may further include an insulating sleeve that circumferentially surrounds the first and second polarized piezoelectric members on the radial outer sides thereof. In some embodiments, the insulating sleeve may be made of ceramic. With these arrangements, the polarized piezoelectric elements can be well protected.

[0015] In a second aspect of the present disclosure, a piezoelectric sensor is provided. The piezoelectric sensor includes: a plurality of pairs of polarized piezoelectric members, the pairs of polarized piezoelectric members being arranged adjacent to each other in a circumferential direction, each pair of the polarized piezoelectric members including a first polarized piezoelectric member and a second polarized piezoelectric member, the first polarized piezoelectric member including a first polarization direction along a central axis, the second polarized piezoelectric member including a second polarization direction opposite to the first polarization direction, the first polarized piezoelectric member including a first circumferential end and a second circumferential end, the second polarized piezoelectric member including a first circumferential end and a second circumferential end, the first circumferential end of the second polarized piezoelectric member being adjacent to the first circumferential end of the first polarized piezoelectric member in the circumferential direction, and the polarization directions of two adjacent polarized piezoelectric members arranged along the circumferential direction being opposite to each other; a plurality of first conductors, the plurality of first conductors being circumferentially provided between the first circumferential ends of each pair of polarized piezoelectric members and connected to the first circumferential ends of each pair of polarized piezoelectric members, the plurality of first conductors being connected in series to form a first output; a plurality of second conductors, the plurality of second conductors being circumferentially provided between the second circumferential end of the first polarized piezoelectric member in the first pair of polarized piezoelectric members and the second circumferential end of the second polarized piezoelectric member in the second pair of polarized piezoelectric members, and connected to the second circumferential end of the first polarized piezoelectric member and the second circumferential end of the second polarized piezoelectric member, the second pair of polarized piezoelectric members being adjacent to the first pair of polarized piezoelectric members in the circumferential direction, the plurality of second conductors being connected in series to form a second output; and a central through hole, the central through hole being centrally located in the piezoelectric sensor along the central axis, the central hole being configured to receive a magnetostrictive wire extending along the central axis.

[0016] In a third aspect of the present invention, a liquid level measurement system is provided. The liquid level measurement system includes: a magnetostrictive wire; a permanent magnet capable of moving along the magnetostrictive wire based on the liquid level; the piezoelectric sensor according to any one of the first and second aspects; and a processing device configured to: send a current to the magnetostrictive wire, the current causing a torsional wave in the magnetostrictive wire; receive a signal from the piezoelectric sensor caused by the torsional wave; and determine the liquid level based on the received signal. Description of the Drawings

[0017] The above and other objects, features and advantages of the exemplary embodiments disclosed herein will become more readily understood by reference to the following detailed description of the drawings. In the drawings, several exemplary embodiments shown herein will be illustrated by way of example and not limitation, wherein:

[0018] Figure 1 is a schematic diagram of a liquid level measurement system according to an exemplary embodiment of the present disclosure;

[0019] Figure 2 is Figure 1 an enlarged view of the circled part in;

[0020] Figure 3 a schematic perspective view of a piezoelectric sensor according to an exemplary embodiment of the present disclosure;

[0021] Figure 4 is Figure 3 a cross-sectional view of the piezoelectric sensor in;

[0022] Figure 5 a schematic perspective view of a piezoelectric sensor according to an exemplary embodiment of the present disclosure; and

[0023] Figure 6 a schematic perspective view of a piezoelectric sensor according to another exemplary embodiment of the present disclosure.

[0024] In all the figures, the same or similar reference numerals are used to denote the same or similar elements. Detailed Description

[0025] Now, the principles of the present disclosure will be described with reference to several exemplary embodiments shown in the drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the description of these embodiments is only for facilitating those skilled in the art to better understand and thereby implement the present disclosure, rather than limiting the scope of the present disclosure in any way.

[0026] The term "comprising" or "including" and its variants should be construed as open-ended terms, meaning "including but not limited to". The term "or" should be understood as "and / or", unless the context clearly indicates otherwise. The term "based on" should be understood as "at least partially based on". The term "operably" refers to a function, action, movement or state that can be achieved through an operation caused by a user or an external institution. The terms "an embodiment" and "embodiments" should be understood as "at least one embodiment". The term "another embodiment" should be understood as "at least one other embodiment". The terms "first", "second", etc. may refer to different or the same objects. Other explicit and implicit definitions may be included below. Unless the context clearly indicates otherwise, the definitions of the terms are consistent throughout the specification.

[0027] The use of the magnetostrictive principle involves generating an initial current pulse within a magnetostrictive wire to create a magnetic field along the length of the wire. The magnetic field interacts with the magnetic field present at the location of the permanent magnet, causing a torsional disturbance in the wire. Since torsional waves are essentially acoustic waves, their propagation speed is slow enough and measurable such that a direct relationship can be established between the time taken for the wave to travel and the distance traveled. When the length of the magnetostrictive wire is known and the initial start time of the torsional pulse is known, detection of the torsional pulse at a suitably positioned detector will provide a travel time value that is directly related to the distance traveled by the torsional pulse. Then, when used with respect to an object of interest, this distance is used to determine the liquid level in a tank or the position of a mechanical tool.

[0028] Piezoelectric sensors are used to detect the arrival of torsional waves. For many applications, piezoelectric sensors have been shown to be very useful in accurately detecting and discriminating the arrival of torsional pulses with sufficient precision. Piezoelectric sensors include piezoelectric materials, including certain ceramics, naturally occurring crystals, and synthetic crystals. Piezoelectric materials can be used to detect torsional waves in the wire and convert the detected torsional waves in the wire into electrical signals.

[0029] The normal operating mode of a piezoelectric sensor is the shear mode. Conventional piezoelectric sensors are composed of multiple piezoelectric crystal segments, each of which is individually polarized in the circumferential direction and circumferentially bonded to form a piezoelectric sensor. However, manufacturing such piezoelectric sensors is labor-intensive. The assembled piezoelectric crystal elements must be machined to very precise tolerances on the inner toroidal surface and adjacent crystal faces. To provide a detector with sufficiently precise characteristics, a large amount of manual labor is required to complete the multi-segment piezoelectric crystal sensor.

[0030] The present disclosure provides a completely new configuration of a piezoelectric sensor that includes a plurality of polarization segments having polarization directions in the axial direction rather than in the circumferential direction. This novel design significantly reduces the assembly labor and time required to manufacture a piezoelectric sensor without compromising torsional wave detection performance. The above features and advantages of the exemplary embodiments disclosed herein will be more readily understood from the following detailed description with reference to the accompanying drawings.

[0031] Figure 1 and Figure 2 FIG. shows a schematic diagram of a liquid level measurement system 100 according to an exemplary embodiment of the present disclosure. As Figure 1As shown, the liquid level measurement system 100 includes a frame 60 and a tube 30. The frame 60 can be installed in place on an object (such as a tank containing liquid). The frame can also include various electrical devices for operating the piezoelectric sensor. For example, the electrical devices can include: a pulse circuit for generating a current pulse to the magnetostrictive wire, which causes a torsional wave in the magnetostrictive wire 20; and microprocessor-based electronics for processing the electrical signal from the piezoelectric sensor caused by the torsional wave to determine the liquid level.

[0032] As Figure 1 shown, a permanent magnet 40 (or called a magnetic float) is installed on or in the tube 30. The permanent magnet 40 floats on the surface of the liquid and can move as the liquid level changes. The piezoelectric sensor 10 is disposed within the tube 30. The piezoelectric sensor 10 is also electrically connected to the microprocessor-based electronics and is configured to detect the electrical signal caused by the torsional wave on the magnetostrictive wire 20. The magnetostrictive wire 20 is disposed in the central hole of the piezoelectric sensor 10 and extends axially within the tube 30.

[0033] The working principle of the system is described below. A current (e.g., a current pulse) is sent to the magnetostrictive wire 20. The current generates a magnetic field that travels down the magnetostrictive wire within the tube 30. The interaction of the magnetic field around the magnetostrictive wire with the magnetic float 40 causes a torsional stress wave to be induced in the magnetostrictive wire. This torsion propagates along the magnetostrictive wire from the position of the magnetic float to both ends of the magnetostrictive wire at a known speed. The piezoelectric sensor 10 is configured to detect the received mechanical torsion as an electrical return signal. The microprocessor-based electronics are configured to determine the time elapsed between the start and return current times of the flight and convert it into a position measurement proportional to the level of the magnetic float. In this way, the liquid level can be reliably determined. By periodically sending a current to the magnetostrictive wire 20, when the position of the magnetic float 40 changes, the liquid level can be detected in a timely manner.

[0034] As Figure 2 shown, the piezoelectric sensor 10 is installed in place, such as at the end point of the magnetostrictive wire 20, and mainly serves as a device for detecting the occurrence of a torsional wave at this end point. The piezoelectric sensor 10 is connected to the microprocessor-based electronics through conductors 16, 18.

[0035] It should be understood that in the example shown, the piezoelectric sensor is shown mainly serving as a device for detecting the occurrence of a torsional wave. This is merely illustrative, and the piezoelectric element can be used in different ways. For example, the piezoelectric element can be used to apply a torsional wave to the magnetostrictive wire 20 while detecting the current in the magnetostrictive wire.

[0036] Now refer Figures 3 - 5 to describe in detail the configuration of the improved piezoelectric sensor. Figure 3It is a schematic perspective view of a piezoelectric sensor according to an exemplary embodiment of the present disclosure.

[0037] Figure 4 It shows a cross-sectional view of a piezoelectric sensor according to an exemplary embodiment of the present disclosure.

[0038] Figure 5 It is a schematic perspective view of a simplified version of a piezoelectric sensor according to an exemplary embodiment of the present disclosure, in which the magnetostrictive wire 20 and the electrical conductor are removed for clarity.

[0039] As Figures 3 - 5 shown, the piezoelectric sensor 10 includes a first polarized piezoelectric element 12 and a second polarized piezoelectric element 14. The first polarized piezoelectric element 12 has a first circumferential end 121 and a second circumferential end 122. The first polarized piezoelectric element 12 has a first polarization direction along the central axis direction. As Figure 5 shown, the first polarization direction of the first polarized piezoelectric element 12 is marked by a plus sign “+”. The central axis direction is also the extending direction of the magnetostrictive wire 20. In the first polarized piezoelectric element 12, the polarization direction is in the central axis direction.

[0040] The second polarized piezoelectric element 14 has the same shape as the first polarized piezoelectric element 12. The second polarized piezoelectric element 14 is circumferentially opposite to the first polarized piezoelectric element 12 and is arranged adjacent to the first polarized piezoelectric element 12 along the circumferential direction. The second polarized piezoelectric member 14 has a first circumferential end 141 that is circumferentially adjacent to the first circumferential end 121 of the first polarized piezoelectric member 12 and a second circumferential end 142 that is circumferentially adjacent to the second circumferential end 122 of the first polarized piezoelectric member 12. The second polarized piezoelectric element 14 has a second polarization direction opposite to the first polarization direction. As Figure 5 shown, the second polarization direction of the second polarized piezoelectric element 14 is marked with a minus sign “-” to distinguish it from the polarization direction of the second polarized piezoelectric element 14.

[0041] The first electrical conductor 16 is also disposed between the first circumferential end 121 of the first polarized piezoelectric element 12 and the first circumferential end 141 of the second polarized piezoelectric element 14. The first electrical conductor 16 is configured to connect to the first circumferential end 121 of the first polarized piezoelectric element 12 and the first circumferential end 141 of the second polarized piezoelectric element 14. The first electrical conductor is made of a conductive material and may have various shapes. In the illustrated example, the first electrical conductor is in the shape of a conductive sheet having a rectangular cross-section. It should be understood that this is merely illustrative, and the first electrical conductor may have any other suitable shape. Through the first electrical conductor 16, an electrical connection can be established between the first circumferential end 121 of the first polarized piezoelectric member 12 and the first circumferential end 141 of the second polarized piezoelectric member 14. In this way, the electrical signals generated at the corresponding electrodes of the first polarized piezoelectric element 12 and the second polarized piezoelectric element 14 can be output.

[0042] Similarly, the second electrical conductor 18 is disposed between the second circumferential end 122 of the first polarized piezoelectric element 12 and the second circumferential end 142 of the second polarized piezoelectric element 14, and is configured to connect to the second circumferential end of the first polarized piezoelectric element 12 and the second circumferential end of the second polarized piezoelectric element 14. Similarly, the second electrical conductor 18 is made of a conductive material. In the illustrated example, the second electrical conductor is in the shape of a conductive sheet having a rectangular cross-section. Through the second electrical conductor 18, an electrical connection can be established between the second circumferential end 122 of the first polarized piezoelectric member 12 and the second circumferential end 142 of the second polarized piezoelectric member 14. In this way, the electrical signals generated at the corresponding electrodes of the first polarized piezoelectric element 12 and the second polarized piezoelectric element 14 can be output.

[0043] The piezoelectric sensor 10 further includes a central through-hole 11 that is centrally located in the piezoelectric sensor 10 along the central axis and is configured to receive a magnetostrictive wire 20 extending along the central axis. The size of the central through-hole 11 is configured to transfer torsional waves or shear forces from the magnetostrictive wire 20 to the first polarized piezoelectric member 12 and the second polarized piezoelectric member 14.

[0044] In the present disclosure, the first polarized piezoelectric member 12 and the second polarized piezoelectric member 14 have polarization directions along the central axis rather than in the circumferential direction. This is different from traditional piezoelectric sensors. The working principle of this polarization mode is described below. According to the present disclosure, when the magnetostrictive wire 20 vibrates in the circumferential direction, the first polarized piezoelectric member 12 and the second polarized piezoelectric member 14 having opposite polarization directions along the central axis are found to generate a vibration mode in the circumferential direction. Therefore, by detecting the electrical output of the circumferential end faces of the first polarized piezoelectric element 12 and the second polarized piezoelectric element 14, the torsional waves on the magnetostrictive wire 20 can be detected with sufficient accuracy.

[0045] In the present disclosure, since the polarization directions of the piezoelectric member 12 and the second polarized piezoelectric member 14 are in the central axis direction, it is easy to manufacture the polarized piezoelectric member. Moreover, assembling the manufactured piezoelectric members is cost-effective. In this way, the cost of the piezoelectric sensor is reduced.

[0046] In particular, the dimensional tolerances of the inner diameter and / or outer diameter of each polarized piezoelectric element can be well controlled. This is because these polarized piezoelectric elements can be directly formed by a piezoelectric molding process, which has quite good mass consistency. For traditional piezoelectric sensors, the polarization direction of the polarization member is in the circumferential direction, and the polarization members must be ground with sandpaper to be close to each other tightly. For the piezoelectric sensor of the present disclosure, there is no need for a grinding operation with sandpaper that may cause large variations.

[0047] In addition, in the present disclosure, the electrodes of the first piezoelectric member 12 and the second polarized piezoelectric member 14 are arranged between the circumferential end regions of the first piezoelectric member 12 and the second polarized piezoelectric member 14. The electrodes of the first piezoelectric element 12 and the second polarized piezoelectric element 14 are also connected to the first conductor 16 and the second conductor 18. The interface for transmitting the torsional wave from the magnetostrictive wire 20 to the piezoelectric member is reduced. The reduction of the interface not only eliminates the tolerance uncertainty, but also reduces the signal attenuation accompanying the propagation due to less material loss.

[0048] In some embodiments, as Figures 3 - 5 shown, the first polarized piezoelectric member 12 and the second polarized piezoelectric member 14 are symmetrically arranged with respect to the central axis. This is advantageous in detecting the vibration mode in the circumferential direction by the first and second polarized piezoelectric members 12, 14 having opposite polarization directions along the axial direction.

[0049] In some embodiments, as Figures 3 - 5 shown, each of the first polarized piezoelectric element 12 and the second polarized piezoelectric element 14 is in the shape of a substantially semi-cylindrical ring. The first polarized piezoelectric element 12 and the second polarized piezoelectric element 14 together form a substantially annular ring. The corresponding first and second circumferential ends have a rectangular cross-sectional shape. This is advantageous for detecting the circumferential vibration mode caused by the torsional wave. Moreover, this is advantageous in manufacturing. This is because the circumferential ends of adjacent piezoelectric elements must be rigid or have a high inertial mass. When the circumferential ends of the piezoelectric member have a rectangular cross-sectional shape, the piezoelectric member can be easily aligned to avoid introducing false signals and eliminate unwanted vibration responses.

[0050] In some embodiments, each of the first polarized piezoelectric member 12 and the second polarized piezoelectric member 14 is in the shape of an arcuate cylindrical cross-section, as long as the circumferential vibration mode can be detected by the piezoelectric material of the piezoelectric member.

[0051] In some embodiments, the central hole 11 is formed by a first polarized piezoelectric member 12 and a second polarized piezoelectric member 14. In other embodiments, an insulating intermediate member 15 may be disposed radially inside the first polarized piezoelectric member 12 and the second polarized piezoelectric member 14 and configured to contact the radially inner surfaces of the first polarized piezoelectric member 12 and the second polarized piezoelectric member 14. A central through hole 11 is formed in the insulating intermediate member 15. By the arrangement of the insulating intermediate member 15, the first polarized piezoelectric member 12 and the second polarized piezoelectric member 14 can be formed to dimensions capable of inducing an enhanced circumferential vibration mode in the piezoelectric member.

[0052] The insulating intermediate member 15 can be formed of any suitable insulating material. In some embodiments, the insulating intermediate member 15 is formed of potting glue. This is advantageous in assembling the piezoelectric sensor. When the first polarized piezoelectric element 12 and the second polarized piezoelectric element 14 are assembled together, the open space formed by the inner surfaces of the first polarized piezoelectric element 12 and the second polarized piezoelectric element 14 can be filled with potting glue. The potting glue is then cured to form a rigid structure. The fit tolerance between the magnetostrictive wire 20 and the first and second polarized piezoelectric elements 12, 14 should be well controlled because the shear force in the magnetostrictive wire 20 will be transmitted to the inner surfaces of the first and second polarized piezoelectric elements 12, 14. Due to the potting glue, the fit tolerance from the magnetostrictive wire 20 to the first and second polarized piezoelectric elements 12, 14 can be eliminated.

[0053] In some embodiments, the dimensions of the first polarized piezoelectric member 12 and the second polarized piezoelectric member 14 satisfy at least one of the following requirements. The inner diameter of the first polarized piezoelectric member 12 and the second polarized piezoelectric member 14 is in the range of 4 mm ± 2 mm, for example 4 mm. The outer diameter of the first polarized piezoelectric member 12 and the second polarized piezoelectric member 14 is in the range of 9 mm ± 2 mm, for example 9 mm. The thickness of the first polarized piezoelectric member 12 and the second polarized piezoelectric member 14 (i.e., the dimension in the central axis direction) is in the range of 5 mm ± 2 mm, for example 5 mm. Experimental tests show that when the dimensions of the polarized piezoelectric element satisfy the above experiments, the circumferential vibration mode of the polarized piezoelectric element for generating an electrical output can be improved.

[0054] The first electrical conductor 16 and the second electrical conductor 18 can be in various forms. In some embodiments, the first electrical conductor 16 and the second electrical conductor 18 are in the form of rectangular sheets. In the example shown, the first electrical conductor 16 and the second electrical conductor 18 cover the entire electrode surface of the first polarized piezoelectric element 12 and the second polarized piezoelectric element 14 disposed at the circumferential ends of the respective polarized piezoelectric elements. In some examples, the first electrical conductor 16 and the second electrical conductor 18 cover a part of the electrode surfaces of the first polarized piezoelectric member 12 and the second polarized piezoelectric member 14.

[0055] In some embodiments, the first electrical conductor 16 is attached to the first circumferential ends 121, 141 of the first polarized piezoelectric member 12 and the second polarized piezoelectric member 14 by a conductive adhesive 13. In this case, the mating tolerances between the first and second polarized piezoelectric members 12, 14 can be removed or absorbed by the conductive adhesive 13. Similarly, the second electrical conductor 18 is attached to the second circumferential ends 122, 142 of the first polarized piezoelectric element 12 and the second polarized piezoelectric element 14 by the conductive adhesive 13.

[0056] In some embodiments, as Figures 3 - 5 shown, the first electrical conductor 16 and the second electrical conductor 18 include portions that protrude above the first and second polarized piezoelectric members 12, 14 in the central axis direction. Using this portion, an electrical connection can be easily established at the first electrical conductor 16 and the second electrical conductor 18.

[0057] In some embodiments, as Figures 3 - 5 shown, the piezoelectric sensor 10 includes an insulating sleeve 19 that circumferentially surrounds the first and second polarized piezoelectric members 12, 14 on the radially outer sides of the first and second polarized piezoelectric members 12, 14. Using the insulating sleeve 19, the piezoelectric elements can be well protected. In some embodiments, the insulating sleeve 19 is made of ceramic. It should be understood that this is merely illustrative. Other protection devices can be provided outside the first and second polarized piezoelectric elements 12, 14 as long as the operation of the piezoelectric elements is not affected.

[0058] Figure 6 FIG. shows a schematic perspective view of a piezoelectric sensor according to another exemplary embodiment of the present disclosure. Figure 6 The piezoelectric sensor shown is substantially the same as Figure 5 shown. The difference is that: in the Figure 6 piezoelectric sensor, there are two pairs of polarized piezoelectric elements instead of one pair of polarized piezoelectric elements as Figure 5 shown.

[0059] As Figure 6 shown, two pairs of polarized piezoelectric elements are arranged adjacent to each other in the circumferential direction. Each pair of polarized piezoelectric elements includes a first polarized piezoelectric element 12a and a second polarized piezoelectric element 12b. The first polarized piezoelectric element 12a has a first polarization direction along the central axis direction (represented by a positive sign “+” in Figure 6 ). The second polarized piezoelectric element 12b has a second polarization direction opposite to the first polarization direction (represented by a negative sign “−” in Figure 6 ).

[0060] In the illustrated embodiment, each of the polarized piezoelectric elements 12a, 12b, 14a, 14b has the same dimensions and has a cylindrical segment shape. Two adjacent polarized piezoelectric elements arranged in the circumferential direction have opposite polarization directions. Specifically, the reference signs “+” and “-” alternate in the circumferential direction. Two adjacent polarized piezoelectric elements can be connected together, for example, by a conductive adhesive 13. Electrical conductors 16a, 16b, 18a, 18b are disposed between and in electrical contact with two adjacent polarized piezoelectric elements.

[0061] Specifically, the first polarized piezoelectric elements 12a, 14a have a first circumferential end and a second circumferential end. The second polarized piezoelectric elements 12b, 14b have a first circumferential end and a second circumferential end that are circumferentially adjacent to the first circumferential end. Two first electrical conductors 16a, 16b are respectively disposed circumferentially between and in electrical contact with the first circumferential ends of each pair of polarized piezoelectric elements. The first electrical conductors 16a, 16b are connected in series to form a first output.

[0062] Similarly, two second electrical conductors 18a, 18b are disposed circumferentially between the second circumferential end of the first polarized piezoelectric element 12a in the first pair of polarized piezoelectric elements and the second circumferential end of the second polarized piezoelectric element 14b in the second pair of polarized piezoelectric elements and are in electrical contact therewith, the second pair of polarized piezoelectric elements being circumferentially adjacent to the first pair of polarized piezoelectric elements. The two second electrical conductors 18a, 18b are connected in series to form a second output.

[0063] With the above arrangement, tests show that the piezoelectric sensor can detect the electrical output from the polarized piezoelectric elements with sufficient accuracy. It should be understood that in the illustrated example, only two pairs of piezoelectric members are included. This is merely illustrative. In some other embodiments, the piezoelectric sensor may include three or more pairs of piezoelectric members.

[0064] From the above description and the teachings provided in the related drawings, those skilled in the art to which this disclosure pertains will appreciate many modifications and other embodiments of the disclosure given herein. Accordingly, it should be understood that the embodiments of the disclosure are not limited to the specific embodiments of the disclosure, and that modifications and other embodiments are intended to fall within the scope of the disclosure. Additionally, although the exemplary embodiments are described above in the context of some illustrative combinations of components and / or functions in the above description and the related drawings, it should be recognized that different combinations of components and / or functions can be provided in alternative embodiments without departing from the scope of the disclosure. In this regard, for example, other combinations of components and / or functions different from those explicitly described above are also expected to fall within the scope of the disclosure. Although specific terms are used herein, they are used only in a general and descriptive sense and not for purposes of limitation.

Claims

1. A piezoelectric sensor (10), comprising: A first polarized piezoelectric member (12), the first polarized piezoelectric member including a first circumferential end (121) and a second circumferential end (122), the first polarization direction of the first polarized piezoelectric member (12) being along the central axis, A second polarized piezoelectric member (14), the second polarized piezoelectric member being arranged adjacent to the first polarized piezoelectric member (12) in the circumferential direction, the second polarized piezoelectric member (14) including a first circumferential end (141) adjacent to the first circumferential end (121) of the first polarized piezoelectric member (12) in the circumferential direction and a second circumferential end (142) adjacent to the second circumferential end (122) of the first polarized piezoelectric member (12) in the circumferential direction, the second polarization direction of the second polarized piezoelectric member (14) being opposite to the first polarization direction, A first electrical conductor (16), the first electrical conductor being disposed between the first circumferential end (121) of the first polarized piezoelectric member (12) and the first circumferential end (141) of the second polarized piezoelectric member (14) and being configured to connect to the first circumferential end (121) of the first polarized piezoelectric member (12) and the first circumferential end (141) of the second polarized piezoelectric member (14); A second electrical conductor (18), the second electrical conductor being disposed between the second circumferential end (122) of the first polarized piezoelectric member (12) and the second circumferential end (142) of the second polarized piezoelectric member (14) and being configured to connect to the second circumferential end (122) of the first polarized piezoelectric member (12) and the second circumferential end (142) of the second polarized piezoelectric member (14); and A central through-hole (11), the central through-hole being centrally located in the piezoelectric sensor (10) along the central axis and being configured to receive a magnetostrictive wire (20) extending along the central axis.

2. The piezoelectric sensor (10) according to claim 1, wherein the first polarized piezoelectric member (12) and the second polarized piezoelectric member (14) are arranged symmetrically with respect to the central axis.

3. The piezoelectric sensor (10) according to any one of the preceding claims, wherein the first polarized piezoelectric member (12) and the second polarized piezoelectric member (14) are arranged as substantially annular rings.

4. The piezoelectric sensor (10) according to claim 3, wherein the first polarized piezoelectric member (12) and the second polarized piezoelectric member (14) are substantially in the shape of semi-cylindrical rings, and the corresponding first circumferential end portions and second circumferential end portions include a rectangular cross-sectional shape.

5. The piezoelectric sensor (10) according to any one of claims 1-4 further comprises an insulating intermediate member (15) which is arranged radially inside the first polarized piezoelectric member (12) and the second polarized piezoelectric member (14) and is configured to contact the radial inner surfaces of the first polarized piezoelectric member (12) and the second polarized piezoelectric member (14), and a central through-hole (11) is formed in the insulating intermediate member (15).

6. The piezoelectric sensor (10) according to claim 5, wherein the insulating intermediate member (15) is formed of a cured potting adhesive.

7. The piezoelectric sensor (10) according to any one of the preceding claims, wherein the first polarized piezoelectric member (12) and the second polarized piezoelectric member (14) include at least one of the following dimensions: The inner diameter of the first polarized piezoelectric member (12) and the second polarized piezoelectric member (14) is in the range of 4 mm ± 2 mm; The outer diameter of the first polarized piezoelectric member (12) and the second polarized piezoelectric member (14) is in the range of 9 mm ± 2 mm; or The thickness of the first polarized piezoelectric member (12) and the second polarized piezoelectric member (14) is in the range of 5 mm ± 2 mm.

8. The piezoelectric sensor (10) according to any one of the preceding claims, wherein the first electrical conductor (16) is attached to the first circumferential end (121) of the first polarized piezoelectric member (12) and the first circumferential end (141) of the second polarized piezoelectric member (14) by a conductive adhesive (13).

9. The piezoelectric sensor (10) according to any one of the preceding claims, wherein the second electrical conductor (18) is attached to the second circumferential end (122) of the first polarized piezoelectric member (12) and the second circumferential end (142) of the second polarized piezoelectric member (14) by a conductive adhesive (13).

10. The piezoelectric sensor (10) according to any one of the preceding claims, wherein both the first electrical conductor (16) and the second electrical conductor (18) include a portion protruding above the first polarized piezoelectric member (12) and the second polarized piezoelectric member (14) on the central axis.

11. The piezoelectric sensor (10) according to any one of the preceding claims further comprises an insulating sleeve (19) which circumferentially surrounds the first polarized piezoelectric member (12) and the second polarized piezoelectric member (14) on the radial outer side thereof.

12. The piezoelectric sensor (10) according to claim 11, wherein the insulating sleeve (19) is made of ceramic.

13. A piezoelectric sensor (10) comprising A plurality of pairs of polarized piezoelectric members, the pairs of polarized piezoelectric members being arranged adjacent to each other in the circumferential direction, each pair of the pairs of polarized piezoelectric members including a first polarized piezoelectric member (12a, 14a) and a second polarized piezoelectric member (12b, 14b), the first polarized piezoelectric member (12a, 14a) including a first polarization direction along the central axis, the second polarized piezoelectric member (12b, 14b) including a second polarization direction opposite to the first polarization direction, the first polarized piezoelectric member (12a) including a first circumferential end and a second circumferential end, the second polarized piezoelectric member (12b, 14b) including a first circumferential end and a second circumferential end, the first circumferential end of the second polarized piezoelectric member being adjacent to the first circumferential end of the first polarized piezoelectric member (12a, 14a) in the circumferential direction, and the polarization directions of two adjacent polarized piezoelectric members arranged along the circumferential direction being opposite; A plurality of first conductors (16a, 16b), the plurality of first conductors being circumferentially provided between the first circumferential ends of each pair of polarized piezoelectric members and connected to the first circumferential ends of each pair of polarized piezoelectric members, the plurality of first conductors (16a, 16b) being connected in series to form a first output; A plurality of second conductors (18a, 18b), the plurality of second conductors being circumferentially provided between the second circumferential end of the first polarized piezoelectric member (12a, 14a) in the first pair of polarized piezoelectric members and the second circumferential end of the second polarized piezoelectric member (12b, 14b) in the second pair of polarized piezoelectric members and connected to the second circumferential end of the first polarized piezoelectric member (12a, 14a) and the second circumferential end of the second polarized piezoelectric member (12b, 14b), the second pair of polarized piezoelectric members being adjacent to the first pair of polarized piezoelectric members in the circumferential direction, the plurality of second conductors (18a, 18b) being connected in series to form a second output; And A central through hole (11), the central through hole being centrally located in the piezoelectric sensor (10) along the central axis, the central hole being configured to receive a magnetostrictive wire (20) extending along the central axis.

14. A liquid level measurement system, comprising A magnetostrictive wire (20); A permanent magnet (40), the permanent magnet being capable of moving along the magnetostrictive wire (20) based on the liquid level; The piezoelectric sensor (10) according to any one of claims 1-13; and A processing device configured to: Send a current to the magnetostrictive wire (20), the current causing a torsional wave in the magnetostrictive wire (20); Receive a signal from the piezoelectric sensor (10) caused by the torsional wave; and Determine the liquid level based on the received signal.

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