A pressure sensor

Abstract

This invention provides a pressure sensor, belonging to the field of sensor technology, comprising a housing, a pressure measuring component, a waterproof and breathable membrane, a piezoelectric vibration element, and a flexible sealing connector. The housing has an installation cavity, a pressure introduction channel, and a venting channel. The waterproof and breathable membrane is disposed on the venting channel, and the piezoelectric vibration element is disposed above the waterproof and breathable membrane. The piezoelectric vibration element includes a first electrode layer, a piezoelectric material layer, and a second electrode layer, and has multiple through holes corresponding to the venting areas of the waterproof and breathable membrane. This invention rapidly removes surface water from the waterproof and breathable membrane through vibration, ensuring unobstructed venting channels. Simultaneously, the flexible sealing connector isolates the transmission of vibration to the housing, avoiding vibration energy loss and component fatigue and loosening. It has advantages such as low energy consumption, fast response, no thermal impact, and high reliability.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and more specifically to a pressure sensor. Background Technology

[0002] A pressure sensor is a measuring device that converts pressure signals into electrical signals. It is widely used in fields such as monitoring intake manifold pressure in automotive engines and detecting atmospheric environmental parameters. In gauge pressure measurement applications, the sensor needs to simultaneously introduce the pressure medium to be measured and the ambient reference pressure, obtaining the relative pressure value through the difference between the two.

[0003] To prevent contaminants such as liquid water and dust from entering the sensor and damaging electronic components, vent holes are typically made in the housing, and these vent holes are covered with a waterproof and breathable membrane. The waterproof and breathable membrane is usually made of expanded polytetrafluoroethylene (PTFE), whose microporous structure allows gas molecules to pass freely while effectively blocking liquid water and particulate matter, thus protecting the internal precision pressure measurement components and electronic parts.

[0004] However, in high-humidity environments or during sensor cleaning tests, moisture in the air can easily accumulate on the surface of the waterproof and breathable membrane, forming visible water. This visible water can clog the micropores of the membrane, reducing or even completely blocking air permeability. This causes a deviation between the reference pressure inside the sensor and the ambient pressure, ultimately resulting in measurement errors. Summary of the Invention

[0005] In view of this, the present invention provides a pressure sensor to solve the problem of measurement error caused by water blockage on the surface of the waterproof and breathable membrane in the prior art, and at the same time solves the problem of vibration energy loss and component fatigue loosening caused by the direct rigid connection of the vibration element to the shell, so that the sensor has both self-cleaning water function and vibration buffering function.

[0006] To achieve the above-mentioned objective, the present invention provides a pressure sensor, comprising: The housing has an internal mounting cavity. A pressure interface tube is fixedly connected to the rear end of the housing. The outer wall of the pressure interface tube is equipped with a seal. The pressure interface tube has a pressure introduction channel that connects to the mounting cavity for introducing the pressure medium to be measured. The housing also has a venting channel for introducing the ambient reference pressure into the mounting cavity. The pressure measurement component, enclosed at one end inside the pressure inlet channel, is used to receive the relative pressure of the medium under test relative to the ambient reference pressure. A waterproof and breathable membrane is installed on the ventilation channels; A piezoelectric vibration element is positioned above the waterproof and breathable membrane; A flexible sealing connector is used to connect the vibrating assembly, which consists of a piezoelectric vibrating element and a waterproof and breathable membrane, to the outer shell, thereby forming a flexible sealing connection between the vibrating assembly and the outer shell.

[0007] Furthermore, the flexible sealing connector has at least a bellows section, the end of which is provided with a flange section. The flange section is connected to the housing or vibration assembly through a mating part of the component, and the mating part of the component adopts a tight fit or a threaded fit.

[0008] Furthermore, the flexible sealing connector is a rubber bellows, silicone bellows, or fluororubber bellows.

[0009] Furthermore, one end of the flexible sealing connector is sealed to the outer edge of the vibration assembly, and the other end is sealed to the boss of the housing or the inner wall of the ventilation channel.

[0010] Furthermore, the piezoelectric vibration element includes: a first electrode layer, a piezoelectric material layer, and a second electrode layer. The first electrode layer and the second electrode layer are respectively disposed on opposite sides of the piezoelectric material layer. The piezoelectric vibration element has at least one through hole, which penetrates the first electrode layer, the piezoelectric material layer, and the second electrode layer along the thickness direction. The through hole corresponds to at least a portion of the breathable area of ​​the waterproof and breathable membrane. The piezoelectric vibrating element generates high-frequency vibration under the action of driving voltage, and transmits the vibration to the waterproof and breathable membrane, so that the water adhering to the waterproof and breathable membrane is atomized and discharged.

[0011] Furthermore, the vibration direction of the piezoelectric vibrating element is its axial extension direction, which is along the thickness direction of the piezoelectric vibrating element, causing the piezoelectric vibrating element to undergo extension and contraction deformation in the thickness direction, thereby driving the waterproof and breathable membrane to vibrate along the thickness direction.

[0012] Furthermore, the through holes are circular, square, or slit-shaped, and multiple through holes are arranged in an array on the piezoelectric vibrating element.

[0013] Furthermore, the first electrode layer is electrically connected to the lower surface of the circuit board of the pressure measuring component through a first conductive adhesive, and the second electrode layer is electrically connected to the lower surface of the circuit board through leads.

[0014] Furthermore, the waterproof and breathable membrane is fixedly bonded to the lower surface of the piezoelectric vibration element by a first adhesive.

[0015] Furthermore, one end of the ventilation channel faces upward and connects to the installation cavity, with a waterproof and breathable membrane placed at one end of the ventilation channel.

[0016] Furthermore, the pressure measurement assembly includes: a substrate sealed to one end of the pressure inlet channel; a pressure-sensitive element fixed to the substrate and receiving the pressure of the medium to be measured and the ambient reference pressure and generating a corresponding differential pressure electrical signal; and a processing circuit disposed on the surface of the substrate and electrically connected to the pressure-sensitive element.

[0017] Furthermore, the piezoelectric vibrating element is electrically connected to a processing circuit, which includes a drive circuit for applying a drive voltage to the piezoelectric vibrating element. The drive voltage is an AC voltage with a frequency range of 20 kHz to 200 kHz, and the drive circuit is configured to drive the piezoelectric vibrating element intermittently.

[0018] Furthermore, the outer casing is provided with multiple terminals, and a fisheye pin is formed on the inner side of one end of each terminal. The pressure measurement component includes a circuit board with multiple metallized connection holes. The fisheye pins are tightly fitted and electrically connected to the metallized connection holes. The circuit board has a C-shaped structure and is made of ceramic or metal material. An upper electrode layer and a lower electrode layer are respectively provided on the upper and lower surfaces of the circuit board. The upper electrode layer is electrically connected to the processing circuit through a conductive adhesive, and the lower electrode layer is electrically connected to the piezoelectric vibration element.

[0019] The working principle of the pressure sensor of this invention is as follows: the pressure medium to be measured enters through the pressure introduction channel and acts on one side of the pressure-sensitive element; the ambient reference pressure enters the mounting cavity through the venting channel, flexible sealing connector, through hole, and waterproof and ventilated membrane, and acts on the other side of the pressure-sensitive element. The pressure-sensitive element outputs an electrical signal based on the pressure difference between the two sides to achieve pressure measurement.

[0020] When water accumulates on the surface of the waterproof and breathable membrane, the drive circuit applies an AC drive voltage to the piezoelectric vibration element. The piezoelectric vibration element generates high-frequency vibration along the thickness direction, driving the waterproof and breathable membrane to vibrate synchronously, causing the water to atomize into tiny droplets and be discharged outward, restoring the air permeability.

[0021] The flexible sealing connector is connected between the vibration component and the housing, effectively absorbing and isolating vibration, preventing vibration energy from being absorbed by the housing and thus suppressing the vibration effect. At the same time, it prevents the vibration component from fatigue and loosening due to the reaction force of the housing, thereby improving the long-term reliability of the sensor.

[0022] Compared with the prior art, the present invention has the following beneficial effects.

[0023] The pressure sensor of this invention generates high-frequency vibration through a piezoelectric vibrating element, driving the waterproof and breathable membrane to vibrate synchronously. This atomizes the water adhering to the surface of the membrane into tiny droplets and discharges them outward, thereby quickly restoring the patency of the ventilation channels, ensuring the accurate introduction of environmental reference pressure, and effectively solving the measurement error problem caused by water blockage. Compared with the existing heating and drying methods, this vibration-based water removal method has advantages such as lower energy consumption, faster response speed, and no thermal impact on surrounding electronic components.

[0024] A flexible sealing connector is installed between the vibration component and the housing, forming a flexible rather than rigid connection between them. This structure effectively isolates the transmission of vibration generated by the piezoelectric vibration element to the housing, preventing vibration energy from being absorbed by the housing and thus suppressing the vibration effect. At the same time, it eliminates the reaction force of the housing on the vibration component, preventing fatigue or loosening of the vibration component due to long-term alternating stress, and significantly improving the long-term reliability and vibration drainage efficiency of the self-cleaning pressure sensor.

[0025] The flexible sealing connector adopts a bellows structure, which has good flexibility and sealing performance. Its end is provided with a flange and is connected to the housing or vibration component through tight fit or threaded fit. This not only ensures the reliability of the connection, but also effectively absorbs and isolates vibration. At the same time, it ensures good airtightness between the venting channel and the installation cavity, preventing moisture or pollutants in the environment from entering the installation cavity through a path that is not filtered by the waterproof and breathable membrane.

[0026] By combining vibration dewatering function with flexible sealing connection structure, this technology can quickly and effectively remove water from the surface of waterproof and breathable membrane while solving the problems of vibration energy loss and component durability caused by rigid connection in existing technologies. It has the advantages of reasonable structure, reliable operation, low energy consumption and long service life, and is particularly suitable for applications such as automobile engine intake manifold pressure monitoring and atmospheric environmental parameter detection where long-term stability and reliability are required. Attached Figure Description

[0027] Figure 1 This is a cross-sectional view of the pressure sensor according to the first embodiment of the present invention; Figure 2 This is a cross-sectional view of a pressure sensor according to another embodiment of the present invention; Figure 3 This is a schematic diagram of the piezoelectric vibration element in this invention.

[0028] The components include: 1. Outer shell; 10. Mounting cavity; 11. Main shell; 11a. Recess; 11b. Vent hole; 12. Top cover; 111. Electrical connection part; 112. Pressure interface pipe; 1120. Pressure introduction channel; 1121. Seal; 113. Hot riveting post; 114. Boss; 115. Support part; 2. Pressure measuring assembly; 20. Pressure-sensitive element; 21. Annular sealing gasket; 21a. Center hole; 22. Base plate; 22a. Pressure through hole; 23. Circuit board; 23a. Stepped hole; 2 3b. Ventilation through-hole; 23c. Metallized connection hole; 201. Lead wire; 231. Upper electrode layer; 232. Lower electrode layer; 3. Terminal; 4a. Fisheye pin; 4b. Fisheye pin; 5. Sealant; 6. Waterproof and breathable membrane; 71. First adhesive; 81. First conductive adhesive; 9. Piezoelectric vibration element; 91. First electrode layer; 92. Piezoelectric material layer; 93. Second electrode layer; 94. Through hole; 100. Flexible sealing connector; 101. Component mating part; 102. Flange part. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0030] First Embodiment Reference Figure 1 and Figure 3 In this embodiment, the pressure sensor mainly includes a housing 1, a pressure measuring component 2, a waterproof and breathable membrane 6, a piezoelectric vibration element 9, and a flexible sealing connector 100.

[0031] The housing 1 includes a main housing 11 and a top cover 12, which are connected by a sealant 5. An installation cavity 10 is formed inside the housing 1. A pressure interface pipe 112 is fixedly connected to the rear end of the housing 1, and a seal 1121 is provided on the outer wall of the pressure interface pipe 112. At least partially, a pressure introduction channel 1120 is defined inside the pressure interface pipe 112, with one inner end of the pressure introduction channel 1120 communicating with the installation cavity 10 for introducing the pressure medium to be measured. The housing 1 also has a vent channel for introducing an ambient reference pressure into the installation cavity 10. An electrical connection portion 111 is provided on the housing 1, with one inner end of several terminals 3 extending into the installation cavity 10 and electrically connected to the pressure measuring assembly 2.

[0032] A ventilation channel is provided on the main housing 11, including a ventilation hole 11b extending vertically, with one outer end connected to the environment and the other inner end connected to the bottom of the mounting cavity 10. The bottom of the cavity 11a of the main housing 11 protrudes inward to form a boss 114, and the inner end of the ventilation channel extends upward to the top surface of the boss 114.

[0033] A waterproof and breathable membrane 6 is disposed on the breathable channel, specifically above the protrusion 114. The waterproof and breathable membrane 6 is preferably made of expanded polytetrafluoroethylene, which has a microporous structure that allows gas to pass through while blocking liquid water.

[0034] The piezoelectric vibrating element 9 is disposed above the waterproof and breathable membrane 6, and the waterproof and breathable membrane 6 is fixedly attached to the lower surface of the piezoelectric vibrating element 9 by the first adhesive 71. The piezoelectric vibrating element 9 and the waterproof and breathable membrane 6 together constitute a vibrating assembly.

[0035] The piezoelectric vibrating element 9 includes a first electrode layer 91, a piezoelectric material layer 92, and a second electrode layer 93. The first electrode layer 91 and the second electrode layer 93 are respectively disposed on opposite sides of the piezoelectric material layer 92, and are formed, for example, by sputtering, vapor deposition, or screen printing. The piezoelectric material layer 92 is preferably a piezoelectric ceramic material, such as lead zirconate titanate. The piezoelectric vibrating element 9 has multiple through holes 94, which penetrate the first electrode layer 91, the piezoelectric material layer 92, and the second electrode layer 93 along the thickness direction. The through holes 94 are circular holes, arranged in an array on the piezoelectric vibrating element 9, and correspond to the breathable areas of the waterproof and breathable membrane 6, ensuring that gas can pass through the piezoelectric vibrating element 9 to reach the waterproof and breathable membrane 6.

[0036] The first electrode layer 91 is electrically connected to the lower surface of the circuit board 23 of the pressure measuring assembly 2 via the first conductive adhesive 81. The second electrode layer 93 is electrically connected to the lower surface of the circuit board 23 via the lead wire 201.

[0037] The piezoelectric vibrating element 9 generates high-frequency vibration under the action of a driving voltage. Specifically, when an AC driving voltage is applied between the first electrode layer 91 and the second electrode layer 93, the piezoelectric material layer 92 undergoes axial expansion and contraction deformation in the thickness direction. This deformation causes the piezoelectric vibrating element 9 to vibrate at a high frequency along the thickness direction, and transmits this vibration to the waterproof and breathable membrane 6. Since the piezoelectric vibrating element 9 is located above the waterproof and breathable membrane 6, it drives the waterproof and breathable membrane 6 to vibrate along the thickness direction during vibration, causing the clear water adhering to the lower surface (outer surface) of the waterproof and breathable membrane 6 to atomize and be discharged.

[0038] like Figure 1As shown, the flexible sealing connector 100 is connected between the vibration assembly and the housing 1, forming a flexible sealing connection between the vibration assembly and the housing 1. Specifically, the flexible sealing connector 100 has at least a bellows portion, and a flange portion 102 is provided at the end of the bellows portion. The flange portion 102 is connected to the housing 1 or the vibration assembly through a mating portion 101 of the component. The mating portion 101 of the component adopts a tight fit or a threaded fit. One end of the flexible sealing connector 100 is sealed to the outer edge of the vibration assembly, and the other end is sealed to the boss 114 of the housing 1. The flexible sealing connector 100 is a rubber bellows, which has good flexibility and elasticity, and can absorb the vibration generated by the piezoelectric vibration element 9, prevent the vibration from being transmitted to the housing 1, and at the same time ensure the airtightness between the venting channel and the mounting cavity 10.

[0039] The pressure measurement assembly 2 includes a substrate 22, a pressure-sensitive element 20, and a circuit board 23. The substrate 22 has a pressure through-hole 22a extending through both sides. One outer end of the pressure through-hole 22a communicates with one inner end of the pressure inlet channel 1120 via the central hole 21a of an annular sealing gasket 21. The pressure-sensitive element 20 is sealed and fixed to the end of the pressure through-hole 22a furthest from the pressure inlet channel 1120, i.e., the upper end in the figure. Further, the pressure measurement assembly 2 may include the annular sealing gasket 21. The circuit board 23 is fixed to the upper side of the substrate 22, and the circuit board 23 may have a vent hole 23b. The upper surface of the circuit board 23 has a processing circuit electrically connected to the pressure-sensitive element 20 via leads. The circuit board 23 is a multilayer circuit board, and it has a stepped hole 23a surrounding the pressure-sensitive element 20 and the leads. The stepped hole 23a is filled with a protective gel covering the pressure-sensitive element 20 and the leads.

[0040] The piezoelectric vibrating element 9 is electrically connected to the processing circuit. The processing circuit includes a drive circuit for applying a drive voltage to the piezoelectric vibrating element 9. The drive voltage is an AC voltage with a frequency range of 20 kHz to 200 kHz. The drive circuit is configured to drive the piezoelectric vibrating element 9 intermittently.

[0041] The outer casing 1 has multiple terminals 3, and a fisheye pin 4a is formed on the inner side of each terminal 3. The pressure measuring component 2 includes a circuit board 23, on which multiple metallized connection holes 23c are correspondingly provided. The fisheye pins 4a are tightly fitted and electrically connected to the metallized connection holes 23c. The pressure sensor may also include at least one fisheye pin 4b, the lower end of which is integrally molded into the main casing 11. The circuit board 23 has a C-shaped structure and is made of ceramic or metal material. An upper electrode layer 231 and a lower electrode layer 232 are respectively provided on the upper and lower surfaces of the circuit board 23. The upper electrode layer 231 is electrically connected to the processing circuit through a conductive adhesive, and the lower electrode layer 232 is electrically connected to the piezoelectric vibration element 9.

[0042] When the pressure sensor is working, the pressure medium to be measured enters through the pressure introduction channel 1120 and acts on the lower surface of the pressure-sensitive element 20. The ambient reference pressure enters the mounting cavity 10 through the vent 11b, the interior of the flexible sealing connector 100, the through hole 94 on the piezoelectric vibration element 9, and the waterproof and breathable membrane 6, and acts on the upper surface of the pressure-sensitive element 20. The pressure-sensitive element 20 outputs a differential pressure electrical signal of the medium to be measured relative to the ambient reference pressure. After being processed by the processing circuit on the circuit board 23, the signal is led out from the electrical connection part 111 through the terminal 3 and the fisheye pin 4a.

[0043] When water accumulates on the surface of the waterproof and breathable membrane 6, the drive circuit in the processing circuit applies an AC drive voltage to the piezoelectric vibration element 9. The piezoelectric vibration element 9 generates high-frequency stretching vibration in the thickness direction, driving the waterproof and breathable membrane 6 to vibrate synchronously, causing the water on the lower surface of the membrane to atomize into micron-sized water droplets, which are then discharged outward under the action of vibration, thereby restoring the unobstructed air passage.

[0044] Second Embodiment Reference Figure 2 In the second embodiment, the flexible sealing connector 100 has a connection structure different from that in the first embodiment. In this embodiment, the flange portion 102 at the bellows end of the flexible sealing connector 100 is connected to the vibration assembly via a mating portion 101 of the component, and the mating portion 101 of the component is threaded. The other end of the flexible sealing connector 100 is sealed to the boss 114 of the housing 1 by an adhesive.

[0045] In this embodiment, the flexible sealing connector 100 is a silicone bellows or a fluororubber bellows. Silicone bellows have good temperature and weather resistance, making them suitable for working environments with a wide temperature range; fluororubber bellows have excellent chemical corrosion resistance, making them suitable for applications involving contact with corrosive gases.

[0046] The other structures in this embodiment are the same as those in the first embodiment, and will not be described again here.

[0047] Third Embodiment Reference Figure 3 This embodiment illustrates the specific structure of the piezoelectric vibrating element 9. The piezoelectric vibrating element 9 includes a first electrode layer 91, a piezoelectric material layer 92, and a second electrode layer 93, on which multiple through holes 94 are formed. The through holes 94 are circular holes arranged in an array. In a third embodiment, the through holes 94 can also be slit-shaped holes, with multiple slit-shaped holes distributed radially or parallelly on the piezoelectric vibrating element 9. This shape of through holes can ensure air permeability while reducing the weakening of the structural strength of the piezoelectric vibrating element 9 and helps to form a more uniform vibration distribution.

[0048] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A pressure sensor, characterized in that, include: The outer shell (1) has an installation cavity (10) inside. A pressure interface pipe (112) is fixedly connected to the rear end of the outer shell (1). A sealing element (1121) is provided on the outer wall of the pressure interface pipe (112). A pressure introduction channel (1120) for introducing the pressure medium to be measured is provided inside the pressure interface pipe (112) and communicates with the installation cavity (10). The outer shell (1) is provided with a venting channel for introducing the ambient reference pressure into the installation cavity (10). The pressure measurement component (2) is enclosed at one end of the inner side of the pressure introduction channel (1120) and is used to receive the relative pressure of the medium to be measured relative to the ambient reference pressure. A waterproof and breathable membrane (6) is disposed on the breathable channel; A piezoelectric vibration element (9) is disposed above the waterproof and breathable membrane (6); A flexible sealing connector (100) is connected between the vibration assembly consisting of the piezoelectric vibration element (9) and the waterproof and breathable membrane (6) and the outer shell (1), so that the vibration assembly and the outer shell (1) form a flexible sealing connection.

2. The pressure sensor according to claim 1, characterized in that, The flexible sealing connector (100) has at least a bellows section, and the end of the bellows section is provided with a flange section. The flange section is connected to the housing (1) or the vibration assembly through a mating part of the component. The mating part of the component adopts a tight fit or a threaded fit.

3. The pressure sensor according to claim 1, characterized in that, The flexible sealing connector (100) is a rubber bellows, silicone bellows, or fluororubber bellows.

4. The pressure sensor according to claim 1, characterized in that, One end of the flexible sealing connector (100) is sealed to the outer edge of the vibration assembly, and the other end is sealed to the boss (114) of the outer shell (1) or the inner wall of the ventilation channel.

5. The pressure sensor according to claim 1, characterized in that, The piezoelectric vibration element (9) includes: a first electrode layer (91), a piezoelectric material layer (92), and a second electrode layer (93). The first electrode layer (91) and the second electrode layer (93) are respectively disposed on opposite sides of the piezoelectric material layer (92). The piezoelectric vibration element (9) has at least one through hole (94). The through hole (94) penetrates the first electrode layer (91), the piezoelectric material layer (92), and the second electrode layer (93) along the thickness direction. The through hole (94) corresponds to at least a portion of the breathable area of ​​the waterproof and breathable membrane (6). The piezoelectric vibration element (9) generates high-frequency vibration under the action of driving voltage and transmits the vibration to the waterproof and breathable membrane (6) so that the water adhering to the waterproof and breathable membrane (6) is atomized and discharged.

6. The pressure sensor according to claim 5, characterized in that, The vibration direction of the piezoelectric vibration element (9) is its axial extension direction, which is along the thickness direction of the piezoelectric vibration element (9), so that the piezoelectric vibration element (9) generates extension and contraction deformation in the thickness direction, thereby driving the waterproof and breathable membrane (6) to vibrate in the thickness direction.

7. The pressure sensor according to claim 1, characterized in that, The through hole (94) is a circular hole, a square hole or a slit-shaped hole, and multiple through holes (94) are arranged in an array on the piezoelectric vibration element (9).

8. The pressure sensor according to claim 1, characterized in that, The first electrode layer (91) is electrically connected to the lower surface of the circuit board (23) of the pressure measuring component (2) through the first conductive adhesive (81), and the second electrode layer (93) is electrically connected to the lower surface of the circuit board (23) through the lead wire (201).

9. The pressure sensor according to claim 1, characterized in that, The waterproof and breathable membrane (6) is fixedly bonded to the lower surface of the piezoelectric vibration element (9) by a first adhesive (71).

10. The pressure sensor according to claim 1, characterized in that, The pressure measurement component (2) includes: A substrate (22) is sealed to one end of the pressure introduction channel (1120). A pressure-sensitive element (20) fixed to the substrate (22) and receiving the pressure of the medium to be measured and the ambient reference pressure and generating a corresponding differential pressure electrical signal; and a processing circuit disposed on the surface of the substrate (22) and electrically connected to the pressure-sensitive element (20).

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