CN115901035A - Pressure sensing assembly, thick film pressure sensitive head and pressure sensor - Google Patents

Abstract

A pressure sensing assembly, comprising: a dielectric layer; at least one pressure sensing circuit covering the top of the dielectric layer and having a plurality of sensing elements and a plurality of bonding pads including a first bonding pad; a layer of protective glaze covering the top of the other part of the pressure sensing circuit except the first bonding pad; and a conductive protection layer covering and combined on the top of the protection glaze, at least covering the sensitive element, and connected with the first bonding pad of each pressure sensing circuit, wherein the conductive protection layer is separated from the part connected with different first bonding pads. According to the pressure sensing assembly, the conductive protective layer is covered on the protective glaze, so that the surface of the glaze layer can be enhanced during severe contraction/stretching of the protective glaze, cracking or peeling of the glaze layer is avoided, electromagnetic interference on a pressure sensing circuit can be shielded, and the measurement accuracy is improved; in addition, the electrical connection stability of the corresponding pad can be improved.

Description

Pressure sensing assembly, thick film pressure sensitive head and pressure sensor

Technical Field

The invention relates to the technical field of pressure sensors, in particular to a pressure sensing assembly, a thick film pressure sensing head and a pressure sensor.

Background

The thick film pressure sensor is a pressure sensor for measuring pressure by utilizing piezoresistive effect of a thick film resistor, and a thick film pressure sensitive head of the thick film pressure sensor obtains a measuring signal through a Wheatstone bridge which is fixed on the back surface of a measuring diaphragm and consists of a piezoresistor. Thick film pressure sensors are capable of measuring relatively large pressures, such as the thick film pressure sensor disclosed in CN112857635A, which can be used for pressure measurement of brake hydraulic systems and the like. Similar thick film pressure sensors are typically provided with a protective encapsulation glaze over the pressure sensing element. The encapsulation glaze belongs to low-temperature glass, and is mostly borate or phosphate glass, and the thermal expansion coefficient of the encapsulation glaze and the dielectric layer has some difference. Therefore, the glaze layer can crack due to repeated or severe temperature changes, the resistance value of the resistor can drift, and even the resistor can be stripped from the dielectric layer to be completely ineffective in severe cases; on the other hand, the pressure sensing circuit is also at risk of being electromagnetically disturbed when in operation.

Disclosure of Invention

In view of the deficiencies of the prior art, the present invention seeks to provide a pressure sensing assembly to improve its service life.

The present invention provides a pressure sensing assembly, comprising:

a dielectric layer;

at least one pressure sensing circuit covering the top of the dielectric layer and having a plurality of sensitive elements and a plurality of bonding pads including a first bonding pad;

a layer of protective glaze covering the top of the other part of the pressure sensing circuit except the first bonding pad;

and a conductive protective layer covering and bonded on top of the protective glaze, covering at least the sensitive elements, and connected to the first pads of each pressure sensing circuit, the conductive protective layer and the parts connected to different first pads being mutually connected.

Preferably, the protective glaze has a first covering part, a first avoidance part and a second avoidance part, the first covering part covers the other parts of the pressure sensing circuit except the bonding pad, the first bonding pad is opposite to the second avoidance part, and the other bonding pads are opposite to the first avoidance part; the first bonding pad penetrates through the second spare position part and is connected with the conductive protective layer.

Preferably, the conductive protection layer has a second covering part and a third relief part, and the second covering part covers the first pad and other parts of the pressure sensing circuit except the pad.

Preferably, the first abdicating part and/or the third abdicating part and/or the second abdicating part include a window provided on the protective glaze and/or a notch formed by inward contraction of the edge of the protective glaze.

Preferably, the pressure third element comprises a first resistor, a second resistor, a third resistor and a fourth resistor which are sequentially connected end to form a Wheatstone bridge; the connection parts of the first resistor and the second resistor, the second resistor and the third resistor, the third resistor and the fourth resistor, and the fourth resistor and the first resistor are electrically connected to the first pad, the second pad, the third pad and the fourth pad in a one-to-one correspondence manner; the first resistor and the third resistor are both piezoresistors.

Preferably, the pressure sensing circuit further comprises a thermistor, the first pad or the third pad is electrically connected to one end of the thermistor, and the other end of the thermistor is electrically connected to the fifth pad.

Preferably, the conductive protective layer is formed by sequentially screen-printing metal slurry on the top of the protective glaze and then firing.

The invention also claims a thick film pressure sensitive head comprising:

the pressure sensing assembly;

the metal cylinder is internally provided with a longitudinally extending leading-in channel of which the bottom end is used for leading in the fluid to be measured, and the top end of the leading-in channel is plugged with an elastic metal diaphragm; the bottom of the medium layer of the pressure sensing assembly is attached and fixed on the outer side wall of the elastic metal diaphragm.

Preferably, a partition board is longitudinally arranged in the guide-in channel, one end of the partition board extends to the inner side wall of the elastic metal membrane and transversely divides the guide-in channel into a first guide-in cavity and a second guide-in cavity; the two pressure sensing circuits are longitudinally corresponding to the first lead-in cavity and the second lead-in cavity one by one.

The invention also requires a pressure sensor comprising the thick film pressure sensitive head.

According to the pressure sensing assembly, the conductive protective layer is covered on the protective glaze, so that the surface of the glaze layer can be enhanced during severe contraction/stretching of the protective glaze, cracking or peeling of the glaze layer is avoided, electromagnetic interference on a pressure sensing circuit can be shielded, and the measurement accuracy is improved; in addition, the electrical connection stability of the corresponding pad can be improved.

Drawings

FIG. 1 is a perspective view of a thick film pressure sensitive head of a preferred embodiment;

FIG. 2 is an exploded view of a thick film pressure sensitive head of a preferred embodiment;

FIG. 3 is a top view of a thick film pressure sensitive head of a preferred embodiment;

FIG. 4 isbase:Sub>A plan cross-sectional view ofbase:Sub>A thick film pressure sensitive head ofbase:Sub>A preferred embodiment taken along A-A shown in FIG. 3;

FIG. 5 is a schematic view of the interlayer structure of a pressure sensitive element according to a preferred embodiment;

FIG. 6 is a perspective view of another preferred embodiment thick film pressure sensitive head;

FIG. 7 is a top view of another preferred embodiment of a thick film pressure sensitive head;

FIG. 8 isbase:Sub>A plan cross-sectional view of another preferred embodiment ofbase:Sub>A thick film pressure sensitive head taken along A-A shown in FIG. 2;

FIG. 9 is a top view of a portion of another preferred embodiment of a pressure sensing assembly;

FIG. 10 is a top view of a portion of a pressure sensing assembly in accordance with yet another preferred embodiment;

FIG. 11 is a perspective view of a preferred embodiment pressure sensor;

FIG. 12 is a top view of a preferred embodiment pressure sensor;

FIG. 13 is a plan sectional view of a preferred embodiment of the pressure sensor taken along B-B shown in FIG. 7;

FIG. 14 is a perspective cross-sectional view (with portions broken away) of a preferred embodiment of the pressure sensor taken along line B-B shown in FIG. 7;

FIG. 15 is a perspective view of a first support of a preferred embodiment;

FIG. 16 is a perspective view of a second support member of a preferred embodiment;

FIG. 17 is a perspective view of a circuit board of a preferred embodiment;

FIG. 18 is a perspective view of a preferred embodiment protective head;

in the figure: 1. a metal cylinder; 10. a connecting seat; 100. a thick film pressure sensitive head; 101. an elastic metal diaphragm; 102. an isolation trench; 103. a mating connection portion; 104. supporting the step surface; 105. a first support surface; 106. A sealing groove; 107. a lead-in channel; 107a, a first introduction cavity; 107b, a second introduction cavity; 108. a partition plate; 109. a circumferential positioning structure; 109a, positioning cutting grooves; 11. a protective head; 110. a flange plate; 111. a columnar head; 112. a recess; 113. a support leg; 114. inserting a core; 117. positioning the blind hole; 115. a gap; 116. positioning and trimming; 12. a second support member; 120. a second support leg; 120a, edges; 130. a support leg positioning notch; 2. a housing; 201. curling; 3. a first support member; 301. a support plate; 302. a first supporting leg plate; 303. a abdication gap; 304. a positioning column; 4. a dielectric layer; 5. a pressure sensing assembly; 50. a pressure sensing circuit; 501. a first resistor; 502. a second resistor; 503. a third resistor; 504. a fourth resistor; 505. a thermistor; 506. a conductor; 50a, a first pad; 50b, a second pad; 50c, a third pad; 50d, a fourth pad; 50e, a fifth pad; 6. a circuit board; 601. a connecting plate; 602. a first mounting plate; 603. a second mounting plate; 604. a second connecting plate; 605. a first connecting plate; 606. positioning the through hole; 607. a pin mounting hole; 7. conditioning the chip; 8. a seal ring; 9. a pin; 140. inserting holes;

Detailed Description

The technical scheme of the invention is clearly and completely described in the following with reference to the accompanying drawings. The following examples are illustrative only and are not to be construed as limiting the invention. In the following description, the same reference numerals are used to designate the same or equivalent elements, and the repetitive description is omitted.

In the description of the present invention, it is to be understood that the terms "upper", "lower", "inside", "outside", "left", "right", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, or the orientations or positional relationships that the products of the present invention are conventionally placed in use, or the orientations or positional relationships that are conventionally understood by those skilled in the art, and are used for convenience of describing the present invention and simplifying the description, but do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention.

In addition, the terms "mounted," "connected," and "connected" are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood as appropriate by those of ordinary skill in the art.

It should be further understood that the term "and/or" as used in this specification and the corresponding claims refers to any and all possible combinations of one or more of the listed items.

As shown in fig. 1-5. In a preferred embodiment of the present invention, the pressure sensing assembly 5 includes a dielectric layer 4, a pressure sensing circuit 50, and a layer of protective glaze 03. The pressure sensing circuit 50 covers the top of the dielectric layer 4, and has a plurality of sensing elements and a plurality of bonding pads, wherein the plurality of bonding pads include a first bonding pad 50a, and the plurality of sensing elements include a plurality of resistors 500. The sensing element and the plurality of pads are electrically connected by a conductor 506. The protective glaze 03 covers the top of the other portions of the pressure sensing circuit 50 except for the first pads 50 a. Preferably, a conductive protection layer 04 covers the top of the protective glaze 03, and the conductive protection layer 04 at least covers the sensitive element and is fixed and electrically connected with the first pad 50 a.

According to the pressure sensing assembly, the conductive protective layer is covered on the protective glaze, so that the surface of the glaze layer can be enhanced during severe contraction/stretching of the protective glaze, cracking or peeling of the glaze layer is avoided, electromagnetic interference on a pressure sensing circuit can be shielded, and the measurement accuracy is improved; in addition, the electrical connection stability of the corresponding pad can be improved.

Specifically, the protective glaze 03 may have a first covering portion 31, a first position-avoiding portion 32 and a second position-avoiding portion 30. The first cover part 31 covers the other portions of the pressure sensing circuit 50 except for the pads. The first pad 50a faces the second escape portion 30, and the other pads face the first escape portion 32. The first pad 50a is connected to the conductive protective layer 04 through the second bit escape portion 30. The conductive protection layer 04 may have a second covering portion 41 and a third position-giving portion 42. The second cover part 41 covers the first pad 50a and the other portions of the pressure sensing circuit 50 except for the pad. The first abdicating part 32, the third abdicating part 42 and the second abdicating part 30 may each include one or more windows formed in the protective glaze 03 and/or one or more notches formed by inward contraction of the edge of the protective glaze 03.

The resistors 500 may include a first resistor 501, a second resistor 502, a third resistor 503, and a fourth resistor 504. The first resistor 501, the second resistor 502, the third resistor 503 and the fourth resistor 504 are sequentially connected end to form a wheatstone bridge. The junctions of the first resistor 501 and the second resistor 502, the second resistor 502 and the third resistor 503, the third resistor 503 and the fourth resistor 504, and the fourth resistor 504 and the first resistor 501 are electrically connected to the first pad 50a, the second pad 50b, the third pad 50c, and the fourth pad 50d in a one-to-one correspondence. The first resistor 501 and the third resistor 503 are both piezoresistors. Preferably, the first resistor 501 and the third resistor 503 are close to each other, and the centers of the first resistor 501 and the third resistor 503 are longitudinally opposite to the center of the first lead-in cavity 107a or the second lead-in cavity 107b.

In other embodiments, the pressure sensing circuit 50 further comprises a thermistor 505. The first pad 50a or the third pad 50c is electrically connected to one end of the thermistor 505. The other end of the thermistor 505 is electrically connected to a fifth pad 50e.

The conductive protective layer 04 can be formed by printing a metal paste on the top of the protective glaze 03 through screen printing and then firing. The resistors and the pads are electrically connected by a conductor 506.

Please refer to fig. 1-4. The thick film pressure sensitive head 100 may include a metal can 1, a diaphragm 108, and pressure sensing circuitry 50. A longitudinally extending introduction passage 107 is provided in the metal tube 1. The bottom end of the introduction channel 107 is used for introducing the fluid to be measured, and the top end of the introduction channel 107 is sealed by the elastic metal diaphragm 101. The bottom of the medium layer 4 of the pressure sensing assembly 5 is attached and fixed on the outer side wall of the elastic metal diaphragm 101.

Referring to fig. 8-10, in other embodiments, the partition 108 is preferably disposed longitudinally in the introduction channel 107, and the top end thereof extends to the inner side wall of the elastic metal diaphragm 101. The partition 108 laterally partitions the introduction passage 107 to form a first introduction chamber 107a and a second introduction chamber 107b. The pressure sensing assembly 5 is fixed to the outer sidewall (i.e., the top end sidewall) of the elastic metal diaphragm 101. The pressure sensing assembly 5 includes two pressure sensing circuits 50. The two pressure sensing circuits 50 are longitudinally in one-to-one correspondence with the first introduction chamber 107a and the second introduction chamber 107b, so as to output corresponding measurement signals according to the deformation of the corresponding two parts of the elastic metal diaphragm 101 under the pressure of the fluid to be measured, respectively.

The thick film pressure sensitive head of the present embodiment measures the amount of deformation of the two portions of the elastic metal diaphragm by dividing the introduction channel into two introduction chambers and correspondingly by two pressure sensing circuits, respectively. The pressure sensing circuit can be manufactured by the original screen printing process at one time, so that the cost is slightly increased. Therefore, through the redundancy design, the failure problem of the pressure sensing circuit can be avoided to a great extent on the premise that the manufacturing cost is slightly improved, and the service life and the reliability of the sensor are improved.

The measurement signal is converted into a digital signal through an analog/digital conversion module, and a pressure measurement result is output after the conditioning is carried out through a conditioning circuit.

Please refer to fig. 10. In other embodiments, two pressure sensing circuits 50 may share a single thermistor 505. Thus, the manufacturing cost can be further reduced. Correspondingly, the second cover part 41 is divided into two independent areas to be respectively connected with the first pads of the two pressure sensing circuits 50.

Please refer to fig. 11-14. A pressure sensor according to a preferred embodiment of the present invention includes the thick film pressure sensitive head 100, a connecting base 10, a housing 2, and a circuit board 6. Wherein, the connecting base 10 is disposed on one side of the top end of the thick film pressure sensitive head 100. The connection socket 10 is connected with the thick film pressure sensitive head 100 through the housing 2. A mounting cavity is defined by the thick film pressure sensitive head 100, the connecting base 10 and the housing 2. The circuit board 6 is disposed in the mounting cavity and connected to the pressure sensing assembly 5.

Wherein, the middle part of the metal cylinder 1 is enlarged to form a matching connection part 103, and the lower part of the shell 2 is sleeved on the matching connection part 103 in an interference manner and is connected to a supporting step surface 104 formed on the metal cylinder 1 towards the bottom end. The upper side of the mating connection portion 103 is recessed inward to form an isolation groove 102, thereby isolating the influence of stress during mounting on the measurement result. The outer wall of the lower part of the metal cylinder 1 may be provided with a sealing groove 106, so that a sealing body is convenient to arrange when the metal cylinder is connected with a container containing a fluid to be measured.

In other embodiments, it is preferable that the middle of the metal tube 1 is provided with a circumferential positioning structure 109. Specifically, the circumferential positioning structure 109 may be a positioning notch 109a, or a straight cut edge.

Please refer to fig. 15. To facilitate the mounting of the circuit board 6, in other embodiments, the first support member 3 may be disposed within the mounting cavity. The mating connection portion 103 has a first support surface 105 facing the tip. The first support 3 includes a support plate 301 perpendicular to the longitudinal direction, and two ends of the support plate 301 in the first transverse direction each extend toward the bottom end side to form a first support foot plate 302 stopped on the first support surface 105.

As shown in fig. 16, a second support member 12 is provided in the mounting cavity to facilitate the connection between the connecting socket 10 and the metal cylinder 1. The top end of the second support member 12 stops on the bottom end of the connecting socket 10. The bottom end of the second supporting member 12 is stopped on the supporting plate 301, or more preferably, two ends of the bottom end of the second supporting member 12 along the second transverse direction respectively extend towards the bottom end to stop on the second supporting foot plate 120 on the metal cylinder 1. Wherein, the transverse first direction is vertical to the transverse second direction. Wherein, two ends of the supporting plate 301 in the second transverse direction may form an abdicating notch 303 relatively to abdicate the second supporting foot plate 120.

In other embodiments, it is preferred that the second support 12 is annular. The lateral cross-section of the second supporting leg plate 120 is arc-shaped. The edges 120a of the two lateral ends of the second supporting foot plate 120 are inwardly abutted against the flat end surface formed at the abdicating notch 303, so as to facilitate the positioning between the first supporting piece 3 and the second supporting piece 12.

As shown in fig. 17, the circuit board 6 may have a connection board 601, a first mounting board 602, and a second mounting board 603 provided in this order from the top side to the bottom side. The connection plate 601 is right from the bottom end side to the first end of the isolation groove 102 in the transverse second direction. The conditioning chip 7 and the analog/digital converter are fixedly connected to the first mounting plate 602. The first pad 50a is connected to a power source terminal, the second pad 50b is connected to a common ground terminal, and the second pad 50b and the fourth pad 50d are connected to input terminals of the analog-to-digital converter, respectively. The second mounting plate 603 has a plurality of pin mounting holes 607, and the pin mounting holes 607 are electrically connected to the bottom ends of the pins 9. In the present invention, the analog-to-digital converter is a dual-mode input analog-to-digital converter for processing the signals measured by the two pressure sensing circuits 50.

A first end of the connecting plate 601 in the transverse second direction is fixedly connected to the top end face of the elastic metal diaphragm 101. The first mounting plate 602 is connected to the first end of the second mounting plate 603 along the second transverse direction by a second longitudinal connecting plate 604. A second end of the elastic metal diaphragm 101 in the transverse second direction is connected to a corresponding end of the first mounting plate 602 by a first connecting plate 605 tilted to the tip side. The first mounting plate 602 is electrically connected to pads of the pressure sensing circuit 50. A plurality of pins 9 are attached to the second mounting plate 603.

In other embodiments, the first mounting plate 602 may have a positioning through hole 606, and the supporting plate 301 may have a positioning post 304 fixed thereon, and the positioning post 304 is disposed in the positioning through hole 606.

In other embodiments, it is preferred that the bottom end of connecting section 10 is relatively enlarged to form a flange 110. The connecting seat 10 is sleeved with a sealing ring 8. The top end of the housing 2 is rolled inward to form a rolled edge 201. The bottom-facing side of the bead 201 presses the sealing ring 8 against the flange 110. The flange 110 stops on the top end of the second support 12 towards the bottom end. The pin 9 is embedded on the connecting seat 10.

Referring to fig. 18, in other embodiments, it is preferable that a protection head 11 is fixed on the top end of the connection base 10. Specifically, the top end of the connecting base 10 is provided with an inserting hole 140 (as shown in fig. 13). The protective head 11 comprises a longitudinally extending cylindrical head 111. The bottom end of the column head 111 correspondingly extends out of a ferrule 114. The ferrule 114 is correspondingly inserted into the insertion hole 140. The bottom end periphery of the column head 111 is protruded toward the bottom end side to form a plurality of legs 113 spaced in the circumferential direction. The top end of the periphery of the connecting base 10 forms a plurality of leg positioning notches 130 for correspondingly accommodating the legs 113. The tip periphery of the cylindrical head 111 is recessed inwardly to form a plurality of circumferentially spaced recesses 112. The pin 9 is inserted through the columnar head 111 and is passed out from a through hole formed in the bottom of the concave portion 112 toward the tip side. The center of the top end of the columnar head 111 is provided with a positioning blind hole 117, and a positioning trimming 116 is formed on the outer wall of the columnar head 111, so that the columnar head can be conveniently connected and positioned with external equipment.

Preferably, the center of the ferrule 114 forms a gap 115, and the gap 115 divides the ferrule 114 in half. In this manner, the ferrule 114 can be made somewhat flexible to facilitate a mating connection with the mating opening 140.

The scope of the present disclosure is defined not by the detailed description but by the claims and their equivalents, and all modifications within the scope of the claims and their equivalents are to be construed as being included in the present disclosure.

Claims (10)

1. A pressure sensing assembly, comprising:

a dielectric layer (4);

at least one pressure sensing circuit (50) overlying the top of the dielectric layer (4) and having a plurality of sensing elements and a plurality of bonding pads including a first bonding pad (50 a);

a layer of protective glaze (03) covering the top of the other part of the pressure sensing circuit (50) except the first bonding pad (50 a);

and a conductive protective layer (04) covering and bonded on top of the protective glaze (03), covering at least the sensitive element, and connected to the first pad (50 a) of each pressure sensing circuit (50), the conductive protective layer (04) being spaced apart from portions to which different first pads (50 a) are connected.

2. The pressure sensing assembly according to claim 1, wherein the protective glaze (03) has a first covering part (31), a first position-avoiding part (32) and a second position-avoiding part (30), the first covering part (31) covers the other parts of the pressure sensing circuit (50) except the bonding pads, the first bonding pad (50 a) is opposite to the second position-avoiding part (30), and the other bonding pads are opposite to the first position-avoiding part (32); the first pad (50 a) is connected to the conductive protective layer (04) through the second dummy portion (30).

3. The pressure sensing assembly according to claim 2, wherein the conductive protection layer (04) has a second covering portion (41) and a third relief portion (42), the second covering portion (41) covering the first pad (50 a) and other portions of the pressure sensing circuit (50) except for the pad.

4. Pressure sensing assembly according to any of claims 1 to 3, characterized in that the first (32) and/or third (42) relief portion and/or the second (30) relief portion comprise a window made in the protective glaze (03) and/or a notch formed by an inward contraction of the edge of the protective glaze (03).

5. A pressure sensing assembly according to any of claims 1 to 3, wherein the pressure third element comprises a first resistor (501), a second resistor (502), a third resistor (503) and a fourth resistor (504) connected end to end in sequence to form a wheatstone bridge; the joints of the first resistor (501) and the second resistor (502), the second resistor (502) and the third resistor (503), the third resistor (503) and the fourth resistor (504), and the fourth resistor (504) and the first resistor (501) are electrically connected to the first pad (50 a), the second pad (50 b), the third pad (50 c) and the fourth pad (50 d) in a one-to-one correspondence manner; the first resistor (501) and the third resistor (503) are both piezoresistors.

6. The thick film pressure sensitive head of claim 5, wherein the pressure sensitive element further comprises a thermistor (505), the first pad (50 a) or the third pad (50 c) being electrically connected to one end of the thermistor (505), the other end of the thermistor (505) being electrically connected to the fifth pad (50 e).

7. A pressure sensing assembly according to any of claims 1 to 3, characterized in that the conductive protection layer (04) is made by firing after screen printing a metal paste on top of the protection glaze (03) in sequence.

8. A thick film pressure sensitive head, comprising:

the pressure sensing assembly (5) of any one of claims 1 to 7;

the metal cylinder (1) is internally provided with a longitudinally extending leading-in channel (107) the bottom end of which is used for leading in the fluid to be tested, and the top end of the leading-in channel (107) is blocked with an elastic metal membrane (101); the bottom of a medium layer (4) of the pressure sensing assembly is attached and fixed to the outer side wall of the elastic metal diaphragm (101).

9. The thick film pressure sensitive head of claim 8, wherein a diaphragm (108) is disposed longitudinally within said introduction channel (107), one end of said diaphragm (108) extending to an inner sidewall of said resilient metal diaphragm (101) and transversely dividing said introduction channel (107) into a first introduction chamber (107 a) and a second introduction chamber (107 b); the pressure sensing circuits (50) are two in number, and are longitudinally corresponding to the first lead-in cavity (107 a) and the second lead-in cavity (107 b) one by one.

10. A pressure sensor comprising a thick film pressure sensitive head as claimed in any one of claims 8 to 9.

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