CN219104228U - 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 covered on top of the dielectric layer having a plurality of sensing elements and a plurality of pads including a first pad; a layer of protective glaze covering the top of the other parts of the pressure sensing circuit except the first bonding pad; and a conductive protection layer covering 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 and the connected parts of the different first bonding pads are mutually connected. According to the pressure sensing component, the conductive protective layer is covered on the protective glaze, so that the surface of the glaze layer can be enhanced during severe shrinkage/stretching of the protective glaze, cracking or stripping of the glaze layer is avoided, electromagnetic interference to a pressure sensing circuit can be shielded, and the measurement accuracy is improved; in addition, the electrical connection stability of the corresponding bonding pads can be improved.

Description

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

Technical Field

The utility model 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 using the piezoresistive effect of a thick film resistor, and a thick film pressure sensitive head obtains a measuring signal through a Wheatstone bridge consisting of piezoresistors and fixed on the back surface of a measuring diaphragm. Thick film pressure sensors are capable of measuring larger pressures, such as the thick film pressure sensors 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 layer of encapsulation glaze over the pressure sensing element. The encapsulation glaze belongs to low-temperature glass, is mostly borate or phosphate glass, and has a certain difference in thermal expansion coefficient with a dielectric layer. The temperature can be cycled for a plurality of times or the temperature can be changed drastically, so that the glaze layer is cracked, the resistance value of the resistor can drift, and even the glaze layer can be stripped from the dielectric layer to be completely invalid when serious; on the other hand, pressure sensing circuits also run the risk of being electromagnetically disturbed during operation.

Disclosure of Invention

In response to the deficiencies of the prior art, the present utility model is directed to providing a pressure sensing assembly to increase its useful life.

The present utility model provides a pressure sensing assembly comprising:

a dielectric layer;

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

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

and a conductive protection layer covering 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 parts of the conductive protection layer connected with the different first bonding pads are mutually connected.

Preferably, the protective glaze has a first covering portion, a first abdicating portion and a second abdicating portion, the first covering portion covers other portions of the pressure sensing circuit except the bonding pad, the first bonding pad is opposite to the second abdicating portion, and other bonding pads are opposite to the first abdicating portion; the first bonding pad passes through the second abdication part and is connected with the conductive protection layer.

Preferably, the conductive protection layer has a second cover portion and a third relief portion, and the second cover portion covers the first pad and other portions of the pressure sensing circuit except for the pad.

Preferably, the first abdicating part and/or the third abdicating part and/or the second abdicating part comprise a window formed on the protective glaze and/or a notch formed by inward shrinkage 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 first resistor, the second resistor, the third resistor, the fourth resistor and the connection parts of the fourth resistor and the first resistor are electrically connected to the first bonding pad, the second bonding pad, the third bonding pad and the fourth bonding pad in a one-to-one correspondence manner; the first resistor and the third resistor are piezoresistors.

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

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

The utility model also claims a thick film pressure sensitive head comprising:

the pressure sensing component;

the metal cylinder is internally provided with a longitudinally extending guide-in channel, the bottom end of the guide-in channel is used for guiding fluid to be tested, and the top end of the guide-in channel is blocked with an elastic metal membrane; the bottom of the dielectric layer of the pressure sensing component is adhered and fixed on the outer side wall of the elastic metal diaphragm.

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

The utility model also claims a pressure sensor comprising said thick film pressure sensitive head.

According to the pressure sensing component, the conductive protective layer is covered on the protective glaze, so that the surface of the glaze layer can be enhanced during severe shrinkage/stretching of the protective glaze, cracking or stripping of the glaze layer is avoided, electromagnetic interference to a pressure sensing circuit can be shielded, and the measurement accuracy is improved; in addition, the electrical connection stability of the corresponding bonding pads 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 is a plan cross-sectional view of a thick film pressure sensitive head of a preferred embodiment taken along A-A shown in FIG. 3;

FIG. 5 is a schematic diagram of an interlayer structure of a pressure sensitive component of 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 thick film pressure sensitive head;

FIG. 8 is a plan cross-sectional view of another preferred embodiment thick film pressure sensitive head taken along A-A shown in FIG. 2;

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

FIG. 10 is a partial structural top view of a pressure sensing assembly of yet another preferred embodiment;

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

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

FIG. 13 is a plan cross-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 (partial structure not broken) of a pressure sensor of a preferred embodiment taken along 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 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 protective head of a preferred embodiment;

in the figure: 1. a metal cylinder; 10. a connecting seat; 100. a thick film pressure sensitive head; 101. an elastic metal membrane; 102. an isolation groove; 103. a mating connection; 104. a support step surface; 105. a first support surface; 106. sealing grooves; 107. an introduction channel; 107a, a first introduction lumen; 107b, a second introduction lumen; 108. a partition plate; 109. a circumferential positioning structure; 109a, positioning slots; 11. protecting the head; 110. a flange plate; 111. a columnar head; 112. a concave portion; 113. a support leg; 114. a core insert; 117. positioning the blind hole; 115. a gap; 116. positioning and trimming; 12. a second support; 120. a second support foot plate; 120a, edges; 130. the landing leg positioning notch; 2. a housing; 201. hemming; 3. a first support; 301. a support plate; 302. a first support foot plate; 303. a relief notch; 304. positioning columns; 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, first bonding pads; 50b, second bonding pads; 50c, a third bonding pad; 50d, a fourth bonding pad; 50e, fifth bonding pads; 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 connection plate; 606. positioning the through hole; 607. pin mounting holes; 7. conditioning the chip; 8. a seal ring; 9. pins; 140. a plug hole;

Detailed Description

The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings. The following examples are illustrative only and are not to be construed as limiting the utility model. In the following description, the same reference numerals are used to designate the same or equivalent elements, and duplicate descriptions are omitted.

In the description of the present utility model, it should be understood that the directions or positional relationships indicated by the terms "upper", "lower", "inner", "outer", "left", "right", etc. are based on the directions or positional relationships shown in the drawings, or the directions or positional relationships conventionally put in place when the inventive product is used, or the directions or positional relationships conventionally understood by those skilled in the art are merely for convenience of describing the present utility model and simplifying the description, and do not indicate or imply that the apparatus or elements referred to must have a specific direction, be configured and operated in a specific direction, and therefore should not be construed as limiting the present utility model.

In addition, the terms "mounted," "connected," "coupled," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present utility model 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 the present description 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 utility model, the pressure sensing component 5 includes a dielectric layer 4, a pressure sensing circuit 50, and a layer of protective glaze 03. The pressure sensing circuit 50 is covered on 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. Electrical connection is made between the sensing element and the plurality of pads via conductors 506. The protective glaze 03 covers the top of the other portion of the pressure sensing circuit 50 except the first pad 50 a. Preferably, a conductive protection layer 04 is covered on top of the protection glaze 03, and the conductive protection layer 04 covers at least the sensitive element and is fixed and electrically connected to the first pad 50a therein.

According to the pressure sensing component, the conductive protective layer is covered on the protective glaze, so that the surface of the glaze layer can be enhanced when the protective glaze contracts or stretches severely, cracking or stripping of the glaze layer is avoided, electromagnetic interference to the pressure sensing circuit can be shielded, and the measurement accuracy is improved; in addition, the electrical connection stability of the corresponding bonding pads can be improved.

Specifically, the protective glaze 03 may have a first covering portion 31, a first relief portion 32, and a second relief portion 30. The first cover 31 covers other portions of the pressure sensing circuit 50 than the pads. The first pad 50a is facing the second relief portion 30 and the other pads are facing the first relief portion 32. The first pad 50a is connected to the conductive protection layer 04 through the second relief portion 30. The conductive protection layer 04 may have a second covering portion 41 and a third relief portion 42. The second cover 41 covers the first pad 50a and 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 include one or more windows formed on the protective glaze 03 and/or one or more notches formed by inward shrinking of the edge of the protective glaze 03.

The plurality of 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 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 junctions of 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 one-to-one correspondence. The first resistor 501 and the third resistor 503 are piezoresistors. Preferably, the first resistor 501 and the third resistor 503 are close together, and the centers of the two are longitudinally opposite to the centers of the first introducing chamber 107a or the second introducing chamber 107b, respectively.

In other embodiments, the pressure sensing circuit 50 further includes 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 may be formed by screen printing a metal paste on top of the protective glaze 03 and firing. The resistors and pads are electrically connected by electrical conductor 506.

Please refer to fig. 1-4 in combination. Thick film pressure sensitive head 100 may include a metal can 1, a diaphragm 108, and a pressure sensing circuit 50. Wherein a longitudinally extending lead-in channel 107 is provided in the metal cylinder 1. The bottom end of the introduction channel 107 is used for introducing the fluid to be tested into the introduction channel 107, and the top end of the introduction channel is blocked by the elastic metal membrane 101. The bottom of the dielectric layer 4 of the pressure sensing component 5 is adhered and fixed on the outer side wall of the elastic metal membrane 101.

Referring to fig. 8-10 in combination, in other embodiments, the partition 108 is preferably disposed longitudinally within the introduction channel 107, with its top end extending to the inside wall of the flexible metal membrane 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 element 5 is fixed to the outer side wall (i.e., the top side wall) of the elastic metal membrane 101. The pressure sensing assembly 5 includes two pressure sensing circuits 50. The two pressure sensing circuits 50 are longitudinally and one-to-one corresponding to the first introducing cavity 107a and the second introducing cavity 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.

The thick film pressure sensitive head of the present embodiment measures the deformation of two parts of the elastic metal diaphragm by dividing the lead-in channel into two lead-in cavities and correspondingly by two pressure sensing circuits. The pressure sensing circuit can be manufactured once through the original screen printing process, so that the cost is increased little. Therefore, through the redundancy design, the failure problem of the pressure sensing circuit can be avoided to a great extent on the premise of manufacturing the sensor with a small amount of improvement, and the service life and the reliability of the sensor are improved.

The measuring signal is converted into a digital signal through an analog-to-digital conversion module, and then the digital signal is conditioned by a conditioning circuit to output a pressure measuring result.

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

Please refer to fig. 11 to fig. 14 in combination. A pressure sensor according to a preferred embodiment of the present utility model comprises, in addition to the thick film pressure sensitive head 100 described above, a connection pad 10, a housing 2 and a circuit board 6. Wherein the connection base 10 is disposed at a top end side of the thick film pressure sensitive head 100. The connection base 10 is connected with the thick film pressure sensitive head 100 through the housing 2. The thick film pressure sensitive head 100, the connector 10 and the housing 2 define a mounting cavity therebetween. A circuit board 6 is disposed within the mounting cavity and is connected to the pressure sensing assembly 5.

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

In other embodiments, the middle of the metal cylinder 1 is preferably provided with a circumferential positioning structure 109. Specifically, the circumferential positioning structure 109 may be a positioning slot 109a, or a straight cut.

Please refer to fig. 15 in combination. To facilitate the mounting of the circuit board 6, in other embodiments, the first support 3 may be provided in the mounting cavity. The mating connection 103 has a first support surface 105 facing the top end. The first support 3 includes a support plate 301 perpendicular to the longitudinal direction, and both ends of the support plate 301 in the first transverse direction protrude toward the bottom end side by a first support foot plate 302 that is stopped on the first support surface 105.

As shown in fig. 16, in order to facilitate the connection between the connection socket 10 and the metal cylinder 1, a second support member 12 is provided in the installation cavity. The top end of the second support 12 is stopped on the bottom end of the connection base 10. The bottom end of the second support member 12 is stopped on the support plate 301, or more preferably, both ends of the bottom end of the second support member 12 in the second lateral direction protrude toward the bottom end, respectively, from the second support foot plate 120 stopped on the metal cylinder 1. Wherein the first transverse direction is perpendicular to the second transverse direction. Wherein, the two ends of the support plate 301 in the second transverse direction may form a yielding notch 303 to yield the second support foot plate 120.

In other embodiments, the second support 12 is preferably annular. The lateral cross section of the second supporting foot plate 120 is arc-shaped. Edges 120a of the two lateral ends of the second supporting foot plate 120 are abutted inwards on the straight end surface formed at the yielding notch 303, so that the positioning between the first supporting piece 3 and the second supporting piece 12 is facilitated.

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 disposed in order from the top side to the bottom side. The connection plate 601 is forward of the first end of the isolation groove 102 in the transverse second direction from the bottom end side. The conditioning chip 7 and the analog-to-digital converter are fixedly connected to the first mounting plate 602. The first pad 50a is connected to the power terminal, the second pad 50b may be connected to the common ground terminal, and the second pad 50b and the fourth pad 50d may be connected to the input terminal of the analog/digital converter, respectively. The second mounting plate 603 is provided with a plurality of pin mounting holes 607, and the pin mounting holes 607 are electrically connected with the bottom ends of the pins 9. In the present utility model, the analog-to-digital converter is a dual-mode input analog-to-digital converter to process the signals measured by the two pressure sensing circuits 50, respectively.

The first end of the connection plate 601 in the transverse second direction is fixedly connected to the top end face of the elastic metal membrane 101. The first mounting plate 602 is connected to a first end of the second mounting plate 603 in a second transverse direction by a second longitudinal connecting plate 604. The second end of the elastic metal membrane 101 in the second direction in the lateral direction is connected to the corresponding end of the first mounting plate 602 by a first connection plate 605 tilted toward the top end side. The first mounting plate 602 is electrically connected to pads of the pressure sensing circuit 50. The second mounting board 603 is connected to a plurality of pins 9.

In other embodiments, the first mounting plate 602 may be provided with a positioning through hole 606, and the supporting plate 301 may be correspondingly fixed with a positioning post 304, where the positioning post 304 is cooperatively disposed in the positioning through hole 606.

In other embodiments, the bottom end of the connector holder 10 is preferably 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 inwardly to form a bead 201. The bottom end side of the bead 201 presses the sealing ring 8 against the flange 110. The flange plate 110 is stopped on the top end of the second support 12 toward the bottom end. The pin 9 is embedded and fixed on the connecting seat 10.

Referring to fig. 18 in combination, in other embodiments, the protection head 11 is preferably fixed to the top end of the connection seat 10. Specifically, the top end of the connection base 10 is provided with a socket hole 140 (as shown in fig. 13). The protective head 11 comprises a longitudinally extending cylindrical head 111. The bottom end of the columnar head 111 correspondingly extends out of a ferrule 114. The ferrule 114 is correspondingly inserted into the insertion hole 140. The bottom peripheral edge of the columnar head 111 protrudes toward the bottom side to form a plurality of circumferentially spaced legs 113. The top end of the periphery of the connecting seat 10 is formed with a plurality of leg positioning notches 130 for accommodating the legs 113. The cylindrical head 111 is recessed inwardly on its top peripheral edge to form a plurality of circumferentially spaced recesses 112. The lead 9 is inserted into the columnar head 111, and is inserted out from the hole formed at the bottom of the recess 112 toward the tip end 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 with external equipment for positioning.

Preferably, a gap 115 is formed in the middle of the ferrule 114, the gap 115 separating the ferrule 114 in half. In this way, the ferrule 114 can be provided with a degree of flexibility to facilitate a mating connection with the mating bore 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) covering the top of the dielectric layer (4) having a plurality of sensing elements and a plurality of pads including a first pad (50 a);

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

and a conductive protection layer (04) covering the top of the protective glaze (03), at least covering the sensitive element, and connected with the first bonding pad (50 a) of each pressure sensing circuit (50), wherein the parts of the conductive protection layer (04) connected with the different first bonding pads (50 a) are mutually connected.

2. The pressure sensing assembly according to claim 1, wherein the protective glaze (03) has a first cover portion (31), a first relief portion (32) and a second relief portion (30), the first cover portion (31) covering other portions of the pressure sensing circuit (50) than the pads, the first pad (50 a) being opposite the second relief portion (30) and the other pads being opposite the first relief portion (32); the first bonding pad (50 a) is connected with the conductive protection layer (04) through the second abdication part (30).

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

4. A pressure sensing assembly according to any of claims 2 to 3, characterized in that the first (32) and/or third (42) and/or second (30) relief portions comprise windows open on the protective glaze (03) and/or notches formed by inward shrinkage of the edges 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 forming a wheatstone bridge; 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 connection parts of the fourth resistor (504) and the first resistor (501) are electrically connected to the first bonding pad (50 a), the second bonding pad (50 b), the third bonding pad (50 c) and the fourth bonding pad (50 d) in a one-to-one correspondence manner; the first resistor (501) and the third resistor (503) are piezoresistors.

6. The pressure sensing assembly of claim 5, wherein the pressure sensing circuit (50) further comprises a thermistor (505), the first pad (50 a) or the third pad (50 c) is electrically connected to one end of the thermistor (505), and the other end of the thermistor (505) is 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 protective layer (04) is formed by sequentially screen printing a metal paste on top of the protective glaze (03) and firing.

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 guide-in channel (107) with the bottom end for guiding fluid to be tested, and an elastic metal membrane (101) is blocked at the top end of the guide-in channel (107); the bottom of the dielectric layer (4) of the pressure sensing component is adhered and fixed on the outer side wall of the elastic metal diaphragm (101).

9. The thick film pressure sensitive head of claim 8, wherein a baffle (108) is disposed longitudinally within said lead-in channel (107), one end of said baffle (108) extending to an inner sidewall of said elastomeric metal diaphragm (101) and laterally dividing said lead-in channel (107) into a first lead-in chamber (107 a) and a second lead-in chamber (107 b); the pressure sensing circuits (50) are respectively arranged at two positions and longitudinally correspond to the first introducing cavity (107 a) and the second introducing 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.

Images