Feed-through and pressure sensor

Abstract

The invention relates to a feed-through (1) for a pressure sensor (2), comprising: a metal main body (3) having a front face (4), an end face (5) opposite the front face (4), at least one first through-hole (6) extending between the front face (4) and the end face (5), and a reference pressure line (7), wherein a recess (8) is arranged in the front face (4), into which the reference pressure line (7) opens; at least one metal connecting element (9), which is introduced into the at least one first through-hole (6); a tube (10) having a predefined length and made of an insulating material, wherein the tube (10) is partially introduced into the recess (8) and protrudes beyond the front face (4) by a defined height (H), wherein the reference pressure line (7) opens into an interior (11) of the tube (10). The invention also relates to a pressure sensor (2).

Description

[0001] Feedthrough and pressure sensor

[0002] The invention relates to a feedthrough for a pressure sensor and a pressure sensor.

[0003] In pressure measurement technology, absolute pressure, differential pressure, and gauge pressure sensors are known. Absolute pressure sensors determine the prevailing pressure of a process medium absolutely, i.e., relative to a vacuum, while differential pressure sensors determine the difference between two different pressures of the process medium or media. With gauge pressure sensors, the pressure of the process medium to be measured is determined relative to a reference pressure, where the prevailing atmospheric pressure in the vicinity of the gauge serves as the reference pressure.

[0004] Pressure sensors have a pressure-sensitive measuring element, the so-called pressure sensor, on whose first and second surfaces pressure is applied. In the case of relative or absolute pressure sensors, the pressure of the process medium to be measured acts on the first surface of the pressure sensor, while an absolute or reference pressure acts on the second surface. In the case of differential pressure sensors, a first and a second pressure of the process medium are applied to each surface. The measuring element bends depending on the relative pressure, which is formed by the difference between the pressures applied to the two surfaces. This bending is converted by an electronic unit into an electrical signal dependent on the relative pressure, which is then available for further processing or evaluation. A distinction is made, among other things, between capacitive and piezoresistive pressure sensors.A large number of such pressure sensors are manufactured and distributed by companies of the Endress+Hauser Group.

[0005] In addition to ceramic pressure sensors, silicon chips are also used as pressure sensors, typically bonded to a silicon substrate. Silicon pressure sensors are generally subjected to the pressure of the medium to be measured via a pressure transmission medium. This medium is, for example, a hydraulic oil such as silicone oil. In the case of relative pressure sensors, one surface of the sensor is subjected to the pressure of the medium, while another surface is subjected to the reference pressure of the ambient air. In the case of differential pressure sensors, both surfaces of the sensor are subjected to the pressure of the medium. The pressure sensor is usually connected to a power supply unit via an electrical feedthrough. Therefore, creepage distances must be observed when installing the pressure sensor, as required, for example, by the IEC 60079-11 standard for intrinsic safety protection.Traditionally, a ceramic disc is glued between the pressure sensor and the feedthrough to electrically isolate the pressure sensor from the feedthrough.

[0006] It is therefore an object of the present invention to provide a feedthrough and a pressure sensor which make it easy to comply with the required creepage distances.

[0007] The problem is solved according to the invention by a device according to claim 1 and a pressure sensor according to claim 9.

[0008] According to the invention, the problem is solved by a feedthrough for a pressure sensor, comprising a base body with an end face, an end face opposite the end face, at least one first through-bore extending between the end face and the end face, and a reference pressure line, wherein a recess is arranged in the end face into which the reference pressure line opens, at least one connecting element which is inserted into the at least one first through-bore, a tube made of an insulating material with a predetermined length and an interior space, wherein the tube is partially inserted into the recess and projects beyond the end face by a defined height, and wherein the reference pressure line opens into the interior space.

[0009] The feedthrough according to the invention ensures that the required creepage distances in the pressure sensor are maintained. The tube serves as an insulator. By extending the tube a defined height beyond the end face, it is ensured that the distance between the pressure sensor and the tube is at least this defined height. Furthermore, the predetermined length of the interior or the tube can be dimensioned such that the pressure sensor is electrically isolated from the feedthrough.

[0010] The design can be used for both gauge pressure sensors and differential pressure sensors. In the context of this application, the term "reference pressure line" refers to a line for a second pressure applied to the pressure sensor. The reference pressure line can be used to transmit a reference pressure from the environment surrounding the gauge pressure sensor, or it can transmit a second pressure from the medium itself, as in the case of a differential pressure sensor. Since creepage distances in air are typically longer than in a liquid medium, the specified length of the tube for a gauge pressure sensor will generally be greater than for a differential pressure sensor.

[0011] The tube can be designed as a hollow cylinder. The length of the interior and the length of the tube can be identical. The base body can be made of stainless steel or an alloy containing at least nickel and chromium. The at least one connecting element can be electrically insulated from the base body. The at least one connecting element serves for the electrical contact of the pressure sensor. Preferably, the feedthrough has two, three, or four connecting elements. The connecting elements can serve for supplying power to the pressure sensor and for data transmission between the pressure sensor and an evaluation unit. The at least one connecting element and / or the base body can be metallic. The feedthrough can be an electrical feedthrough or a current feedthrough.

[0012] In one version, the tube is made of ceramic.

[0013] In one embodiment, the ceramic is aluminum oxide.

[0014] In one embodiment, the tube is inserted into the recess by means of a glass insert. The tube is positively connected to the metallic base body by means of a glass element and electrically insulated from the base body.

[0015] In one embodiment, the specified length is designed such that a creepage distance over the length of the interior fulfills a specified type of ignition protection. For example, the length can be 1-2 mm.

[0016] In one embodiment, the specified type of ignition protection is the Ex-i intrinsic safety type of ignition protection.

[0017] In one embodiment, the base body has a longitudinal axis, with the tube arranged parallel to this longitudinal axis. The tube can be arranged parallel to the at least one first through-hole.

[0018] In one embodiment, the at least one connecting element is inserted into at least one first through-hole by means of a glass-metal seal. The glass-metal seal serves to electrically insulate the at least one connecting element from the base body. For example, the at least one connecting element can be inserted into the at least one first through-hole by means of a glaze insert.

[0019] The problem underlying the present application is further solved according to the invention by a pressure sensor for determining and / or monitoring a first pressure of a medium, comprising a measuring unit with a recess having a bottom surface, a feedthrough according to one of the preceding claims, wherein the feedthrough is inserted into the recess such that a space is formed between the end face and the bottom surface, a pressure sensor arranged in the space and electrically connected to the at least one connecting element, which can be subjected to the first pressure of the medium on a first surface, wherein the pressure sensor is connected to the tube such that the pressure sensor can be subjected to a reference pressure on a second surface and is located a predetermined height away from the end face, and a second through-bore arranged in the measuring unit which overlaps with the reference pressure line.a first separating membrane which can be subjected to the first pressure, wherein the first separating membrane is designed to transmit the first pressure to a first pressure transmission line, the first pressure transmission line which is designed to transmit the first pressure from the first separating membrane to the first surface.

[0020] In the pressure sensor according to the invention, the pressure sensor is spaced from the feedthrough by a predetermined height. This predetermined height ensures electrical isolation of the pressure sensor from the feedthrough. In particular, the predetermined height can be adapted to a required creepage distance between the pressure sensor and the feedthrough. The reference pressure can be ambient pressure or a second pressure of the medium. The pressure sensor can be designed as a relative or differential pressure sensor.

[0021] If the pressure sensor is a differential pressure sensor, the differential pressure sensor has a second separating diaphragm and a second pressure transmission line, wherein the second separating diaphragm is configured to transmit the second pressure to the second pressure transmission line, and wherein the second pressure transmission line is configured to transmit the second pressure from the second separating diaphragm, in particular by means of the reference pressure line, to the second surface. In particular, the reference pressure line is located in the second

[0022] The pressure transmission line is arranged or is a section thereof. The second separating diaphragm can be arranged at the measuring unit. The second pressure transmission line can be arranged in the measuring unit. The differential pressure sensor can have an overload diaphragm arranged in the measuring unit. The overload diaphragm can comprise a first side and, in particular, a second side opposite the first side. In particular, the overload diaphragm is arranged such that the first side is located in the first pressure transmission line and the second side in the second pressure transmission line, or that the first side can be subjected to the first pressure and the second side to the second pressure.

[0023] The first pressure transmission line and / or the second pressure transmission line can be filled with a pressure transmission fluid. The pressure transmission fluid can be hydraulically designed and / or, for example, a silicone or vegetable oil.

[0024] In one embodiment, the pressure sensor is connected to the tube by means of gluing or soldering.

[0025] In one embodiment, the pressure sensor is connected to the at least one connecting element by means of wire bonding.

[0026] In one embodiment, the specified height is designed such that the creepage distance between the pressure sensor and the end face fulfills the specified type of ignition protection. The specified type of ignition protection can be intrinsic safety (Ex i).

[0027] The present invention will now be explained in more detail with reference to the following figures, Figs. 1-4. They show:

[0028] Fig. 1 : an embodiment of the implementation according to the invention.

[0029] Fig. 2: an embodiment of the relative pressure sensor according to the invention.

[0030] Fig. 3: a detail view of Fig. 2.

[0031] Fig. 4: an embodiment of the differential pressure sensor according to the invention.

[0032] Figure 1 shows an embodiment of a feedthrough 1 according to the invention for a pressure sensor 2. The feedthrough 1 serves for the electrical contacting of the pressure sensor 17. The feedthrough 1 comprises a metallic base body 3 with an end face 4 and an end face 5 opposite the end face 4. The base body 3 can have a cylindrical shape. At least one first through-hole 6 extends between the end face 4 and the end face 5. The at least one metallic connecting element 9 is arranged in the at least one first through-hole 6. By way of example, four first through-holes 6 with four connecting elements 9 inserted therein are shown. The at least one connecting element 9 can project beyond the end face 4 and / or the end face 5. The at least one connecting element 9 can be connected to the pressure sensor 17.The base body 3 further comprises a reference pressure line 7, which opens into a recess 8 arranged in the end face 4. The reference pressure line 7 can be configured as a bore. Ambient pressure can be supplied to the pressure sensor 17 via the reference line 7 in the case of a relative pressure sensor.

[0033] The assembly 1 also includes a tube 10 made of an insulating material, which has a predetermined length L and an interior space 11. The tube 10 can be designed as a hollow cylinder. The tube 10 is partially inserted into the recess 8 and projects a defined height H beyond the end face 4. The reference pressure line 7 opens into the interior of the tube 10. The tube 10 can be made of a ceramic, such as, in particular, aluminum oxide. The predetermined height H allows a distance between the pressure sensor 17 and the end face 4 to be set. In particular, the predetermined height H can be designed such that a creepage distance between the pressure sensor 17 and the end face 4 meets a predetermined type of ignition protection, in particular intrinsic safety. A pressure transmission element is arranged between the pressure sensor 17 and the end face 4.

[0034] The tube 10 and / or the at least one connecting element 9 can be inserted into the recess 8 or the at least one first through-hole 6 by means of a glaze insert 21. The use of glass enables electrical insulation between the connecting element and the base body or between the reference air in the interior and the base body. The base body 3 can have a longitudinal axis A. The at least one through-hole 6 and / or the tube 10 can be arranged parallel to the longitudinal axis A. The tube can be arranged such that the interior is located on a longitudinal axis 11 of the passage 1 or parallel to the at least one through-hole 6.

[0035] Figure 2 shows an embodiment of a pressure sensor 2 according to the invention, which in this example is configured as a relative pressure sensor. A detailed view is shown in Figure 3. The pressure sensor 2 comprises a measuring element 13 with a recess 14, which has a bottom surface 15. The recess 14 can be cylindrical. The feedthrough 1 is inserted into the recess 14 such that a space 16 is formed between the end face 4 and the bottom surface 15. The recess 14 can have a receiving surface 23 and the feedthrough a bearing surface 24. The receiving surface 23 and the bearing surface 24 can be configured to correspond to each other and / or to be circumferential. The receiving surface 23 can be configured to receive the bearing surface 24. Thus, the feedthrough 1 can be inserted into the recess 14 by means of the receiving surface 23 and the bearing surface 24.The feedthrough 1 and the measuring instrument 3 can be connected by means of a circumferential weld. The weld is designed in such a way that the reference pressure can pass from the second through-bore 18 into the reference pressure line 7 and, in particular, does not obstruct the transition between the reference pressure line 7 and the second through-bore 18. The feedthrough 1 can be inserted into the recess 14 up to the receiving surface 23. The feedthrough 1 can be inserted into the recess 14 such that the tube 10 faces the chamber 16.

[0036] The pressure sensor 17 is arranged in space 16. The pressure sensor 17 is electrically connected to the at least one connecting element and has a first surface 17a which can be subjected to the first pressure p1 of the medium 12. The pressure sensor 17 is connected to the tube 10 such that the pressure sensor 17 can be subjected to the reference pressure p2 on a second surface 17b, which is located opposite the first surface 17a, and is positioned a predetermined height H away from the end face 4. The pressure sensor 17 can be connected to the tube 10 by means of adhesive bonding or soldering. The measuring device 13 includes a second through-hole 18 which overlaps, and in particular aligns, with the reference pressure line 7. The reference pressure p2 can thus enter the reference pressure line 7 in the form of ambient air through the second through-hole 18 and be provided to the pressure sensor 17 on the second surface 17b through the interior 11.The first pressure p1 of the medium is transferred to the first surface 17a by means of a first separating membrane 19 and a first pressure transmission line 20, which may be filled with a pressure transmission medium.

[0037] Figure 4 shows an embodiment of a pressure sensor 2 according to the invention, which in this example is configured as a differential pressure sensor. In contrast to the previously described relative pressure sensor, the reference pressure line 7 does not overlap with a second through-bore 18, by means of which an ambient pressure is provided. Instead, the reference pressure line 7 overlaps with a second pressure transmission line 27. The differential pressure sensor also has a second separating diaphragm 26, which is configured to be subjected to a second pressure p2 of the medium 12. The second pressure transmission line 27 is configured to transmit the second pressure p2 from the second separating diaphragm 26 to the second surface 17b of the pressure sensor 17. The reference pressure line 7 can be considered a section of the second pressure transmission line 27.

[0038] Optionally, the differential pressure sensor has an overload diaphragm 28 arranged in the measuring unit 13. The overload diaphragm 28 can have a first side 28a and a second side 28b. The first side 28a can be arranged in the first pressure transmission line 20 and the second side 28b in the second pressure transmission line 27. The first pressure transmission line 20 can be configured to transmit the first pressure p1 from the first separating diaphragm 19 to the first surface 17a via the overload diaphragm 28. The second pressure transmission line 27 can be configured to transmit the second pressure p2 from the second separating diaphragm 26 to the second surface 17b via the overload diaphragm 28 and the reference pressure line 7.

[0039] Fig. 4 further shows two filling bores 29, by means of which the pressure sensor 2 can be filled with the pressure transmission medium. The filling bores 29 are closed after the filling process.

[0040] Reference symbol list

[0041] 1. Implementation 2. Pressure sensor

[0042] 3 basic shapes

[0043] 4 Front surface

[0044] 5 End surface

[0045] 6 first through hole

[0046] 7 Reference pressure line

[0047] 8 Recess 9 Connecting element

[0048] 10 tubes

[0049] 11 Interior 12 Medium

[0050] 13 Measuring device 14 Recess 15 Floor area

[0051] 16 Room 17 Pressure sensor 17a First surface 17b Second surface 18 Second through hole

[0052] 19 First separating membrane 20 First pressure transmission line 21 Glassing 22 Oil filling tube 23 Receiving surface

[0053] 24 Contact surface 25 Wire bond 26 Second separating membrane 27 Second pressure transmission line 28 Overload membrane

[0054] 28a first page 28b second page 29 Filling hole H specified height L specified length A longitudinal axis

Claims

Patent claims 1. Design (1) for a pressure sensor (2), comprising a base body (3) with an end face (4), an end face (5) opposite the end face (4), at least one first through-bore (6) extending between the end face (4) and the end face (5), and a reference pressure line (7), wherein a recess (8) is arranged in the end face (4) into which the reference pressure line (7) opens, at least one connecting element (9) which is inserted into the at least one first through-bore (6), a tube (10) made of an insulating material with a predetermined length (L), and an interior space (11), wherein the tube (10) is partially inserted into the recess (8) and projects beyond the end face (4) by a defined height (H), and wherein the reference pressure line (7) opens into the interior space (11).

2. Implementation (1) according to claim 1, wherein the tube (10) is made of a ceramic.

3. Implementation (1) according to claim 2, wherein the ceramic is aluminium oxide.

4. Implementation (1) according to one of the preceding claims, wherein the tube (10) is inserted into the recess (8) by means of a glazing (21).

5. Implementation (1) according to one of the preceding claims, wherein the specified length (L) is designed such that a creepage distance over the length of the interior (11) fulfills a specified type of ignition protection.

6. Implementation (1) according to claim 5, wherein the specified type of ignition protection is the Ex-i intrinsic safety type of ignition protection.

7. Implementation (1) according to one of the preceding claims, wherein the base body (3) has a longitudinal axis (A), wherein the tube (10) is arranged parallel to the longitudinal axis (A).

8. Implementation (1) according to one of the preceding claims, wherein the at least one connecting element (9) is inserted into the at least one first through-hole (6) by means of a glass-metal seal.

9. Pressure sensor (2) for determining and / or monitoring a first pressure (p1) of a medium (12), with a measuring mechanism (13) with a recess (14) which forms a base area (15) comprises a passage (1) according to one of the preceding claims, wherein the passage (1) is inserted into the recess (14) such that a space (16) is formed between the end face (4) and the bottom face (15), a pressure sensor (17) arranged in the space (16) and electrically connected to the at least one connecting element (9), which can be subjected to the first pressure (p1) of the medium (12) on a first surface (17a), wherein the pressure sensor (17) is connected to the tube (10) such that the pressure sensor (17) can be subjected to a reference pressure (p2) on a second surface (17b) and is located from the end face (4) by the predetermined height (H), a second through-bore (18) arranged in the measuring device (13), which overlaps with the reference pressure line (7), a first separating membrane (19), which is subjected to the first pressure (p1) is capable of being actuated, wherein the first separating membrane (19) is designed toto transmit the first pressure (p1) to a first pressure transmission line (20), the first pressure transmission line (20) which is designed to transmit the first pressure (p1) from the first separating membrane (19) to the first surface (17a).

10. Pressure sensor (2) according to claim 9, wherein the pressure sensor (17) is connected to the tube (10) by means of gluing or soldering.

11. Pressure transducer (2) according to one of claims 9-10, wherein the pressure sensor (17) is connected to the at least one connecting element (9) by means of wire bonding.

12. Pressure sensor (2) according to one of claims 9-11, wherein the predetermined height (H) is designed such that the length of the creepage distance between the pressure sensor (17) and the end face (4) fulfills the predetermined type of ignition protection.

13. Pressure sensor (2) according to one of claims 9-11, wherein the pressure sensor (2) is a relative pressure sensor.

14. Pressure sensor (2) according to one of claims 9-11, wherein the pressure sensor (2) is a differential pressure sensor, wherein the differential pressure sensor has a second separating diaphragm and a second pressure transmission line, wherein the second separating diaphragm (26) is configured to transmit the second pressure (p2) to the second pressure transmission line (27) to transmit, wherein the second pressure transmission line (27) is designed to transmit the second pressure (p2) from the second separating membrane (26) to the second surface (17b).

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