Pressure transducer

Abstract

The invention relates to a pressure transducer (1) for determining and / or monitoring a first pressure (p1) of a medium (2), comprising - a housing (3) with a first pressure sensor (5) provided therein, - a process adapter (8) with a membrane system (9) having a first separating membrane (10) and a second separating membrane (11) which are arranged with respect to one another in such a way that a first intermediate space (12) is enclosed between the first separating membrane (10) and the second separating membrane (11), - a capillary (14) with a through-opening (15), - a sleeve (16) which is pressure-tightly connected to the process adapter (8) and to the housing (3) and surrounds the capillary (14) such that a second intermediate space (17) is formed between the capillary (14) and the sleeve (16), the second intermediate space being fluidically connected to the first intermediate space (12), and the sleeve (16) and the capillary (14) being designed, in at least one portion in which the sleeve (16) surrounds the capillary (14), in such a way that the cross-section of the pressure transducer (1) has a material proportion of at most 90% in the at least one portion, and - a monitoring unit (19) which is designed to monitor the second intermediate space (17).

Description

[0001] Pressure sensor

[0002] The invention relates to a pressure sensor for determining and / or monitoring a first pressure of a medium.

[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] A ceramic pressure sensor, for example, comprises a ceramic base and a ceramic measuring diaphragm, which is pressure-tightly bonded to the base using an active brazing alloy to form a measuring chamber. Silicon chips, typically bonded to a silicon substrate, are also known as pressure sensors. Furthermore, the pressure sensor usually includes a transducer for converting pressure-dependent deformation of the measuring diaphragm into a primary electrical signal, as well as a primary signal path extending through the base. The transducer can be, for example, a capacitive or a resistive transducer. The primary signal path usually includes at least one electrical feedthrough through the base.

[0006] In the case of absolute and relative pressure sensors, the pressure of the medium is measured by means of one, and in the case of differential pressure sensors, by means of two, pressure-sensitive diaphragms facing the process. Each diaphragm has an associated diaphragm bed, which typically serves to emboss the diaphragm and to limit its movement in case of overload. Additionally, a pressure transmission medium is used, which transmits the pressure of the medium acting on the diaphragm to one of the two surfaces of the pressure sensor via a pressure transmission path. The diaphragm is usually mounted on a process adapter.

[0007] If the diaphragm breaks or is damaged, the medium can penetrate the pressure sensor and contaminate and / or even damage it. To prevent this, German patent application DE 199 49 831 B4 discloses a diaphragm system consisting of two parallel diaphragms, one facing the medium and the other facing the pressure fluid. A vacuum-sealed space is provided between the two diaphragms. A sensing device monitors changes in the vacuum within this space. Because the sensing device is mounted on the process flange and thus close to the process, it is exposed to potentially high process temperatures. Therefore, such a pressure sensor can only be used at low process and ambient temperatures.It is therefore an object of the present invention to provide a pressure sensor which can also be used at elevated process and ambient temperatures.

[0008] The problem is solved according to the invention by claim 1.

[0009] According to the invention, the problem is solved by a pressure sensor for determining and / or monitoring a first pressure of a medium with

[0010] - a housing with a measuring mechanism arranged therein and a first pressure sensor arranged in the measuring mechanism, which can be subjected to the first pressure of the medium on a first surface and to a second pressure on a second surface,

[0011] - a process adapter with a membrane system comprising a first separation membrane and a second separation membrane, which are arranged relative to each other such that the first separation membrane faces the medium and the second separation membrane faces away from the medium and a first space is enclosed between the first separation membrane and the second separation membrane, wherein the first separation membrane and the second separation membrane are pressure-tightly attached to the process adapter, forming a pressure chamber between the second separation membrane and the process adapter, wherein the membrane system is designed to transmit the first pressure to the pressure chamber,

[0012] - a capillary with a through-hole, wherein the capillary is designed to transmit the initial pressure from the pressure chamber to the first surface,

[0013] - a sleeve which is pressure-tightly connected to the process adapter and the housing and surrounds the capillary in such a way that a second space is formed between the capillary and the sleeve, wherein the second space is fluidically connected to the first space by means of a first channel arranged in the process adapter, wherein the sleeve and the capillary are designed in at least one section in which the sleeve surrounds the capillary in such a way that a cross-section of the pressure sensor in the at least one section has a material content of at most 90%,

[0014] - a monitoring unit designed to monitor the second interstitial space.

[0015] By ensuring that the material fraction in the cross-section of at least one section is a maximum of 90%, the thermal resistance between the process connection and the housing is increased, thus reducing heat flow from the process connection to the housing. Due to the lower heat flow and the positioning of the monitoring unit at a distance from the process adapter, the pressure sensor can be used at higher temperatures than previously possible. A cross-section is defined as a view of the pressure sensor perpendicular to a longitudinal axis of the sleeve and / or the capillary. The monitoring unit can be located in the sleeve or in the housing. The monitoring unit is specifically located in the space between the sleeve and the housing. The materials of the sleeve and the capillary are considered the material or part of the material fraction. Any pressure transmission fluid or other fluid present in the through-hole is also considered.Fluid present in the second space is not included in the material fraction. Only solids are counted towards the material fraction. At least one section can extend over at least half the length of the sleeve, and in particular over at least three-quarters of the sleeve's length. This increases the thermal resistance particularly effectively.

[0016] The proportion of air or vacuum and pressure transmission fluid is at least 10% in at least one section. The first and second spaces are, in particular, evacuated or contain a vacuum. Thus, absolute pressure is zero in both spaces, where "absolute pressure zero" as used in the application refers to a technically feasible vacuum with a pressure of less than 100 mbar, and in particular less than 10 mbar. The sleeve may have an access bore designed to allow evacuation of the first and second spaces. After the vacuuming process, the access bore is closed, for example, with a bolt or pin. A fluidic connection may, in particular, be pneumatically designed when a gas or a vacuum is present.

[0017] The second space is arranged around the sleeve. The pressure chamber and the through-hole can be filled with a pressure transmission fluid, particularly a hydraulic fluid. The capillary is designed such that the diameter of the through-hole is larger than the thickness of a wall of the capillary. The wall of the capillary can therefore be narrow compared to the through-hole. Thus, the through-hole is surrounded by a relatively thin wall and separated from the second space by this wall. The sleeve and the capillary are arranged between the housing and the process adapter. The pressure sensor is, in particular, a silicon chip. The first surface can be arranged opposite the second surface. The first separating membrane and the second separating membrane can be connected to a circumferential edge of the process adapter. If necessary,The measuring device can have a pressure transmission line that fluidically connects the through-hole to the first surface.

[0018] In the event of a leak, i.e., damage to the first separating membrane, medium will enter the first and second intermediate spaces. This is detected by the monitoring unit. Optionally, the pressure sensor can have a display unit designed to receive a signal from the monitoring unit and display a warning in the event of a leak. The monitoring unit can be designed to send a signal to the display unit indicating a leak. The monitoring unit can also be designed to monitor the condition of the second intermediate space.

[0019] In one embodiment, the monitoring unit is a second pressure sensor. Alternatively, the monitoring unit can be a conductivity sensor or a capacitive sensor. Regarding a possible embodiment of the monitoring unit as a second pressure sensor, reference is made to patent application DE 102024123597.7. Other pressure sensors, such as mechanical pressure switches, can also be used as alternatives.

[0020] In one embodiment, the second space is fluidically connected to a recess in the sleeve by means of a second channel arranged in the sleeve, with the monitoring unit being located in the recess. The recess can be located in a region of the sleeve adjacent to the housing.

[0021] In one embodiment, the capillary and the sleeve are aligned coaxially with each other. For the purposes of the application, coaxial means that two components, in particular the capillary and the sleeve, have the same axis of rotation. The axis of rotation can be identical to the longitudinal axis of the sleeve and / or the capillary.

[0022] In one embodiment, the distance between the capillary and the sleeve is a multiple of the diameter of the through-hole.

[0023] In one embodiment, the sleeve and the capillary are designed in at least one section where the sleeve surrounds the capillary such that the cross-section of the pressure sensor in this section has a material content of no more than 70%. This design further increases the thermal resistance and allows the pressure sensor to be used at higher temperatures.

[0024] In one embodiment, the sleeve and the capillary are designed in at least one section where the sleeve surrounds the capillary such that the cross-section of the pressure sensor in this section has a material content of no more than 50%. This design further increases the thermal resistance, allowing the pressure sensor to be used at higher temperatures, particularly at ambient temperatures up to 85°C and process temperatures up to 160°C.

[0025] In one embodiment, the pressure sensor comprises a first capillary adapter with a first end region, a second end region, and a first bore, which is configured to transmit the initial pressure from the pressure chamber to the through-hole. The first end region of the first capillary adapter is connected to the process adapter, and the second end region of the first capillary adapter is connected to the capillary. The first capillary adapter connects the capillary to the process adapter and ensures the transmission of the initial pressure from the process adapter or pressure chamber to the capillary or through-hole.

[0026] In one embodiment, the pressure sensor has a second capillary adapter with a first end region, a second end region, and a second bore, which is designed to transmit the first pressure from the through-hole to the first surface, wherein the first end region of the second capillary adapter is connected to the capillary and the second end region of the second capillary adapter is connected to the measuring mechanism. The second capillary adapter connects the capillary to the housing and ensures the transmission of the first pressure from the capillary or the through-hole to the first surface of the pressure sensor.

[0027] In one embodiment, one or more cooling fins are arranged on an outer wall of the sleeve. The cooling fins are designed to increase the heat radiation from the sleeve, particularly compared to a sleeve with a cylindrical outer wall. The use of cooling fins increases heat radiation and thus further reduces the heat flow from the process adapter to the housing. The cooling fins can be arranged in a lamellar pattern around the sleeve.

[0028] In one embodiment, the cooling fins are arranged perpendicular to a longitudinal axis of the sleeve.

[0029] In one embodiment, the first channel leads from an area between the first separating membrane and the second separating membrane to an end face of the process adapter facing the sleeve.

[0030] In one embodiment, the process adapter is connected to the sleeve by means of a circumferential, in particular orbital, weld. In another embodiment, the sleeve is connected to the housing by means of a circumferential, in particular orbital, weld.

[0031] The present invention will now be explained in more detail with reference to the following figures, Figs. 1-3. They show:

[0032] Fig. 1 : a first embodiment of the pressure sensor according to the invention.

[0033] Fig. 2: a detailed view of the membrane system.

[0034] Fig. 3: a second embodiment of the pressure sensor according to the invention.

[0035] Figure 1 shows a first embodiment of the pressure sensor 1 according to the invention. The pressure sensor 1 comprises a housing 3, a process adapter 8, a capillary 14, and a sleeve 16. A measuring unit 4 is arranged in the housing 3, in which a pressure sensor 5 is arranged. The first pressure sensor 5 can be subjected to the first pressure p1 of the medium 2 on a first surface 6 and to a second pressure, for example, ambient pressure or a second pressure of the medium 2, on a second surface 7.

[0036] The process adapter 8 has a membrane system 9, which is shown in more detail in Fig. 2. The membrane system 9 comprises a first separating membrane 10 and a second separating membrane 11, which are arranged relative to each other such that the first separating membrane 10 faces the medium 2 and the second separating membrane 11 faces away from the medium 2, and a first space 12 is enclosed between the first separating membrane 10 and the second separating membrane 11. The first separating membrane 10 and the second separating membrane 11 are pressure-tightly attached to the process adapter 8, in particular at their respective circumferential edges 10a, 11a, forming a pressure chamber 13. The membrane system 9 is designed to transmit the first pressure p1 to the pressure chamber 13. A membrane bed 27 can be associated with the first separating membrane 10. The capillary 14 has a through-opening 15 and is designed to transmit the first pressure p1 from the pressure chamber 13 to the first surface 6.The capillary 14 can optionally be attached to the process adapter 8 and the measuring device 4 by means of a first capillary adapter 22 and a second capillary adapter 24. The measuring device 4 and the process adapter 8 can each have a first pressure transmission line 28a and a second pressure transmission line 28b, which are designed to transmit the pressure from the pressure chamber 13 to the through-opening 15 and from the through-opening 15 to the first surface 6, respectively.

[0037] The sleeve 16 is pressure-tightly connected to the process adapter 8 and the housing 3 and surrounds the capillary 14 such that a second space 17 is formed between the capillary 14 and the sleeve 16. The second space 17 is fluidically, in particular pneumatically, connected to the first space 12 by means of a first channel 18 arranged in the process adapter 8. The first channel 18 can run between the space 12 and an end face 8a of the process adapter 8. The capillary 14 and the sleeve 16 can be coaxially aligned with each other. The sleeve 16 and the capillary 14 are designed in at least one section 29, in which the sleeve 16 surrounds the capillary 14, such that a cross-section of the pressure sensor 1 in the at least one section 29 has a material fraction of at most 90%. This means that a fluid and / or vacuum content of at least 10% is present in this area. In the example shown in Fig.1. At least one section 29 extends over more than half the length of the sleeve 16, so that the thermal resistance in the pressure sensor 1 is significantly increased.

[0038] The pressure sensor 1 further comprises a monitoring unit 19, which is configured to monitor the second space 17. The monitoring unit 19 can be arranged in a recess 21 of the sleeve 16 or the housing 3. In the example of Fig. 1, the monitoring unit 19 is arranged in the sleeve 16, with the recess 21 being connected to the second space 17 by means of a second channel 20. Alternatively, the second channel 20 could extend into the housing 3, and the monitoring unit 19 could be arranged at an end region of the channel 20 facing the housing 3. In Figures 1 and 3, two monitoring units 19 are shown in each figure; however, one monitoring unit 19 is sufficient. The monitoring unit 19 is, in particular, a second pressure sensor and is optionally configured to monitor the third pressure or vacuum in the second space 17.

[0039] The pressure sensor 1 can have a first capillary adapter 22 and / or a second capillary adapter 24. The first capillary adapter 22 has a first end region 22a, a second end region 22b, and a first bore 23. The first bore 23 is configured to transmit the first pressure p1 from the pressure chamber 13 to the through-hole 15. The first end region 22a and the second end region 22b of the first capillary adapter 22 are connected to the process adapter 8 and the capillary 14, respectively. The second capillary adapter 24 is connected to the capillary 14 at a first end region 24a and to the measuring unit 4 at a second end region 24b. The second capillary adapter 24 also has a second bore 25, which is configured to transmit the first pressure p1 from the through-hole to the first surface 6.

[0040] Fig. 3 shows an embodiment of the pressure sensor 1 according to the invention, in which the outer wall 16a of the sleeve 16 is provided with one or more cooling fins 26. The cooling fins 26 improve heat dissipation compared to the pressure sensor 1 in Fig. 1, in which the outer wall 16a forms a cylinder. The cooling fins 26 are arranged, in particular, perpendicular to a longitudinal axis of the sleeve 16. List of reference numerals

[0041] 1 pressure sensor

[0042] 2 Medium

[0043] 3 cases

[0044] 4 Measuring instrument

[0045] 5 first pressure sensor

[0046] 6 first area

[0047] 7 second area

[0048] 8 process adapters

[0049] 8a Front face of the process adapter

[0050] 9 Membrane system

[0051] 10 first separation membrane

[0052] 10a Edge area of ​​the first separation membrane

[0053] 11 second separating membrane

[0054] 11 a Edge area of ​​the second separating membrane

[0055] 12 first space

[0056] 13 Pressure chamber

[0057] 14 capillaries

[0058] 15 Through opening

[0059] 16 Sleeve

[0060] 16a Outer wall of the sleeve

[0061] 16b Inner wall of the sleeve

[0062] 17 second space

[0063] 18 first channel

[0064] 19 monitoring units

[0065] 20 second channel

[0066] 21 Exclusion

[0067] 22 first capillary adapter

[0068] 22a first end area of ​​the first capillary adapter

[0069] 22b second end area of ​​the first capillary adapter

[0070] 23 first borehole

[0071] 24 second capillary adapter

[0072] 24a first end area of ​​the second capillary adapter

[0073] 24b second end area of ​​the second capillary adapter 25 second bore

[0074] 26 cooling fins

[0075] 27 Membrane bed

[0076] 28a first pressure transmission line 28b second pressure transmission line

[0077] Section 29

Claims

Patent claims 1. Pressure sensor (1) for determining and / or monitoring a first pressure (p1) of a medium (2) with - a housing (3) with a measuring instrument (4) arranged therein and a first pressure sensor (5) arranged in the measuring instrument (4), which can be subjected to the first pressure (p1 ) of the medium (2) on a first surface (6) and to a second pressure on a second surface (7), - a process adapter (8) with a membrane system (9) comprising a first separation membrane (10) and a second separation membrane (11), which are arranged such that the first separation membrane (10) faces the medium (2) and the second separation membrane (11) faces away from the medium (2), and a first space (12) is enclosed between the first separation membrane (10) and the second separation membrane (11), wherein the first separation membrane (10) and the second separation membrane (11) are pressure-tightly attached to the process adapter (8) forming a pressure chamber (13) between the second separation membrane (11) and the process adapter (8), wherein the membrane system (9) is designed to transmit the first pressure (p1) to the pressure chamber (13), - a capillary (14) with a through-opening (15), wherein the capillary (14) is designed to transmit the first pressure (p1 ) from the pressure chamber (13) to the first surface (6), - a sleeve (16) which is pressure-tightly connected to the process adapter (8) and the housing (3) and surrounds the capillary (14) such that a second space (17) is formed between the capillary (14) and the sleeve (16), wherein the second space (17) is fluidically connected to the first space (12) by means of a first channel (18) arranged in the process adapter (8), wherein the sleeve (16) and the capillary (14) are designed in at least one section in which the sleeve (16) surrounds the capillary (14) such that a Cross-section of the pressure sensor (1 ) in which at least one section has a material content of at most 90%, - a monitoring unit (19) designed to monitor the second space (17).

2. Pressure transducer (1) according to claim 1, wherein the monitoring unit (19) is a second pressure sensor.

3. Pressure sensor (1 ) according to one of the preceding claims, wherein the second space (17) is fluidically connected to a recess (21 ) of the sleeve (3) by means of a second channel (20) arranged in the sleeve (16), wherein the monitoring unit (19) is arranged in the recess (21 ).

4. Pressure sensor (1) according to one of the preceding claims, wherein the capillary (14) and the sleeve (16) are aligned coaxially with each other.

5. Pressure sensor (1 ) according to one of the preceding claims, wherein the distance between the capillary (14) and the sleeve (16) is a multiple of the diameter of the through-hole (15).

6. Pressure sensor (1 ) according to one of the preceding claims, wherein the sleeve (16) and the capillary (14) are designed in at least one section in which the sleeve (16) surrounds the capillary (14) such that a cross-section of the pressure sensor (1 ) in the at least one section has a material content of at most 70%.

7. Pressure sensor (1 ) according to one of the preceding claims, wherein the sleeve (16) and the capillary (14) are designed in at least one section in which the sleeve (16) surrounds the capillary (14) such that a cross-section of the pressure sensor (1 ) in the at least one section has a material content of at most 50%.

8. Pressure sensor (1) according to one of the preceding claims, wherein the pressure sensor (1) has a first capillary adapter (22) with a first end region (22a), a second end region (22b) and a first bore (23), which is configured to transmit the first pressure (p1) from the pressure chamber (13) to the through-hole (15), wherein the first end region (22a) of the first capillary adapter (22) is connected to the process adapter (8) and the second end region (22b) of the first capillary adapter (22) is connected to the capillary (14).

9. Pressure sensor (1) according to one of the preceding claims, wherein the pressure sensor (1) has a second capillary adapter (24) with a first end region (24a), a second end region (24b) and a second bore (25), which is configured to transmit the first pressure (p1) from the through-hole (15) to the first surface (6), wherein the first end region (24a) of the second capillary adapter (24) is connected to the capillary (14) and the second end region (24b) of the second capillary adapter (24) is connected to the measuring mechanism (4).

10. Pressure sensor (1 ) according to one of the preceding claims, wherein one or more cooling fins (26) are arranged on an outer wall of the sleeve (16).

11. Pressure sensor (1) according to claim 10, wherein the cooling fins (26) are arranged perpendicular to a longitudinal axis of the sleeve (16).

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