Pressure detector for determining and / or monitoring a first pressure of a medium

Abstract

The invention relates to a pressure detector (1), comprising - a measuring unit (3) having a first pressure sensor (4), - a process adapter (7) having a membrane system (8) with a first separating membrane (9) and a second separating membrane (10) which are arranged relative to each other in such a way that the first separating membrane (9) faces the medium (2) and the second separating membrane (10) faces away from the medium (2) and a first intermediate space (11) is enclosed between the first separating membrane (9) and the second separating membrane (10) - a diaphragm seal (14), - a sleeve (17) which is pressure-tightly connected to the process adapter (7) and the diaphragm seal (14) and surrounds the diaphragm seal (14) at least in sections, so that a second intermediate space (18) is formed between an outer wall (14a) of the diaphragm seal (14) and an inner wall (17a) of the sleeve (17), the second intermediate space (18) being fluidically connected to the first intermediate space (11) by means of a channel (19) arranged in the process adapter (7), - a monitoring unit (20) which is designed to monitor the second intermediate space (18).

Description

[0001] Pressure sensor for determining and / or monitoring the initial pressure of a medium

[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 pressure-sensitive diaphragm facing the process, and in the case of differential pressure sensors, by means of two. 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 the use of 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 detection device or monitoring unit, such as a pressure sensor, monitors changes in the vacuum space. The detection device is located on a bore in the process adapter, which runs along a transverse axis through the process adapter and connects the detection device to the vacuum space.The sensing device is thus arranged on the same surface of the process adapter as the pressure transmitter, which carries the pressure of the medium to the pressure sensor. Such an arrangement limits the free space in this area of ​​the process adapter and makes welding the process adapter to the sensing device more difficult.

[0008] The object of the present invention is therefore to provide a pressure sensor which enables the monitoring unit to be easily attached to the pressure sensor.

[0009] According to the invention, the problem is solved by a pressure transducer for determining and / or monitoring a first pressure of a medium, comprising a measuring mechanism 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, a process adapter with a membrane system comprising a first separating membrane and a second separating membrane, which are arranged relative to each other such that the first separating membrane faces the medium and the second separating membrane faces away from the medium and a first space is enclosed between the first separating membrane and the second separating membrane, wherein the first and second separating membranes are pressure-tightly attached to a circumferential edge on the process adapter, forming a pressure chamber between the second separating membrane and the process adapter, wherein the membrane system is designed toto transmit the first pressure to the pressure chamber, a pressure transmitter with a cylindrical base body and a first pressure transmission path arranged in the base body, which is designed to transmit the first pressure from the pressure chamber to the first surface, wherein the pressure transmitter is arranged between the measuring device and the process adapter, a sleeve which is pressure-tightly connected to the process adapter and the pressure transmitter and surrounds the pressure transmitter at least partially, so that a second space is formed between an outer wall of the pressure transmitter and an inner wall of the sleeve, wherein the second space is fluidically connected to the first space by means of a channel arranged in the process adapter, a monitoring unit which is arranged on the sleeve and is designed to monitor the second space.

[0010] Positioning the monitoring unit on the sleeve simplifies the manufacturing of the pressure sensor. Since the monitoring unit is not attached to the process adapter, the adapter can be made smaller, as is common practice in hygienic processes. Furthermore, the monitoring unit is better protected from the potentially high temperatures of the medium because it is not mounted on the process adapter. Additionally, the sleeve provides improved vibration resistance for the pressure sensor.

[0011] The second space is arranged around the pressure transmitter. The pressure chamber and the first pressure transmission path can be filled with a pressure transmission fluid, particularly a hydraulic fluid. In the event of a leak, i.e., damage to the first separating membrane, the medium will enter the first and second spaces. This is detected by the monitoring unit. Optionally, the pressure sensor can have a display unit configured to receive a signal from the monitoring unit and display a warning in the event of a leak. The monitoring unit can be configured to send a signal to the display unit indicating a leak. A fluidic connection can be pneumatically configured, particularly if a gas or vacuum is present.

[0012] Preferably, the second space is arranged coaxially with the first pressure transmission path. In particular, the sleeve can be arranged coaxially with the pressure transmitter. For the purposes of this application, coaxial means that two components, in particular the second space and the first pressure transmission path, have the same axis of rotation. The coaxial arrangement of the second space and the pressure transmission path facilitates the manufacturing of the pressure sensor. In particular, it simplifies the joining, especially welding, of the process adapter to the pressure transmitter and the sleeve, as well as the attachment of the monitoring unit.

[0013] In one embodiment, the channel leads from an area between the circumferential edges of the first separating membrane and the second separating membrane to an end face of the process adapter facing the pressure transmitter.

[0014] In a further embodiment, the process adapter is connected to the pressure transmitter and / or the sleeve by means of a circumferential, in particular orbital, weld.

[0015] One embodiment provides that the sleeve has a widening in an end region facing the process adapter, in particular such that the second space in the area of ​​the widening has a larger diameter than in a region of the sleeve adjacent to the widening. The widening can be designed as a circular shape. The widening can be designed in the form of a foot, which facilitates the connection to the process adapter, in particular by means of a weld, especially an orbital weld. The widening facilitates an overlap of the channel with the second space, since the second space is radially widened in the area of ​​the widening.

[0016] In a further embodiment, the outer wall of the sleeve is designed such that it has a wave-like contour in cross-section. This wave-like contour achieves improved temperature decoupling of the measuring instrument from the temperature of the medium.

[0017] In a further development, the monitoring unit is arranged in a recess of the sleeve. The recess can be designed such that it connects the second space to the monitoring unit. The monitoring unit can be arranged such that it is located at the second space. Preferably, the monitoring unit is a second pressure sensor, which is designed to monitor a third pressure in the second space. Alternatively, the monitoring unit can be a conductivity sensor or a capacitive sensor.

[0018] Preferably, the first and second cavities are evacuated. Thus, absolute pressure zero prevails in both cavities, 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 configured to allow the first and second cavities to be filled with or evacuated from a medium. After the filling or vacuuming process, the access bore is closed, for example, with a bolt or pin.

[0019] In one embodiment, the pressure transmitter has a stop surface in a first end area facing the measuring device and / or in a second end area facing a process adapter, wherein the measuring device and / or the process adapter have a support surface which is designed corresponding to the stop surface.

[0020] The present invention will now be explained in more detail with reference to the following figures, Figs. 1-3. They show:

[0021] Fig. 1 : an embodiment of the pressure sensor according to the invention.

[0022] Fig. 2: a detailed view of the membrane system.

[0023] Fig. 3: one embodiment of the sleeve.

[0024] Figure 1 shows a schematic embodiment of a pressure sensor 1 according to the invention. The pressure sensor 1 comprises a measuring unit 3, a pressure transmitter 14, a process adapter 7, and a sleeve 17. A first pressure sensor 4 is arranged in the measuring unit 3. This sensor can be subjected to the first pressure p1 of the medium 2 on a first surface 5 and to a second pressure on a second surface 6, in particular opposite the first surface 5. The second pressure can be ambient pressure, absolute pressure, or another pressure of the medium 2. The pressure sensor 4 can be connected to an evaluation unit 28, which determines the first pressure p1 based on a measured value generated by the pressure sensor 4. The evaluation unit 28 can be connected to a display unit 29, which is configured to display the first pressure p1.The pressure transmitter 14 has a cylindrical base body 15 and a first pressure transmission path 16 arranged therein, which may be filled with a pressure transmission fluid. The pressure transmitter 14 is arranged between the measuring unit 3 and the process adapter 7. The process adapter 7 can be connected to the pressure transmitter 14 and / or the sleeve 17, in particular by means of a circumferential, especially orbital, weld 21.

[0025] The process adapter 7 has a membrane system 8, which is arranged on the medium side. The membrane system 8 comprises a first separating membrane 9 and a second separating membrane 10, which are arranged relative to each other such that the first separating membrane 9 faces the medium 2 and the second separating membrane 10 faces away from the medium 2, and a first space 11 is enclosed between the first separating membrane 9 and the second separating membrane 10. The first separating membrane 9 and the second separating membrane 10 are each pressure-tightly attached to a circumferential edge 12a, 12b on the process adapter 7, so that a pressure chamber 13 is formed between the second separating membrane 10 and the process adapter 7. A membrane bed 26 can be associated with the second separating membrane 10.

[0026] The membrane system 8 is configured to transmit the first pressure p1 to the pressure chamber 13. The process adapter 7 can have a second pressure transmission path 16, which is fluidically connected to the pressure chamber 13. The second pressure transmission path 16 can be configured to transmit the first pressure p1 from the pressure chamber 13 to the first pressure transmission path 16. The first pressure transmission path 16 can be configured to transmit the first pressure p1 from the pressure chamber 13 or the second pressure transmission path 30 to the first surface 5. A further, third pressure transmission path 31 can also be arranged in the measuring device 3, which fluidically connects the first pressure transmission path 16 to the first surface 5.

[0027] The sleeve 17 surrounds the pressure transmitter 14, at least partially, so that a second space is formed between an outer wall 14a of the pressure transmitter 14 and an inner wall 17a of the sleeve 17. As shown in Fig. 1, the sleeve 17 can surround the pressure transmitter 14 from its first end region 24 to its second end region 25. The sleeve 17 is pressure-tightly connected to both the process adapter 7 and the pressure transmitter 14, in particular by means of a weld 21, especially an orbital weld. The process adapter 7 has a channel 19, which is arranged and configured such that the channel 19 fluidically connects the first space 11 with the second space 18. The channel 19 can lead from an area between the circumferential edges 12a, 12b of the first separating membrane 9 and the second separating membrane 10 to an end face 7a of the process adapter facing the pressure transmitter 14. As shown in Fig.As shown in Figure 1, the channel 19 in the area between the circumferential edges 12a, 12b of the first separating membrane 9 and the second separating membrane 10 can initially have a section arranged perpendicular to the front surface 7a, which leads into an obliquely running section, which finally leads to the second space 18.

[0028] The sleeve 17 can have a widening 22 in an end region 17b facing the process adapter 7. The widening 22 can be designed such that the second gap 18 in the region of the widening 22 has a larger diameter than in a region of the sleeve 17 adjacent to the widening 22. The widening allows the channel 19 to easily overlap with the second gap 18. Optionally, the outer wall 17c of the sleeve 17 can be designed such that the outer wall 17c has a wave-like contour in cross-section, as shown in Fig. 3. This reduces heat flow from the medium 2 to the measuring device 3.

[0029] A monitoring unit 20 is arranged on the sleeve 17 and is configured to monitor the second intermediate space 18. The monitoring unit 20 can be arranged in a recess 23 of the sleeve 17. The recess 23 can connect the monitoring unit 20 to the second intermediate space 18. Preferably, the first intermediate space 11 and the second intermediate space 18 are evacuated. The monitoring unit 20 can be a second pressure sensor configured to monitor a third pressure in the second intermediate space 18. In the event of a leak, medium 2 enters the first intermediate space 11 and the second intermediate space 18, causing the pressure in both spaces 11 and 18 to rise. In this way, the monitoring unit 20 can detect that a leak is present. The monitoring unit 20 can also be electrically connected to the evaluation unit 28 and / or the display unit 29.The monitoring unit 20 can be configured to determine a measurement signal that corresponds to the state, in particular the third pressure, of the second intermediate space 18, and to transmit the measurement signal to the evaluation unit 28 and / or the display unit 29. The evaluation unit 28 can be configured to detect a leak based on the transmitted measurement signal and to send a warning to the display unit 29. The display unit 29 can be configured to display the warning that a leak is present.

[0030] The sleeve 17 may further have an opening 27. The second intermediate space 18 and the first intermediate space 11 can be evacuated or filled via the opening 27. After evacuation or filling, the opening 27 can be closed. The second intermediate space 18 is, in particular, arranged coaxially with the pressure transmission path 16. The second intermediate space 18 can be arranged such that it surrounds the pressure transmission path 16. In particular, the second intermediate space 18 is arranged radially between the sleeve 17 and the pressure transmitter 14, especially such that the pressure transmission path 16 lies on a longitudinal axis of the second intermediate space 18. The outer wall 14a of the pressure transmitter 14 can be cylindrical. The inner wall 17a of the sleeve 17 can be cylindrical. The second intermediate space 18 can essentially be in the form of a hollow cylinder.

[0031] The pressure transmitter 14 can have a stop surface 32 in a first end region 24 facing the measuring instrument 3 and / or in a second end region 25 facing a process adapter 7, wherein the measuring instrument 3 and / or the process adapter 7 have a support surface 33 which is designed corresponding to the stop surface 32. The pressure transmitter 14, the measuring instrument 3, and / or the process adapter 7 can have a projection, a shoulder, or a recess in the area of ​​the stop surface 32 or the support surface 33 in order to guide the pressure transmitter 14, the measuring instrument 3, and / or the process adapter 7 during the connection of the respective components. In Fig. 1, the pressure transmitter 14 has, by way of example, a stop surface 32 formed by a recess in the first end region 24 and a stop surface 32 formed by a shoulder in the second end region.

[0032] Reference symbol list

[0033] 1 pressure sensor

[0034] 2 Medium

[0035] 3 Measuring instrument

[0036] 4 first pressure sensor

[0037] 5 first area

[0038] 6 second area

[0039] 7 process adapters

[0040] 7a Front face of the process adapter

[0041] 8 Membrane system

[0042] 9 first separating membrane

[0043] 10 second separating membrane

[0044] 11 first space

[0045] 12a circumferential edge of the first separating membrane

[0046] 12b circumferential edge of the second separating membrane

[0047] 13 Pressure chamber

[0048] 14 pressure transmitters

[0049] 14a Outer wall of the pressure transmitter

[0050] 15 basic shapes

[0051] 16 first pressure transmission path

[0052] 17 Sleeve

[0053] 17a Inner wall of the sleeve

[0054] 17b End of the sleeve

[0055] 17c Outer wall of the sleeve

[0056] 18 second space

[0057] Channel 19

[0058] 20 monitoring units

[0059] 21 circumferential welds

[0060] 22 Expansion

[0061] 23 recess

[0062] 24 first end area of ​​the pressure transmitter

[0063] 25 second end area of ​​the pressure transmitter

[0064] 26 Membrane bed

[0065] 27 Opening

[0066] 28 evaluation units

[0067] 29 Display unit

[0068] 30 second pressure transmission path

[0069] 31 third pressure transmission path

[0070] 32 Stop surface 33 Support surface

Claims

Patent claims 1. Pressure transducer (1) for determining and / or monitoring a first pressure (p1) of a medium (2), comprising a measuring unit (3) and a first pressure sensor (4) arranged in the measuring unit (3), which can be subjected to the first pressure (p1) of the medium (2) on a first surface (5) and to a second pressure on a second surface (6), a process adapter (7) with a membrane system (8) comprising a first separating membrane (9) and a second separating membrane (10), which are arranged relative to each other such that the first separating membrane (9) faces the medium (2) and the second separating membrane (10) faces away from the medium (2) and a first space (1 1) is enclosed between the first separating membrane (9) and the second separating membrane (10),wherein the first separating membrane (9) and the second separating membrane (10) are attached to the process adapter (7) in a pressure-tight manner at a circumferential edge (12), forming a pressure chamber (13) between the second separating membrane (10) and the process adapter (7), wherein the membrane system (8) is configured to transmit the first pressure (p1) to the pressure chamber (13), a pressure transmitter (14) with a cylindrical base body (15) and a first pressure transmission path (16) arranged in the base body (15), which is configured to transmit the first pressure (p1) from the pressure chamber, (13) to transfer to the first surface (5), wherein the pressure transmitter (14) is arranged between the measuring instrument (3) and the process adapter (7), a sleeve (17) which is connected to the process adapter (7) and the pressure transmitter (14) is connected in a pressure-tight manner and surrounds the pressure transmitter (14) at least section by section, so that a second space (18) is formed between an outer wall (14a) of the pressure transmitter (14) and an inner wall (17a) of the sleeve (17), wherein the second space (18) is fluidically connected to the first space (11) by means of a channel (19) arranged in the process adapter (7), a monitoring unit (20) which is arranged on the sleeve (17) and is designed to monitor the second space (18).

2. Pressure sensor (1) according to claim 1, wherein the second space (18) is arranged coaxially with the first pressure transmission path (16).

3. Pressure sensor (1) according to one of the preceding claims, wherein the channel (19) leads from an area between the circumferential edges (12) of the first separating membrane (9) and the second separating membrane (10) to an end face (7a) of the process adapter (7) facing the pressure transmitter (14).

4. Pressure sensor (1) according to one of the preceding claims, wherein the process adapter (7) is connected to the pressure transmitter (14) and / or the sleeve (17) by means of a circumferential weld (21).

5. Pressure sensor (1) according to one of the preceding claims, wherein the sleeve (17) has an expansion (22) in an end region (17b) facing the process adapter (7), in particular such that the second space (18) in the region of the expansion (22) has a larger diameter than in a region of the sleeve (17) adjacent to the expansion (22).

6. Pressure sensor (1) according to one of the preceding claims, wherein an outer wall (17c) of the sleeve (17) is designed such that it has a wave-shaped contour in cross-section.

7. Pressure sensor (1) according to one of the preceding claims, wherein the monitoring unit (20) is arranged on a recess (23) of the sleeve (17).

8. Pressure transducer (1) according to one of the preceding claims, wherein the monitoring unit (20) is a second pressure sensor which is configured to monitor a third pressure in the second space (18).

9. Pressure sensor (1) according to one of the preceding claims, wherein the first space (11) and the second space (18) are evacuated.

10. Pressure transducer (1) according to one of the preceding claims, wherein the pressure transmitter (14) has a stop surface (32) in a first end region (24) facing the measuring device (3) and / or in a second end region (25) facing a process adapter (7), wherein the measuring device (3) and / or the process adapter (7) have a support surface (33) which is designed corresponding to the stop surface (32).

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