Pressure sensor for detecting a leak in a first separating membrane

Abstract

The invention relates to a pressure sensor (1) for detecting a leakage in a first separating membrane (8), with - a process adapter (6) with a membrane system (7) comprising the first separation membrane (8) and a second separation membrane (9), which are arranged such that the first separation membrane (8) faces the medium (24) and the second separation membrane (9) faces away from the medium (24) and a first intermediate space (10) is enclosed between the first separation membrane (8) and the second separation membrane (9), which has a vacuum, - a sensor unit (14) with a carrier (15), a second pressure sensor (16) and a communication unit (17), wherein the sensor unit (14) is attached to the pressure sensor (1) in a pressure-tight manner by means of the carrier (15) and is arranged such that the second pressure sensor (16) monitors the vacuum in the first space (10), wherein the second pressure sensor (16) and the communication unit (17) are electrically connected to each other and are arranged on a surface of the carrier (15) facing the vacuum.

Description

[0001] The invention relates to a pressure sensor for detecting a leakage in a first separating membrane.

[0002] 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.

[0003] 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.

[0004] 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.

[0005] 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.

[0006] 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 monitors any changes in the vacuum within this space.

[0007] Such a detection device can be designed as a capacitive sensor. Mechanical pressure switches or mechanically operated drag pointers with switching contacts or pressure transmitters are also common.

[0008] The requirements for a vacuum sensor intended for use as a detection device are, firstly, the monitoring of the vacuum between the two membranes and, secondly, the ability to withstand potentially high process pressures in the event of a leak. Such vacuum sensors are not currently available on the market.

[0009] It is therefore an object of the present invention to provide a pressure sensor with a sensor unit which monitors the vacuum between the two membranes in a simple manner and which withstands the process pressure in the event of leakage.

[0010] The problem is solved according to the invention by a pressure sensor according to claim 1.

[0011] The problem is solved according to the invention by a pressure sensor for detecting a leakage in a first separating membrane, with - a measuring instrument and a first pressure sensor arranged in the measuring instrument, 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 separation membrane and a second separation membrane, which are arranged 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 and second separation membranes, which is vacuum-filled, wherein the first and second separation membranes are pressure-tightly attached to the process adapter at a circumferential edge, forming a pressure chamber between the second separation membrane and the process adapter, and wherein the membrane system is designed to transmit the first pressure to the pressure chamber. - a pressure transfer path designed to transfer the initial pressure from the pressure chamber to the first surface, - a sensor unit comprising a carrier, a second pressure sensor and a communication unit, wherein the sensor unit is attached to the pressure sensor in a pressure-tight manner by means of the carrier and is arranged such that the second pressure sensor monitors the vacuum in the first space, wherein the second pressure sensor and the communication unit are electrically connected to each other and are arranged on a surface of the carrier facing the vacuum.

[0012] The sensor unit is attached to the pressure sensor in a pressure-tight manner by means of the carrier, so that in the event of a leakage of the first separating membrane, the medium cannot pass through the sensor unit into the interior of the pressure sensor and potentially escape from the pressure sensor. The pressure-tight arrangement of the carrier within the pressure sensor ensures the overload resistance of the sensor unit even at high initial pressures of the medium. The communication unit and the second pressure sensor are located within the vacuum. The second pressure sensor is designed to monitor the vacuum. The pressure sensor according to the invention thus enables vacuum monitoring by means of the second pressure sensor while simultaneously ensuring pressure resistance of the sensor unit.

[0013] The first and / or second pressure sensor can be configured to output a measured value. The pressure sensor can include an evaluation unit, which is specifically configured to process a measured value from the first and / or second pressure sensor. The evaluation unit can be electrically connected to the first and / or second pressure sensor. The carrier can be configured to establish an electrical connection between the communication unit and the evaluation unit of the pressure sensor. The communication unit can be configured to transmit a measured value from the second pressure sensor to the evaluation unit. The first and / or second pressure sensor can be piezoresistive pressure sensors, for example, silicon chips. The sensor unit can be arranged on the process adapter, the measuring mechanism, or another component of the pressure sensor.

[0014] The first space is vacuum-sealed or evacuated. The absolute pressure in the first space is zero, whereby "zero absolute pressure" 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.

[0015] In one embodiment, the second pressure sensor and / or the communication unit is configured to output a loss of vacuum and / or an error signal in the event of a leak in the first separating membrane. If the first separating membrane leaks, medium will enter the first space. Depending on the type of medium entering, its pressure, and its velocity, the second pressure sensor will initially output a measured value that correlates with a loss of vacuum in the first space, thus indicating that a leak in the first separating membrane has occurred. If the pressure of the entering medium exceeds the measuring range of the second pressure sensor, the second pressure sensor may output an error signal.On the other hand, the ingress of medium can cause a short circuit in the electrical connections between the second pressure sensor and the communication unit, resulting in an error signal being output by the communication unit.

[0016] In one embodiment, the communication unit is configured as a printed circuit board with one or more contact pads, wherein the second pressure sensor is electrically, and in particular mechanically, connected to the printed circuit board by means of one or more contact pads. The second pressure sensor can be arranged on a surface of the printed circuit board facing the substrate or on a surface of the printed circuit board facing away from the substrate.

[0017] In one embodiment, the communication unit is electrically connected to the carrier. The carrier can have at least one connection pin for this purpose, by means of which the carrier and the communication unit are electrically connected. Preferably, the carrier can have at least two connection pins; one of the connection pins can be used to supply a voltage to the communication unit, and the other connection pin can be used to transmit data.

[0018] In one embodiment, the carrier is a cable gland. The cable gland can be configured to provide an electrical connection to the communication unit. The cable gland can have a base plate and at least one connection pin arranged transversely to the base plate and insulated from the base plate. The base plate and / or the at least one connection pin can be metallic.

[0019] In one embodiment, the support is connected to the pressure sensor by means of a pressure-tight weld. The support can be made of a metal. If the support is configured as a current feedthrough, a base plate of the current feedthrough can be welded to the pressure sensor.

[0020] In one embodiment, the pressure sensor has a pressure transmitter with a base body and the pressure transmission path arranged in the base body, which is designed to transmit the first pressure from the pressure chamber to the first surface.

[0021] In one embodiment, the pressure transmitter is arranged between the measuring unit and the process adapter. The pressure transmitter can be mechanically connected to the measuring unit and / or the process adapter, in particular by welding.

[0022] In one embodiment, the pressure sensor has a sleeve that is pressure-tightly connected to the process adapter and the pressure transmitter and at least partially surrounds the pressure transmitter, so that a second space is formed between an outer wall of the pressure transmitter and an inner wall of the sleeve. This second space is fluidically connected to the first space via a channel arranged in the process adapter. The sleeve allows the sensor unit to be positioned at the second space, thus enabling the sensor unit to be located at a distance from the medium.

[0023] In one embodiment, the sensor unit is arranged on the sleeve. The sleeve can have a recess that connects the sensor unit to the second space. The carrier can be pressure-tightly connected to the sleeve.

[0024] In one embodiment, the sensor unit, particularly its entirety, is inserted into the sleeve. The sensor unit can be arranged within an interior space of the sleeve. The carrier can be pressure-tightly connected to this interior space. Inserting the sensor unit into the sleeve offers the advantage that the sensor unit is protected from environmental influences.

[0025] The invention is to be explained using the following figures Fig. 1-4 will be explained in more detail. They show: Fig. 1: a first embodiment of the pressure sensor according to the invention. Fig. 2: a design of the membrane system. Fig. 3: a design of the sensor unit. Fig. 4: a second embodiment of the pressure sensor according to the invention.

[0026] In Fig. Figure 1 shows a schematic embodiment of a pressure sensor 1 according to the invention. The pressure sensor 1 comprises a measuring unit 2, a process adapter 6, and a sensor unit 14. A first pressure sensor 3 is arranged in the measuring unit 2. This sensor can be subjected to the first pressure p1 of the medium 24 on a first surface 4 and to a second pressure on a second surface 5, in particular opposite the first surface 4. The second pressure can be ambient pressure, absolute pressure, or another pressure of the medium 24. The pressure sensor 3 can be connected to an evaluation unit 28, which determines the first pressure p1 based on a measured value generated by the pressure sensor 3. The evaluation unit 28 can be connected to a display unit 29, which can be configured to display the first pressure p1.

[0027] The process adapter 6 has a membrane system 7, which is arranged on the medium side and in Fig. Figure 2 is shown in detail. The membrane system 7 comprises a first separation membrane 8 and a second separation membrane 9, which are arranged such that the first separation membrane 8 faces the medium 24 and the second separation membrane 9 faces away from the medium 24, and a first intermediate space 10 is enclosed between the first separation membrane 8 and the second separation membrane 9. The first intermediate space 10 is evacuated or has a vacuum. The first separation membrane 8 can be pressurized with the first pressure p1. The first separation membrane 8 and the second separation membrane 9 are each pressure-tightly attached to the process adapter 6 at a circumferential edge 11a, 11b, so that a pressure chamber 12 is formed between the second separation membrane 9 and the process adapter 6. A membrane bed 26 can be associated with the second separation membrane 9.

[0028] The membrane system 7 is configured to transmit the initial pressure p1 to the pressure chamber 12. The process adapter 6 can include a section of the pressure transmission path 13, which is fluidically connected to the pressure chamber 12. The pressure transmission path 13 can be configured to transmit the initial pressure p1 from the pressure chamber 12 to the first surface 4. A further section of the pressure transmission path 13 can also be arranged in the measuring device 3.

[0029] The sensor unit 14 comprises a carrier 15, a second pressure sensor 16 and a communication unit 17, as exemplified in Fig. Figure 3 shows the sensor unit 14 being arranged in the first space 10 or in a second space 18 of the pressure sensor that is fluidically connected to the first space. The sensor unit 14 is pressure-tightly attached to the pressure sensor 1 by means of the carrier. For example, the sensor unit 14 can be arranged on the process adapter 6 and connected to the first space 10. The second pressure sensor 16 and the communication unit 17 are electrically connected to each other and arranged on a surface of the carrier 15 facing the vacuum. The second pressure sensor 16 is designed to monitor the vacuum in the first space 10.

[0030] In Fig. In Figure 3, the communication unit 17 is exemplified as a printed circuit board 19, which has one or more contact surfaces 32. The second pressure sensor 16 is electrically and, in particular, mechanically connected to the printed circuit board 19 by means of at least one of the contact surfaces 32, for example, by means of a solder joint. The carrier 15 is exemplified as a current feedthrough. The current feedthrough can have a base plate 34 and one or more connection pins 20. The communication unit 17 can be electrically connected to the carrier 15, for example, by means of at least one connection pin 20. The carrier 15 can be connected to the pressure sensor 1 by means of a pressure-tight weld. For example, the base plate 34 can be pressure-tightly welded to the pressure sensor 1.

[0031] The second pressure sensor 16 and / or the communication unit 17 can be configured to output a loss of vacuum and / or an error signal in the event of a leakage of the first separating membrane 8. The communication unit 17 can be electrically connected to the evaluation unit 28, for example by means of the carrier 15, which can be configured as a current feedthrough. The communication unit 17 can be configured to transmit a measured value from the second pressure sensor 16 to the evaluation unit 28. The evaluation unit 28 can be configured to detect a leakage based on the measured value transmitted by the communication unit 17 and, in particular, to send a warning about the leakage to the display unit 29. The display unit 29 can be configured to display the warning about the leakage.The evaluation unit 28 can also be designed to detect a leak based on an error signal from the communication unit and, in particular, to send a warning about the leak to the display unit 29.

[0032] The pressure sensor 1 can have a pressure transmitter 21 with a cylindrical base body 21a and the pressure transmission path 13 arranged therein, which can be filled with a pressure transmission fluid. The pressure transmitter 21 can be arranged between the measuring unit 2 and the process adapter 6.

[0033] The pressure sensor 1 can further comprise a sleeve 22. The sleeve 22 surrounds the pressure transmitter 21 at least partially, such that a second space 18 is formed between an outer wall 21b of the pressure transmitter 21 and an inner wall 22a of the sleeve 22. As in Fig. As shown in Figure 4, the sleeve 22 can surround the pressure transmitter 21 from its first end region 30 to its second end region 31. The sleeve 22 can be pressure-tightly connected to both the process adapter 6 and the pressure transmitter 21, in particular by means of a weld, especially an orbital weld. The weld points are shown as black, round dots.

[0034] The second space 18 is arranged, in particular, coaxially with the pressure transmission path 13. The second space 18 can be arranged such that it surrounds the pressure transmission path 13. The base body 21a of the pressure transmitter 21 can be cylindrical. The inner wall 22a of the sleeve 22 can be cylindrical. The second space 18 can essentially be in the form of a hollow cylinder.

[0035] The process adapter 6 can have a channel 23, which is arranged and configured such that the channel 23 fluidically connects the first intermediate space 10 with the second intermediate space 18. The channel 23 can lead from a region between the circumferential edges 11a, 11b of the first separating membrane 8 and the second separating membrane 9 to an end face 6a of the process adapter facing the pressure transmitter 21. As shown in Fig. As shown in Figure 1, the channel 23 in the area between the circumferential edges 11a, 11b of the first separating membrane 8 and the second separating membrane 9 can initially have a section arranged perpendicular to the front surface 6a, which leads into an obliquely running section, which finally leads to the second space 18.

[0036] The sensor unit 14 can be inserted into the sleeve 22, as shown in Fig. 1 shown, or arranged on the sleeve 22, as shown in Fig.Figure 4 shows that in both cases the sensor unit 14 is pressure-tightly connected to the sleeve. In the second case, the sensor unit 14 can be arranged in a recess 27 of the sleeve 22.

[0037] The sleeve 22 may also have an opening 25. The second space 18 and the first space 10 can be evacuated via the opening 25. After evacuation, the opening 25 can be closed by means of a sealing device. Reference symbol list 1 pressure sensor 2 Measuring instrument 3 first pressure sensor 4 first area 5 second area 6 process adapters 6a Front face of the process adapter 7 Membrane system 8 first separating membrane 9 second separating membrane 10 first space 11a circumferential edge of the first separating membrane 11b circumferential edge of the second separating membrane 12 Pressure chamber 13 Pressure transmission path 14 Sensor unit 15 carriers 16 second pressure sensor 17 Communication unit 18 second space 19 printed circuit board 20 connection pins 21 pressure transmitters 21a Basic body 21b Outer wall of the pressure transmitter 22 Sleeve 22a Inner wall of the sleeve Channel 23 24 Medium 25 Opening 26 Membrane bed 27 recess 28 evaluation units 29 Display unit 30 first end area of ​​the pressure transmitter 31 second end area of ​​the pressure transmitter 32 contact area 34 Base plate QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 199 49 831 B4

[0006]

Claims

[1] Pressure sensor (1) for detecting a leakage of a first separating membrane (8), with - a measuring instrument (2) and a first pressure sensor (3) arranged in the measuring instrument (2), which can be subjected to the first pressure (p1) of the medium (24) on a first surface (4) and to a second pressure on a second surface (5), - a process adapter (6) with a membrane system (7) comprising a first separation membrane (8) and a second separation membrane (9), which are arranged such that the first separation membrane (8) faces the medium (24) and the second separation membrane (9) faces away from the medium (24), and a first space (10) is enclosed between the first separation membrane (8) and the second separation membrane (9), which is vacuum-sealed, wherein the first separation membrane (8) and the second separation membrane (9) are attached to the process adapter (6) at a circumferential edge (11) in a pressure-tight manner, forming a pressure chamber (12) between the second separation membrane (9) and the process adapter (6), wherein the membrane system (7) is designed to transmit the first pressure (p1) to the pressure chamber (12), - a pressure transfer path (13) designed to transfer the first pressure (p1) from the pressure chamber (12) to the first surface (4), - a sensor unit (14) with a carrier (15), a second pressure sensor (16) and a communication unit (17), wherein the sensor unit (14) is attached to the pressure sensor (1) in a pressure-tight manner by means of the carrier (15) and is arranged such that the second pressure sensor (16) monitors the vacuum in the first space (10), wherein the second pressure sensor (16) and the communication unit (17) are electrically connected to each other and are arranged on a surface of the carrier (15) facing the vacuum. [2] Pressure transducer (1) according to claim 1, wherein the second pressure sensor (16) and / or the communication unit (17) is configured to output a loss of vacuum and / or an error signal in the event of a leakage of the first separating membrane (8). [3] Pressure sensor (1) according to one of the preceding claims, wherein the communication unit (17) is designed as a printed circuit board (19) with one or more contact surfaces (32), wherein the second pressure sensor (16) is electrically connected to the printed circuit board (19) by means of the one or more contact surfaces (32). [4] Pressure sensor (1) according to one of the preceding claims, wherein the communication unit (17) is electrically connected to the carrier (15). [5] Pressure transducer (1) according to one of the preceding claims, wherein the communication unit (17) is configured to transmit a measured value from the second pressure sensor (16) to an evaluation unit (28) of the pressure transducer (1). [6] Pressure sensor (1) according to one of the preceding claims, wherein the carrier (15) is a current feedthrough. [7] Pressure sensor (1) according to one of the preceding claims, wherein the carrier (15) is connected to the pressure sensor (1) by means of a pressure-tight weld. [8] Pressure sensor (1) according to one of the preceding claims, wherein the pressure sensor (1) has a pressure transmitter (21) with a base body (21a) and the pressure transmission path (13) arranged in the base body (21a), which is configured to transmit the first pressure (p1) from the pressure chamber (12) to the first surface (4). [9] Pressure sensor (1) according to claim 8, wherein the pressure transmitter (21) is arranged between the measuring unit (2) and the process adapter (6). [10] Pressure sensor (1) according to one of claims 8-9, wherein the pressure sensor (1) has a sleeve (22) which is pressure-tightly connected to the process adapter (6) and the pressure transmitter (21) and surrounds the pressure transmitter (21) at least partially, so that a second space (18) is formed between an outer wall (21b) of the pressure transmitter (21) and an inner wall (22a) of the sleeve (22), wherein the second space (18) is fluidically connected to the first space (10) by means of a channel (23) arranged in the process adapter (6). [11] Pressure sensor (1) according to claim 10, wherein the sensor unit (14) is arranged on the sleeve (22). [12] Pressure sensor (1) according to claim 10, wherein the sensor unit (14) is inserted into the sleeve (22).

Images