Relative-pressure transducer

Abstract

The invention relates to a relative-pressure transducer (1) for determining and / or monitoring a pressure (p1) of a medium (2), having - a housing (3) with a wall (20) and an interior space (21), - a pressure sensor (4), which is provided in the interior space (21) and has a first area (2) and a second area (6), wherein the first area (5) can be subjected to the pressure (p1) of the medium (2) and the second area (6) can be subjected to a reference pressure (p2), - an opening (7), which is provided in the wall (20), - a reference-pressure feed (8), which is designed to feed the reference pressure (p2) from the opening (7) to the second area (6), - an alignment sensor (9), which is designed to detect an alignment of the relative-pressure transducer (1), - an evaluation unit (10), which is designed to determine an orientation of the opening (7) on the basis of the alignment detected, - a warning unit (11), which is designed to issue a warning if the orientation determined corresponds to a specified misalignment.

Description

[0001] Relative pressure sensor

[0002] The invention relates to a relative pressure sensor for determining and / or monitoring the 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, with the atmospheric pressure prevailing in the vicinity of the gauge pressure sensor serving as the reference pressure.

[0004] Relative pressure sensors have a pressure-sensitive measuring element, the so-called pressure sensor, whose first surface is subjected to the pressure of the medium to be measured. Atmospheric pressure, which is supplied to the measuring element via a reference pressure supply from the surroundings of the relative pressure sensor, acts on a second surface of the measuring element. The measuring element bends depending on the prevailing relative pressure, which is formed from the difference between the pressure of the medium to be measured and the atmospheric pressure. 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 between capacitive and piezoresistive pressure sensors, among others. A large number of such relative pressure sensors are manufactured and distributed by companies in the Endress+Hauser Group.

[0005] Relative pressure sensors are often used in industrial processes where they are exposed to significant temperature fluctuations and differences between the process and the environment. Sudden cooling can cause the dew point of the air inside the relative pressure sensor to be exceeded, leading to condensation of humidity on cold parts within the sensor. Humidity can enter the relative pressure sensor, particularly through the sensor's opening to the environment, which is necessary to provide the reference pressure for the measuring element, and through the reference pressure supply.

[0006] The pressure sensor and the electronics unit are generally very sensitive to moisture. As a result of moisture, hysteresis effects can occur at the pressure sensor, for example. For reliable pressure determination, it is therefore necessary to ensure that little or no moisture enters or condenses within the relative pressure sensor. Ideally, the relative pressure sensor, and especially the reference pressure supply, is designed so that only dry air reaches the pressure sensor and the evaluation unit. The reference pressure supply typically carries the ambient pressure from an opening in the relative pressure sensor, which is often located in the relative pressure sensor housing, to the pressure sensor.In some cases, a drying chamber containing a moisture-absorbing material is arranged between the opening and the pressure sensor. This material removes moisture from the ambient air supplied from the reference pressure supply, thus drying the ambient air. Additionally or alternatively, the opening can be sealed with a moisture-impermeable membrane.

[0007] When installing the gauge pressure sensor in the process plant, the opening is randomly aligned. However, aligning the opening on a vertical axis is disadvantageous because condensate forming at the opening cannot drain away but instead collects in the area of ​​the opening. This can lead to the opening being covered by condensate, preventing ambient air from reaching the gauge pressure sensor. Condensate can potentially penetrate the gauge pressure sensor and thus damage it.

[0008] The object of the present invention is therefore to provide a relative pressure sensor in which a desired orientation of the opening can be easily checked. According to the invention, the object is achieved by a

[0009] Relative pressure sensor according to claim 1 and a method according to claim 9.

[0010] With regard to the relative pressure sensor, the object is achieved according to the invention by a relative pressure sensor for determining and / or monitoring a pressure of a medium, with

[0011] - a housing with a wall and an interior,

[0012] - a pressure sensor arranged in the interior space with a first surface and a second surface, wherein the first surface can be subjected to the pressure of the medium and the second surface to a reference pressure,

[0013] - an opening arranged in the wall,

[0014] - a reference pressure supply which is designed to supply the reference pressure from the opening to the second surface,

[0015] - an alignment sensor which is designed to detect an alignment of the relative pressure sensor,

[0016] - an evaluation unit which is designed to determine an orientation of the opening based on the detected orientation,

[0017] - a warning unit designed to issue a warning if the determined orientation corresponds to a predetermined misalignment.

[0018] By means of the relative pressure sensor according to the invention, after attaching the relative pressure sensor to a container, e.g., a tank or a pipe, it is checked in a simple and automated manner whether the opening is correctly aligned. If this is not the case, a warning is issued informing the operator of the misalignment. The operator can then change the orientation of the relative pressure sensor and attach it to the container in such a way that the opening is not misaligned. If no warning about misalignment appears after the alignment has been changed, the relative pressure sensor is correctly aligned. If necessary, a message can be issued via the display unit indicating that the relative pressure sensor is correctly aligned. The opening is designed, in particular, as a through-hole.The orientation sensor is preferably assigned a predefined position in the relative pressure sensor, which is stored as information in the evaluation unit. The evaluation unit advantageously also stores information about how the opening is arranged relative to the orientation sensor. Using the information about the predefined position of the orientation sensor and the information about the arrangement of the opening relative to the orientation sensor, the evaluation unit can determine an orientation of the opening based on the detected orientation. The orientation sensor can, in particular, be arranged such that it detects an orientation of the relative pressure sensor with respect to a vertical axis.

[0019] The alignment sensor is preferably located inside the interior, but can also be mounted on the wall outside the interior. The evaluation unit is preferably located inside the interior. The warning unit can be located outside the housing. The alignment sensor is electronically connected to at least the evaluation unit. The warning unit is electronically connected to at least the evaluation unit.

[0020] In one embodiment, the warning unit is a display unit designed to display the warning. The display unit can display the warning visually, for example, using an LED or a display, or acoustically using a warning signal. The display unit, in particular, has a display.

[0021] In a further development, the specified misalignment corresponds to an orientation of the opening which encloses an angle of less than ±45° with a vertical axis. The vertical axis is defined as an axis perpendicular to the earth's surface. The angle can be formed between a plumb line perpendicular to the diameter of the opening and the vertical axis. In the event of such a misalignment, condensate formed in the area of ​​the opening may have difficulty draining away from the opening or may drip from the opening. If the opening is oriented away from the earth's surface, the condensate may be trapped within the opening or may enter the reference pressure supply through the opening. If the opening is oriented towards the earth's surface, the condensate may form a drop at the opening which, depending on its size, does not drip completely but partially or completely wets the opening.

[0022] In particular, the specified misalignment corresponds to an orientation of the aperture that encloses an angle of less than ±25° with a vertical axis. Such an orientation is particularly disadvantageous.

[0023] The specified misalignment may, in particular, correspond to an orientation of the opening that encloses an angle of less than ±10° with a vertical axis. Such an orientation is particularly disadvantageous.

[0024] In one embodiment, the opening is closed by an air-permeable and moisture-impermeable membrane. The membrane is in particular attached to the housing or in the opening. The membrane is arranged in such a way that it closes the opening. The membrane ensures that only ambient air, but no moisture, enters the reference pressure supply. If the opening is misaligned, condensate can form in the area of ​​the membrane, which makes it difficult for ambient air to pass through the membrane and may even prevent it completely. The membrane is attached to the housing in the area of ​​the opening, for example, by means of adhesive bonding, welding, or soldering. If the opening is misaligned, in the worst case scenario, condensate can bypass the membrane and enter the reference pressure supply. The present invention is therefore also extremely advantageous for openings closed with a membrane.

[0025] Preferably, the alignment sensor is an acceleration sensor. An acceleration sensor is designed to detect its own acceleration. For example, the acceleration sensor can have a sprung mass whose deflection is detected as a result of an acceleration. The detection of the deflection can be capacitive or inductive, among other things. With regard to the method, the object is achieved according to the invention by a method for checking the alignment of an opening of a relative pressure sensor according to one of the preceding embodiments, comprising at least the following method steps:

[0026] - Attaching the relative measuring sensor to a container,

[0027] - Detecting the orientation of the relative pressure sensor using the orientation sensor,

[0028] - Determining the orientation of the opening based on the detected orientation,

[0029] - Issue a warning if the detected orientation corresponds to a specified misalignment.

[0030] The warning indicates, in particular, that the opening is misaligned. The method according to the invention checks whether the opening is correctly aligned or whether the orientation corresponds to a misalignment. By issuing a warning to the operator, they can identify and correct the misalignment.

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

[0032] Fig. 1 : a schematic representation of a misalignment of the opening of the relative pressure sensor according to the invention.

[0033] Fig. 2: a first embodiment of a relative pressure sensor according to the invention.

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

[0035] Fig. 1 shows, by way of example, a relative pressure sensor 1 according to the invention attached to a container 19. The container 19 is, for example, a tank, a pipe, or another container. The relative pressure sensor 1 is shown schematically in a plan view, wherein, for reasons of clarity, only the opening 7 in the housing 3 is shown. The opening 7 has an orientation that encloses an angle a with a vertical axis. The angle a can be determined in particular by drawing a line perpendicular to the center or the diameter of the opening 7 and determining the angle of this line with the vertical axis b.In particular at small angles a of less than ±45°, in particular less than ±25°, in particular less than ±10°, condensate formed at the opening 7 cannot completely flow or drip off the opening 7, so that the condensate partially or completely closes the opening 7 and thus the reference pressure supply 8 is partially or completely blocked.

[0036] To avoid this problem, a first embodiment of the relative pressure measuring sensor 1 according to the invention is proposed in Fig. 1. The relative pressure measuring sensor 1 for determining and / or monitoring a pressure p1 of a medium 2 has a housing 3 with a wall 20 and an interior space 21. The opening 7, which is designed in particular as a through-bore, is arranged in the wall 20. A pressure sensor 4 is arranged in the interior space 21 and has a first surface 5 to which the pressure p1 of the medium 2 can be applied, and a second surface 6 to which a reference pressure p2 can be applied. The first surface 5 and the second surface 6 are preferably arranged opposite one another. The reference pressure p2 is an ambient pressure from the environment of the relative pressure measuring sensor 1. In order to supply the reference pressure p2 from the opening 7 to the second surface 6, a reference pressure supply 8 is provided.The reference pressure supply 8 is designed, for example, in sections as a channel, cannula or gap.

[0037] Furthermore, the relative pressure sensor 1 can have a medium pressure supply 18, which supplies the pressure p1 of the medium 2 to the first surface 5. A separating membrane 15 is connected upstream of the medium pressure supply 18 and is designed to apply the pressure p1 of the medium 2 to the first surface 5 by means of the medium pressure supply 18. A membrane bed 17 can be assigned to the separating membrane 15. A pressure chamber 16 is optionally arranged between the separating membrane 15 and the membrane bed 17. Alternatively, the first surface 5 can also be subjected to the pressure p1 of the medium 2 without an upstream separating membrane 15 and without a medium pressure supply 18. In this case, the first surface 5 is arranged in contact with the medium.

[0038] The relative pressure sensor 1 further comprises an orientation sensor 9, which is designed to detect an orientation of the relative pressure sensor 1. The orientation sensor 9 is, for example, an acceleration sensor. Furthermore, the relative pressure sensor 1 comprises an evaluation unit 10 and a warning unit 11. The orientation sensor 9 can be designed to transmit information about the orientation of the relative pressure sensor 1 to the evaluation unit 10. The evaluation unit 10 is designed to determine an orientation of the opening 7 based on the detected orientation. If necessary, information about the arrangement of the opening 7 with respect to the orientation sensor 9 is stored in the evaluation unit 10, which information can be used by the evaluation unit 10 to determine the orientation of the opening 7.The evaluation unit can be configured to compare the determined orientation of opening 7 with a predetermined misalignment. If the determined orientation corresponds to a predetermined misalignment, the evaluation unit 10 can transmit information about the misalignment to the warning unit 11. The warning unit 11 is configured to issue a warning if the determined orientation corresponds to a predetermined misalignment. For example, the warning unit 11 is an LED lamp that turns on when a warning is issued or lights up and off again at a predetermined rhythm.

[0039] The warning unit 11 can also be configured as a display unit 12, as shown in Fig. 3. The display unit can have a display 13 on which the warning is displayed, in particular as text. The display is, for example, an LCD display. Fig. 3 further shows an embodiment of the relative pressure sensor 1, in which the relative pressure sensor 1 has an air-permeable and moisture-impermeable membrane 14, which is arranged and configured such that it closes the opening 14.

[0040] In the method according to the invention, the orientation of the opening 7 is checked. For this purpose, after the relative pressure sensor 1 is attached to a container 19, the orientation of the relative pressure sensor 1 is detected by the orientation sensor 9. Subsequently, the orientation of the opening 7 is determined by the evaluation unit 10 based on the detected orientation. If it is determined that the determined orientation corresponds to a predetermined misalignment, a warning is issued by the warning unit 11.

[0041] List of reference symbols

[0042] 1 relative pressure sensor

[0043] 2 Medium

[0044] 3 housings

[0045] 4 Pressure sensor

[0046] 5 first area

[0047] 6 second area

[0048] 7 Opening

[0049] 8 Reference print feed

[0050] 9 Alignment sensor

[0051] 10 Evaluation unit

[0052] 11 Warning unit

[0053] 12 Display unit

[0054] 13 Display

[0055] 14 Membran

[0056] 15 Separation membrane

[0057] 16 pressure chamber

[0058] 17 Membrane bed

[0059] 18 Medium pressure supply

[0060] 19 Container

[0061] 20 wall

[0062] 21 Interior a Angle between opening and vertical axis b Vertical axis

Claims

Patent claims 1 . Relative pressure sensor (1 ) for determining and / or monitoring a pressure (p1 ) of a medium (2), with - a housing (3) with a wall (20) and an interior (21), - a pressure sensor (4) arranged in the interior (21) with a first surface (5) and a second surface (6), wherein the first surface (5) can be subjected to the pressure (p1) of the medium (2) and the second surface (6) can be subjected to a reference pressure (p2), - an opening (7) arranged in the wall (20), - a reference pressure supply (8) which is designed to supply the reference pressure (p2) from the opening (7) to the second surface (6), - an alignment sensor (9) which is designed to detect an alignment of the relative pressure sensor (1), - an evaluation unit (10) which is designed to determine an orientation of the opening (7) based on the detected orientation, - a warning unit (11) which is designed to issue a warning if the determined orientation corresponds to a predetermined misalignment.

2. Relative pressure sensor (1) according to claim 1, wherein the warning unit (11) is a display unit (12) which is designed to display the warning.

3. Relative pressure measuring sensor (1) according to claim 2, wherein the display unit (12) has a display (13).

4. Relative pressure sensor (1) according to one of the preceding claims, wherein the predetermined misalignment corresponds to an orientation of the opening (7) which encloses an angle of less than ±45° with a vertical axis.

5. Relative pressure sensor (1) according to one of claims 1 - 3, wherein the predetermined misalignment corresponds to an orientation of the opening (7) which encloses an angle of less than ±25° with a vertical axis.

6. Relative pressure sensor (1) according to one of claims 1 - 3, wherein the predetermined misalignment corresponds to an orientation of the opening (7) which encloses an angle of less than ±10° with a vertical axis.

7. Relative pressure sensor (1) according to one of the preceding claims, wherein the opening (7) is closed by an air-permeable and moisture-impermeable membrane (14).

8. Relative pressure sensor (1) according to one of the preceding claims, wherein the orientation sensor (9) is an acceleration sensor.

9. Method for checking the alignment of an opening (7) of a relative pressure sensor (1) according to one of the preceding claims, comprising at least the following method steps: - Attaching the relative measuring sensor (1) to a container (19), - detecting the orientation of the relative pressure sensor (1) by means of the orientation sensor (9), - Determining the orientation of the opening (7) based on the detected orientation, - Issue a warning if the detected orientation corresponds to a specified misalignment.

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