Vibration sensor and method for equalizing a vibration sensor

Abstract

The invention discloses a vibration sensor comprising a mechanically oscillatable unit (1) having an outer tube (10) and an inner tube (11). Via a continuous recess in the vibration sensor (110, 20, 30), a compensation component (4) can be introduced into the mechanically oscillatable unit (1) and / or changed. The invention also relates to a method for equalizing a vibration sensor.

Description

[0001] Vibration sensor and method for calibrating a vibration sensor

[0002] The invention relates to a vibration sensor. Furthermore, the invention relates to a method for calibrating a vibration sensor. The vibration sensor is used, for example, to determine and / or monitor a process variable of a medium. The process variable is, for example, the fill level, density, or viscosity, and the medium is, for example, a liquid, a gas, or a bulk solid.

[0003] Vibration sensors are known in the prior art that have a mechanically oscillating unit that is excited to mechanical vibrations by a transducer device acting as a drive / receiver unit. The vibrations resulting from the interaction with a medium are received and evaluated by the transducer device. The transducer device has, for example, piezo elements that convert between electrical signals and mechanical vibrations. For a measurement, for example, the fact that the vibration frequency or amplitude changes when the mechanically oscillating unit transitions from an uncovered state to one covered by the medium is exploited. This allows, for example, the monitoring of the fill level of the medium in a container.

[0004] It is known that the mechanically oscillating unit can be in the form of a tuning fork with two prongs, as a pure diaphragm, or even as a so-called single-rod device. One issue with the devices described above is that, if possible, no vibration energy should be transferred to the clamping of the mechanically oscillating unit. The clamping is the area over which the device, and in particular the mechanically oscillating unit, is attached to the measuring point. If, for example, the fill level of a medium in a container is to be monitored, the mechanically oscillating unit is usually partially inserted and fixed into the actual measuring chamber, i.e., the interior of the container, via a recess in the container wall.If the mechanically oscillating unit were to transfer mechanical energy to the clamping system, this would also affect other equipment that is mechanically coupled to the container or even the process itself, which may be taking place in the container. This could even excite resonances in the container. To avoid this, the mechanically oscillating unit must be calibrated so that no vibration energy flows away via the clamping system. For this purpose, for example, the tines of a tuning fork are calibrated with each other. It is also common practice to calibrate a single-rod. This takes advantage of the fact that the single-rod usually consists of two components, each of which is machined in such a way that their vibrations just compensate each other in the clamping system.

[0005] According to DE 102004 011 377 A1, the single-rod is coupled to an adjustment unit whose stiffness is adjusted electrically. Adjustment of a single-rod is performed in DE 102004 009 495 A1, as well as DE 10 2012 103 165 A1 or DE 196 51 362 C1, by moving an additional component in the inner tube of the single-rod. In DE 10 2015 122 648 A1, the vibration behavior of a single-rod is adjusted by adjusting the extent to which an inner vibrating body extends into the outer tube.

[0006] It turns out that the setup for the comparison is relatively complex. This is accompanied by increased costs and complexity, which can itself lead to problems.

[0007] The invention is based on the object of simplifying the adjustment of a single rod as a mechanically oscillating unit.

[0008] The invention solves the problem by a vibration sensor with a single rod and by a method for adjusting a vibration sensor and especially the mechanically oscillating unit.

[0009] The object is achieved by a vibration sensor having a mechanically oscillatable unit, a transducer device, a housing, and a compensating component, wherein the transducer device excites the mechanically oscillatable unit to mechanical vibrations and / or receives mechanical vibrations from the mechanically oscillatable unit, wherein the mechanically oscillatable unit has an outer tube, an inner tube, and a terminal unit, wherein the outer tube has an interior space, a first end face, and a second end face, wherein the inner tube is arranged in the interior space of the outer tube, wherein the outer tube is connected to the housing via the first end face, wherein the interior space of the outer tube is delimited at the second end face by the terminal unit, wherein the compensating component is arranged at least partially in the interior space of the outer tube and / or adjacent to the interior space of the outer tube,and wherein the compensating component is mechanically coupled to the outer tube and / or to the inner tube, and wherein the vibration sensor has a continuous recess through which the compensating component can be inserted and / or changed.

[0010] The vibration sensor according to the invention has a mechanically oscillatable unit and a transducer device. The transducer device converts between electrical signals and vibrations of the mechanically oscillatable unit. A housing and a compensating component are also present. The housing also encloses, for example, an electronics unit of the sensor. The mechanically oscillatable unit is connected to the housing by an outer tube of the mechanically oscillatable unit being connected to the housing at one end. An opposite end is connected to a terminal unit, which can also include the one-piece design of the outer tube and terminal unit. The terminal unit and the outer tube thus enclose an interior space in which an inner tube of the mechanically oscillatable unit is located.The compensation component serves to compensate for the mechanically oscillatable unit and is located at least partially or completely within the interior of the outer tube and / or is arranged adjacent to the interior of the outer tube. Furthermore, the compensation component is mechanically coupled to the outer tube and / or the inner tube, such that the compensation component influences the affected vibration behavior. The vibration sensor has a continuous recess through which the compensation component can be introduced and / or changed. It is thus possible to introduce and / or change the compensation component via the recess, which should also include changing an amount of the compensation component. In one embodiment, the continuous recess is located on the side of the outer tube facing away from the termination unit. In this embodiment, the recess thus runs within the interior of the vibration sensor.

[0011] The following designs relate to where the recess is located by discussing which components form the recess.

[0012] One embodiment of the vibration sensor provides for the inner tube to have a continuous recess. Thus, in this embodiment, the inner tube is essentially designed as a hollow cylinder.

[0013] A supplementary or alternative embodiment of the vibration sensor provides that the transducer device has a continuous recess.

[0014] A supplementary or alternative embodiment of the vibration sensor provides for the housing to have a continuous recess. In a supplementary embodiment, the continuous recess is located on one end of the housing, to which the mechanically oscillating unit is connected. Thus, in this embodiment, the end of the housing faces the medium when the vibration sensor is in use.

[0015] A supplementary or alternative design of the vibration sensor includes the outer tube being essentially circularly cylindrical, and the closure unit closing the outer tube at the second end face. The closure unit can thus be understood as the cover or base of the outer tube, depending on its orientation.

[0016] A supplementary or alternative embodiment of the vibration sensor provides that the transducer device comprises at least one piezoelectric element. In a supplementary embodiment, the transducer device is formed by at least one annular piezoelectric element.

[0017] A supplementary or alternative embodiment of the vibration sensor includes a recess in the terminal unit, and the compensating component is at least partially arranged in the recess of the terminal unit. In this embodiment, the terminal unit has, for example, a blind hole that at least partially accommodates the compensating component.

[0018] A supplementary or alternative embodiment of the vibration sensor provides that the compensation component consists at least partially of a hardenable fluid, and that the fluid is designed such that a viscosity of the fluid depends on a shear force acting on the fluid. The fluid is preferably introduced into the mechanically oscillating unit via the continuous recess in a not yet hardened state and is hardened there - e.g. by an external influence or by itself. The fluid is preferably designed such that, when shear forces act on it, it has a low viscosity - i.e., pseudoplastic or shear-thinning. However, if no shear forces act on it, the fluid is highly viscous. The fluid is preferably designed such that it can be removed from the mechanically oscillating unit again if necessary.

[0019] A supplementary or alternative embodiment of the vibration sensor includes the compensation component consisting at least partially of a fixable powder. The powder is preferably introduced into the mechanically oscillating unit during calibration and is fixed there by the powder being transformed into a solid unit or connected to a larger component. The powder is fixed, for example, by laser welding, by applying an electrical voltage, or by a chemical reaction triggered, for example, by compressive force or suitable catalysts.

[0020] A supplementary or alternative embodiment of the vibration sensor provides that the compensation component consists at least partially of a mass element and a fastening device, that the mass element is fastened in the interior of the outer tube via the fastening device, that the fastening device has at least two stable deformation states, and that the fastening device changes from one deformation state to the other deformation state—preferably by applying a mechanical force. This embodiment exploits the fact that the effect of a mass element depends on its position relative to the mechanically oscillatable unit or to the subcomponents inner tube and outer tube.For this purpose, a mass element is fastened in the interior via such a fastening device, which can assume at least two different deformation states, i.e. in particular does not automatically return from one state to the other through purely elastic deformation. The two deformation states are particularly associated with the mass element each assuming a different position in the interior. In one embodiment, each deformation state is associated with a different position of the mass element along a longitudinal axis of the mechanically oscillatable unit. The continuous recess allows, for example, a mechanical force to be exerted on the mass element and / or the fastening device when calibrating the mechanically oscillatable unit, so that the transition from one deformation state to the other takes place. In particular, a permanent deformation from one deformation state to the other takes place.

[0021] Furthermore, the invention solves the problem by a method for calibrating a vibration sensor, wherein the vibration sensor has a mechanically oscillatable unit, wherein the method comprises at least the following step: that a compensating component is introduced into the mechanically oscillatable unit via a continuous recess of the vibration sensor and / or a compensating component is changed in the mechanically oscillatable unit.

[0022] According to the invention, the calibration of a vibration sensor with a mechanically oscillatable unit takes place by introducing a compensating component into the mechanically oscillatable unit via a continuous recess in the vibration sensor and / or changing a compensating component in the mechanically oscillatable unit. The vibration sensor thus has a continuous recess that allows a compensating component to be introduced into the mechanically oscillatable unit and / or to change, i.e., modify, a compensating component that is already present in the mechanically oscillatable unit. The calibration is carried out, for example, during manufacture of the vibration sensor, during installation at the application site, or as part of the adjustment during use. Depending on the design or type of application, the continuous recess is reversibly or irreversibly closed after the calibration has been completed.

[0023] One embodiment of the method involves inserting a cannula as a tool into the continuous recess – preferably temporarily – and inserting the compensating component into the mechanically oscillating unit through the cannula. In this embodiment, a cannula is inserted into the recess, through which the compensating component is guided to enter the mechanically oscillating unit. This simplifies the process and also prevents the compensating component from being positioned in undesired locations.

[0024] An alternative or supplementary embodiment of the method provides for the introduced compensating component to be acted upon in such a way that the compensating component hardens. In this embodiment, the compensating component is initially in a liquid or powdery, i.e., non-solid, state within the mechanically oscillating unit. Accordingly, it is provided that the compensating component hardens, for example, thermally, mechanically, through the introduction of UV light, through a chemical reaction, or through the application of electric or magnetic fields.

[0025] An alternative or supplementary embodiment of the method involves inserting a punch as a tool into the continuous recess - preferably temporarily - and exerting a mechanical force on the compensating component by the punch. In this embodiment, the compensating component is designed such that it reacts to a mechanical force. This can be, for example, a change in position or compression of the compensating component. The compensating component can, for example, already be arranged in the mechanically oscillatable unit before the adjustment is carried out. Alternatively, the compensating component can first be inserted during the adjustment - e.g. via the aforementioned cannula - and then processed via the punch.

[0026] An alternative or supplementary embodiment of the method provides that the method comprises the further steps of mechanically coupling the mechanically oscillatable unit - preferably temporarily - to a clamping device, and introducing a sufficient amount of compensation component into the mechanically oscillatable unit and / or modifying the compensation component in the mechanically oscillatable unit such that mechanical vibration of the mechanically oscillatable unit is essentially free from the transmission of forces and / or moments from the mechanically oscillatable unit to the clamping device. In this embodiment, the mechanically oscillatable unit is connected - temporarily or permanently - to a clamping device. The clamping device can be a tool for the production of the vibration sensor. Alternatively, the clamping device is part of the process that the vibration sensor is intended to monitor. For example, it can beThis could be the wall of a container. The goal of the balancing is to ensure that as little energy as possible is transferred from the mechanically vibrating unit to the clamping device. To achieve this, the balancing component is acted upon by introducing an appropriate amount of balancing component material into the mechanically vibrating unit, depending on its design, or by influencing it accordingly.

[0027] The statements and explanations of the procedure also apply to the vibration sensor and vice versa, so there is no need to repeat them.

[0028] The invention is explained in more detail with reference to the following figures.

[0029] Fig. 1 shows a section through a schematic representation of a first embodiment of a vibration sensor,

[0030] Fig. 2 shows a section through a second embodiment of a vibration sensor, Fig. 3 shows a section through a third embodiment of a vibration sensor with a first deformation state of the compensation component,

[0031] Fig. 4 shows a section through a part of the vibration sensor of Fig. 3 with a second deformation state of the compensation component and

[0032] Fig. 5 shows a third deformation state of the compensation component.

[0033] Fig. 1 shows a first embodiment of the vibration sensor during calibration.

[0034] The vibration sensor has a mechanically oscillating unit 1, which is excited to oscillate by a transducer device 2. In the illustrated embodiment, the transducer device 2 also receives the mechanical vibrations from the mechanically oscillating unit 1 and converts them into electrical signals. Based on the received signals, it can then be determined—for example, by an electronic evaluation unit not shown here—whether a fill level has been reached or what properties the medium with which the mechanically oscillating unit 1 is in contact has.

[0035] The mechanically oscillating unit 1 is designed as a single-rod structure. A circular-cylindrical inner tube 11 is located within the interior space 100 of a likewise circular-cylindrical outer tube 10. The outer tube 10 has two end faces 101, 102: the first end face 101 of the outer tube 10 is connected to a housing 3. The housing 3 encloses the transducer device 2 and other components of the vibration sensor (not shown here). The second end face 102 is closed by a closure unit 12, which can also be understood as a cover or base. The inner tube 11 is located in this interior space 100, which is closed to the outside and is sealed off from the medium (not shown here).

[0036] As shown, the transducer device 2 is firmly fixed relative to the housing 3. For calibration, the vibration sensor has a continuous recess in its interior, which is created here by the continuous recess 110 of the inner tube 11, by the continuous recess 30 in the housing 3, and by the continuous recess 20 in the transducer device 2. The recesses 20, 30, 110 are each located axially one behind the other, resulting in a continuous recess into which a cannula has been inserted as a tool 5.

[0037] The still-flowable compensating component 4 is introduced into the interior 100 of the outer tube 10 via the cannula 5 in order to change its mass and thus its vibration behavior relative to that of the inner tube 11. Once sufficient material for the compensating component 4 has been introduced, the cannula 5 is removed and the hardening process is initiated so that the compensating component 4 cannot migrate during vibrations.

[0038] The design of the vibration sensor in Fig. 2 is similar to the variant in Fig. 1 , so only the differences are discussed here.

[0039] The state shown is that the tool for inserting or machining the compensating component 4 has already been removed from the continuous recess. In the illustrated embodiment, the compensating component 4 is located in a recess 120 of the end unit 12, which is significantly thicker here than in the embodiment of Fig. 1. The compensating component 4 is thus located in the recess 120 designed as a blind hole and borders the interior 100 of the outer tube 10. In this embodiment, a part—namely that of the recess 120—of the end unit 12 is at least partially replaced by the material of the compensating component 4.

[0040] If, for the adjustment in the embodiments of Fig. 1 and Fig. 2, material was introduced into or adjacent to the interior 100 of the outer tube 10, the variant of Fig. 3 refers to a compensation component 4 already located in the mechanically oscillatable unit 1.

[0041] In the embodiment of Fig. 3, only the differences from the variant of Fig. 1 are discussed. Located on the inside of the outer tube 10, and thus in the interior space 100 of the outer tube 10, is the compensating component 4, which here consists of a mass element 40 and a fastening device 41. The fastening device 41 serves to connect the mass element 40 to the inner tube 100. The compensating component 4 is located outside the movement path of the inner tube 11 in the direction of the closure unit 12.

[0042] The vibration sensor is connected here via the housing 3 to a clamping element 6, which may be, for example, the wall of a container. A punch 5 is inserted into the continuous recess of the vibration sensor as a tool, via which a mechanical force is exerted on the compensating component 4. The compensating component 4 is influenced in such a way that the vibration sensor does not transmit any forces and moments to the clamping element 6, and thus the forces and moments of the vibrations of the outer tube 10 and inner tube 11 just compensate each other. To detect this, a force sensor 7, for example, is located on the clamping element 6.

[0043] Fig. 3 shows a first deformation state of the compensating component 4. It can be seen that the mass element 40 and the fastening device 41 are located at the same height along a longitudinal axis of the mechanically oscillatable unit 1.

[0044] Fig. 4 shows a second deformation state, in which the mass element 40 is arranged away from the termination unit 12. For this displacement of the mass element 40, the stamp (see Fig. 3) has, for example, a magnet.

[0045] Fig. 5, in turn, shows a third deformation state, in which the mass element 40 has been moved toward the terminal unit 12. Each deformation state is accompanied by a different moment of inertia. List of reference symbols: mechanically oscillatable unit

[0046] converter device

[0047] Housing

[0048] Compensation component

[0049] Tool

[0050] clamping

[0051] force sensor

[0052] outer tube

[0053] inner tube

[0054] Termination unit continuous recess of the converter device continuous recess of the housing

[0055] Mass element

[0056] Fastening device

[0057] Interior first end face second end face continuous recess of the inner tube

[0058] Recess of the final unit

Claims

Patent claims 1 . Vibration sensor, with a mechanically oscillatable unit (1), with a transducer device (2), with a housing (3) and with a compensation component (4), wherein the transducer device (2) excites the mechanically oscillatable unit (1) to mechanical vibrations and / or receives mechanical vibrations from the mechanically oscillatable unit (1), wherein the mechanically oscillatable unit (1) has an outer tube (10), an inner tube (11) and a termination unit (12), wherein the outer tube (10) has an interior space (100), a first end face (101) and a second end face (102), wherein the inner tube (11) is arranged in the interior space (100) of the outer tube (10), wherein the outer tube (10) is connected to the housing (3) via the first end face (101), wherein the interior space (100) of the outer tube (10) is connected to the second end face (102) via the termination unit (12) is limited,wherein the compensating component (4) is arranged at least partially in the interior (100) of the outer tube (10) and / or adjacent to the interior (100) of the outer tube (10), and wherein the compensating component (4) is mechanically coupled to the outer tube (10) and / or to the inner tube (11), and wherein the vibration sensor has a continuous recess (110, 20, 30) through which the compensating component (4) can be introduced and / or changed.

2. Vibration sensor according to claim 1, wherein the inner tube (11) has a continuous recess (110), and / or wherein the transducer device (2) has a continuous recess (20), and / or wherein the housing (3) has a continuous recess (30).

3. Vibration sensor according to claim 1 or 2, wherein a recess (120) is present in the termination unit (12), and wherein the compensation component (4) is arranged at least partially in the recess (120) of the termination unit (12).

4. Vibration sensor according to one of claims 1 to 3, wherein the compensating component (4) consists at least partially of a curable fluid, and wherein the fluid is designed such that a viscosity of the fluid depends on a shear force acting on the fluid.

5. Vibration sensor according to one of claims 1 to 4, wherein the compensating component (4) consists at least partially of a fixable powder.

6. Vibration sensor according to one of claims 1 to 5, wherein the compensation component (4) consists at least partially of a mass element (40) and a fastening device (41), wherein the mass element (40) is fastened in the interior (100) of the outer tube (10) via the fastening device (41), wherein the fastening device (41) has at least two stable deformation states, and wherein the fastening device (41) changes from one deformation state to the other deformation state - preferably by the application of a mechanical force.

7. A method for adjusting a vibration sensor, wherein the vibration sensor has a mechanically oscillatable unit (1), wherein the method comprises at least the following step: that a compensation component (4) is inserted into the mechanically oscillatable unit (1) is introduced and / or a compensating component (4) in the mechanically oscillatable unit (1) is changed.

8. Method according to claim 7, wherein a cannula is introduced as a tool (5) into the continuous recess (110, 20, 30) - preferably temporarily - and wherein the compensating component (4) is introduced into the mechanically oscillatable unit (1) through the cannula (5).

9. Method according to claim 7 or 8, wherein a stamp is introduced into the continuous recess (110, 20, 30) - preferably temporarily - as a tool (5), and wherein a mechanical force is exerted on the compensating component (4) by the stamp (5).

10. The method according to any one of claims 7 to 9, wherein the method comprises as further steps that the mechanically oscillatable unit (1) is mechanically coupled - preferably temporarily - to a clamping device (6), and that such a quantity of compensation component (4) is introduced into the mechanically oscillatable unit (1) and / or the compensation component (4) in the mechanically oscillatable unit (1) is changed in such a way that a mechanical oscillation of the mechanically oscillatable unit (1) is substantially free from a transmission of forces and / or moments from the mechanically oscillatable unit (1) to the clamping device (6).

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