Device for determining and / or monitoring a process variable

Abstract

The invention discloses a device for determining and / or monitoring a process variable of a medium. The two oscillating components (11) of a mechanically oscillatory unit (1) and the two delimiting components (23) of a time-of-flight measurement unit (2) are arranged at different heights along a longitudinal axis (A).

Description

[0001] Device for determining and / or monitoring a process variable

[0002] The invention relates to a device for determining and / or monitoring at least one process parameter of a medium.

[0003] In the prior art, so-called vibronic multisensors are known that allow the measurement of various process variables of a medium (see, for example, DE 10 2018 127 526 A1 or DE 10 2020 116 278 A1). The device is based on a so-called vibrating fork with two fork tines. Each tine (or more precisely, its root) contains a piezoelectric element. These two piezoelectric elements serve, on the one hand, to excite the vibrating fork to mechanical vibrations and to receive these vibrations. On the other hand, the piezoelectric elements allow the transmission and reception of ultrasonic signals. The various process variables can be determined from the mechanical vibrations and the transit time of the ultrasonic signals.The dual function of the piezoelectric elements and the application of such significantly different frequency ranges (ultrasound as opposed to mechanical vibrations with a frequency less than 1 kHz) make it difficult to optimize the multisensor, since both sensor principles are coupled, so compromises are necessary.

[0004] A tuning fork with a closed cavity behind it for ultrasonic measurements is disclosed in DE 102015 112 055 A1.

[0005] Ultrasonic measurement can be disrupted, for example, by the presence of suspended particles in the medium. This is particularly disadvantageous because one application of these multisensors is in the monitoring of fermentation processes. To reduce such interference, it has proven advantageous to maximize the effective ultrasonic area. However, this would necessitate a large and therefore excessively rigid root area of ​​the fork tines. To counteract this, the resonant frequency of the fork tines would have to be correspondingly very wide or very long. This would render the dimensions of the vibratory fork too impractical for the application. The invention therefore aims to propose a vibronic multisensor whose ultrasonic measurements are as insensitive as possible to suspended particles in the medium being measured or monitored.

[0006] The problem is solved by a device for determining and / or monitoring at least one process parameter of a medium, comprising a mechanically vibrating unit, a transit-time measuring unit, and a transducer device for exciting the mechanically vibrating unit to mechanical vibrations and for receiving mechanical vibrations from the mechanically vibrating unit, wherein the mechanically vibrating unit has at least two vibration components, wherein the transit-time measuring unit has an ultrasonic device for transmitting and receiving ultrasonic signals, wherein the transit-time measuring unit has two limiting components at a predefinable distance between travel distances, and wherein the two vibration components and the two limiting components are designed and arranged relative to each other such that one limiting component and one vibration component are arranged at different heights along a longitudinal axis of the device.

[0007] The invention thus describes a vibronic multisensor which, as in the prior art, implements two completely different measurement principles, but which, through its radical decoupling of the two principles, allows for separate optimization of the respective components involved. This is achieved here by axial offset. Therefore, it is possible, for example, to increase the effective area for the ultrasound signals without requiring corresponding countermeasures in the principle of evaluating mechanical vibrations.

[0008] One embodiment provides that the converter device has at least two converter components, and that a converter component is arranged in each of the at least two vibration components.

[0009] One embodiment includes the fact that the ultrasound device has at least two subcomponents, that one subcomponent of the two subcomponents is designed as a transmitting / receiving component for transmitting and / or receiving ultrasound signals, that another subcomponent of the two subcomponents is designed as a transmitting / receiving component or as a reflector, and that a subcomponent is arranged in each of the two boundary components.

[0010] One embodiment provides that the two limiting components and the two vibration components each have a continuous recess in pairs, and that a transducer component and a sub-component are arranged in each of these continuous recesses. A common recess simplifies manufacturing with regard to inserting the components and, for example, their wiring. At the same time, the vibration components and the limiting components are also arranged in pairs in such a way that a continuous recess can be formed.

[0011] One embodiment involves arranging the two subcomponents and the two converter components at different heights along the longitudinal axis. In this embodiment, the subcomponents and the converter components are also located at different heights along the longitudinal axis, thus further improving the separation of the two measurement principles.

[0012] According to one embodiment, the two subcomponents and the two converter components are arranged radially offset from each other. In this embodiment, the subcomponents and the converter components are arranged in pairs not aligned, but radially offset from each other. In this embodiment, a radial offset refers to the center point of the component at which the vibration components and the limiting components are located.

[0013] One embodiment provides that the device further comprises a support component, that the two limiting components are arranged on the support component, and that the two vibrating components are arranged on the two limiting components. The support component is, for example, a solid disk or plate that forms one side of a housing of the device. In this application, the outer surface of the support component faces the medium. The two limiting components are located on the support component, and the two vibrating components are mounted on these. Therefore, in this embodiment, the vibrating fork components are located further away from the support component than the limiting components. Each support component and each limiting component form a pair. The embodiment can thus be described as each limiting component acting as a base for a vibrating component.

[0014] One embodiment includes the fact that the two boundary components are essentially planar, at least in their opposing areas. The boundary components are preferably planar, at least in the area where the ultrasound waves enter and exit.

[0015] One embodiment provides that the mechanically oscillating unit is a rocker fork, and that the two oscillating components are each designed in the form of a fork tine.

[0016] One embodiment includes the two converter components being designed as piezoelectric elements, and at least the subcomponent designed as a transmit / receive component being designed as a piezoelectric element.

[0017] One embodiment provides that the device further includes a temperature sensor, and that the temperature sensor is arranged on the support component.

[0018] One embodiment includes the device further comprising a control unit, and the control unit being designed to control the transducer device and the ultrasound device and to determine and / or monitor at least one process variable based on signals from the transducer device and / or the ultrasound device.

[0019] The invention is explained in more detail with reference to the following figures. Fig. 1 shows a section through a schematic embodiment of a device.

[0020] Fig. 2 shows another view of the device of Fig. 1 and

[0021] Fig. 3 shows a top view of the device of Fig. 1.

[0022] Figure 1 shows an embodiment of the device for determining and / or monitoring at least one process variable. The process variable is, for example, the density, the fill level, or the speed of sound in a medium (not shown here).

[0023] The device has a mechanically oscillating unit 1 and a transit-time measuring unit 2.

[0024] The mechanically vibrating unit 1 is excited to mechanical vibrations by the transducer device 10. When the mechanically vibrating unit 1 comes into contact with the medium, the vibrations are influenced by the medium itself as well as by its properties or process parameters. To evaluate this, the transducer device 10 receives the mechanical vibrations and converts them into electrical signals, which are then fed to a control unit 3 for further processing. In an alternative embodiment (not shown), the received signals are fed to a separate processing device.

[0025] The mechanically oscillating unit 1 is designed here as a tuning fork and has two oscillating components 11, which can also be referred to as fork tines. For excitation and reception of the signals, each of the oscillating components 11 contains a transducer component 12 as part of the transducer device 10. The transducer components 12 are, in particular, piezoelectric elements. The transit-time measuring unit 2 serves to measure the transit time of ultrasonic signals between the two limiting components 23. For this purpose, the ultrasonic device 20 has two subcomponents 21 and 22.

[0026] Regarding the subcomponents 21 and 22, there are several different embodiments: a) In a first embodiment, one subcomponent 21 is a transmitting / receiving component that both transmits and receives ultrasound signals. The other subcomponent 22 is a reflector for ultrasound signals. Therefore, the ultrasound signals traverse the distance between the two subcomponents 21 and 22 twice. b) In a second embodiment, both subcomponents 21 and 22 are transmitting / receiving components that both transmit and receive ultrasound signals. Therefore, the ultrasound signals traverse the distance only once, but the direction of the ultrasound signals can be changed. c) In a third embodiment, both subcomponents 21 and 22 are transmitting / receiving components, but they only transmit or only receive ultrasound signals, respectively. Therefore, the ultrasound signals traverse the distance only once and with a fixed direction.

[0027] The transmitting / receiving components are primarily polarized piezoelectric elements. Depending on whether they function as both a transmitting and receiving component or solely as a transmitting or receiving component, the type of connections or contact arrangement may vary depending on the specific design.

[0028] In the illustrated case, the two subcomponents 21 and 22 are essentially identical in design and are both configured to transmit and receive ultrasonic signals. The control unit 3 interacts with the subcomponents 21 and 22 to trigger the transmission of the ultrasonic signals and to detect their arrival time. The limiting components 23 are mounted on the outside of a solid support component 4. In the illustrated embodiment, the support component 4 extends laterally into a housing that encloses the inside of the device and also accommodates the control unit 3.

[0029] Each boundary component 23 has a vibration component 11 mounted on it. Relative to the support component 4, the vibration components 11 are located further out along the longitudinal axis A than the boundary components 23.

[0030] The vibration components 11 and the limiting components 23 each have a common recess 5 in pairs, in which the subcomponents 21, 22 and the transducer components 12 are located. The subcomponents 21, 22 and transducer components 12 are arranged at different heights along the longitudinal axis A. The transducer components 12 are located directly within the vibration components 11 without any clearance, whereas the subcomponents 21, 22 are located on the inside of the recess 5 at the same height as the limiting components 23. This results in an axial offset between the components 1, 10, 11, 12 used for applying the mechanical vibrations and the components of the transit-time measurement unit 2, 20, 21, 22, 23. Thus, a separation or decoupling is achieved between the mechanical vibrations and the ultrasonic signals.

[0031] Furthermore, there is a radial offset between the converter components 12 and the subcomponents 21, 22. The subcomponents 21, 22 are located radially further inwards than the converter components 12.

[0032] Since several process parameters, including the ultrasonic velocity, depend on the temperature of the medium, the device is equipped with a temperature sensor 6 located in a projection of the support component 4. Alternatively, the temperature sensor 6 can be a separate component positioned remotely from the device.

[0033] Fig. 2 shows a type of section perpendicular to the section in Fig. 1. The paddle shape of the vibrating component 11 is visible, with the transducer component 12 located in the root section. Below the transducer component 12, in the region of the limiting component 23, is a subcomponent 22 of the ultrasonic device 20. This makes it clear that not only the vibrating component 11 and the limiting component 23, but also the transducer component 12 and the subcomponent 22 are located at significantly different heights along the longitudinal axis A.

[0034] It can also be seen that the converter component 12 and the sub-component 22 each have a rectangular shape, with the converter component 12 being arranged vertically and the sub-component 22 tilted at a right angle to it.

[0035] The limiting component 23 sits on the support component 4 as a kind of wall or turret. The temperature sensor 6 is located laterally offset from the vibrating component 11, so that there is no interference with the ultrasonic signals.

[0036] The top view of Fig. 3 shows how the boundary components 23 are shaped and arranged on the support component 4.

[0037] The two opposing, and therefore inner, sections of the boundary components 23 each have a flat surface, between which the track section L is located. The outer sections of the boundary components 23 are semicircular. In an alternative variant – not shown here – the outer sections also each have a flat / planar profile.

[0038] Directly behind the inner sections of the limiting components 23 are the subcomponents 21 and 22 for transmitting and receiving the ultrasonic signals, respectively. Further out, in order to be located in the region of the center of gravity of the limiting components 23 in the illustrated embodiment, are the vibrating components 11. Depending on the configuration, the transducer components 12 in the vibrating components 11 can be controlled such that the vibrating components 11 oscillate in the plane in which the paddle is located or perpendicular to it. The position of the temperature sensor 6, far from the subcomponents 21 and 22 designed as ultrasonic transducers, can also be seen here.

[0039] Reference symbol

[0040] 1 mechanically oscillating unit

[0041] 2 Time-of-flight measuring unit

[0042] 3 Control unit

[0043] 4 T carrier component

[0044] 5 recesses

[0045] 6 Temperature sensor

[0046] 10 Converter device

[0047] 11 Vibration component

[0048] 12 converter components

[0049] 20 Ultrasound device

[0050] 21, 22 subcomponent

[0051] 23 Limiting component

[0052] A Longitudinal axis

[0053] L Running distance

Claims

Patent claims 1. Device for determining and / or monitoring at least one process parameter of a medium, comprising a mechanically vibrating unit (1), a transit-time measuring unit (2), and a transducer device (10) for exciting the mechanically vibrating unit (1) to mechanical vibrations and for receiving mechanical vibrations from the mechanically vibrating unit (1), wherein the mechanically vibrating unit (1) has at least two vibration components (11), wherein the transit-time measuring unit (2) has an ultrasonic device (20) for transmitting and receiving ultrasonic signals, wherein the transit-time measuring unit (2) has two limiting components (23) at a predefinable distance (L), and wherein the two vibration components (11) and the two limiting components (23) are designed and arranged relative to each other,that a limiting component (23) and a vibration component (11) are arranged at different heights along a longitudinal axis (A) of the device.

2. Device according to claim 1, wherein the transducer device (10) has at least two transducer components (12), wherein a transducer component (12) is arranged in each of the at least two vibrating components (11), wherein the ultrasound device (20) has at least two subcomponents (21, 22), wherein one subcomponent (21) of the two subcomponents (21, 22) is configured as a transmitting / receiving component for transmitting and / or receiving ultrasound signals, wherein another subcomponent (22) of the two subcomponents (21, 22) is configured as a transmitting / receiving component or as a reflector, and wherein in each of the two boundary components (23) a subcomponent (21 , 22) is arranged.

3. Device according to claim 2, wherein the two limiting components (23) and the two vibration components (11) each have a continuous recess (5) in pairs, and wherein a transducer component (12) and a subcomponent (21, 22) are arranged in each of the continuous recesses (5).

4. Device according to claim 2 or 3, wherein the two sub-components (21 , 22) and the two converter components (12) are arranged at different heights along the longitudinal axis (A).

5. Device according to one of claims 2 to 4, wherein the two sub-components (21 , 22) and the two converter components (12) are arranged radially offset from each other.

6. Device according to one of claims 1 to 5, wherein the device further comprises a support component (4), wherein the two limiting components (23) are arranged on the support component (4), and wherein the two vibration components (11) are arranged on the two limiting components (23).

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