DE102022115591A1 - Modular vibronic multisensor - Google Patents

Abstract

The present invention relates to a modular vibronic sensor (1) for determining and/or monitoring at least one process variable of a medium (M) with a sensor unit (2), which sensor unit (2) has a, in particular electrically insulating, first base body (7). first oscillating element (8), which has a first (9a) and second (9b) piezoelectric element, and a second oscillating element (10), which has a third (11a) and fourth (11b) piezoelectric element. According to the invention, the first (8) and second oscillating element (10) are each fastened in a first end region (E1) on or in the first base body (7), the first (9a) and second (9b) or the third (11a) and fourth (11b) piezoelectric element of the first (8) or second oscillating element (10) are each fastened to one another via a connecting surface (V), the connecting surfaces (V) of the first (9a) and second (9b) or third (11a) and fourth (11b) piezoelectric elements each have the same polarization. The invention further relates to a measuring cell (15) with a sensor (1) according to the invention, a portable measuring device (16) with a measuring cell (15) according to the invention and a method for operating a sensor (1) according to the invention.

Description

The invention relates to a modular vibronic sensor for determining and/or monitoring at least one process variable of a medium. The present invention further relates to a measuring cell comprising a sensor according to the invention, a portable measuring device for analyzing a medium with a measuring cell according to the invention and a method for operating a sensor according to the invention. The medium is located, for example, in a container, for example in a container or in a pipeline, or in the measuring cell.

Vibronic sensors are often used in process and/or automation technology. In the case of level measuring devices, they have at least one mechanically oscillatable unit, such as a tuning fork, a single rod or a membrane. During operation, this is excited to mechanical vibrations by means of a drive/receiver unit, often in the form of an electromechanical converter unit, which in turn can be, for example, a piezoelectric drive or an electromagnetic drive. The applicant produces a wide variety of corresponding field devices and sells them, for example, under the names LIQUIPHANT or SOLIPHANT. The underlying measurement principles are in principle known from a large number of publications. The drive/receiver unit stimulates the mechanically oscillatable unit to mechanical oscillations by means of an electrical excitation signal. Conversely, the drive/receiver unit can receive the mechanical vibrations of the mechanically oscillatable unit and convert them into an electrical received signal. The drive/receiver unit is accordingly either a separate drive unit and a separate receiver unit or a combined drive/receiver unit.

In many cases, the drive/receiver unit is part of a feedback electrical oscillating circuit, by means of which the mechanically oscillatable unit is excited to produce mechanical oscillations. For example, for a resonant oscillation, the resonant circuit condition, according to which the amplification factor is ≥1 and all phases occurring in the resonant circuit result in a multiple of 360°, must be fulfilled. In order to excite and fulfill the resonant circuit condition, a certain phase shift between the excitation signal and the received signal must be guaranteed. Therefore, a predeterminable value for the phase shift, i.e. a setpoint for the phase shift between the excitation signal and the received signal, is often set. For this purpose, a wide variety of solutions, both analog and digital methods, have become known from the prior art, such as those in the documents DE102006034105A1 , DE102007013557A1 , DE102005015547A1 , DE102009026685A1 , DE102009028022A1 , DE102010030982A1 or DE102010030982A1 described.

Both the excitation signal and the received signal are characterized by their frequency ω, amplitude A and/or phase Φ. Accordingly, changes in these variables are usually used to determine the respective process variable. The process variable can be, for example, a fill level, a predetermined fill level, or the density or viscosity of the medium, as well as the flow. With a vibronic level switch for liquids, for example, a distinction is made as to whether the oscillatable unit is covered by the liquid or vibrates freely. These two states, the free state and the covered state, are distinguished, for example, based on different resonance frequencies, i.e. based on a frequency shift.

The density and/or viscosity can only be determined with such a measuring device if the oscillatable unit is completely covered by the medium. In connection with the determination of the density and/or viscosity, various options have also become known from the prior art, such as those in the documents DE10050299A1 , DE102007043811A1 , DE10057974A1 , DE102006033819A1 , DE102015102834A1 or DE102016112743A1 revealed.

With a vibronic sensor, several process variables can be determined and used to characterize the respective process. In many cases, however, further information about the process, in particular knowledge of other physical and/or chemical process variables and/or parameters, is required for comprehensive process monitoring and/or control. This can be achieved, for example, by integrating additional field devices into the respective process. The measured values provided by the various measuring devices can then be appropriately processed further in a unit that is higher-level to the devices.

In addition, various vibronic multisensors have become known with which other process variables can be determined. For example, such sensors have been disclosed in which, in addition to the vibronic measuring principle, the Ultra sound measuring principle is used, such as the sensors DE102018127526A1 , DE102019116150A1 , DE102019116151A1 , DE102019116152 , DE102019110821A1 , DE102020105214A1 , DE102020116278A1 , or the previously unpublished German patent application with the file number 102021122534.5.

Based on the stated prior art, the present invention is based on the object of further increasing the functionality of a vibronic sensor.

This object is achieved by the modular, vibronic sensor according to claim 1, by the measuring cell according to claim 11, the portable measuring device according to claim 12, the method according to claim 13, and by the use of a sensor according to the invention according to claim 18.

The sensor according to the invention is a modular, vibronic sensor for determining and/or monitoring at least one process variable of a medium with a sensor unit. The sensor unit comprises a, in particular electrically insulating, first base body and a first oscillating element, which has a first and second piezoelectric element, and a second oscillating element, which has a third and fourth piezoelectric element.

According to the invention, the first and second oscillating elements are each fastened in a first end region on or in the first base body. In addition, the first and second and the third and fourth piezoelectric elements are each fastened to one another via a connecting surface, in particular glued to one another. The connecting surfaces of the first and second or third and fourth piezoelectric elements each have the same polarization. So there are equally polarized surfaces facing each other in relation to the first and second or third and fourth piezoelectric elements.

The two oscillating elements form a mechanically oscillatable unit, for example in the form of a tuning fork. The first and second and the third and fourth piezoelectric elements each form a drive/reception unit for generating mechanical vibrations of the oscillating elements by means of a suitable excitation signal. In the event that the oscillating elements are at least partially covered by medium, the mechanical vibrations are influenced by the properties of the medium, so that a statement about the at least one process variable can be generated based on at least one reception signal received by the oscillating elements, which represents the oscillations of the oscillating elements is.

The piezoelectric elements can also serve to generate a transmission signal, which is received in the form of a response signal. If the transmission signal passes through the medium at least temporarily and in sections on its path, it is also influenced by the physical and/or chemical properties of the medium and can accordingly be used to determine a process variable of the medium.

It is therefore also possible to implement at least two measuring principles in a single device, namely the vibronic measuring principle and the ultrasonic measuring principle. In particular, this also allows the simultaneous determination and/or monitoring of several, in particular different, process variables. The received signal and the response signal can advantageously be evaluated independently of one another and the number of process variables that can be determined can be significantly increased, which results in a higher functionality of the respective sensor or in an expanded area of application.

The modular sensor concept according to the invention enables particularly easy adaptability to different geometries. The dimensions of the oscillating elements and the base body can be selected adaptively. In principle, differently designed oscillating elements can be used with the same base body. The freedom of design not only affects the dimensions and choice of geometry, but also the materials used. This particularly advantageously allows miniaturization of corresponding vibronic sensors.

In addition, a sensor according to the invention can be produced particularly easily and inexpensively. For example, no production of a separate drive/receiver unit is necessary. Rather, the production of oscillating elements and drive/receiver unit takes place together in one step. In addition, the base body can have a partial area for accommodating electronics, so that a simplification of the sensor structure can also be achieved in this context.

In one embodiment, each of the piezoelectric elements is an elongated, flat body, in particular a body with a substantially rectangular cross-sectional area. But other shapes for the cross-sectional area are also conceivable and fall within the scope of the present invention. corners of the piezoelectric In some designs, elements can also be rounded.

In a further embodiment, each piezoelectric element of each oscillating element is individually electrically contacted. In particular, the piezoelectric elements are each electrically contacted via a contact surface, which contact surface is arranged opposite the respective connection surface. The piezoelectric elements that are fastened to one another are therefore each electrically contacted on sides facing away from one another.

It is advantageous if the piezoelectric elements are electrically contacted in the first end region, i.e. in the region in which the oscillating elements are attached to or in the base body.

It is also advantageous if the two oscillating elements are arranged along an imaginary line through a center of a cross-sectional area of the base body and at the same distance from the center and are aligned parallel to one another. The contact surfaces of the first and second oscillating elements are advantageously aligned parallel to one another. In this way, mechanical vibration decoupling is achieved.

In an advantageous embodiment, the oscillating elements are at least partially provided with a coating. The oscillating elements are advantageously provided with the coating at least in an area in contact with the media. A wide variety of coating materials can be used. For example, it can be an insulating coating. But it can also be a water-absorbing coating.

In another advantageous embodiment, the sensor according to the invention comprises a second base body, in particular an electrically insulating one, wherein the first and second oscillating elements are each fastened in a second end region on or in the second base body. In this embodiment, the two oscillating elements are therefore attached in both end regions.

In this context, it is advantageous if for each oscillating element there is a first electrical contact in the first end region and by means of the two contact surfaces and a second electrical contact in the second end region and in the region of the connecting surfaces facing each other of the respective two piezoelectric elements. Such a contacting concept is advantageous for use with conductive media without additional measures.

In a further embodiment, the sensor according to the invention comprises a filter element which is designed and/or arranged in such a way that it at least partially surrounds the two oscillating elements. The filter element comprises, for example, a, preferably porous, membrane or a selective membrane. The filter element can be fastened in particular in the area of at least the first and/or second base body.

The object on which the invention is based is further achieved by a measuring cell for analyzing a medium comprising a modular vibronic sensor according to the invention. According to the invention, a measuring cell is in principle understood to mean a closed volume with a, for example, universal connection for connecting a sensor. The modular vibronic sensor according to the invention can be introduced into the measuring cell, for example, by means of the first base body. For this purpose, the base body can be provided with a connecting element that is complementary to the connecting element of the measuring cell.

The object on which the invention is based is also achieved by a portable measuring device for analyzing a medium, comprising a measuring cell according to the invention, electronics and a device for sampling. The electronics can, for example, have a display unit. The portable measuring device is used, for example, to determine and/or monitor a process variable of a medium such as, but not exclusively, the density, viscosity or speed of sound of a medium or a concentration of a substance contained in the medium.

Furthermore, the object on which the invention is based is achieved by a method for operating a modular vibronic sensor according to the invention for determining and/or monitoring at least a first process variable of a medium, the sensor unit being excited to mechanical vibrations by means of an excitation signal, the mechanical vibrations of the sensor unit are received and converted into a received signal, and the at least one first process variable is determined based on the received signal. The process variable is, for example, the fill level, the density or the viscosity of the medium. The sensor unit includes the first and second oscillating elements.

The excitation signal is, for example, an electrical signal with at least one predeterminable frequency, in particular a sinusoidal or a rectangular signal. Preferably, the sensor unit is stimulated to resonate at least temporarily. The mechanical vibrations are influenced by the medium surrounding the vibrating rods, so that conclusions can be drawn about various properties of the medium based on a received signal representing the vibrations.

The transmission signal is preferably an ultrasonic signal, in particular a pulsed one, in particular at least one ultrasonic pulse. The second measurement method used in the context of the present invention is therefore an ultrasound-based measurement. The transmission signal emitted at least partially passes through the medium and its properties are influenced by it. Accordingly, conclusions about different media can also be drawn based on the response signal received.

With regard to the method according to the invention, it is advantageous if the first piezoelectric element of the first oscillating element and the fourth piezoelectric element of the second oscillating element are acted upon by the excitation signal, and if the received signal comes from the second piezoelectric element of the first oscillating element and the third piezoelectric element of the second Vibrating element is received. In this embodiment, in particular, piezoelectric elements of each oscillating element that face and face away from one another are controlled together. This results in anti-phase oscillations of the sensor unit.

In an alternative embodiment of the method according to the invention, the first piezoelectric element of the first oscillating element and the third piezoelectric element of the second oscillating element are subjected to the excitation signal, the received signal being received by the second piezoelectric element of the first oscillating element and the fourth piezoelectric element of the second oscillating element. In this way, the second basic mode of the sensor unit can be excited, in which the first and second oscillating elements carry out parallel oscillations.

Excitation of the sensor unit in different modes is particularly advantageous in the event that additional condition monitoring, preferably predictive maintenance, is to be carried out using the method according to the invention. The different vibration modes can be excited alternately. However, it is also conceivable to only activate the additional mode when necessary.

In another embodiment of the method according to the invention, at least a second process variable of the medium is determined or monitored. For this purpose, a transmission signal is sent out and a response signal is received, with the at least one second process variable being determined based on the response signal. The second process variable is, for example, the speed of sound of the medium.

In this context, it is advantageous if the first oscillating element is acted upon by the transmission signal, with the response signal being received by the second oscillating element.

It is also advantageous if the at least one first and second process variable are determined alternately. However, it is also possible for the sensor unit to be acted upon simultaneously by means of the excitation signal and by means of the transmission signal, with the excitation signal and the transmission signal being superimposed on one another.

The process variables that can be determined according to the invention are, for example, given by a predeterminable fill level, the density, the viscosity, the speed of sound or a variable derived from at least one of these variables. The concentration(s) of one or two different substances in the medium can also be determined. Particularly preferably, the density and/or viscosity of the medium is determined based on the received signal and the speed of sound within the medium is determined based on the response signal. However, it goes without saying that in addition to the process variables explicitly mentioned here, other process variables and/or parameters that are accessible by means of the two measurements carried out can also be determined and used to characterize the respective medium.

A sensor according to the invention, a measuring cell, a portable measuring device and the method can be used, for example, to monitor a fermentation process. During fermentation, sugar is converted into ethanol. In order to ensure qualitative monitoring, it is therefore necessary to determine both the concentration of sugar and ethanol.

In addition, the sensor according to the invention can also advantageously be used as a single-use sensor. The sensor can be specifically adapted to the respective task. It is also advantageous to use it in a laboratory, in particular to determine the respective process size based on a comparatively small volume of liquid or a small sample amount. Another advantageous use relates to the validation of sensors, due to the simple and inexpensive manufacturability of the sensor according to the invention. Finally, an advantageous use relates to the use of a sensor according to the invention as a gas sensor for determining and/or monitoring a gaseous medium. In particular, a resonance frequency of a sensor according to the invention can be individually adapted to the respective application.

It should be noted that the configurations described in connection with the sensor according to the invention can also be applied mutatis mutandis to the measuring cell according to the invention, the portable measuring device according to the invention and the method according to the invention and vice versa.

• 1: eine schematische Skizze eines vibronischen Sensors gemäß Stand der Technik,
• 2 eine erste mögliche Ausgestaltung eines modularen vibronischen Sensors mit einem Grundkörper;
• 3 eine zweite mögliche Ausgestaltung eines modularen vibronischen Sensor mit einem ersten und einem zweiten Grundkörper;
• 4 eine bevorzugte Möglichkeit zur Kontaktierung der piezoelektrischen Elemente eines Schwingelements;
• 5 eine schematische Darstellung einer bevorzugten Anordnung der Schwingstäbe auf dem Grundkörper,
• 6 eine erfindungsgemäße Messzelle, und
• 7 ein tragbares Messgerät.

The invention is explained in more detail using the following figures. It shows:

• 1 : a schematic sketch of a vibronic sensor according to the prior art,
• 2 a first possible embodiment of a modular vibronic sensor with a base body;
• 3 a second possible embodiment of a modular vibronic sensor with a first and a second base body;
• 4 a preferred option for contacting the piezoelectric elements of a vibrating element;
• 5 a schematic representation of a preferred arrangement of the vibrating rods on the base body,
• 6 a measuring cell according to the invention, and
• 7 a portable measuring device.

In the figures, the same elements are each provided with the same reference number.

In 1 a vibronic sensor 1 with a sensor unit 2 is shown. The sensor has a mechanically oscillatable unit 4 in the form of a tuning fork, which is partially immersed in a medium M which is located in a container 3. The oscillatable unit 4 is excited to mechanical vibrations by means of the excitation/reception unit 5, and can be, for example, by a piezoelectric stack or bimorph drive. Other vibronic sensors have, for example, electromagnetic drive/receiver units 5. It is possible to use a single drive/receiver unit 5, which serves to excite the mechanical vibrations and to detect them. However, it is also conceivable to implement a drive unit and a receiving unit. Is shown in 1 furthermore an electronic unit 6, by means of which the signal is recorded, evaluated and/or fed.

A first exemplary embodiment of a modular vibronic sensor 1 according to the invention is shown in 2 sketched. The sensor 1 has a sensor unit 2 comprising a, in particular insulating, first base body 7, a first oscillating element 8, which has at least a first 9a and a second 9b piezoelectric element, and a second oscillating element 10, which has at least a third 11a and fourth 11b has piezoelectric element.

The two oscillating elements 8, 10 are fastened in a first end region E ₁ in the base body 7 and the first 9a and second 9b or the third 11a and fourth 11b piezoelectric elements of the first 8 and second oscillating element 10 are each by means of a connecting surface V attached to each other. The geometric shape of the piezoelectric elements 9a, 9b, 11a, 11b each preferably has an elongated cross-sectional area. They can be modeled on conventional oscillating rods of a vibronic sensor.

In addition, each piezoelectric element 9a, 9b, 11a, 11b is contacted individually via a connecting line 12a-12d via the connecting surfaces V to contact surfaces K lying opposite each other. All contacts are thus arranged in the first end region E ₁ .

It is then possible, for example, to apply a suitable excitation signal to the first 9a and fourth 11b piezoelectric element by means of the first 12a and fourth 12d connecting line and to receive a received signal from the second 9b and third 11a piezoelectric element by means of the second 12b and third 12c connecting line, to realize the vibronic measuring principle, or vice versa. To implement the ultrasonic measuring principle, it is again conceivable to send a transmission signal from the first 9a and second 9b piezoelectric element by means of the first 12a and second 12b connecting cable and a response signal from the third 11a and fourth 11b piezoelectric element by means of the third 12c and fourth 12d connecting cable to receive, or vice versa. But other electrical contacting options for the piezoelectric elements 9a, 9b, 11a, 11b are also conceivable and also fall under the present invention.

A further advantageous embodiment for a sensor according to the invention is the subject of 3 . In contrast to the design 2 The sensor unit 2 additionally comprises a second base body 13, the oscillating elements 8, 10 being fastened in the second end region E ₂ in the second base body 13.

For such a design, but not only for such, shows 4 another preferred option for contacting the piezoelectric elements 9a, 9b, 11a, 11b. The piezoelectric elements 9a, 9b of each oscillating element 8, 10 (for the sake of simplicity, only the first oscillating element 8 is shown) are electrical via the connecting surfaces V by means of a second connecting line 14b and via the two contact surfaces K by means of a first connecting line 14a contacted, i.e. in both end areas E ₁ and E ₂ . Such contact is particularly advantageous for using the sensor 1 with conductive media M.

A preferred arrangement of the two oscillating elements 8, 10 relative to each other and to the base body 7 is in 5 shown. The two oscillating elements 8, 10 are arranged along an imaginary line I through a center point m of a cross-sectional area of the base body 7 and at the same distance from the center point m and aligned parallel to one another. In the present case, the cross-sectional area has a round shape. However, such a design of the cross-sectional area of the base body 1 is not absolutely necessary. In the event that two base bodies 7, 13 are used, both base bodies can be designed with identical cross-sectional areas and their centers can be arranged one above the other.

In 6 is a measuring cell 15 according to the invention with a sensor 1 according to the invention similar to that shown 2 , shown. In the base body of the sensor variant 6 The base body 7 is also designed to accommodate the electronics 6. Such an embodiment of a sensor 1 according to the invention is particularly compact and the necessary manufacturing steps are further reduced.

A portable measuring device 16 according to the invention is finally in 7 sketched. The measuring device 16 comprises a housing 17 with an optional handle 17a and a device for sampling 18, a measuring cell 15 according to the invention with a sensor 1 according to the invention, not shown here, and electronics 19 with an optional display unit.

Reference symbol list

1

Vibronic sensor

2

Sensor unit

3

container

4

Oscillating unit

5

Drive/receiver unit

6

electronics

7

First basic body

8th

first oscillating elements

9a, 9b

first and second piezoelectric elements

10

second oscillating elements

11a, 11b

third and fourth piezoelectric elements

12a-12d

Connection cables

13

Second basic body

14a, 14b

Connection cables

15

measuring cell

16

portable measuring device

17

Housing

17a

Handle

18

Sampling device

19

Electronics with display unit

M

medium

E1, E2

first and second end regions of the oscillating elements

K

Contact surface

v

Connection surface

m

Focus

I

imaginary line

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102006034105 A1 [0003]
• DE 102007013557 A1 [0003]
• DE 102005015547 A1 [0003]
• DE 102009026685 A1 [0003]
• DE 102009028022 A1 [0003]
• DE 102010030982 A1 [0003]
• DE 10050299 A1 [0005]
• DE 102007043811 A1 [0005]
• DE 10057974 A1 [0005]
• DE 102006033819 A1 [0005]
• DE 102015102834 A1 [0005]
• DE 102016112743 A1 [0005]
• DE 102018127526 A1 [0007]
• DE 102019116150 A1 [0007]
• DE 102019116151 A1 [0007]
• DE 102019116152 [0007]
• DE 102019110821 A1 [0007]
• DE 102020105214 A1 [0007]
• DE 102020116278 A1 [0007]

Claims (18)

Modular vibronic sensor (1) for determining and/or monitoring at least one process variable of a medium (M) with a sensor unit (2), which sensor unit (2) has a, in particular electrically insulating, first base body (7), a first oscillating element (8) , which has a first (9a) and second (9b) piezoelectric element, and a second oscillating element (10), which has a third (11a) and fourth (11b) piezoelectric element, wherein the first (8) and second Oscillating element (10) are each fastened in a first end region (E ₁ ) on or in the first base body (7), the first (9a) and second (9b) or the third (11a) and fourth (11b) being piezoelectric elements of the first (8) or second oscillating element (10) are each fastened to one another via a connecting surface (V), the connecting surfaces (V) of the first (9a) and second (9b) or third (11a) and fourth (11b) piezoelectric element each have the same polarization. Modular vibronic sensor (1) according to Claim 1 , wherein each of the piezoelectric elements (9a, 9b, 11a, 11b) is an elongated, flat body, in particular a body with a substantially rectangular cross-sectional area. Modular vibronic sensor (1) according to Claim 1 or 2 , wherein each piezoelectric element (9a, 9b, 11a, 11b) of each oscillating body (8, 10) is individually electrically contacted, in particular wherein the piezoelectric elements (9a, 9b, 11a, 11b) each have a contact surface (K) are electrically contacted, which contact surface (K) is arranged opposite the respective connection surface (V). Modular vibronic sensor (1) according to at least one of the preceding claims, wherein the piezoelectric elements (9a, 9b, 11a, 11b) are electrically contacted in the first end region (E ₁ ). Modular vibronic sensor (1) according to at least one of the preceding claims, wherein the two oscillating elements (8, 10) along an imaginary line (I) through a center point (m) of a cross-sectional area of the base body (7) and at the same distance from the center point ( m) are arranged and aligned parallel to one another. Modular vibronic sensor (1) according to at least one of the preceding claims, wherein the oscillating elements (8, 10) are at least partially provided with a coating. Modular vibronic sensor (1) according to at least one of the preceding claims, comprising a, in particular electrically insulating, second base body (13), the first and second oscillating elements (8, 10) each being in or in a second end region (E ₂ ). second base body (13) are attached. Modular vibronic sensor (1) according to Claim 7 , wherein for each oscillating element (8,10) a first electrical contact (14a) in the first end region (E ₁ ) and by means of the two contact surfaces (K) and a second electrical contact (14b) in the second end region (E ₂ ) and in the area of the facing connecting surfaces (V) of the respective two piezoelectric elements (9a, 9b, 11a, 11b). Modular vibronic sensor (1) according to at least one of the preceding claims, comprising a filter element which is designed and/or arranged in such a way that it at least partially surrounds the two oscillating elements (8, 10), wherein the filter element can be fastened in particular in the area of at least the first (7) and/or second base body (13). Measuring cell (15) for analyzing a medium (M), comprising a modular vibronic sensor (1) according to at least one of Claims 1 - 9 . Portable measuring device (16) for analyzing a medium, comprising a measuring cell (15). Claim 10 , electronics (6) and a sampling device (18). Method for operating a modular vibronic sensor (1) according to at least one of Claims 1 - 9 for determining and/or monitoring at least a first process variable of a medium (M), wherein a sensor unit (2) is excited to mechanical vibrations by means of an excitation signal, the mechanical vibrations of the sensor unit (2) being received and converted into a received signal, and where the at least one first process variable is determined based on the received signal. Procedure according to Claim 12 , wherein the first piezoelectric element (9a) of the first oscillating element (8) and the fourth piezoelectric element (11b) of the second oscillating element (10) are acted upon by the excitation signal, and wherein the received signal from the second piezoelectric element (9b) of the first oscillating element (8) and the third piezoelectric element (11a) of the second oscillating element (10). Procedure according to Claim 12 , wherein the first piezoelectric element (9a) of the first oscillating element (8) and the third piezoelectric element (11a) of the second oscillating element (10) are acted upon by the excitation signal, and wherein the received signal from the second piezoelectric element (9b) of the first oscillating element (8) and the fourth piezoelectric element (11b) of the second oscillating element (10). Method according to at least one of the Claims 12 - 14 for determining and/or monitoring at least a second process variable of a medium (M), wherein a transmission signal is sent out, a response signal is received, and the at least one second process variable is determined based on the response signal. Procedure according to Claim 15 , wherein the first oscillating element (8) is acted upon by the transmission signal, and wherein the response signal is received by the second oscillating element (10). Method according to at least one of the Claims 12 - 16 , whereby the at least one first and second process variable are determined alternately. Use of a modular vibronic sensor (1) according to at least one of Claims 1 - 9 as a single-use sensor, in a laboratory, for validating sensors, as a gas sensor for determining and/or monitoring a gaseous medium (M).

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