VIBRONIC MULITSENSOR

Abstract

A device and a method for measuring and/or monitoring at least one process variable of a medium is provided. The device comprises a sensor unit with a mechanically vibrating unit, at least one reflection unit, a piezoelectric element which is attached to the membrane, and an electronic. The device is designed to excite the mechanically vibrating unit to mechanical vibrations using an excitation signal, to receive the mechanical vibrations of the vibrating unit and convert them into a first reception signal, to emit a transmission signal, and to receive a second reception signal. The electronic unit is designed to determine the at least one process variable of the medium based on the first and/or second reception signal.

Claims

1-15. (canceled)

16. A device for measuring or monitoring at least one process variable of a medium, comprising a sensor unit including: a mechanically vibrating unit; at least one reflection unit; a piezoelectric element which is attached to the membrane; and an electronic unit; wherein the device is designed to excite the mechanically vibrating unit to mechanical vibrations using an excitation signal; to receive the mechanical vibrations of the vibrating unit and convert them into a first reception signal; to transmit a transmission signal; and to receive a second reception signal; wherein the electronic unit is designed to determine the at least one process variable of the medium using the first or second reception signal.

17. The device according to claim 16, wherein the reflection unit is designed to reflect the transmission signal back to the piezoelectric element.

18. The device according to claim 16, comprising a unit for measuring and or monitoring a temperature of the medium; wherein the unit for measuring or monitoring the temperature comprises a temperature sensor in the form of a resistor element or a thermocouple.

19. The device according to claim 16, wherein the mechanically vibrating unit has a membrane and two vibrating rods integrally formed on the membrane, wherein the reflection unit is oriented, at least in segments, perpendicular to the vibrating rods, and wherein the piezoelectric element is attached to the membrane in a region of the membrane facing away from the vibrating rods.

20. The device according to claim 19, wherein at least two reflection units are present which are respectively integrally formed on the vibrating rods in an end region facing away from the membrane.

21. The device according to claim 20, wherein the reflection units are designed to be cuboid, wherein a respective surface of each of the reflection units is oriented parallel to a surface of the membrane, said surface facing toward the process.

22. The device according to claim 21, wherein the reflection units are oriented in a manner facing toward one another, starting from the vibrating rods.

23. The device according to claim 22, wherein a respective reflective coating is applied to the reflection units, at least in the region of a surface facing toward the membrane.

24. The device according to claim 23, wherein a sum of the two surfaces of the two reflection units, said surface facing toward the membrane, is at least 20% of the surface of the membrane or of the piezoelectric element, the surface facing toward the process.

25. A method for measuring or monitoring at least one process variable of a medium using a device, wherein the device includes a sensor unit including a mechanically vibrating unit, at least one reflection unit, a piezoelectric element which is attached to the membrane, and an electronic unit, the method comprising steps of: exciting a sensor unit to mechanical vibrations using an excitation signal; receiving the mechanical vibrations by the sensor unit and converting into a first reception signal; emitting by the sensor unit a transmission signal and receiving a second reception signal; and determining the at least one process variable using the first or second reception signal.

26. The method according to claim 25, wherein the temperature of the medium is measured.

27. The method according to claim 25, wherein at least two different process variables are determined, wherein a first process variable is determined using the first reception signal, and wherein a second process variable is determined using the second reception signal.

28. The method according to claim 27, wherein the at least one process variable is a specifiable fill level, density, viscosity, sound velocity, or a variable derived from at least one of these variables.

29. The method according to claim 28, wherein a first concentration of a first substance contained in the medium and a second concentration of a second substance contained in the medium are determined using the first and second reception signals or using the first and second process variables.

30. The method according to claim 29, wherein it is determined, using the first and second reception signals or using the first and second process variables, whether a deposit has been formed on the sensor unit and/or whether a drift and/or an aging of the sensor unit is present.

Description

[0043] The invention is explained in greater detail with reference to the following Figures. The following is shown:

[0044] FIG. 1: a schematic drawing of a vibronic sensor according to the prior art, and

[0045] FIG. 2: exemplary embodiments of a device according to the invention.

[0046] In Figures, identical elements are respectively provided with the same reference signs.

[0047] FIG. 1 shows a vibronic sensor 1 having a sensor unit 2. The sensor has a mechanically vibrating unit 4 in the form of a tuning fork, which is partially immersed into a medium M which is located in a reservoir 3. The vibrating unit 4 is excited by the excitation/receiving unit 5 to mechanical vibrations and can, for example, be excited by means of a piezoelectric stack drive or biomorphic drive. Other vibronic sensors have, for example, electromagnetic driving/receiving units 5. It is possible to use a single driving/receiving unit 5, which serves to excite the mechanical vibrations and to detect them. However, it is also conceivable to implement one each, a driving unit and a receiving unit. FIG. 1 furthermore shows an electronic unit 6, by means of which the signal acquisition, evaluation and/or feeding takes place.

[0048] FIG. 2 shows exemplary embodiments of a sensor unit 2 according to the invention, in the form of vibrating forks. However, the present invention is in no way limited to such an embodiment of the vibrating unit 4. The mechanically vibrating unit 4 shown in FIG. 2a comprises two vibrating rods 9a, 9b, which are mounted on a membrane 8 and which are therefore also referred to as fork prongs. The membrane 8 is part of a housing 7 of the sensor 1 in which, for example, the electronic unit 6 (not shown here) can be arranged. In the present instance, the housing 7 terminates with the membrane 8 in a region facing toward the medium M. The driving/receiving unit 5 is designed in the form of a piezoelectric element which is attached to the membrane 8 in the region facing away from the medium M. The piezoelectric element 5 is thus located within the housing 7. A respective reflection unit 10, 10b is integrally formed in the end regions of the vibration rods 9a, 9b facing away from the membrane 8, said reflection unit respectively being arranged perpendicular to the respective vibration rod 9a, 9b. Both reflection units 10, 10b are designed to be cuboid for the shown embodiment and run radially inward, starting from the vibration rods 9a, 9b, relative to a center point P of the surface O1 of the membrane 8, said surface O1 facing toward the medium M.

[0049] The reflection units 10a, 10b are arranged such that a surface O2 of each of the two reflection units 10a, 10b runs parallel to the surface O1 of the membrane 8, said surface O1 facing toward the medium M.

[0050] The shown sensor unit 2 also has a unit 11 for measuring and/or monitoring the temperature T of the medium M, which unit is likewise arranged within the housing 7. This can, for example, comprise a temperature sensor in the form of a resistor element or a thermocouple.

[0051] For the embodiment shown in FIG. 2a, both reflection units 10a, 10b are made of a reflective material, for example a metal. This is advantageous especially in the event of a metallic vibrating unit 4.

[0052] An alternative embodiment is shown in FIG. 2b. In contrast to the embodiment shown in FIG. 2a, a reflective, preferably metallic coating 12a, 12b is applied onto each of the two reflection units 10a, 10b in the region of the surface O2 facing toward the membrane 8. In this instance, the reflection units 10a, 10b may be made of any other material, preferably the same material as that used for the vibration rods 9a, 9b.

LIST OF REFERENCE SIGNS

[0053] 1 Vibronic sensor [0054] 2 Sensor unit [0055] 3 Reservoir [0056] 4 Vibrating unit [0057] 5 Driving/receiving unit [0058] 6 Electronic unit [0059] 7 Housing [0060] 8 Membrane [0061] 9a, 9b Vibrating elements [0062] 10a, 10b Reflection units [0063] 11 Unit for measuring and/or monitoring the temperature [0064] 12a,12b Reflective coating [0065] M Medium [0066] P Process variable [0067] T Temperature [0068] O1 Surface of the membrane facing toward the process [0069] O2 Surface of the reflection unit arranged parallel to O1 [0070] P Center point of the surface O1 of the membrane