VIBRONIC MULTISENSOR

Abstract

A device and a method for determining and/or monitoring at least one process variable of a medium include a sensor unit having a mechanically oscillatable unit, at least a first piezoelectric element, a conductivity/capacitance detecting unit for determining and/or monitoring a conductivity and/or capacitance of the medium and an electronics unit. The device is embodied to excite the mechanically oscillatable unit by means of an excitation signal such that mechanical oscillations are executed, to receive the mechanical oscillations of the oscillatable unit, to convert them into a first received signal, to transmit a transmitted signal, and to receive a second received signal. The electronics unit is embodied, based on the first and/or second received signal, to determine the at least one process variable of the medium.

Claims

1-18. (canceled)

19. A device for determining and/or monitoring at least one process variable of a medium, the device comprising: a sensor unit comprising: a mechanically oscillatable unit; at least one piezoelectric element; a conductivity/capacitance detection unit adapted to determine and/or monitor a conductivity and/or capacitance of the medium, wherein the sensor unit is configured to excite the mechanically oscillatable unit using an excitation signal such that mechanical oscillations are executed, to detect the mechanical oscillations of the oscillatable unit, to convert the mechanical oscillations into a first received signal, to transmit a transmitted signal, and to receive a second received signal; and an electronics unit configured to determine, based on the first received signal and/or the second received signal, the at least one process variable and, based on a third received signal from the conductivity/capacitance detection unit, to determine the conductivity and/or capacitance of the medium.

20. The device of claim 19, wherein: the at least one piezoelectric element includes a first piezoelectric element and a second piezoelectric element; the first piezoelectric element and the second piezoelectric element are adapted to excite the mechanically oscillatable unit via the excitation signal such that mechanical oscillations are executed, to detect the mechanical oscillations of the oscillatable unit, and to convert the mechanical oscillations into the first received signal; the first piezoelectric element is adapted to transmit the transmitted signal; and the second piezoelectric element is adapted to receive the transmitted signal as the second received signal.

21. The device of claim 20, wherein the mechanically oscillatable unit is an oscillatory fork including a first oscillatory element and a second oscillatory element, and wherein the first piezoelectric element is disposed, at least partially, in the first oscillatory element, and the second piezoelectric element is disposed, at least partially, in the second oscillatory element.

22. The device of claim 19, wherein the conductivity/capacitance detecting unit for determining and/or monitoring the conductivity and/or capacitance of the medium comprises a capacitive and/or conductive measuring probe including at least one probe electrode.

23. The device of claim 22, wherein the measuring probe includes a guard electrode.

24. The device of claim 19, wherein the sensor unit further comprises a device configured to determine and/or monitor a pressure of the medium and/or a device configured to determine and/or monitor a temperature of the medium.

25. A method for determining and/or monitoring at least one process variable of a medium using a sensor unit, the method comprising: exciting a sensor unit via an excitation signal such that the sensor unit executes mechanical oscillations; detecting the mechanical oscillations using the sensor unit; converting the detected mechanical oscillations into a first received signal; transmitting a transmitted signal using the sensor unit; receiving a second received signal via the sensor unit; and based on the first received signal and/or the second received signal, determining the at least one process variable and, based on a third received signal, determining a conductivity and/or a capacitance of the medium.

26. The method of claim 25, wherein at least two different process variables are determined, wherein a first process variable is determined based on the first received signal, and wherein a second process variable is determined based on the second received signal.

27. The method of claim 25, wherein the at least one process variable is a fill level, a density, a viscosity, a velocity of sound or a variable derived from at least one of the foregoing process variables.

28. The method of claim 25, the method further comprising determining an electrical impedance and/or a dielectric constant of the medium.

29. The method of claim 28, the method further comprising: recording, as a function of time, at least one of: an electrical conductivity of the medium; the dielectric constant of the medium; and a degree of coverage of a conductivity/capacitance detecting unit configured to determine and/or monitor the conductivity and/or the capacitance of the medium; and monitoring at least one process occurring in a containment containing the medium based on the conductivity, the dielectric constant and/or the degree of coverage as a function of time.

30. The method of claim 26, the method further comprising determining a first concentration of a first substance contained in the medium and a second concentration of a second substance contained in the medium based on the first received signal and the second received signal and/or based on the first process variable and the second process variable.

31. The method of claim 26, the method further comprising determining, based on the first received signal and the second received signal and/or based on the first process variable and the second process variable, whether an accretion has formed on the sensor unit and/or whether a drift and/or an aging of the sensor unit has occurred.

32. The method of claim 26, the method further comprising determining whether an accretion has formed on the sensor unit and/or whether a drift and/or an aging of the sensor unit has occurred based on at least one of: the conductivity, the capacitance, an electrical impedance and a dielectric constant of the medium; at least one variable derived from at least one of the conductivity, the capacitance, the electrical impedance and the dielectric constant of the medium; and at least one of the conductivity, the capacitance, the electrical impedance and the dielectric constant of the medium as a function of time.

33. The method of claim 26, the method further comprising: determining a first information based on the first received signal and the second received signal and/or based on the first process variable and the second process variable; and determining a second information based on at least one of: the conductivity, the capacitance, an electrical impedance and a dielectric constant of the medium; at least one variable derived from at least one of the conductivity, the capacitance, the electrical impedance and the dielectric constant of the medium; and at least one of the conductivity, the capacitance, the electrical impedance and the dielectric constant of the medium as a function of time.

34. The method of claim 33, the method further comprising comparing the first information and the second information with respect to at least one of an accretion formed on the sensor unit, a drift of the sensor unit and an aging of the sensor unit.

35. The method of claim 34, the method further comprising monitoring a condition of at least one component of the sensor unit based on the comparison.

36. The method of claim 31, the method further comprising reducing or compensating for an influence of at least one of the accretion on, the drift of and the aging of the sensor unit on the first received signal and/or on the second received signal.

37. The method of claim 25, the method further comprising determining a thickness and/or a conductivity of an accretion formed on the sensor unit.

Description

[0046] The invention will now be explained in greater detail based on the appended drawing, the figures of which show as follows:

[0047] FIG. 1 a schematic view of a vibronic sensor according to the state of the art;

[0048] FIG. 2 embodiments known per se in the state of the art for a sensor unit and suitable for performing the method of the invention; and

[0049] FIG. 3 an embodiment of a device of the invention.

[0050] In the figures, equal elements are provided with equal reference characters.

[0051] FIG. 1 shows a vibronic sensor 1 having a sensor unit 2. The sensor has a mechanically oscillatable unit 4 in the form of an oscillatory fork, which is partially immersed in a medium M located in a container 3. The oscillatable unit 4 is excited by means of the exciter/receiving unit 5, such that the oscillatable unit 4 executes mechanical oscillations, and can be, for example, a piezoelectric stack—or bimorph drive. Other vibronic sensors use, for example, electromagnetic exciter/receiving units 5. It is possible to use a single exciter/receiving unit 5, which serves both for exciting the mechanical oscillations as well as also for their detection. Likewise, it is an option to implement a separate driving unit and a separate receiving unit. FIG. 1 shows, furthermore, an electronics unit 6, by means of which signal registration,—evaluation and/or—feeding occurs.

[0052] Shown in FIG. 2, by way of example, are different sensor units 2, which are suitable for performing a method of the invention. The mechanically oscillatable unit 4 shown in FIG. 2a includes, applied on a base 8, two oscillatory elements 9a,9b, which are also referred to as fork tines. Optionally, moreover, in each case, paddles (not shown) can be formed at the ends of the two oscillatory elements 9a,9b. Provided in each of the two oscillatory elements 9a,9b is, in each case, an, especially pocket-like, hollow space 10a, 10b, in which, in each case, at least one piezoelectric element 11a, 11b of the exciter/receiving unit 5 is arranged. Preferably, the piezoelectric elements 11a and 11b are cast within the hollow spaces 10a and 10b. The hollow spaces 10a, 10b can, in such case, be so created that the two piezoelectric elements 11a, 11b are located completely or partially in the region of the two oscillatory elements 9a, 9b. Such an arrangement as well as similar arrangements are described at length in DE102012100728A1.

[0053] Another example of an embodiment of a sensor unit 2 is shown in FIG. 2b. The mechanically oscillatable unit 4 in such case includes two parallel, rod shaped, oscillatory elements 9a, 9b, which are mounted on a disc shaped element 12 and which can be excited separately from one another to execute mechanical oscillations, and in the case of which the oscillations can likewise be received and evaluated separately from one another. The two oscillatory elements 9a and 9b have, in each case, a hollow space 10a and 10b, into which, in each case, at least one piezoelectric element 11a, 11b is arranged in the region toward the disc shaped element 12. Regarding the embodiment of FIG. 2b, reference is made to DE102017130527A1, which was unpublished as of the earliest filing date of this application.

[0054] As shown schematically in FIG. 2b, according to the invention, sensor unit 2 is, on the one hand, supplied with an excitation signal E, in such a manner that the oscillatable unit 4 is excited such that mechanical oscillations are executed. The oscillations are produced, in such case, by means of the two piezoelectric elements 11a and 11b. The two piezoelectric elements can be supplied with the same excitation signal E or the first oscillatory element 11a can be supplied with a first excitation signal E.sub.1 and the second oscillatory element 11b with a second excitation signal E.sub.2. Likewise, an option is that a first received signal R.sub.E is received based on the mechanical oscillations, or that separate received signals R.sub.E1, R.sub.E2 are received by the oscillatory elements 9a,9b.

[0055] Moreover, transmitted from the first piezoelectric element 11a is a transmitted signal S, which is received by the second piezoelectric element 11b in the form of a second received signal R.sub.S. Since the two piezoelectric elements 11a and 11b are arranged at least in the region of the oscillatory elements 9a and 9b, the transmitted signal S passes through the medium M when the sensor unit 2 is in contact with the medium M and is correspondingly influenced by the properties of the medium M. Preferably, the transmitted signal S is an, especially pulsed, ultrasonic signal, having especially at least one ultrasonic pulse. Likewise, it is, however, also an option that the transmitted signal S from the first piezoelectric element 11a is transmitted in the region of the first oscillatory element 9a and reflected on the second oscillatory element 9b. In such case, the second received signal R.sub.S is received by the first piezoelectric element 11a. The transmitted signal S passes, in this case, twice through the medium M, this leading to a doubling of a travel time τ of the transmitted signal S

[0056] Besides these two illustrated embodiments of a device 1 of the invention, numerous other variants are possible, which likewise fall within the scope of the invention. For example, it is possible in the embodiments of FIGS. 2a and 2b to use only one piezoelectric element 11a,11b and to arrange such at least in one of the two oscillatory elements 9a, 9b. In such case, the piezoelectric element 11a serves for producing the excitation signal, and the transmitted signal S, as well as for receiving the first R.sub.1 and second received signal R.sub.2. The transmitted signal is, in this case, reflected on the second oscillatory element 9b lacking piezoelectric element 11b.

[0057] FIG. 2c shows another embodiment, by way of example. In such case, a third piezoelectric element 11c is provided in the region of the membrane 12. The third piezoelectric element 11c serves to produce the excitation signal E and for receiving the first received signal R.sub.1, while the first 11a and second piezoelectric element 11b serve to produce the transmitted signal S and to receive the second received signal R.sub.2. Alternatively, it is, for example, possible to produce with the first 11a and/or second piezoelectric element 11b the excitation signal E and the transmitted signal S as well as to receive the second received signal R.sub.2, wherein the third piezoelectric element 11c serves for receiving the first received signal R.sub.1. Likewise, it is possible to produce the transmitted signal S with the first 11a and/or second piezoelectric element 11b and the excitation signal E with the third piezoelectric element 11c and to receive the first R.sub.1 and/or second received signal R.sub.2 with the first 11a and/or second piezoelectric element 11b. Also in the case of FIG. 2c, it is possible in other embodiments to omit the first 11a or second piezoelectric element 11b.

[0058] Another embodiment of the device 1 is shown in FIG. 2d. This device is based on the embodiment of FIG. 2b and includes a third 9c and a fourth oscillatory element 9d. These do not serve, however, for oscillation production. Rather, a third 11c and a fourth piezoelectric element 11d are arranged in the additional elements 9c, 9d, respectively. In such case, vibronic measuring is performed by means of the first two piezoelectric elements 11a, 11b and ultrasonic measuring is performed by means of the other two piezoelectric elements 11c,11d. Also in this case, for each measuring principle, one of piezoelectric elements, e.g. 11b and 11d, can be omitted. For reasons of symmetry, it is, however, advantageous, always to use two additional oscillatory elements 9c, 9d.

[0059] The first R.sub.E and second received signal R.sub.S result from different measuring methods and can be evaluated independently of one another as regards at least one process variable P. In this regard, reference is made to German patent application No. 102018127526.9, which was unpublished as of the earliest filing date of this application and to which comprehensive reference is taken in the context of the present invention.

[0060] Moreover, according to the invention, the conductivity σ and/or capacitance C of the medium can be determined and/or monitored. For this, the device of the invention has a conductivity/capacitance detecting unit 13 for determining and/or monitoring the conductivity σ and/or capacitance C having a capacitive and/or conductive measuring probe 14, such as shown in FIG. 3. FIG. 3 shows a sensor unit 2 analogous to the embodiment of FIG. 2a. Arranged between the two oscillatory elements 9a and 9b of the oscillatable unit 4 embodied in the form of an oscillatory fork is the conductivity/capacitance detecting unit 13 for determining and/or monitoring the conductivity σ and/or capacitor C of the medium M and having the capacitively and conductively working measuring probe 14, which has a sensor electrode 15 and a guard electrode 16 coaxially surrounding the sensor electrode 15. Arranged between the two electrodes 15 and 16 and between the measuring probe 14 and the mechanically oscillatable unit 4 in each case are insulating layers 17.

LIST OF REFERENCE CHARACTERS

[0061] 1 vibronic sensor [0062] 2 sensor unit [0063] 3 container [0064] 4 oscillatable unit [0065] 5 exciter/receiving unit [0066] 6 electronics unit [0067] 8 base [0068] 9a, 9b oscillatory elements [0069] 10a, 10b hollow spaces [0070] 11a, 11b piezoelectric elements [0071] 12 disc shaped element [0072] 13 conductivity/capacitance detecting unit for determining and/or monitoring conductivity and/or capacitance [0073] 14 capacitive and/or conductive measuring probe [0074] 15 sensor electrode [0075] 16 guard electrode [0076] 17 insulating layers [0077] M medium [0078] P process variable [0079] σ conductivity [0080] C capacitance [0081] E excitation signal [0082] S transmitted signal [0083] R.sub.E first received signal [0084] R.sub.S second received signal [0085] R.sub.σ/C third received signal [0086] Δϕ predeterminable phase shift