VIBRONIC SENSOR WITH REDUCED FACILITY FOR GAS BLASTING

Abstract

A device for determining and/or monitoring at least one process variable of a medium includes a mechanically vibratable unit, a drive/receiver unit and an electronic unit. The drive/receiver unit is designed to excite the mechanically vibratable unit to produce mechanical vibrations using an electrical excitation signal, and to receive the mechanical vibrations of the mechanically vibratable unit and convert them into an electrical reception signal. The electronics unit is designed to generate the excitation signal on the basis of the received signal, to set a frequency of the excitation signal in such a way that there is a predeterminable phase shift between the excitation signal and the received signal, and to determine the at least one process variable on the basis of the received signal, the mechanically vibratable unit comprising a diaphragm, and a surface of the diaphragm facing the process being curved.

Claims

1-14. (canceled)

15. A device for determining or monitoring at least one process variable of a medium, comprising: a mechanically vibratable unit, a drive/receiver unit, and an electronics unit; wherein the drive/receiver unit is designed to excite the mechanically vibratable unit to produce mechanical vibrations by means of an electrical excitation signal, and to receive the mechanical vibrations of the mechanically vibratable unit and convert them into an electrical reception signal; wherein the electronics unit is designed to generate the excitation signal on the basis of the reception signal, to set a frequency of the excitation signal in such a way that there is a predeterminable phase shift between the excitation signal and the reception signal, and to determine the at least one process variable using the reception signal; wherein the mechanically vibratable unit comprises a diaphragm; and wherein a surface of the diaphragm facing toward the process is curved.

16. The device according to claim 15, wherein the surface of the diaphragm is convex at least in sections.

17. The device according to claim 15, wherein the surface of the diaphragm is concave at least in sections.

18. The device according to claim 15, wherein the surface is conical, frusto-conical, hemispherical, or in the form of a spherical segment.

19. The device according to claim 15, wherein the surface is rounded in the region of a center point of the surface.

20. The device according to claim 15, wherein the surface has a tip in the region of a center point of the surface.

21. The device according to claim 20, wherein the surface is designed to be symmetrical with respect to the center point of the surface.

22. The device according to claim 15, wherein at least one vibrating element is integrally formed on the diaphragm.

23. The device according to claim 22, wherein a transition region between the diaphragm and the vibrating element has a respective predeterminable transition radius.

24. The device according to claim 15, wherein an angle between a plane parallel to a longitudinal axis through the diaphragm and a tangent to the surface of the diaphragm is less than or equal to 45°.

25. The device according to claim 15, comprising: at least one first piezoelectric element which serves as a drive/receiver unit; wherein the device is designed to excite the mechanically vibratable unit to produce mechanical vibrations by means of an excitation signal, to receive the mechanical vibrations of the vibratable unit and convert them into a first reception signal, and to emit a transmission signal and receive a second reception signal; wherein the electronics are designed to determine the at least one process variable of the medium using the first and/or second reception signal.

26. The device according to claim 25, further comprising: at least one second piezoelectric element; wherein the first and second piezoelectric elements are designed to excite the mechanically vibratable unit to produce mechanical vibrations by means of an excitation signal, and to receive the mechanical vibrations of the vibratable unit and convert them into a first reception signal; wherein the first piezoelectric element is designed to emit a transmission signal; wherein the second piezoelectric element is designed to receive the transmission signal in the form of a second reception signal.

27. The device according to claim 26, wherein the mechanically vibratable unit is a vibrating fork with a first and a second vibrating element; and wherein the first piezoelectric element is at least partially arranged in the first vibrating element and the second piezoelectric element is at least partially arranged in the second vibrating element.

28. The device according to claim 15, wherein the mechanically vibratable unit is a vibration rod; and wherein an extent of the diaphragm parallel to a longitudinal axis of the vibrating element is less than 20% of a length of the vibration rod parallel to the longitudinal axis.

Description

[0030] The invention is explained in greater detail with reference to the following Figures. The following is shown:

[0031] FIG. 1: a schematic drawing of a vibronic sensor according to the prior art,

[0032] FIG. 2 a vibratable unit in the form of a vibrating fork with a (a) planar and (b) curved surface of the diaphragm, and

[0033] FIG. 3 various exemplary embodiments for a curved diaphragm.

[0034] In the Figures, identical elements are respectively provided with the same reference signs. FIG. 1 shows a vibronic sensor 1 having a sensor unit 2. The sensor has a mechanically vibratable unit 4, in the form of a vibrating fork, which is partially dipped into a medium M which is located in a reservoir 3. The vibratable unit 4 is excited by the drive/receiver unit 5 to produce mechanical vibrations and, for example, can be a piezoelectric stack drive or bimorphic drive. Other vibronic sensors have electromagnetic drive/receiver units 5, for example. It is possible to use a single drive/receiver unit 5 which serves both to excite the mechanical vibrations and to detect them. However, it is likewise conceivable to realize one each, a drive unit and a receiver unit. Furthermore depicted in FIG. 1 is an electronics unit 6 by means of which the signal acquisition, evaluation, and/or feed takes place.

[0035] Depicted in FIG. 2 is a respective vibratable unit 4 in the form of a vibrating fork. The unit 4 has a diaphragm 7, on whose surface O, which in the state as introduced into the container 3 is the medium M, are integrally formed two vibrating elements 8a, 8b. In FIG. 2a, the surface O of the diaphragm 7 is designed to be planar. As a result, gas bubbles contained in the medium M can accumulate on the surface O of the diaphragm 7 and are trapped there according to the Archimedean principle.

[0036] In the variant according to the invention as depicted in FIG. 2b, the surface O of the diaphragm 7 is, by contrast, curved so that gas bubbles pass from the center of the surface O to its edge and can escape from there. Thus, a curved design significantly reduces the sensitivity of a vibronic sensor with respect to the adhesion of gas bubbles, and the associated disadvantageous measuring effects.

[0037] Numerous embodiments are conceivable for a diaphragm according to the invention, some of which are depicted by way of example in FIG. 3, respectively in the form of a sectional drawing. For example, the surface O can be designed to be convex, as shown in FIG. 3a, or concave, as shown in FIG. 3b, especially depending on the installation position of the sensor 1. In both instances, the surface O is rounded. Alternatively, the surface O can also have the shape of a hemisphere or of a spherical segment. Moreover, as depicted in FIG. 3c, a surface O with a tip or, for example, in the form of a truncated cone as illustrated in FIG. 3d is also conceivable. In addition to the embodiments shown here, numerous further possibilities are also conceivable, all of which fall under the present invention. It is also noted that the surface O does not necessarily need to be designed to be symmetrical, as is so for the variants depicted in FIG. 3. Rather, the surface O can be selected specific to the application.

LIST OF REFERENCE SIGNS

[0038] 1 Vibronic sensor [0039] 2 Sensor unit [0040] 3 Reservoir [0041] 4 Vibratable unit [0042] 5 Drive/receiver unit [0043] 6 Electronics [0044] 7 Diaphragm [0045] 8a, 8b Vibrating elements [0046] 9 Gas bubbles [0047] M Medium [0048] P Process variable