VIBRONIC MEASURING DEVICE AND METHOD FOR SIGNAL PROCESSING IN SUCH A MEASURING DEVICE

Abstract

A vibronic measuring device, e.g. limit level sensor, for determining and/or monitoring at least one process variable, includes a mechanically oscillatory unit, which is excited to vibrate by at least one drive unit based on an electrical signal S.sub.A. A receiving unit receives and converts mechanical vibrations into an electrical signal S.sub.E. A control and evaluation unit applies closed- and/or open-loop control of the vibrational excitation, and evaluates the signal S.sub.E with respect to the process variable. A vibration sensor pick up a sensor signal S.sub.S at the vibration sensor, and an analysis unit is supplied with signals S.sub.E and S.sub.S, and applies self-learning analysis of the input signals and transmits reliability information for the signal S.sub.E to the control and evaluation unit.

Claims

1. A vibronic measuring device, particularly a limit level sensor, for determining and/or monitoring at least one process variable of a medium in a container, having comprising at least one mechanically oscillatory unit, at least one drive and receiving unit for exciting the mechanically oscillatory unit to vibrate mechanically by means of an electrical excitation signal S.sub.A and for receiving and converting mechanical vibrations into an electrical receiving signal (S.sub.E), and at least one control and evaluation unit for closed-loop control and/or open-loop control of the vibrational excitation and for evaluation of the receiving signal S.sub.E with respect to the process variable, wherein the vibronic measuring device comprises at least one vibration sensor is coupled with the vibronic measuring device in such a manner that vibrations are transmitted from the measuring device to the vibration sensor to pick up a sensor signal at the vibration sensor, wherein the vibronic measuring device comprises an analysis unit connected to the control and evaluation unit, wherein the electrical receiving signal (S.sub.E) and the sensor signal (S.sub.S) are supplied to the analysis unit as input signals, wherein the analysis unit performs self-learning analysis of the input signals supplied to it, and wherein the analysis unit transmits at least one piece of reliability information for the electrical receiving signal (S.sub.E) to the control and evaluation unit.

2. The vibronic measuring device according to claim 1, wherein the electrical receiving signal S.sub.E and/or the sensor signal (S.sub.S) are supplied to the analysis unit in the time domain (S.sub.SZ) and in the spectral domain (S.sub.SS).

3. The vibronic measuring device according to claim 1, wherein a temperature signal (T) is supplied to the analysis unit as a further input signal.

4. The vibronic measuring device according to claim 1, wherein the analysis unit is detects periodic events.

5. The vibronic measuring device according to claim 1, wherein the analysis unit is detects frequency patterns.

6. The vibronic measuring device according to claim 1, wherein the analysis unit is generates and outputs a warning signal (W) when a quality of a desired signal that can be extracted from the electrical receiving signal (S.sub.E) is too low.

7. The vibronic measuring device according to claim 1, wherein the analysis unit outputs a signal for adjusting at least one adaptive filter filtering the receiving signal (S.sub.E) for delivery to the control and evaluation unit.

8. The vibronic measuring device according to claim 1, wherein the analysis unit detects and classifies events which cause extraneous vibrations and provides a classifier (K) to the control and evaluation unit.

9. The vibronic measuring device according to claim 1, wherein the control and evaluation unit adjusts a measuring rate and/or signal processing, particularly filtering, on the basis of a classification of an event.

10. A method for signal processing in a vibronic measuring device comprising providing a mechanically oscillatory unit, providing at least one drive and receiving unit for exciting the mechanically oscillatory unit to vibrate mechanically by means of an electrical excitation signal S.sub.A and for receiving and converting mechanical vibrations into an electrical receiving signal (S.sub.E), a control and evaluation unit for closed-loop control and/or open-loop control of the vibrational excitation and for evaluation of the receiving signal S.sub.E with respect to the process variable, and coupling at least one vibration sensor with the vibronic measuring device in such a manner that vibrations are transmitted from the measuring device to the vibration sensor to pick up a sensor signal (S.sub.S) at the vibration sensor, wherein the vibronic measuring device comprises an analysis unit connected to the control and evaluation unit, the method comprising supplying the electrical receiving signal (S.sub.E) and the sensor signal S.sub.S to the analysis unit as input signals, and transmitting at least one piece of reliability information (Z) for the electrical receiving signal (S.sub.E) from the analysis unit to the control and evaluation unit, and analyzing the input signals that are supplied to the analysis unit in a self-learning manner.

11. The method according to claim 10, wherein the electrical receiving signal S.sub.E and/or the sensor signal (S.sub.S) are supplied to the analysis unit in the time domain (S.sub.EZ) and in the spectral domain (S.sub.ES).

12. The method according to claim 10, wherein a temperature signal (T) is supplied to the analysis unit as a further input signal.

13. The method according to claim 10, wherein the analysis unit carries out a detection of periodic events.

14. The method according to claim 10, wherein the analysis unit carries out a detection of frequency patterns.

15. The method according to claim 10, wherein the analysis unit generates and outputs a warning signal (W) when a quality of a desired signal that can be extracted from the electrical receiving signal (S.sub.E) is too low.

16. The method according to claim 10, wherein the analysis unit outputs a signal for adjusting at least one adaptive filter for the receiving signal (S.sub.E) to the control and evaluation unit.

17. The method according to claim 10, wherein the analysis unit detects and classifies events which cause extraneous vibrations and outputs a piece of information about this, particularly a classifier.

18. The method according to claim 10, wherein the control and evaluation unit adjusts a measuring rate and/or signal processing, particularly filtering, on the basis of the classification and/or the type of an event.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention is explained in more detail in the following with reference to the attached figures. In the figures:

[0041] FIG. 1 shows a measuring arrangement having a vibronic measuring device, which is designed as a limit level sensor, according to the prior art,

[0042] FIG. 2 shows an exemplary embodiment of a vibronic measuring device, which is designed as a limit level sensor, according to the present application, and

[0043] FIG. 3 shows an exemplary embodiment of an analysis unit as may be used in the limit level sensor according to FIG. 2.

DETAILED DESCRIPTION OF THE DRAWINGS

[0044] FIG. 1 shows a typical use case of a vibronic measuring device 2 as limit level sensor 2 according to the prior art.

[0045] The limit level sensor 2 is installed in a tank 1 as overfill protection. Filling the tank 1 by means of an inlet 4a, which is arranged in an upper region of the tank 1, is effected by means of a pump 5a and is controlled by means of the limit level sensor 2. If the limit level sensor 2 detects a medium 3, then the pump 5a is switched off in order to prevent an overflow of the tank 1. The limit level sensor 2 here uses a piezoelectric drive as electromechanical transducer, which acts as drive and receiving device 31. Alternatively, electromagnetic transducer units are also possible. By means of the electromechanical transducer, a mechanically oscillatory unit 40 is excited at its resonant frequency. By means of the resonant frequency and the amplitude of the vibration, the sensor can detect the presence of a medium 3.

[0046] Emptying of the tank 1 takes place by means of an outlet 4b, which is arranged in a lower region, close to a bottom of the tank 1, and is effected by means of a second pump 5b.

[0047] If vibrations of the pump 5a are transmitted to the limit level sensor 2, it may come to pass in unfavourable cases that the limit level sensor 2 senses these vibrations as a measurement signal. This may result in a malfunction of the limit level sensor 2. If the vibrations of the pump 5a are located in a region which the limit level sensor 2 would detect as covered, an incorrect switching signal may be output. If the vibrations are located in a region which the limit level sensor 2 would detect as uncovered, exceeding of the limit level may not be detected, which in the worst case has overfilling of the tank 1 as a consequence.

[0048] FIG. 2 shows a limit level sensor 2 according to the present application.

[0049] An analysis unit 32 is integrated in the limit level sensor 2, which can detect extraneous vibrations. The analysis unit 32 is coupled with a vibration sensor 20 which is designed as an inertial sensor in the present exemplary embodiment. The vibration sensor 20 is arranged in the limit level sensor 2 in such a manner that it is on the one hand mechanically decoupled from the mechanically oscillatory unit 40, but on the other hand mechanically coupled with a housing of the limit level sensor 2 in such a manner that extraneous vibrations acting on the limit level sensor 2 can be detected as well as possible. The vibration sensor 20 is ideally arranged in the region of a process connection 35 of the limit level sensor 2, so that to the greatest extent possible, only the extraneous vibrations which act on the limit level sensor 2 are evaluated by the vibration sensor 20. Without mechanical decoupling, the vibrations of the mechanically oscillatory unit 40, which are generated by the drive unit 31, cannot be distinguished from extraneous vibrations.

[0050] Mechanical decoupling is already achieved if the mechanical vibrations generated by the drive unit 31 for the measurement are present at the vibration sensor 20 to a considerably reduced extent, particularly with an amplitude reduced by a factor of 5, preferably by a factor of 10. A complete mechanical decoupling is not possible however, owing to the arrangement in the same housing.

[0051] Further processing of the output signals of the analysis unit 32 takes place in the control and evaluation unit 30. The analysis unit 32 can also be integrated into the control and evaluation unit 30.

[0052] A function of the analysis unit 32 is assisted by integrated artificial intelligence in the present case. In this case, various functions can be realized for improving, stabilizing or adjusting the measurement function of the control and evaluation unit 30.

[0053] In the present exemplary embodiment, the electrical receiving signal S.sub.E, the sensor signal S.sub.S and the electrical excitation signal S.sub.A are supplied as input signals to the analysis unit 32 in each case in the time domain and also, following a fast Fourier transform, in the spectral domain. A temperature signal T of a temperature sensor, which is arranged adjacent to the mechanically oscillatory unit 40, is supplied to the analysis unit 32 as further input signal.

[0054] As output signal, the analysis unit 32 provides a piece of reliability information Z, which identifies a quality and reliability of the receiving signal S.sub.E, filter parameters for adjusting an adaptive filter and also a piece of information about regularity of a fault due to extraneous vibrations.

[0055] Depending on the piece of reliability information Z, the receiving signal is identified as valid or unreliable by the control and evaluation unit 30. The adjustment of the adaptive filter enables improvement of the piece of reliability information Z. Due to the piece of information about regularity of the fault due to extraneous vibrations, it is possible in the case of regularly recurring faults for a countermeasure to be taken in advance of the fault already, for example an increase of the measuring rate can be carried out, the filter setting can be adjusted and/or influencing of the natural vibration by the extraneous vibration can be reduced, for example by increasing an amplitude of the excitation signal S.sub.A or exciting a less influenced or uninfluenced natural vibration of the mechanically oscillatory unit 40.

[0056] Further functions are also conceivable. If the pump 5a is not in operation permanently, but rather only sporadically, this can be detected by the AI. If the vibration of the pump 5a is detected, then the measuring rate of the limit level sensor 2 can be increased after that, in order thereby to detect reaching of a maximum fill level more reliably and faster. In an alternative embodiment, it would also be conceivable that measurement and pump 5a are controlled by a common control unit. In this scenario, the operating times of pump and measurement can alternate. Thus, it is possible to check by means of the sensor, in a pause of the pumping process, whether pumping further is permitted.

[0057] FIG. 3 shows an exemplary embodiment of an analysis unit 32 as may be used in the limit level sensor 2 according to FIG. 2.

[0058] The analysis unit 32 according to FIG. 3 in the simplified illustration shown in FIG. 3 has six signal inputs 301-306 and four signal outputs 311-314.

[0059] At the first signal input 301, the excitation signal S.sub.A is supplied to the analysis unit 32 in the spectral domain S.sub.AS. At the second and third signal inputs 302, 303, the receiving signal SE is applied in the time domain S.sub.EZ and in the spectral domain S.sub.ES. At the fourth and fifth signal inputs 304, 305, the sensor signal S.sub.S is applied in the time and in the spectral domain S.sub.SZ, S.sub.SS. At the sixth signal input 306, the temperature signal T of the temperature sensor is applied.

[0060] At the first signal output 301, the piece of reliability information Z can be picked up. At the second signal output 302, a classifier K for extraneous vibrations can be picked up. At the third signal output 303, an adjustment signal E for adjusting the adaptive filter can be picked up, and at the fourth signal output 304, a warning signal can be picked up, which in addition to the piece of reliability information Z represents a warning if the quality of the input signal compared to extraneous vibrations decreases below a threshold value. for example in the sense of a signal to noise ratio.

REFERENCE LIST

[0061] 1 Container, tank [0062] 2 Vibronic measuring device/limit level sensor [0063] 3 Medium [0064] 4a Inlet [0065] 4b Outlet [0066] 5a Pump [0067] 5b Pump [0068] 20 Vibration sensor [0069] 30 Control and evaluation unit [0070] 31 Drive and receiving unit [0071] 32 Analysis unit [0072] Mechanically oscillatory unit [0073] 301-306 Signal inputs [0074] 311-314 Signal outputs [0075] E Adjustment signal [0076] K Classifier [0077] S.sub.A Excitation signal [0078] S.sub.E Receiving signal [0079] S.sub.S Sensor signal [0080] T Temperature signal [0081] W Warning signal [0082] Z Piece of reliability information