PARAMETERIZATION OF A FIELD DEVICE

Abstract

Disclosed is a method for parametering an apparatus for determining and/or monitoring a predeterminable fill level, wherein the apparatus includes a sensor unit and an electronics. The method includes determining an influence interval for a received signal received by the sensor unit as a function of an environmental parameter, determining a first value for the received signal or for a variable derived from the received signal corresponding to a first switch state, determining a second value for the received signal or for a variable derived from the received signal corresponding to a second switch state, and determining a third value for the received signal or for a variable derived from the received signal corresponding to a first switching point based on the first switch state and/or the second switch state and taking into consideration the at least one influence interval.

Claims

1-15. (canceled)

16. A method for parametering an apparatus for determining and/or monitoring a predeterminable fill level, wherein the apparatus includes a sensor unit and an electronics, the method comprising: determining an influence interval for a received signal received by the sensor unit as a function of an environmental parameter; determining a first value for the received signal or for a variable derived from the received signal corresponding to a first switch state at which value the sensor unit is located in a first state; determining a second value for the received signal or for a variable derived from the received signal corresponding to a second switch state at which value the sensor unit is located in a second state; and determining a third value for the received signal or for a variable derived from the received signal corresponding to a first switching point based on the first and/or second switch state and taking into consideration the influence interval.

17. The method as claimed in claim 16, wherein the environmental parameter is temperature, pressure, humidity, density, or viscosity.

18. The method as claimed in claim 16, wherein influence intervals lie symmetrically around the first switch state and the second switch state, and the first value and second value for the received signal or the variable derived therefrom.

19. The method as claimed in claim 16, further comprising: determining a fourth value for the received signal or for a variable derived from the received signal corresponding to a second switching point based on the first switch state and/or the second switch state and taking into consideration the influence interval.

20. The method as claimed in claim 19, wherein the first switching point and/or second switching point are/is determined such that the third value and/or fourth value for the received signal or the variable derived from the received signal lies/lie between the first value and the second value for the received signal or the variable derived from the received signal corresponding to the first switch state and the second switch state.

21. The method as claimed in claim 20, wherein the first switching point and the second switching point have a predeterminable switching interval relative to one another that is given by a magnitude of a difference between the third value and the fourth value for the received signal or the variable derived from the received signal.

22. The method as claimed in claim 21, wherein the predeterminable switching interval is maximized taking into consideration the first switch state and/or the second switch state and the influence interval.

23. The method as claimed in claim 21, wherein the predeterminable switching interval is selected such that the switching interval is greater than the influence interval.

24. The method as claimed in claim 19, further comprising: ascertaining for the received signal or for the variable derived from the received signal based on the at least one influence interval a first value range and/or a second value range that contain/contains the first value and/or second value of the received signal or the variable derived from the received signal, wherein the first value range and/or second value range correspond/corresponds to the first switch state and/or the second switch state.

25. The method as claimed in claim 24, wherein the first switching point and/or the second switching point are/is selected in such a manner that the third value and/or fourth value for the received signal or the variable derived from the received signal lie/lies outside of the first value range and/or second value range corresponding to the first switch state and/or the second switch state.

26. The method as claimed in claim 24, wherein the first and second switching point are selected such that the third value and fourth value for the received signal or the variable derived from the received signal lie/lies outside of the first value range and/or second value range corresponding to the first switch state and/or second switch state.

27. The method as claimed in claim 24, wherein in the case of a magnitude of a difference between a maximum value of the first value range corresponding to the first switch state and a minimum value of the second value range corresponding to the second switch state being less than the influence interval, the first or second switching point is selected such that the third or fourth value for the received signal or the variable derived from the received signal lies outside of the first value range and/or second value range corresponding to the first and/or second switch state.

28. The method as claimed in claim 16, wherein the sensor unit is free of medium in the first switch state.

29. The method as claimed in claim 16, wherein the sensor unit is covered at least partially with medium in the second switch state.

30. The method as claimed in claim 16, wherein the first switching point and/or second switching point correspond/corresponds to a predeterminable degree of coverage of the sensor unit.

Description

[0041] The invention will now be explained in greater detail based on the appended drawing, the figures of which show as follows:

[0042] FIG. 1 a vibronic field device according to the state of the art;

[0043] FIG. 2 a field device according to the state of the art working according to a capacitive and/or conductive operating mode;

[0044] FIG. 3 a schematic view illustrating the determining of the two switch states and the influence interval (a) when a single switching point is determined, and (b) when two switching points are determined, and

[0045] FIG. 4 different positions of the switch states and switching points taking into consideration the influence interval.

[0046] In the figures, equal elements are provided with equal reference characters.

[0047] The present invention is applicable for all types of field devices 1 in the form of limit level switches. For purposes of simplification, the following description is, however, directed to the examples of a vibronic fill-level measuring device (FIG. 1) and a field device working according to the capacitive and/or conductive operating mode (FIG. 2), such as they are schematically shown in FIGS. 1 and 2.

[0048] FIG. 1 shows a vibronic fill-level measuring device 1 having a sensor unit 2 with an oscillatable unit 3. Fill-level measuring device 1 is suitable for registering a predetermined fill level, or for determining density and/or viscosity. Corresponding field devices are produced and sold by the applicant under the marks, LIQUIPHANT and SOLIPHANT. The relevant underpinning measuring principles are known from a large number of publications. Sensor unit 2 of the field device 1 includes a mechanically oscillatable unit 3 in the form of an oscillatory fork. The oscillatable unit is excited by a driving/receiving unit 3a by means of an electrical excitation signal to cause the mechanically oscillatable unit to execute mechanical oscillations, especially with the resonant frequency of the oscillatory fork 3. Moreover, the driving/receiving unit 3a receives the mechanical oscillations of the oscillatable unit 3 and converts them into an electrical, received signal. The driving/receiving unit 3a is preferably composed of one or more piezoelectric elements. The reaching of a predetermined fill level can, in such case, be detected, for example, based on a change of the frequency of the oscillations of the mechanically oscillatable unit 3, as derived from the received signal received from the oscillatable unit 3. Sensor unit 2 is, in turn, connected by means of the neck tube 5a with an electronics unit 6, which is arranged in a field device housing 5. Shown here is, thus, an example of a field device 1 of compact construction, in the case of which the electronics unit 6 and the sensor unit 2 are arranged together.

[0049] A limit level switch working according to the capacitive and/or conductive measuring method is shown in FIG. 2. The capacitive measuring principle and the conductive measuring principle are likewise known per se in the state of the art. Corresponding field devices are produced and sold by the applicant, for example, under the mark, LIQUIPOINT. The field device 1 of FIG. 2 includes a sensor unit 2, which, when the field device 1 is introduced into a container, essentially front-flushly seals with the container. Sensor unit 2 is essentially coaxially constructed and includes a measuring electrode 4a, a guard electrode 4b and a ground electrode 4c. The housing 5 of the field device 1 in the illustrated embodiment includes, furthermore, a socket for a connecting plug 5b.

[0050] In the case of the limit level switch 1 of FIG. 2, thus, the electronics 6 is arranged separately from the sensor unit 2.

[0051] FIG. 3 illustrates the determining of the first switch state S.sub.1 and the second switch state S.sub.2 according to the invention for a limit level switch as well as for determining a first switching point P.sub.1 (FIG. 3a), and a first switching point P.sub.1 and second switching point P.sub.2 (FIG. 3b), taking into considering an influence interval ΔE.

[0052] First, an influence interval ΔE(U) for a signal received E(F,U) received by the sensor unit 2 as a function of at least one environmental parameter U is ascertained. The received signal E is, in such case, a function of fill level F and the environmental parameter U. According to the invention, the influence of the environmental parameter should be reduced or eliminated based on the influence interval ΔE(U), or of the influence interval ΔE(U). The influence interval can be determined once for a certain type of limit level switch 1 or for each individual limit level switch 1, for example, by determining the received signal E(F,U) as a function of a predeterminable value range for the environmental parameter U, within which the measuring device 1 is applied in ongoing operation.

[0053] Moreover, a first value E.sub.1 is determined for the received signal E or for a variable derived from the received signal corresponding to a first switch state S.sub.1, at which value the sensor unit 2 is located in a first state. Likewise, a second value E.sub.2 is determined for the received signal E or for a variable derived from the received signal corresponding to a second switch state S.sub.2, at which value the sensor unit 2 is located in a second state. In the present case, the sensor unit 2 in the first switch state S.sub.1 is free of medium, i.e. the current fill level F is such that the sensor unit 2 is free of medium M. In the second switch state S.sub.2, the sensor unit 2 is, in contrast, completely covered with the medium M. For the embodiment in FIG. 3a, as well as for all subsequent embodiments, the influence interval ΔE(U) lies, in each case, symmetrically around the first switching point S1 and the second switching point S2. Such an arrangement of the influence interval ΔE(U) relative to the switching points S.sub.1 and S.sub.2 is, however, not absolutely necessary in the context of the present invention.

[0054] It is, furthermore, also an option to determine for the first switch state S.sub.1 and/or the second switch state S.sub.2, in each case, corresponding value ranges ΔE.sub.1 and/or ΔE.sub.2 for the received signal E or the variable derived therefrom, which ranges include the first value E.sub.1 and the second value E.sub.2 for the received signal E or the variable derived therefrom.

[0055] Finally, at least a third value E.sub.3 is determined for the received signal E or for a variable derived from the received signal E corresponding to a first switching point P.sub.1 based on the first switch state S.sub.1 and/or second switch state S.sub.2 and taking into consideration the at least one influence interval ΔE(U). Preferably, such as shown in the case of FIG. 3a, the switching point P1 is selected in such a manner that it lies outside of the influence intervals ΔE(U) of the first switch state S.sub.1 and second switch state S.sub.2.

[0056] FIG. 3b shows supplementally to the first switching point P.sub.1 a second switching point P.sub.2. Corresponding to this second switching point P.sub.2 is a fourth value E.sub.4 for the received signal E or a variable derived therefrom. The two switching points P.sub.1 and P.sub.2 define a switching point-hysteresis loop with a predeterminable switching interval ΔP. The switching interval ΔP is, in such case, given by the magnitude of the difference between the third value E.sub.3 and the fourth value E.sub.4 for the received signal E or the variable derived from the received signal E.

[0057] Both the first switching point P.sub.1 as well as also the second switching point P.sub.2 are selected in such a manner that they lie between the values E.sub.1 and E.sub.2 for the received signal E or the variable derived therefrom corresponding to the first switch state S.sub.1 and second switch state S.sub.2. The third value E.sub.3 for the received signal E has thus a first distance d.sub.1 from a maximum value E.sub.1,max of the first value range ΔE.sub.1, while the fourth value E.sub.4 for the received signal E has a second distance d.sub.2 from a minimum value E.sub.2,min of the second value range Δ.sub.E2, wherein d.sub.1,d.sub.2>0. The distances d.sub.1 and d.sub.2 can, in such case, be equally large or different.

[0058] Preferably, however, not absolutely, the switching interval ΔP is furthermore selected to be as large as possible, especially greater than the influence interval ΔE(U). The embodiment shown in FIG. 3b shows, in principle, the ideal case for an embodiment with two switching points P.sub.1 and P.sub.2. In some cases, it can occur that the switching points P.sub.1 and P.sub.2 cannot be selected such that the switching interval ΔP is greater than the influence interval ΔE(U). Furthermore, it can also not always be assured that the third value E.sub.3 for the received signal E has a first distance di from a maximum value E.sub.1,max of the first value range ΔE.sub.1 and the fourth value E.sub.4 for the received signal E has a second distance d.sub.2 from a minimum value E.sub.2,min of the second value range ΔE.sub.2.

[0059] FIG. 4 shows, by way of example, three cases, which occur, when it is not possible to determine all parameters of the field device 1 according to the described ideal case.

[0060] FIG. 4a shows a schematic view of a first case, wherein the distance di between the third value E.sub.3 for the received signal E and the maximum value E.sub.1,max of the first value range is ΔE.sub.1<0. In such case, there is a critical region k.sub.1, in which an unintended switching or non-switching as a result of the environmental parameter U can occur. A similar case is shown in FIG. 4b. In such case, the distance d.sub.2 between the fourth value E.sub.4 for the received signal E and the minimum value E.sub.2,min of the second value range is ΔE.sub.1<0. In such case, there is a critical region k.sub.2, in which an unintended switching or non-switching as a result of the environmental parameter U can occur. In the worst case, as shown in FIG. 4c, both d.sub.1 as well as also d.sub.2 are <0, so that the two critical regions k.sub.1 and k.sub.2 occur simultaneously.

[0061] According to the invention, the switching point P.sub.1 or the switching points P.sub.1 and P.sub.2 preferably is/are selected in such a manner that an embodiment as shown in FIG. 3b is created. For example, for this purpose, the switching interval ΔP can be lessened, in case one of the distances d.sub.1 or d.sub.2 is <0. Advantageously by means of the present invention, an error-free switching of the measuring device 1 can be assured in simple manner, independently of the at least one environmental parameter U.

LIST BY REFERENCE CHARACTERS

[0062] 1 field device [0063] 2 sensor unit [0064] 3 oscillatory fork, with 3a driving/receiving unit [0065] 4 a measuring electrode, b guard electrode, c ground electrode [0066] 5 housing, 5a neck tube, 5b connection plug [0067] 6 electronics unit [0068] M medium [0069] U environmental parameter [0070] F fill level [0071] E received signal [0072] E.sub.1-E.sub.4 first-fourth values for the received signal or the variable derived therefrom [0073] E.sub.1,max maximum value of the first value range [0074] E.sub.2,min minimum value of the second value range [0075] ΔE(U) influence interval [0076] S.sub.1, S.sub.2 first, second switching points [0077] ΔE.sub.1, ΔE.sub.2 first, second value ranges [0078] P.sub.1, P.sub.2 first, second switching points [0079] d.sub.1, d.sub.2 first, second distances [0080] k.sub.1, k.sub.2 first, second critical regions