Parameterization of field devices

Abstract

The invention relates to a method for parameterizing a device (1) for determining and / or monitoring a predeterminable filling level, the device comprising at least one sensor unit (2) and an electronic device (6). The method comprises the following method steps: determining at least one influence interval (ΔE(U)) of a received signal (E) received by the sensor unit (2) as a function of at least one environmental parameter (U), determining a first value (E1) of the received signal (E) or a variable derived from the received signal (E) corresponding to a first switching state (S1), at which first value the sensor unit (2) is in the first state, determining a second value (E2) of the received signal (E) or a variable derived from the received signal (E) corresponding to a second switching state (S2), at which second value the sensor unit (2) is in the second state, and determining at least a third value (E3) of the received signal (E) or a variable derived from the received signal (E) corresponding to a first switching point (P1) based on the first switching state (S1) and / or the second switching state (S2) and taking into account the at least one influence interval (ΔE(U)).

Description

Technical Field

[0001] The invention relates to a method for parameterizing a device for determining and / or monitoring a predefinable fill level. Background Art

[0002] Field devices in the form of limit level switches in process and / or automation technology can operate according to a large number of different measuring principles for determining and / or monitoring fill levels. These measuring principles are known per se in the prior art and are therefore not discussed in detail here.

[0003] Examples of limit level switches for determining and / or monitoring a predeterminable fill level are, for example, vibration sensors or capacitive and / or conductive sensors having at least one mechanically oscillatable unit. The applicant manufactures corresponding field devices and sells them, for example, under the trade names LIQUIPHANT and / or SOLIPHANT in the case of vibrating fill-level measuring devices and, for example, under the trade name LIQUIPOINT in the case of capacitive and / or conductive measuring devices.

[0004] For example, in the case of a vibration limit level switch, it can be distinguished whether the oscillatable unit is covered by a medium or is oscillating freely. In this case, for example, the two states, free state and covered state, can be distinguished based on different resonance frequencies and thus frequency shifts.

[0005] In the case of a conductive limit fill level switch, in contrast, it is detected whether there is an electrical contact between the probe electrode and the wall of the conductive container or the second electrode via the conductive medium. In the case of a measuring device based on the capacitive measuring principle, in contrast, the fill level is ascertained from the capacitance of the capacitor formed by the probe electrode and the wall of the container or the second electrode. Depending on the conductivity of the medium, the medium or the probe insulation layer forms the dielectric of the capacitor.

[0006] Independently of the measuring principle used, in the case of a limit level switch of a device for determining and / or monitoring a predeterminable filling level, for example, two switching states are distinguished. In the first switching state, the sensor unit is free of medium, while in the second switching state, the sensor unit is at least partially covered by medium. In such a case, the first switching state and the second switching state correspond in each case to a specific value or value range of the received signal received from the sensor unit or to different variables derived from the received signal and applied to the signal processing. These variables can be, for example, the frequency, amplitude or phase of the received signal.

[0007] Between the two switching states, at least one switching point is defined. The device switches back and forth between the two switching states if the received signal or a selected variable derived therefrom reaches a predeterminable value corresponding to the switching point. In this case, the specific switching point corresponds to a predeterminable covering of the sensor unit by the medium. In this case, it can be a complete covering of the sensor unit by the medium or a predeterminable partial covering of the sensor unit by the medium, wherein the sensor unit is usually arranged at a predeterminable position, in particular at a predeterminable height, on a container wall of a container for the medium.

[0008] Limit level switches are often used in safety-critical applications. Therefore, reliable switching between the two switching states of the device is very important.

[0009] In this respect, a vibration limit level switch is known from EP 0 614 519 B1, in which case, in the case described here, the switching point of the switching frequency is set according to the resonant frequency of the oscillatable unit. The exact position of the resonant frequency of the oscillatable unit varies from sensor to sensor. In order to ensure reliable switching of the sensor, a specific switching point must be selected according to the resonant frequency.

[0010] From EP 0 1 336 083 B1 a vibration limit level switch is again known, in which case disturbance variables are taken into account for determining the switching point. In this way, faults of the measuring device are excluded, by which the temperature and / or pressure difference could falsely indicate the reaching of the switching point. The various disturbance variables taken into account can be measured directly, or characteristic lines or curves can be created, which reflect the influence of the disturbance variables on the frequency of the oscillatable unit. However, in each case, a specific disturbance variable must be continuously provided in order to compensate for its influence on the measuring behavior of the vibration sensor, and this obviously involves increased construction and metrological work. Summary of the invention

[0011] Starting from this prior art, the object of the invention is to provide a method for parameterizing a limit level switch which can be implemented in a simple manner.

[0012] The object is achieved by a method for parameterizing a device for determining and / or monitoring a predeterminable filling level, the device comprising a sensor unit and an electronic device. The method comprises the following method steps:

[0013] determining, as a function of at least one environmental parameter, at least one influencing interval of a reception signal received by the sensor unit,

[0014] determining a first value of the received signal or of a variable derived from the received signal corresponding to a first switching state, at which first value the sensor unit is in a first state,

[0015] determining a second value of the received signal or of a variable derived from the received signal corresponding to a second switching state, at which second value the sensor unit is in a second state, and

[0016] At least a third value of the received signal or of a variable derived from the received signal, which corresponds to a first switching point, is determined based on the first switching state and / or the second switching state and taking into account the at least one influencing interval.

[0017] According to the invention, at least one influencing interval is determined, which takes into account the dependency of the received signal or a variable derived therefrom on at least one environmental parameter. In this case, for example, the influencing interval can be determined separately for each measuring device before starting the measuring device. However, it is also possible to choose to determine at least one influencing interval based on a large number of measuring devices and then take it into account for all measuring devices of a given type.

[0018] Parameters of the field device relevant to the invention are, for example, two switching states and at least one switching point. The variable derived from the received signal can be, for example, the amplitude, frequency or phase of the received signal. In this case, which variable is derived from the signal received directly from the sensor unit depends in particular on the measurement principle and the specific received signal, which can be, for example, a current or a voltage.

[0019] In the context of the present invention, many options are available for determining the influence interval. On the one hand, the influence of at least two different environmental parameters on the received signal or the variable derived therefrom can be examined individually and / or together, and then a single influence interval can be determined based on the at least two environmental parameters. For example, this may be advantageous when the correlation of the received signal or the variable derived therefrom is similar for at least two environmental parameters, for example, has a similar or analogous functional relationship.

[0020] However, likewise, for different values ​​of the received signal or a variable derived therefrom, determining and taking into account different influence intervals is an option. This may again be advantageous when the difference between the first and second values ​​of the received signal or a variable derived therefrom is particularly large.

[0021] Advantageously, the environmental parameter of the invention does not need to be determined or ascertained continuously. Instead, at least one influencing interval can be determined once and then taken into account for the ongoing operation. In this case, at least one switching point is optimally matched to the two switching states and the at least one influencing interval. In this case, the determination of the at least one switching point can occur at least partially automatically. Compared to the prior art, the solution of the invention provides a considerable simplification both in terms of structure and in terms of metrology. In the ongoing measuring operation, no additional measurement or computer determination of the value of the environmental parameter is required.

[0022] Embodiments of the method include that the environmental parameter is temperature, pressure, humidity, density or viscosity. On the one hand, the environmental parameter may refer to the medium at least partially surrounding the sensor unit and / or surrounding the sensor based on time, or to the environment surrounding the measuring device outside the medium.

[0023] Advantageously, within the context of the method of the invention, the influence interval is located symmetrically around the first and second switching state and around the first and second value of the received signal or of a variable derived therefrom.

[0024] The impact interval can extend over a predeterminable value range of the environmental parameter, which value range corresponds, for example, to a specific field of use of the environmental parameter when the device is in operation. For example, a certain temperature, pressure, humidity, density or viscosity range can be specified for the device within which it can be used. For this value range of the environmental parameter, the relevance of the received signal of the device or a variable derived from the received signal is then ascertained, and the impact interval is determined based on the value range of the received signal or a variable derived therefrom. The impact interval thus describes the variation of the received signal with the environmental parameter.

[0025] If the value range of the environmental parameter is known, the first switching state and the second switching state can, for example, be determined at the average value of the value range of the environmental parameter. In this way, the influence interval is automatically arranged symmetrically around the first switching state and the second switching state. Therefore, the influence interval is in each case symmetrically placed around the first switching state and the second switching state, because the first switching state and the second switching state are at the average value of the value range of the environmental parameter.

[0026] In a particularly preferred embodiment, at least a fourth value of the received signal or a variable derived from the received signal, corresponding to the second switching point, is determined based on the first switching state and / or the second switching state and taking into account at least one influencing interval. By determining two switching points, a so-called switching point hysteresis can be taken into account. In this case, what is understood under switching point hysteresis is the difference between the forward and backward switching points. The change from the first switching state to the second switching state and from the second switching state to the first switching state accordingly occurs at two different switching points.

[0027] In this case, it is advantageous if the first switching point and / or the second switching point are determined so that the third and / or fourth value of the received signal or of a variable derived from the received signal is between the first and second values ​​of the received signal or of a variable derived from the received signal corresponding to the first switching state and the second switching state.

[0028] Furthermore, it is advantageous if the first switching point and the second switching point have a predeterminable switching interval relative to one another, which is given by the size of the difference between the third and fourth value of the received signal or of a variable derived from the received signal.

[0029] With regard to the switching interval, it is advantageous if the predefinable switching interval is maximized taking into account the first and / or second switching state and the influencing interval.

[0030] Furthermore, it is advantageous if the predeterminable switching interval is selected such that the switching interval is greater than the influencing interval.

[0031] By appropriately choosing the predeterminable switching interval, it is possible to take into account the influence of at least one environmental parameter for such a value of the received signal or of a variable derived therefrom which is between a first and a second value of the received signal or of a variable derived therefrom, corresponding to the first and the second switching state. The respective values ​​of the received signal or of a variable derived therefrom correspond to different partial coverages of the sensor unit.

[0032] Another particularly preferred embodiment comprises determining a first and / or second value range for the received signal or a variable derived from the received signal based on at least one influence interval, the first and / or second value range containing the first and / or second value of the received signal or of the variable derived from the received signal, wherein the first and / or second value range corresponds to the first and / or second switching state. Instead of determining a single value for the received signal or a variable derived therefrom for the switching state, the value range of the switching state is thus ascertained as a function of at least one environmental parameter.

[0033] In this respect, it is advantageous if the first and / or second switching point is selected such that the third and / or fourth value for the received signal or a variable derived therefrom is located outside the first and / or second value range corresponding to the first and / or second switching state. Thus, the first and / or second switching point in each case has a predeterminable distance greater than zero from the first and second value ranges of the received signal or a variable derived therefrom. For example, the third value for the received signal or a variable derived therefrom is smaller than the fourth value for the received signal or a variable derived therefrom.

[0034] Accordingly, the first switching point is at a lower value than the second switching point. Then, a third value of the received signal or a variable derived therefrom is selected such that it is greater than the maximum value of the first value range of the first switching state. Likewise, a fourth value of the received signal or a variable derived therefrom is selected such that it is less than the minimum value of the second value range of the second switching state.

[0035] A further preferred embodiment provides that the first and second switching points are selected such that the third and fourth values ​​of the received signal or of a variable derived therefrom are outside the first and second value ranges corresponding to the first and second switching states.

[0036] Alternatively, or where this is not possible, a preferred embodiment comprises selecting the first or second switching point such that the third or fourth value of the received signal or a variable derived from the received signal is outside the first or second value range corresponding to the first or second switching point, in particular when the size of the difference between the maximum value of the first value range corresponding to the first switching state and the minimum value of the second value range corresponding to the second switching state is smaller than the influencing interval.

[0037] With reference to the method according to the invention, it is advantageous if the sensor unit is free of medium in the first switching state.

[0038] It is also advantageous if the sensor unit is at least partially covered by the medium in the second switching state.

[0039] Finally, it is advantageous if the first and / or second switching point corresponds in each case to a predeterminable coverage of the sensor unit.

[0040] Likewise, the object on which the invention is based is achieved by an apparatus realized to perform the method of the invention as defined in at least one of the embodiments described in conjunction with the method of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The invention will now be explained in more detail based on the accompanying drawings, the figures of which are shown as follows:

[0042] Figure 1 It is a vibrating field device according to the prior art;

[0043] Figure 2 is a field device operating according to the prior art in accordance with a capacitive and / or conductive mode of operation;

[0044] Figure 3 is a schematic diagram illustrating determination of two switching states and an influencing interval (a) when determining a single switching point and (b) when determining two switching points; and

[0045] Figure 4 The switching states and different positions of the switching points taking into account the influencing interval are shown.

[0046] In the drawings, the same elements are provided with the same reference numerals. DETAILED DESCRIPTION

[0047] The invention is applicable to all types of field devices 1 in the form of limit level switches. However, for the sake of simplicity, the following description is directed to a vibrating fill level measuring device ( Figure 1 ) and field devices operating in capacitive and / or conductive modes of operation ( Figure 2 ), such as those in Figure 1 and 2It is schematically shown in FIG.

[0048] Figure 1 A vibrating filling level measuring device 1 having a sensor unit 2 with an oscillatable unit 3 is shown. The filling level measuring device 1 is suitable for recording a predeterminable filling level or for determining density and / or viscosity. The applicant produces and sells corresponding field devices under the trademarks LIQUIPHANT and SOLIPHANT. The relevant basic measuring principle can be known from a large number of publications. The sensor unit 2 of the field device 1 comprises a mechanical oscillatable unit 3 in the form of an oscillating fork. The oscillatable unit is excited by a drive / receiving unit 3a with the aid of an electrical excitation signal so that the mechanical oscillatable unit performs mechanical oscillations, in particular at the resonant frequency of the oscillating fork 3. In addition, the drive / receiving unit 3a receives the mechanical oscillations of the oscillatable unit 3 and converts them into an electrical receiving signal. The drive / receiving unit 3a preferably consists of one or more piezoelectric elements. In this case, for example, the reaching of a predetermined filling level can be detected based on a change in the oscillation frequency of the mechanical oscillatable unit 3 derived from the receiving signal received from the oscillatable unit 3. The sensor unit 2 is in turn connected to an electronic unit 6 by means of a neck tube 5a, which is arranged in a field device housing 5. Shown here is therefore an example of a compactly constructed field device 1 , in which case the electronics unit 6 and the sensor unit 2 are arranged together.

[0049] Figure 2 A limit level switch operating according to the capacitive and / or conductive measuring method is shown. The capacitive measuring principle and the conductive measuring principle are also known per se in the prior art. The applicant produces and sells corresponding field devices, for example under the trademark LIQUIPOINT. Figure 2 The field device 1 comprises a sensor unit 2 which, when the field device 1 is introduced into the container, is sealed essentially flush with the front face of the container. The sensor unit 2 is essentially coaxially constructed and comprises a measuring electrode 4a, a guard electrode 4b and a ground electrode 4c. In the embodiment shown, the housing 5 of the field device 1 also comprises a socket for connecting a plug 5b. Thus, in Figure 2 In the case of the limit level switch 1 , the electronics unit 6 is arranged separately from the sensor unit 2 .

[0050] Figure 3 The determination of the first switching state S1 and the second switching state S2 of the limit level switch according to the invention and the first switching point P1 ( Figure 3 a) and the first switching point P1 and the second switching point P2 ( Figure 3 b) determination.

[0051] Firstly, an influence interval ΔE(U) of the signal E(F, U) received by the sensor unit 2 as a function of at least one environmental parameter U is ascertained. In this case, the received signal E is a function of the fill level F and the environmental parameter U. According to the invention, the influence of the environmental parameter should be reduced or eliminated on the basis of or with the influence interval ΔE(U). For a certain type of limit level switch 1 or for each individual limit level switch 1, the influence interval can be determined once, for example, by determining the received signal E(F, U) as a function of a predeterminable value range of the environmental parameter U, within which the measuring device 1 is applied in ongoing operation.

[0052] Furthermore, a first value E1 of the received signal E or a variable derived from the received signal is determined, corresponding to the first switching state S1, at which the sensor unit 2 is in the first state. Likewise, a second value E2 of the received signal E or a variable derived from the received signal is determined, corresponding to the second switching state S2, at which the sensor unit 2 is in the second state. In the present case, the sensor unit 2 in the first switching state S1 is free of medium, i.e. the current filling level F is such that the sensor unit 2 is free of medium M. In the second switching state S2, on the other hand, the sensor unit 2 is completely covered by the medium M. For Figure 3 In the embodiment in a and all subsequent embodiments, the influence interval ΔE(U) is in each case located symmetrically around the first switching point S1 and the second switching point S2. However, in the context of the present invention, such an arrangement of the influence interval ΔE(U) relative to the switching points S1 and S2 is not absolutely necessary.

[0053] Furthermore, it is also possible to optionally determine in each case for the first switching state S1 and / or the second switching state S2 a corresponding value range ΔE1 and / or ΔE2 of the received signal E or a variable derived therefrom, which range includes the first value E1 and the second value E2 of the received signal E or a variable derived therefrom.

[0054] Finally, at least a third value E3 of the received signal E or a variable derived from the received signal E corresponding to the first switching point P1 is determined based on the first switching state S1 and / or the second switching state S2 and taking into account at least one influence interval ΔE(U). Figure 3 As shown in case a, the switching point P1 is selected such that it lies outside the influence interval ΔE(U) of the first switching state S1 and the second switching state S2 .

[0055] Figure 3b shows a second switching point P2 which supplements the first switching point P1. Corresponding to this second switching point P2 is a fourth value E4 of the received signal E or a variable derived therefrom. The two switching points P1 and P2 define a switching point hysteresis loop with a predeterminable switching interval ΔP. In this case, the switching interval ΔP is given by the size of the difference between the third value E3 and the fourth value E4 for the received signal E or a variable derived therefrom.

[0056] The first switching point P1 and the second switching point P2 are selected such that they are located between the values ​​E1 and E2 of the received signal E or of a variable derived from the received signal E, which correspond to the first switching state S1 and the second switching state S2. Thus, the third value E3 of the received signal E is approximately equal to the maximum value E of the first value range ΔE1. 1,max The first distance d1 is separated from the fourth value E4 of the received signal E and the minimum value E of the second value range ΔE2. 2,min A second distance d2 is separated, wherein d1, d2> 0. In this case, the distances d1 and d2 may be equal or different in size.

[0057] However, preferably, but not absolutely, the switching interval ΔP is also selected to be as large as possible, in particular larger than the influencing interval ΔE(U).

[0058] Figure 3 The embodiment shown in FIG. 1 b shows in principle the ideal case of an embodiment with two switching points P1 and P2. In some cases, it may happen that the switching points P1 and P2 cannot be selected so that the switching interval ΔP is greater than the influence interval ΔE(U). Furthermore, it cannot always be ensured that the third value E3 of the received signal E is equal to the maximum value E of the first value range ΔE1. 1,max At the first distance d1, the fourth value E4 of the received signal E is equal to the minimum value E of the second value range ΔE2. 2,min A second distance d2 is separated from each other.

[0059] Figure 4 Three situations are shown by way of example, which occur when not all parameters of the field device 1 can be determined according to the described ideal situation.

[0060] Figure 4 a shows a schematic diagram of a first situation, in which the third value E3 of the received signal E and the maximum value E of the first value range ΔE1 1,max The distance d1 between is <0. In this case, there is a critical region k1 in which an unexpected switching or non-switching may occur due to the environmental parameter U. Figure 4 A similar situation is shown in FIG. b. In this case, the fourth value E4 for the received signal E is the same as the minimum value E of the second value range ΔE1. 2,minThe distance d2 between them is <0. In this case, there is a critical region k2 in which unexpected switching or non-switching may occur due to the environmental parameter U. In the worst case, if Figure 4 As shown in c, d1 and d2 are both <0, so the two critical sections k1 and k2 occur simultaneously.

[0061] According to the present invention, the switching point P1 or the switching points P1 and P2 are preferably selected so that the following is created: Figure 3 b. For example, for this purpose, the switching interval ΔP can be reduced if one of the distances d1 or d2 is less than 0. Advantageously, with the invention, error-free switching of the measuring device 1 can be ensured in a simple manner, independently of at least one environmental parameter U.

[0062] Reference Symbols List

[0063] 1 Field equipment

[0064] 2 Sensor unit

[0065] 3 Vibrating fork with 3a drive / receiver unit

[0066] 4 a measuring electrode, b guard electrode, c grounding electrode

[0067] 5 housing, 5a neck tube, 5b connecting plug

[0068] 6 Electronic unit

[0069] M Medium

[0070] U Environmental parameters

[0071] F Fill level

[0072] E Receive signal

[0073] E1-E4 Receives the first to fourth values ​​of a signal or a variable derived from it

[0074] E 1,max Maximum value of the first value range

[0075] E 2,min The minimum value of the second value range

[0076] ΔE(U) influence interval

[0077] S1, S2 first switching point, second switching point

[0078] ΔE1, ΔE2 first value range, second value range

[0079] P1, P2 first switching point, second switching point

[0080] d1, d2 first distance, second distance

[0081] k1, k2 first critical region, second critical region

Claims

1. A method for parameterizing a device (1) for determining and / or monitoring a predeterminable filling level, the device comprising a sensor unit (2) and an electronic device (6), The method comprises the following steps: At least one influence interval (ΔE(U)) of a received signal (E) received by the sensor unit (2) is determined as a function of at least one environmental parameter (U), wherein: the influence interval (ΔE(U)) extends within a predefinable value range of the environmental parameter for the received signal (E) and thereby describes a variation of the received signal (E) with the environmental parameter, determining a first value (E1) of the received signal (E) or of a variable derived from the received signal (E) corresponding to a first switching state (S1), at which the sensor unit (2) is in a first state, determining a second value (E2) of the received signal (E) or of a variable derived from the received signal (E) corresponding to a second switching state (S2), at which second value the sensor unit (2) is in a second state, and determining at least a third value (E3) of the received signal (E) or of a variable derived from the received signal (E), corresponding to a first switching point (P1), based on the first switching state (S1) and / or the second switching state (S2) and taking into account the at least one influence interval (ΔE(U)), wherein a first value range (ΔE1) of the received signal (E) or of the variable derived from the received signal (E) is determined based on the at least one influence interval (ΔE(U)), which includes the first value (E1) of the received signal (E) or of the variable derived from the received signal (E), wherein the first value range (ΔE1) corresponds to the first switching state (S1), wherein a second value range (ΔE2) of the received signal (E) or of the variable derived from the received signal (E) is determined based on the at least one influence interval (ΔE(U)), which includes the second value (E2) of the received signal (E) or of the variable derived from the received signal (E), wherein the second value range (ΔE2) corresponds to the second switching state (S2), wherein at least a fourth value (E4) of the received signal (E) or of a variable derived from the received signal (E) corresponding to a second switching point (P2) is determined based on the first switching state (S1) and / or the second switching state (S2) and taking into account the at least one influence interval (ΔE(U)), wherein the first switching point (P1) and the second switching point (P2) are selected such that the third value (E3) and the fourth value (E4) of the received signal (E) or of the variable derived from the received signal (E) are outside the first value range (ΔE1) and the second value range (ΔE2) corresponding to the first switching state (S1) and / or the second switching state (S2), wherein the first switching point (P1) and the second switching point (P2) have a predeterminable switching interval (ΔP) relative to each other, the switching interval (ΔP) being given by the size of the difference between the third value (E3) and the fourth value (E4) of the received signal (E) or of a variable derived from the received signal (E), and Therein, the predeterminable switching interval (ΔP) is maximized taking into account the first switching state ( S1 ) and the second switching state ( S2 ) and the influencing interval (ΔE(U)).

2. The method according to claim 1, in, The environmental parameter (U) is temperature, pressure, humidity, density or viscosity.

3. The method according to claim 1, in, The predeterminable switching interval (ΔP) is selected such that the switching interval (ΔP) is greater than the influencing interval (ΔE(U)).

4. The method according to claim 1 or 2, in, The sensor unit (2) is free of a medium (M) in the first switching state (S1), and the sensor unit (2) is at least partially covered by a medium (M) in the second switching state (S2).

5. The method according to claim 1, in, The first switching point (P1) and the second switching point (P2) correspond to a predeterminable coverage of the sensor unit (2).

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