Method for operating a filling device with a filling valve

Abstract

Method (1) for operating a filling device (2) with a filling valve (3) for controlling a medium flow, with a magnetic-inductive flow sensor (4) for measuring the medium flow released by the filling valve (3) and with a control and evaluation unit (5) for controlling the filling valve (3), wherein the magnetic-inductive flow sensor (4) has a measuring tube (6) for guiding the medium flow, a magnetic field generating device (7) for generating a magnetic field (B) passing through the measuring tube (6) perpendicular to the flow direction of the medium flow, wherein the control and evaluation unit (5) controls the magnetic field generating device (7) such that in standard operation (9) the magnetic field (B) changes its polarity at a standard magnetic field frequency (f_stand) as the working magnetic field frequency (f_work),wherein the control and evaluation unit (5) determines at least one flow measurement value (flow) as a work calibration (kal_work) in the interval (10) of a constant magnetic field polarity and a stable magnetic field (B) based on a standard calibration (kal_stand), characterized in that the control and evaluation unit (5) controls the filling valve (3) to carry out a filling process (11) with at least one plateau phase (12) of the flow and an associated plateau flow measurement value (flow_plat) with a defined target filling quantity according to a filling curve (13), wherein the filling curve (13) specifies the opening degree (O) of the filling valve (3), that in a test phase (14) the control and evaluation unit (5) operates the magnetic field generating device (7) with a test magnetic field frequency (f_test) that is greater than the set work magnetic field frequency (f_work), wherein checked (15) willwhether a stable magnetic field (B) is generated at the test magnetic field frequency (f_test) within an interval (10) of constant magnetic field polarity, and that when a stable magnetic field (B) is generated, the test magnetic field frequency (f_test) is set and used as the new working magnetic field frequency (f_work).

Description

The invention relates to a method for operating a filling device having a filling valve for controlling a medium flow, having a magnetoinductive flow sensor for metrological detection of the medium flow released by the filling valve, and having a control and evaluation unit for controlling the filling valve, wherein the magnetoinductive flow sensor has a measuring tube for guiding the medium flow, a magnetic field generating device for generating a magnetic field passing through the measuring tube perpendicular to the flow direction of the medium flow, wherein the control and evaluation unit controls the magnetic field generating device such that, in a standard operation, the magnetic field changes its polarity with a standard magnetic field frequency as the working magnetic field frequency, wherein the control and evaluation unit determines at least one flow measurement value as the work calibration in the interval of a constant magnetic field polarity and a stable magnetic field on the basis of a standard calibration. In addition, the invention also relates to a corresponding filling device.The filling devices mentioned above are known, for example, from DE 196 21 132 A1. Further prior art relating to filling devices with a magnetoinductive flow sensor is shown in EP 4 009 009 A1.The control and evaluation unit controls the filling valve to carry out a filling process with at least one plateau phase of the flow and an associated plateau flow measurement value with a defined desired filling quantity according to a filling curve, wherein the filling curve indicates the opening degree of the filling valve.Filling devices of the aforementioned type are widely used in process technology, for example in the chemical industry, but above all also in the food and beverage industry. In filling devices, flow sensors can in principle be used which are based on arbitrary measurement principles for the flow, but in the present case the use of magnetoinductive flow sensors is concerned. Magnetoinductive flow sensors have the advantage that no mechanically moved parts are required for carrying out a measurement, unlike, for example, in vortex flow measuring devices or Coriolis mass flow measuring devices. Industrially used process-related filling systems often have a multiplicity of the filling devices described above, which could also be referred to as filling stations within a filling system.The measuring principle of magnetoinductive flow measurement is based on the force effect on moving charge carriers in a magnetic field (Lorentz force) and the charge separation in the medium current brought about thereby in the region of the magnetic field. For the functionality of the measuring principle, it is therefore necessary for the medium to have a minimum electrical conductivity. The separated charge carriers generate an electric field in the medium, the strength of which is proportional to the velocity of the medium. By means of two measuring electrodes on the circumference of the measuring tube, a measuring voltage proportional to the flow of the medium can be tapped, which is then further processed to form a flow measurement value.It is usual to change the polarity of the magnetic field generated by the magnetic field generating device with a magnetic field frequency, so that the polarity of the measurement voltage picked up by the measurement electrodes also changes. Reasons for the regular change of the polarity of the magnetic field are, for example, the possibility of calculating parasitic electrode voltages that do not change with the polarity of the magnetic field and also the avoidance of electrochemical processes at the electrodes that are associated with charge carriers of constant polarity. The magnetic field frequency is typically in the range of several tens to hundreds Hz.The switching over of the magnetic field cannot take place abruptly, since the change in the current supply of the magnetic field generating device takes a certain time via the decrease and build-up of voltage-time areas. The voltage of the measuring electrodes is only used to determine flow measurement values when the magnetic field is stable, i.e. has a constant strength. In the interval of a constant magnetic field polarity and a stable magnetic field-i.e. a magnetic field of constant strength-the measurement voltage is sampled at high frequency, usually by an A / D converter with a sampling rate which is usually orders of magnitude higher than the magnetic field frequency, and a flow measurement value is then determined from the plurality of raw measurement values thus obtained. The magnetic field frequency thus also indicates the measurement rate at which the magnetoinductive flow sensor determines and makes available flow measurement values.For flow sensors, specification values such as accuracy (absolute accuracy and repeatability) and measurement range (minimum and maximum detectable flows) are specified for a particular operating range such as temperature (minimum, maximum ambient and / or medium temperature). Compliance with the specification is ensured within the operating range specified as permissible.The operation of the flow sensor in the permissible operating range has been referred to as standard operation at the beginning, in which the flow sensor operates with a standard magnetic field frequency as the operating magnetic field frequency. At this standard magnetic field frequency, the flow sensor is calibrated-usually at the factory-and a calibration curve is therefore determined which describes the relationship between the measurement voltage at the electrodes and the average flow rate of the medium flow through the measuring tube. The calibration curve is often a straight line with a slope (transmitter constant) and a zero-point offset (electrode voltage at zero flow), but more than two points can also be used to describe the calibration curve. In the standard mode of operation, the standard calibration is used, and the standard calibration is therefore the work calibration in the standard mode of operation.When the flow sensor is operated in this standard operation, it is ensured, for example, that measured values with a specific measurement rate are present in the temperature range specified as permitted, which means, on the basis of the explanation given above of the relationship between magnetic field frequency and measurement rate, that the magnetic field can also be generated with the required magnetic field frequency in the entire temperature range, that is to say in such a way that a stable magnetic field is generated over a sufficient time with a constant magnetic field polarity, so that raw measurement data can be recorded to a sufficient extent, from which raw measurement data the flow measurement value is then determined.The filling device described at the beginning comprises the filling valve, the flow sensor and the control and evaluation unit as central components. The filling valve can be implemented in various ways, technically, it can be a valve with a single controllable actuating element, but it can also comprise a plurality of controllable components, for example a combination of switching valve and regulating valve. The control and evaluation unit controls the filling valve, wherein in the case considered here a filling curve is traversed which describes the degree of opening of the filling valve as a function of the detected filling quantity. As a result, the filling process can be set very finely; for example, a slow opening of the filling valve at the beginning of the filling process can be selected in order to prevent foaming or swirling of the medium; in the middle of the filling process, a large valve opening can be set constant over a certain filling section (plateau phase) until the end of the filling, in which the valve opening is reduced stepwise or even continuously. A filling process can also have a plurality of plateau phases, that is to say intervals of constant throughflow (plateau throughflow), it being assumed that the filling process has at least one plateau phase at any rate.Apart from the fact that the most precise possible dosing of a medium is always desirable within the scope of a filling process, the accuracy of a filling process is of increased importance when filling into containers which are intended for delivery to end consumers (bottles, canisters, cans). Here, a minimum amount, usually the amount indicated on the container, must be guaranteed to be contained, so that tolerances in the filling always increase the burden of the manufacturer, i.e. an overfilling is always used.It is the object of the present invention to configure and further develop the method for operating the filling device and a corresponding filling device such that the filling process can be carried out with increased accuracy.The object derived and shown above is achieved in the method for operating a filling device in that, in a test phase, the control and evaluation unit operates the magnetic field device with a test magnetic field frequency that is greater than the set working magnetic field frequency, wherein a check is carried out to determine whether a stable magnetic field is also generated at the test magnetic field frequency in an interval of a constant magnetic field polarity, and in that, when a stable magnetic field is generated, the test magnetic field frequency is set and used as a new working magnetic field frequency. If a stable magnetic field cannot be generated with the test magnetic field frequency, it is possible to react in various ways, for example, the work magnetic field frequency that has been assumed can be easily maintained as the work magnetic field frequency.The invention is based on the finding that the standard operation is designed such that the flow sensor can operate according to specifications, i.e. even under unfavourable conditions-for example at high temperatures at which the ohmic resistance of the magnetic field generating device has increased-a stable magnetic field at the standard magnetic field frequency and thus a correspondingly high measurement rate for the determination of flow measurement values can still be achieved quite reliably. The design of a flow sensor is usually also carried out in such a way that even in the event of a slight deviation from the permissible operating range, an operation of the flow sensor and thus of the filling device according to the specification is still possible. Conversely, this means that, with more favorable operating conditions within the operating range, a better performance can be achieved with regard to some parameters than would be expected from its specification.The invention aims at increasing the measurement rate with which flow measurements are determined, and thus at increasing the working magnetic field frequency of the magnetic field beyond the standard magnetic field frequency. The increase in the working magnetic field frequency and thus the measurement rate of the flow measurement values has a direct effect on an improvement in the absolute measurement accuracy and on the repeatability during filling operations, since the continuous course of the flow is scanned with a higher frequency and is thus resolved more finely over time.In an advantageous embodiment of the method, it is provided that the check as to whether a stable magnetic field is generated in an interval of a constant magnetic field polarity is carried out by evaluating a magnetic field sensor and assessing the stationarity of the magnetic field. Additionally or alternatively, the stationarity of a current impressed into the magnetic field generating device and / or of a voltage applied to the magnetic field generating device is assessed. The stationarity of the variables is preferably assessed by time-series analysis of the detected magnetic field strength and / or the detected impressed current and / or the detected applied voltage. Known statistical deviation measures, such as standard deviation, can be used to assess stationarity.In a preferred embodiment of the method, the test phase is repeated several times. If a stable magnetic field can always be generated in the multiple repetitions, the operating magnetic field frequency-and thus the measurement rate at which flow measurement values are generated-is increased stepwise. The repetitions are preferably continued until the greatest test magnetic field frequency has been determined, at which a stable magnetic field is generated in an interval of a constant magnetic field polarity. Of course, the test magnetic field frequency is also set here as the working magnetic field frequency if the magnetic field has proven to be stable.In a further development of the above-described exemplary embodiment, the test magnetic field frequency is increased in the repetitions of the test phase in constant frequency steps (for example 60 Hz, 65 Hz, 70 Hz, etc.), alternatively the test magnetic field frequency is first increased in large frequency steps, then in decreasing frequency steps (for example 60 Hz, 75 Hz, 85 Hz, 90 Hz, 92 Hz), in a further alternative the test magnetic field frequency is changed according to the principle of interval interleaving. In the case of interval interleaving, for example, the interval step width may bisect each other at each repetition of the test phase, with the jumping direction depending on the result of the stability test of the magnetic field (for example, the complete interval comprises 50 Hz to 100 Hz: 50 Hz (stable), 100 Hz (unstable), 75 Hz (stable), 87.5 Hz (stable), 93.75 Hz (stable), termination upon falling short of the minimum step width).If it is taken into account that the magnetic field frequencies, as in the examples given, are often in the range of a few 10 Hz, then it becomes clear that finding also the highest possible working magnetic field frequency takes up only seconds fractions.A further development of the method is characterized in that the check for a stable magnetic field is carried out without the magnetic field frequency being changed-as in test operation. It can thus be ensured that the working magnetic field frequency set deviating from the standard magnetic field frequency still represents a valid operating mode. In particular, this check can be carried out continuously, that is to say each time the polarity of the magnetic field is switched over.A further development of the method is characterized in that the working magnetic field frequency is switched back to the standard magnetic field frequency and the test phase is run through anew starting from standard operation. The switch back to the standard operation can take place at regular time intervals or after a certain number of filling intervals or even after it has been established that a stable magnetic field can no longer be generated at the set operating magnetic field frequency.In a particularly advantageous embodiment of the method, the flow sensor is operated at the working magnetic field frequency deviating from the standard magnetic field frequency and the flow sensor is re-calibrated by determining a test calibration curve between at least two points of known flow during the filling process and associated detected voltage values at two measuring electrodes of the flow sensor, wherein the test calibration curve is subsequently used as working calibration.In a further development of the aforementioned method, the plateau throughflow during the plateau phase of the throughflow and the associated voltage value at the measurement electrodes of the throughflow sensor are used as a point of known throughflow. Alternatively or additionally, a zero flow rate with the filling valve closed during the filling process and the associated voltage value at the measuring electrodes of the flow sensor are used as another point. From the values determined in this way, a calibration straight line can be determined with the slope as a so-called transmitter constant and the zero point offset at zero flow rate.In a development of the method described above, the zero flow rate is validated by checking the opening degree of the filling valve for complete closure and / or by checking the zero flow rate through the flow measurement value of the flow sensor during a transition to the standard operation with the standard magnetic field frequency on the basis of the standard calibration and subsequent change to the stable test magnetic field frequency, which deviates from the standard magnetic field frequency and for which the calibration curve is determined.With regard to the method extensions with the determination of a calibration curve, it is provided in a further development that the flow sensor is switched over to standard operation by setting the standard magnetic field frequency as the working magnetic field frequency and the standard calibration as the working calibration, furthermore, when a filling process is subsequently carried out, a current plateau flow measurement value is determined in the plateau phase of the flow, wherein, in the case of a deviation of the current plateau flow measurement value from the previously determined (or given) plateau flow measurement value with standard calibration or from the previously determined flow measurement value in the plateau phase with increased test magnetic field frequency, a new test calibration curve is determined as the working calibration and is set as the working calibration. This procedure prevents the assumption of an unsatisfactory value for the plateau throughflow in the event of a change in the filling behavior (for example by changed process pressure), which would also lead to an erroneous calibration.In a further advantageous embodiment of the method, at least one temperature of the flow sensor is determined, in particular a temperature of the magnetic field generating device and / or a medium temperature of the medium flow flowing through the flow sensor and / or an ambient temperature of the flow sensor is determined. All of these temperatures have an influence on the flow sensor, although the immediacy of the influence is different. The use of the aforementioned temperatures is expedient because the ohmic resistance of the magnetic field generating device is clearly temperature-dependent and the ohmic resistance is decisive for the voltages with which currents can be injected into the magnetic field generating device, i.e. the ohmic resistance is determining for the time behavior of the switching of the magnetic fields of interest. Depending on the at least one temperature of the flow sensor, a starting test magnetic field frequency is determined and used as the test magnetic field frequency in the test phase, which is close to the maximum stable test magnetic field frequency that can be reached at the determined temperature of the flow sensor. At which temperature which start-test magnetic field frequency can be expediently selected, which dependence exists between the start-test magnetic field frequency and the at least one determined temperature of the flow sensor, can be determined empirically, for example, in particular for a specific type of flow sensor or filling device.As mentioned at the beginning, filling systems often have a multiplicity of the filling devices described above. In this context, a further advantageous embodiment of the method has the property that the work magnetic field frequency and / or test calibration curve determined for a specific flow sensor in a specific filling device are transmitted as work calibration to other flow sensors in other filling devices, in particular to other flow sensors in other filling devices which are operated together with the specific filling device in a filling system.The described object is also achieved with a corresponding and previously described filling device having a filling valve for controlling a medium flow, with a magnetoinductive flow sensor for metrological detection of the medium flow released by the filling valve, and with a control and evaluation unit for controlling the filling valve, wherein the control and evaluation unit controls the filling valve to carry out a filling process with a defined desired filling quantity according to a filling curve, wherein the filling curve indicates the degree of opening of the filling valve, wherein the magnetoinductive flow sensor has a measuring tube for guiding the medium flow, a magnetic field generating device for generating a magnetic field passing through the measuring tube perpendicular to the flow direction of the medium flow, wherein the control and evaluation unit controls the magnetic field generating device in this way, that in a standard operation the magnetic field with a standard magnetic field frequency changes its polarity as the working magnetic field frequency, wherein the control and evaluation unit determines at least one flow measurement value in the interval of a constant magnetic field polarity and a stable magnetic field on the basis of a standard calibration as the working calibration, characterized in that the control and evaluation unit is designed and configured such that it carries out the method described above in detail, including its further developments, during operation of the filling device.In particular, there are now a plurality of possibilities for embodying and developing the method according to the invention for operating a filling device and the filling device according to the invention. In this regard, reference is made, on the one hand, to the patent claims subordinate to the independent patent claims, and, on the other hand, to the following description of exemplary embodiments in conjunction with the drawing. The drawing shows FIG. 1 schematically shows a method for operating a filling device together with such a filling device, as are known from the prior art, FIG. 2 schematically shows the switching of the polarity of the magnetic field of the flow sensor, FIG. 3 schematically shows the change of the magnetic field frequency and test to a stable magnetic field in a test phase, FIG. 4 shows schematically the repeated multiple times of the test phase for the purpose of systematically increasing the magnetic field frequency, and FIG. 5 schematically shows the recalibration of the flow sensor.FIGS. 1, 2, 3, 4 to 5 schematically show, in various embodiments and at various levels of detail, the method 1 for operating a filling device 2 having a filling valve 3 for controlling a medium flow, having a magnetoinductive flow sensor 4 for metrological detection of the medium flow released by the filling valve 3 and having a control and evaluation unit 5 for controlling the filling valve 3, and corresponding filling devices 2.FIG. 1 shows the method 1 for operating a filling device 2 and such a filling device 2, as are known from the prior art. The magnetoinductive flow sensor 4 has a measuring tube 6 for guiding the medium flow, a magnetic field generating device 7 for generating a magnetic field B passing through the measuring tube 6 perpendicular to the flow direction of the medium flow. The control and evaluation unit 5 controls the magnetic field generation device 7 such that, in a standard operation 9, the magnetic field B changes its polarity with a standard magnetic field frequency f_stand as the work magnetic field frequency f_work, wherein the control and evaluation unit 5 determines at least one flow measurement value flow in the interval 10 of a constant magnetic field polarity and a stable magnetic field B on the basis of a standard calibration kal_stand as the work calibration kal_work.The control and evaluation unit 5 controls the filling valve 3 to carry out a filling process 11 with at least one plateau phase 12 of the flow and an associated plateau flow measurement value flow_plate with a defined desired filling quantity according to a filling curve 13. The filling curve 13 indicates the opening degree O of the filling valve 3. The filling curve 13 is plotted in FIG. 1 over the filling quantity V. The filling quantity V is obtained by integration of the flow measurement values flow over time. If the process conditions are constant, then the filling curve 13 could also be plotted over time, which is indicated in FIG. 1.The standard operation 9 is distinguished by the use of standard parameters (f_stand, cal_stand), with which the flow sensor 4 and thus the filling device 2 have been calibrated at the factory. The flow sensor 4 is designed such that it can determine flow measurement values within the scope of the specification applicable to it over the specified operating range (for example a temperature range), that is to say for example with a specific measurement rate and with a specific accuracy.The control and evaluation unit 5 serves on the one hand for controlling the filling valve 3, but it also serves for controlling the magnetoinductive flow sensor 4 and for evaluating the raw measurement data obtained from the flow sensor 4 and for determining flow measurement values flow. In FIG. 1, the control and evaluation unit 5 is shown as a unit, but this is not important. Such control and evaluation units 5 are usually implemented in hardware on the basis of microcontrollers and / or digital signal processors. Whether the control and evaluation unit 5 is implemented as a technical device module or by means of a plurality of technical device modules which communicate with one another is not important for the description of the method 1 of interest here and the filling apparatus 2 of interest here.FIG. 2 shows the time profile of the magnetic field B generated by the magnetic field generating device 7. the magnetic field B is switched with respect to its polarity in the standard mode at the standard magnetic field frequency f_stand. Three switching intervals 10' of the magnetic field polarity are shown, which are almost coincident with the intervals 10 of constant magnetic field polarity. If the polarity of the voltage at the magnetic field generating device 7 is changed at the beginning of the changeover interval 10', it takes a certain time until the magnetic field B first decreases in one direction and builds up in the other direction. The time until the magnetic field B has completely cleared from the one polarity is the time offset between the constant magnetic field polarity interval 10 and the switching interval 10'. It is in any case important that only voltages at the measuring electrodes 8 can be used for the calculation of flow measurement values flow if the magnetic field B is stable, i.e. has reached a constant and predetermined height.In FIG. 2, the intervals are marked in which the magnetic field B meets these stability requirements (B!=stable). The sampled voltages at the measuring electrodes 8, indicated by the arrows in these time ranges, can be used to calculate a flow measurement value flow in each interval. The measurement rate at which the flow sensor 4 generates flow measurement values thus depends directly on the magnetic field frequency at which the magnetic field B changes its polarity.FIG. 3 shows a method 1 aimed at increasing the magnetic field frequency compared to the original calibration in order to increase the measurement rate for the flow measurement of the flow sensor 4 and thus to improve the measurement accuracy and the repeatability of the flow sensor 4. The starting point is the standard operation 9. In a subsequent test phase 14, the control and evaluation unit 5 operates the magnetic field generating device 7 with a test magnetic field frequency f_test that is greater than the set working magnetic field frequency f_work. A check is then made 15 (B?=stable) as to whether a stable magnetic field B is also generated at the test magnetic field frequency f_test in an interval 10 of a constant magnetic field polarity. When generating a stable magnetic field B, the test magnetic field frequency f_test is set and used as a new work magnetic field frequency f_work. If a stable magnetic field cannot be achieved at the higher magnetic field frequency, the old working magnetic field frequency f_work_alt, in this case the standard magnetic field frequency, is reset as the working magnetic field frequency in the illustrated exemplary embodiment.The check 15 as to whether a stable magnetic field B is generated in an interval 10 of a constant magnetic field polarity is carried out by evaluating the stationarity of a current impressed into the magnetic field generating device 7 and of a voltage applied to the magnetic field generating device 7, in the present case by time series analysis of the detected impressed current and the detected applied voltage.In the method according to FIG. 4, the test phase 14 is repeated a number of times, in the present case until the greatest test magnetic field frequency f_test has been determined, at which a stable magnetic field B is generated in an interval 10 of a constant magnetic field polarity, wherein this test magnetic field frequency f_test is then of course set as the working magnetic field frequency f_work. When the test phase 14 is repeated, the test magnetic field frequency f_test is increased in constant frequency steps. As in FIG. 3, in FIG. 4 the identifier f_work_old has been introduced in order to keep the old work magnetic field frequency available in order to be able to revert to the value in the case of the required return step.Method 1 is designed here such that test phase 14 is not repeated as soon as a maximum test magnetic field frequency f_test has been found and set as working magnetic field frequency f_work.Furthermore, method 1 is designed such that working magnetic field frequency f_work is switched back to standard magnetic field frequency f_stand and test phase 14 is run through anew starting from standard operation 9, the switching back to standard operation 9 being carried out at regular time intervals. This ensures that a set working magnetic field frequency f_work, with which reliable operation of the flow sensor 4-for whatever reason-is no longer possible, is detected and a safe fall-back position, namely the standard operation 9, is set again.The method 1 according to FIG. 5 is characterized in that the flow sensor 4 is operated with the working magnetic field frequency f_work deviating from the standard magnetic field frequency f_stand, and the flow sensor 4 is re-calibrated 16 by ascertaining a test calibration curve 17 between two points of known flow flow rate flow1, flow2during the filling process 11 and associated detected voltage values U1, U2at two measuring electrodes 8 of the flow sensor 4, wherein the test calibration curve 17 is used as the working calibration cal_work. In other embodiments, a calibration is performed with more than two calibration points.In the present case, the plateau flow rate flow_plate during the plateau phase 12 of the flow and the associated voltage value U 1 at the measuring electrodes of the flow sensor 4 are used as a point known flowl, and a zero flow rate flow 2 is used as a second point when the filling valve 3 is closed during the filling process 11 and the associated voltage value U 2 at the measuring electrodes 8 of the flow sensor 4.In addition, it is realized that the zero flow rate is validated by checking the opening degree O of the filling valve 3 for complete closure.In one embodiment of method 1, flow sensor 4 is switched to standard operation 9 by setting standard magnetic field frequency f_stand as working magnetic field frequency f_work and standard calibration cal_stand as working calibration cal_work, a current plateau flow measurement value being ascertained in plateau phase 12 of the flow when a filling process 11 is subsequently carried out, wherein, in the case of a deviation of the current plateau flow measurement value from the previously determined or given plateau flow measurement value flow_plate with standard calibration cal_stand or from the previously determined flow measurement value flow_plate in the plateau phase 12 with increased test magnetic field frequency f_test, a new test calibration curve 17 is determined as work calibration cal_work with the test calibration curve 17 and is set as work calibration cal_work. This method variant ensures that plateau flow measurement values flow_plat assumed to be valid, which are no longer correct, are recognized and corrected as being inaccurate.In a further development of method 1, at least one temperature T of the flow sensor 4 is determined, in particular a temperature T of the magnetic field generating device 7 and / or a medium temperature of the medium flow flowing through the flow sensor 4 and / or an ambient temperature of the flow sensor 4, wherein, as a function of the at least one temperature T of the flow sensor 4, in the test phase 14, a starting test magnetic field frequency f_test_start is determined and used as a test magnetic field frequency f_test, which lies close to the maximum stable test magnetic field frequency f_test attainable at the determined temperature T of the flow sensor 4, in particular wherein the dependence of the starting test magnetic field frequency f_test_start on the at least one determined temperature T of the flow sensor 4 has been determined empirically, In particular for a specific type of flow sensor 4 or a specific type of filling device 2.If the method 1 is used in a filling system with many filling devices 2 of the same type, then it is provided in an advantageous embodiment that the work magnetic field frequency f_work and / or test calibration curve 17 determined for a specific flow sensor 4 in a specific filling device 2 are transmitted as work calibration cal_work to other flow sensors 4 in other filling devices 2, in particular to other flow sensors 4 in other filling devices 2, which are operated together with the specific filling device 2 in a filling system.As a result, the described method 1 and the appropriately configured filling devices 2 lead to an improvement in the absolute accuracy and the repeatability of the measurement, so that filling processes can be carried out with lower safety requirements and thus with lower raw material requirements.Reference numerals denote reference numerals1 Method 2 Filling device 3 Filling valve 4 Magnetic-inductive flow sensor 5 Control and evaluation unit 6 Measuring tube 7 Magnetic field generation device 8 Measuring electrodes 9 Standard operation 10 Interval of constant magnetic field polarity 10' Switching interval of magnetic field polarity 11 Filling process 12 Plateau phase of the flow 13 Filling curve 14 Test phase 15 Checking for stable magnetic field 16 Recalibration of the flow sensor 17 Test calibration curve B Magnetic field U Electric voltage at the measuring electrodes f_stand Standard magnetic field frequency f_work Working magnetic field frequency f_test Test magnetic field frequency kal_stand Standard calibration kal_work Working calibration flow flow flow flow value flow_pat Plateau flow value O Opening degree of the filling valve Stably stable magnetic field flow 1, Flow measurement values for recalibration flow2 U1, U2 Sensing electrode voltages at flow1, flow2

Claims

Method (1) for operating a filling device (2) having a filling valve (3) for controlling a medium flow, having a magnetoinductive flow sensor (4) for metrological detection of the medium flow released by the filling valve (3) and having a control and evaluation unit (5) for controlling the filling valve (3), wherein the magnetoinductive flow sensor (4) has a measuring tube (6) for guiding the medium flow, a magnetic field generating device (7) for generating a magnetic field (B) which passes through the measuring tube (6) perpendicularly to the flow direction of the medium flow, wherein the control and evaluation unit (5) controls the magnetic field generating device (7) in this way, in a standard operation (9), the magnetic field (B) with a standard magnetic field frequency (f_stand) as the working magnetic field frequency (f_work) changes its polarity, wherein the control and evaluation unit (5) determines at least one flow measurement value (flow) as the working calibration (cal_work) in the interval (10) of a constant magnetic field polarity and a stable magnetic field (B) on the basis of a standard calibration (cal_stand), characterized in that the control and evaluation unit (5) controls the filling valve (3) according to a filling curve (13) for carrying out a filling process (11) with at least one plateau phase (12) of the flow and an associated plateau flow measurement value (flow_pat) with a defined setpoint filling quantity, wherein the filling curve (13) indicates the degree of opening (O) of the filling valve (3) that in a test phase (14) the control and evaluation unit (5) operates the magnetic field generating device (7) with a test magnetic field frequency (f_test) which is greater than the set working magnetic field frequency (f_work), wherein it is checked (15) whether a stable magnetic field (B) is also generated at the test magnetic field frequency (f_test) in an interval (10) of a constant magnetic field polarity and that when a stable magnetic field (B) is generated the test magnetic field frequency (f_test) is set and used as a new working magnetic field frequency (f_work).Method (1) according to Claim 1, characterized in that the check (15) as to whether a stable magnetic field (B) is generated in an interval (10) of a constant magnetic field polarity is carried out in that a magnetic field sensor is evaluated and the stationarity of the magnetic field (B) is assessed, and / or in that the stationarity of a current impressed into the magnetic field generating device (7) and / or of a voltage applied to the magnetic field generating device (7) is assessed, in particular by time-series analysis of the detected magnetic field strength and / or of the detected impressed current and / or of the detected applied voltage.Method (1) according to Claim 1 or 2, characterized in that the test phase (14) is repeated a plurality of times, in particular until the greatest test magnetic field frequency (f_test) has been determined, at which a stable magnetic field (B) is generated in an interval (10) of a constant magnetic field polarity, this test magnetic field frequency (f_test) being set as the working magnetic field frequency (f_work).Method (1) according to Claim 3, characterized in that the test magnetic field frequency (f_test) is increased in constant frequency steps, or in that the test magnetic field frequency (f_test) is increased first in large frequency steps, then in decreasing frequency steps, or in that the test magnetic field frequency (f_test) is changed according to the principle of interval interleaving.Method (1) according to one of Claims 1 to 4, characterized in that the working magnetic field frequency (f_work) is switched back to the standard magnetic field frequency (f_stand) and the test phase (14) is run through anew starting from the standard operation (9), in particular wherein the switching back to the standard operation (9) takes place at regular time intervals or filling intervals.Method (1) according to one of Claims 1 to 5, characterized in that the flow sensor (4) is operated with the working magnetic field frequency (f_work) deviating from the standard magnetic field frequency (f_stand), and the flow sensor (4) is re-calibrated (16) by ascertaining a test calibration curve (17) between at least two points of known flow (flow1, flow2) during the filling process (11) and associated detected voltage values (U1, U2) at two measuring electrodes (8) of the flow sensor (4), wherein the test calibration curve (17) is used as a working calibration (cal work).Method (1) according to Claim 6, characterized in that the plateau throughflow (flow_plate) during the plateau phase (12) of the throughflow and the associated voltage value (U1) at the measuring electrodes (8) of the throughflow sensor (4) are used as one point known throughflow (flow1), and / or in that a zero throughflow (flow2) when the filling valve (3) is closed during the filling process (11) and the associated voltage value (U2) at the measuring electrodes (8) of the throughflow sensor (4) are used as another point.Method (1) according to Claim 7, characterized in that the zero flow rate (flow2) is validated by checking the degree of opening (O) of the filling valve (3) for complete closure and / or by checking the zero flow rate (flow2) by the flow measurement value (flow) of the flow sensor (4) when switching back to the standard operation (9) at the standard magnetic field frequency (f_stand) in a transitional manner and subsequently changing to the stable test magnetic field frequency (f_test) which deviates from the standard magnetic field frequency (f_stand), for which the test calibration curve (17) is determined.Method (1) according to one of Claims 6 to 8, characterized in that the flow sensor (4) is switched over to standard operation (9) by setting the standard magnetic field frequency (f_stand) as working magnetic field frequency (f_work) and the standard calibration (kal_stand) as working calibration (kal work), in that, when a filling operation (11) is subsequently carried out, a current plateau flow measurement value is determined in the plateau phase (12) of the flow, wherein, in the case of a deviation of the current plateau flow measurement value from the previously determined or given plateau flow measurement value (flow_plate) with standard calibration (cal_stand) or from the previously determined flow measurement value (flow_plate) in the plateau phase (12) with increased test magnetic field frequency (f_test), a new test calibration curve (17) is determined with the test calibration curve (17) as work calibration (cal_work) and is set as work calibration (cal_work).Method (1) according to one of Claims 1 to 9, characterized in that at least one temperature (T) of the flow sensor (4) is determined, in particular a temperature (T) of the magnetic field generating device (7) and / or a medium temperature of the medium flow flowing through the flow sensor (4) and / or an ambient temperature of the flow sensor (4), in that, as a function of the at least one temperature (T) of the flow sensor (4) in the test phase (14), a starting test magnetic field frequency is determined and used as a test magnetic field frequency (f_test), which is close to the maximum stable test magnetic field frequency (f_test) which can be reached at the determined temperature (T) of the flow sensor (4), in particular, wherein the dependence of the start test magnetic field frequency on the at least one determined temperature (T) of the flow sensor (4) has been determined empirically, in particular for a specific type of flow sensor (4) or filling device (2).Method (1) according to one of claims 1 to 10, characterised in that the work magnetic field frequency (f_work) and / or test calibration curve (17) determined for a specific flow sensor (4) in a specific filling device (2) are transmitted as work calibration (cal work) to other flow sensors (4) in other filling devices (2), in particular to other flow sensors (4) in other filling devices (2) which are operated together with the specific filling device (2) in a filling plant.Filling device (2) with a filling valve (3) for controlling a medium flow, with a magnetoinductive flow sensor (4) for metrological detection of the medium flow released by the filling valve (3) and with a control and evaluation unit (5) for controlling the filling valve (3), wherein the magnetoinductive flow sensor (4) has a measuring tube (6) for guiding the medium flow, a magnetic field generating device (7) for generating a magnetic field (B) traversing the measuring tube (6) perpendicular to the flow direction of the medium flow, wherein the control and evaluation unit (5) controls the magnetic field generating device (7) such that in a standard operation (9) the magnetic field (B) changes its polarity with a standard magnetic field frequency (f_stand) as the working magnetic field frequency (f_work), wherein the control and evaluation unit (5) determines at least one flow measurement value (flow) in the interval (10) of a constant magnetic field polarity and a stable magnetic field (B) on the basis of a standard calibration (kal_stand) as the work calibration (kal work), characterized in that the control and evaluation unit (5) is designed and configured such that it carries out the method (1) according to one of claims 1 to 11 during operation of the filling apparatus (2).

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