DE102021132093B3 - Weighing device and method for its operation - Google Patents

Abstract

The invention relates to a method for operating a weighing device (10), which has a load receiver (12) that can be vertically deflected relative to a base, - a transmission lever (26) that is pivotably mounted in a vertical plane about a lever joint (28) that is fixed to the base and has a - the sensor having a first moving coil arrangement (30a), the first moving coil arrangement (30a) having two sensor elements which can be moved relative to one another in the vertical direction , namely a magnet (302a) and a coil (301a) immersed in the magnetic field of the magnet (302a), and acts on the lever arm (262) on the sensor side by having one of its sensor elements rigidly connected to the lever arm (262) on the sensor side and the other rigidly is connected to the base, wherein the sensor-side lever arm (262) in addition to the first moving coil assembly (30a) a second Plunger coil arrangement (30b) engages, and both plunger coil arrangements (30a,b) are arranged in opposite directions vertically spaced from the sensor-side lever arm (262), comprising the steps of: - placing a load (22) on the load receiver (12), - Energizing the exchange coil arrangements (30a,b) with a compensation current in such a way that a deflection of the transmission lever (26) caused by the load is electromagnetically compensated, - Calculating the mass of the load (22) from the strength of the compensation current, The invention is characterized by this that a predetermined effective system stiffness is set by a corresponding distribution of the compensation current to the two plunger coil arrangements (30a, b).

Description

field of invention

• - einen gegenüber einer Basis vertikal auslenkbaren Lastaufnehmer,
• - einen in einer vertikalen Ebene um ein basisfestes Hebelgelenk schwenkbar gelagerten Übertragungshebel mit einem am Lastaufnehmer angelenkten, lastaufnehmerseitigen Hebelarm und einem mit einem Sensor gekoppelten, sensorseitigen Hebelarm,
• - den eine erste Tauchspulenanordnung aufweisenden Sensor, wobei die erste Tauchspulenanordnung zwei in vertikaler Richtung relativ zueinander bewegbare Sensorelemente, nämlich einen Magneten und eine in das Magnetfeld des Magneten eingetauchte Spule, umfasst und an dem sensorseitigen Hebelarm angreift, indem eines ihrer Sensorelemente starr mit dem sensorseitigen Hebelarm und das andere starr mit der Basis verbunden ist,

wobei am sensorseitigen Hebelarm zusätzlich zur ersten Tauchspulenanordnung eine zweite Tauchspulenanordnung angreift, und beide Tauchspulenanordnungen in einander entgegengesetzter Richtung vertikal von dem sensorseitigen Hebelarm beabstandet angeordnet sind,
aufweist, umfassend die Schritte:

• - Auflegen einer Last (22) auf den Lastaufnehmer (12),
• - Bestromen der Tauschspulenanordnungen (30a,b) mit einem Kompensationsstrom derart, dass eine durch die Last hervorgerufene Auslenkung des Übertragungshebels (26) elektromagnetisch kompensiert wird,
• - Berechnen der Masse der Last (22) aus der Stärke des Kompensationsstroms.

The invention relates to a method for operating a weighing device which

• - a load receptor that can be vertically deflected relative to a base,
• - a transmission lever pivoted in a vertical plane about a base-fixed lever joint with a load receptor-side lever arm articulated on the load receptor and a sensor-side lever arm coupled to a sensor,
• - the sensor having a first plunger coil arrangement, the first plunger coil arrangement comprising two sensor elements that can be moved in a vertical direction relative to one another, namely a magnet and a coil that is immersed in the magnetic field of the magnet, and acts on the sensor-side lever arm by one of its sensor elements being rigidly connected to the sensor-side lever arm and the other rigidly connected to the base,

wherein a second plunger coil arrangement acts on the sensor-side lever arm in addition to the first plunger coil arrangement, and both plunger coil arrangements are arranged in opposite directions vertically spaced from the sensor-side lever arm,
has, comprising the steps:

• - Placing a load (22) on the load receptor (12),
• - Energizing the exchange coil arrangements (30a,b) with a compensation current in such a way that a deflection of the transmission lever (26) caused by the load is electromagnetically compensated,
• - Calculating the mass of the load (22) from the strength of the compensation current.

State of the art

Such an operating method is known from DE 2 224 135 A .

Gravimetric measuring devices, ie weighing devices, that work according to the principle of electromagnetic compensation have long been known to the person skilled in the art. For example, the EP 2 690 415 A1 a typical such weighing device.

The basic principle of such a weighing device is that the deflection of a load receptor caused by the weight of a load in relation to a base is transmitted by means of a transmission lever in terms of force and displacement to a sensor, which in turn is able to exert an electromagnetic force on the lever arm in the opposite direction to the deflection. This compensating force is dependent on the current with which the coil of a plunger coil arrangement generating the compensating force is energized. If the current is selected in such a way that the load-related deflection of the transmission lever is exactly compensated, i.e. the lever arm is in its equilibrium position despite the load being applied, the compensation current represents an exact measure of the required compensation force and therefore of the weight of the load applied.

To adjust the weighing window, ie the weight range in which the load must be in order to be weighed accurately, the EP 2 690 415 A1 proposed the arrangement of a slidable weight on the transmission lever. The aforementioned, generic DE 2 224 135 A proposes, on the other hand, to avoid such a mechanism, in addition to the sensor-moving-coil arrangement, to couple a preload-moving coil arrangement to the transmission lever in order to generate a pre-loading or pre-relief by electrical means, with the coil current required for this from a second scale on which a mechanical preload weight can be applied.

Technically, an electromagnetically compensating weighing system is usually implemented as follows: The so-called load receptor is linked to a fixed base by means of a parallel link arrangement, whereby its degrees of freedom of movement are limited to a purely vertical movement when the weighing device is set up correctly - at least in the case of small deflections . The load receiver is articulated to a transmission lever, in particular to its lever arm on the load receiver side, via a so-called coupling band. The transmission lever is pivotably mounted on a base-fixed lever joint. The bearing point represents the boundary between the load receiver-side lever arm and the sensor-side lever arm of the transmission lever. The coil of a plunger coil arrangement is fixed at the end of the sensor-side lever arm. It is immersed in the magnetic field of a base-fixed, mostly pot-shaped magnet, usually a permanent magnet. The reverse arrangement with a base-fixed coil and a lever-fixed (permanent) magnet is also conceivable, but is unusual. The position of the transmission lever in a given reference load situation (usually unloaded with conventional scales, loaded with comparators) represents its equilibrium position. This can be determined using a separate position sensor, which is usually works on an optical principle, can be detected or the lever can be adjusted in such a way that, when the load receptor is unloaded, it is arranged in a position interpreted by the position sensor as an equilibrium position. When the coil is energized, a magnetic field corresponding to the coil current is generated, which interacts with the magnetic field of the permanent magnet, resulting in a force acting on the lever arm on the sensor side. Conversely, placing a load on the load receptor causes a mechanical force to act on the lever arm on the load receptor side. By means of a suitable regulation, such a device can be operated in such a way that each (infinitesimal) load-related deflection of the transmission lever is detected by the position sensor and converted into a compensatory change in the coil current. In this way, the transmission lever remains (apart from infinitesimal deflections) in its equilibrium position, with the current flowing through the coil at the end of a transient process being representative of the load placed on the load receptor, the weight of which can be determined with great precision by measuring the coil current accordingly.

The mechanical part of this complex system is often referred to in technical jargon as a weighing system. These are extremely precisely manufactured, often monolithic devices that, despite the use of the most sophisticated precision technology, can exhibit deviations from an ideal system. In particular, the so-called rigidity of the joints in such a weighing system represents such a deviation from the ideal system. Rigidity is the restoring force that a real joint (in contrast to an ideal joint) opposes to its deflection. Because of this rigidity, part of the load-related deflection of the transmission lever is already mechanically compensated. The electromagnetic compensation that is additionally required for the overall compensation of the deflection is therefore correspondingly lower. Since, as explained above, only the electrical part of the compensation is included in the calculation of the load weight, the stiffness leads to a systematic underestimation of the load weight. As long as the rigidity is explicitly known, this can be corrected by calculation; however, a so-called astasis, i. H. a correction made to the mechatronic system itself is considered.

Various astasis approaches are known to those skilled in the art. The aim of the astasation is to set a predetermined effective stiffness in the overall system, which is composed of the intrinsic stiffness of individual elements, especially the joints, on the one hand and their (partly incomplete, partly overcompensating) corrective measures on the other hand. In the context of the present description, the term “effective system rigidity” should be used in this regard. This is often desired to be exactly zero; however, there are practical cases where a (positive or negative) non-zero effective system stiffness is specifically desired.

As an astasis measure, it is known, for example, to design the transmission lever in such a way that its center of gravity is above the lever joint, i. H. lies above its exact pivot point. This leads to a destabilization of the equilibrium position of the transmission lever: Every deflection of the lever leads to a torque that amplifies the deflection due to the high center of gravity. This counteracts the reverse stiffness torque of the lever pivot. Conversely, by shifting the center of gravity of the lever under its joint pivot point, stabilization and thus an increase in the effective system rigidity can be achieved. The disadvantage of this approach is that both the joint stiffness and the position of the center of gravity of the transmission lever are subject to manufacturing deviations and therefore only compensate each other exactly in exceptional cases. In addition, the system is more sensitive to tilting.

As a further stabilization measure, it is known to make the center of gravity of the transmission lever adjustable by means of vertically displaceable trimming weights. However, this also leads to a significant increase in the tilting sensitivity of such a system and must be viewed as a disadvantage overall.

Also those in the above mentioned EP 2 690 415 A1 The displaceable trimming weights disclosed represent a further astasizing measure. They can be used to apply an adjustable torque that compensates for the rigidity to one (or both) of the lever arms of the transmission lever. However, such arrangements are mechanically very complex and difficult to operate, since the transmission lever is not usually accessible from the outside of a ready-to-use weighing device.

And finally, it is known as yet another astasizing measure to design the transmission lever in such a way that its two lever arms are at an angle other than 180° to one another. If they form an angle that is open vertically upwards, the force application point of the transmission lever is shifted upwards compared to the pivot point of the lever joint, which tends to make the system unstable. Conversely, it is achieved by an inverted, roof-shaped design of the transmission lever offset below, which tends to stabilize the system.

task

It is the object of the present invention to specify a generic operating method for a basically known weighing device in such a way that the effective system rigidity can be adjusted in a simple manner and over further ranges.

Presentation of the invention

This object is achieved in connection with the features of the preamble of claim 1 in that a predetermined effective system rigidity is set by appropriately distributing the compensation current to the two plunger coil arrangements (30a,b).

Preferred embodiments of the invention are subject of the dependent claims.

The inventors have recognized that the effect of mechanical stasis can also be achieved electrically by vertical trimming weights at the point of application of the joint, namely by a plunger coil arrangement which is attached to any axial position of the transmission lever, but is itself positioned at a vertical distance from the lever arm. The purely mechanical weight of the trimming weight can therefore be replaced by the electromagnetically generated force of the plunger coil arrangement. When constructing the weighing sensor, it is usually attempted with comparatively great effort to place the center of the interaction between the magnetic fields of the coil and the magnet exactly in the horizontal central plane of the lever arm on the sensor side (which is in the position of equilibrium). In contrast to this, the invention now provides for the conscious maintenance of a—basically known—vertical distance between this center of interaction and the horizontal central plane of the lever arm on the sensor side. This is what is meant by the simplified formulation of a plunger coil arrangement “spaced” from the lever arm. In particular, a plunger coil arrangement which is spaced vertically from the lever arm on the sensor side and which exerts a force on it which is directed away from the lever arm has a stabilizing, i. H. an effect that increases the effective system rigidity, whereas such a plunger coil arrangement, which exerts a force on the lever arm directed in the direction of the latter, has an unstable, d. H. has an effect reducing the effective system stiffness. The particular advantage of such an electrical branching lies in its easier adjustability. In implementing this finding, the invention now provides two plunger coil arrangements, preferably of basically identical construction, of which one is arranged above and the other below the lever arm on the sensor side and thus act on the lever arm in opposite directions. During operation, both plunger coil arrangements are energized, so that their two force effects on the lever arm on the sensor side add vectorially to the total compensation force. However, with the same resulting total compensation force, the distribution of the individual partial forces on the two plunger coil arrangements and in particular the distribution of the energization of the two coils leads to different astasis effects, so that overall a desired (predetermined) effective system stiffness can be set precisely.

• - Auflegen einer Last auf den Lastaufnehmer,
• - Bestromen der Tauchspulenanordnungen mit einem Kompensationsstrom derart, dass eine durch die Last hervorgerufene Auslenkung des Übertragungshebels elektromagnetisch kompensiert wird,
• - Berechnen der Masse der Last aus der Stärke des Kompensationsstroms,

wobei eine vorbestimmte effektive Systemsteifigkeit durch eine entsprechende Verteilung des Kompensationsstroms auf die beiden Tauchspulenanordnungen eingestellt wird.There are various approaches to operating a weighing device according to the invention. What they have in common is that they represent a process that includes the following steps:

• - placing a load on the load receptor,
• - Energizing the plunger coil arrangements with a compensation current in such a way that a deflection of the transmission lever caused by the load is electromagnetically compensated,
• - calculate the mass of the load from the strength of the compensation current,

wherein a predetermined effective system stiffness is set by a corresponding distribution of the compensation current to the two plunger coil arrangements.

In a first variant of the method or in a first operating mode, it is provided that the plunger coil arrangements are energized in the same direction so that the resulting force effects of both plunger coil arrangements on the sensor-side lever arm are rectified. In other words, in this variant of the method, the effect of the single plunger coil arrangement known from the prior art is replaced by the two plunger coil arrangements, the sum of which coil currents form the compensation current required for deflection compensation. One of the plunger coil arrangements exerts a pulling effect on the lever arm on the sensor side and therefore has a stabilizing effect; the other exerts a compressive force and has a labilizing effect. If both coils are supplied with the same current, the astatic effects cancel each other out. In the case of unequal energization, this leads to a different weighting of the astasis contributions and to a non-vanishing resulting astasis effect that, together with the stiffness of the rest of the system, leads to the effective system stiffness.

Those skilled in the art will understand that in the above explanation, to simplify understanding, plunger coil arrangements of exactly the same construction are assumed, which are arranged at the same distance from the lever arm on the sensor side and act on the same axial position of the lever arm on the sensor side. Indeed, this is also the preferred embodiment. If this is deviated from, it is possible that the distribution of the coil currents that leads to the exact cancellation of the astasation contributions does not correspond to an equal distribution of the current to the two coils. However, this does not represent a fundamental problem that cannot be solved by appropriately designing the control and regulation algorithms. For the sake of simplicity, however, this preferred design will continue to be used in the following—without restricting the general validity. This also preferably provides that the vertical central planes of the two plunger coil arrangements and the lever arm on the sensor side are identical. In this way, lateral tilting moments on the lever can be avoided.

Regular attempts will be made to mechanically compensate for joint stiffness. For this purpose it is preferably provided that the force application point of the transmission lever is above the joint. In the ideal case, the entire mechanical subsystem of the weighing device then already has the desired (in particular vanishing) effective system rigidity. However, as explained above, this case cannot always be reliably guaranteed due to manufacturing deviations. The electromagnetic astasis according to the invention can then be used for fine adjustment of the effective system rigidity.

In the above-described operating mode of plunger coil arrangements with rectified current, in the event that an effective rigidity of the mechanical subsystem of the weighing device is greater than the desired, predetermined effective system rigidity, that of the two plunger coil arrangements that generates a force acting on the lever arm on the sensor side can be energized more strongly . In other words, in the event that the interaction of mechanical rigidity and mechanical stabilization measures lead to an overall system rigidity that is too great, the plunger coil arrangement that exerts a compressive force on the lever arm on the sensor side is energized more strongly, thereby tending to make the system unstable overall. The other plunger coil arrangement, which tends to exert a stabilizing effect in the operating mode under consideration, is correspondingly less energized. Nothing changes in the total current, which is representative of the applied load.

Conversely, in the above-described operating mode of plunger coil arrangements with rectified current, in the event that an effective rigidity of the mechanical subsystem of the weighing device is less than the desired, predetermined effective system rigidity, that of the two plunger coil arrangements that generates a force acting on the lever arm away from the sensor side can be energized more strongly . In other words, in the event that the interaction of mechanical rigidity and mechanical stabilization measures lead to an overall insufficient effective system rigidity, the plunger coil arrangement that exerts a tensile force on the lever arm on the sensor side is energized more strongly, thereby tending to stabilize the system as a whole. The other plunger coil arrangement, which tends to exert a labilizing effect in the operating mode under consideration, is correspondingly less energized. Nothing changes in the total current, which is representative of the applied load.

• - vor dem Auflegen der Last eine vorläufige effektive Systemsteifigkeit eingestellt wird, indem die Tauchspulenanordnungen einander entgegengesetzt bestromt werden, sodass die resultierenden Krafteinwirkungen beider Tauchspulenanordnungen auf den sensorseitigen Hebelarm einander entgegengesetzt gleich sind und
• - beim Auflegen der Last die Bestromung der Tauchspulenanordnungen derart verändert wird, dass die zur elektromagnetischen Kompensation der durch die Last hervorgerufenen Auslenkung des Übertragungshebels erforderliche Kraft aus einer Differenz der Bestromungsstärken der beiden Tauchspulenanordnungen resultiert.

However, the weighing device can also be operated according to the invention according to a second variant of the method or in a second operating mode. This provides that

• - A provisional effective system stiffness is set before the load is applied by the plunger coil arrangements being energized in opposite directions so that the resulting force effects of both plunger coil arrangements on the sensor-side lever arm are equal and opposite to one another
• - When the load is applied, the energization of the plunger coil arrangements is changed in such a way that the force required for electromagnetic compensation of the deflection of the transmission lever caused by the load results from a difference in the energization intensities of the two plunger coil arrangements.

In this embodiment, both plunger coil arrangements have the same astasis effect, namely either stabilizing or labilizing, depending on the direction of current flow. The former is the case when both voice coil arrangements exert an (opposite) pulling force on the lever. The latter is the case when both plunger coil assemblies exert an (opposite) compressive force on the lever. With a suitable, in particular equal, distribution of the currents to the two plunger coil arrangements, the forces compensate each other so that the lever is not deflected from its equilibrium position. The level However, the stabilization or labilization effect depends on the sum of the coil currents and can therefore be set exactly in advance of a weighing, ie before the load is placed. If the load is then applied, the distribution of the currents through the two coils is varied via a controller so that they deviate from one another, with the difference in the currents leading to a resultant force on the lever arm on the sensor side, which is adjusted in such a way that the load-related Deflection exactly compensated. Thus, the difference in the coil currents in this operating mode represents the weight of the load, whereas the sum of the coil currents determines the strength of the stabilizing or labilizing astasis. In particular, it is provided that in the event that an effective rigidity of the mechanical subsystem of the weighing device is greater than the predetermined effective system rigidity, the moving coil arrangements are energized before the load is applied in such a way that a force is directed in the vertical direction towards the sensor-side lever arm is produced. Conversely, it is then provided that in the event that an effective rigidity of the mechanical subsystem of the weighing device is greater than the predetermined effective system rigidity, the moving coil arrangements are energized before the load is applied in such a way that a force is directed in the vertical direction onto the sensor-side lever arm is produced.

For reasons of symmetry, it is preferably provided that the change in the current flow generated when the load is applied is distributed symmetrically over the two plunger coil arrangements. In other words, after the required stabilization or lability level has been set when the load is applied and the current difference compensating for the load-related design is generated, the current through which one plunger coil arrangement is reduced by exactly the amount by which the energization of the other plunger coil arrangement is increased will. Those skilled in the art will recognize that this of course presupposes the preferred, symmetrical configuration of the device described above. However, he will also recognize that deviations from the preferred mechanical symmetry can be compensated for by corresponding asymmetries in the electrical control.

Further details and advantages of the invention result from the following specific description and the drawings.

character list

• 1: eine stark schematisierte Darstellung einer erfindungsgemäß betreibbaren, an sich grundsätzlich bekannten Wägevorrichtung.

It shows:

• 1 1: a highly schematized representation of a weighing device that can be operated according to the invention and is basically known per se.

Description of Preferred Embodiments

1 shows a basically known weighing device 10 in a highly schematic representation. The weighing device 10 comprises a load receiver 12, which is articulated via a parallel link arrangement on a base that is only indicated. In particular, two parallel-aligned links 14a, 14b are each articulated via a link joint 16a, 16b on the one hand on the base and via a respective load receiver joint 18a, 18b on the load receiver 12. A weighing goods carrier 20 is fixed to the load receiver 12, onto which the load 22 to be weighed can be placed.

The load receiver 12 is articulated on the transmission lever 26 via a coupling strap 24, for which purpose the coupling strap 24 is articulated via coupling strap joints 241a, 241b on the one hand on the load receiver 12 and on the other hand on the load receiver-side lever arm 261 of the transfer lever 26.

The transmission lever 26 is pivotably mounted on a lever joint 28, from which the aforementioned lever arm 261 on the load receptor side extends in the direction of the load receptor 12 and a lever arm 262 on the sensor side extends in the opposite direction. In the illustrated embodiment, the two lever arms 261, 262 of the transmission lever 26 are at an angle other than 180° to one another, in particular at an angle that is open vertically upwards. As a result, the point of force application of the transmission lever 26 is offset upwards with respect to the pivot point 281 of the lever joint 28 (the simplified representation of 1 however, is not intended to indicate any elevation of the center of gravity; this should generally be at the level of the lever joint in order to minimize the tipping sensitivity). Due to the higher displacement of the point of application of force in relation to the pivot point 281, every deflection of the transmission lever 26 from its in 1 illustrated equilibrium position to a deflection tending to increase torque; ie to an unstable equilibrium. This counteracts the stabilizing effect of the intrinsic rigidity of the lever joint 28 and the joints 16a,b, 18a,b and 241a,b caused by the choice of material and shape. However, at least due to manufacturing deviations, a complete, reciprocal cancellation of the stabilizing and labilizing effects will not be possible. Applications are also conceivable in which the precise setting of a (positive or negative) non-zero effective system stiffness is desired.

In order to make such an adjustability of the effective system stiffness available in a simple manner, the sensor-side lever arm 262 is rigidly connected to the coils 301a, 301b of two plunger coil arrangements 30a, 30b, which in turn are inserted into the magnetic field of a respective associated magnet 302a, 302b, in particular a permanent magnet, are immersed. The coils 301a, 301b can be energized via a control and regulation device, not shown, with a current flow through each of the coils 301a, b leading to a magnetic field which interacts with the magnetic field of the respectively assigned magnet 302a, b and thus creates a corresponding force on the sensor-side lever arm 262 affects.

Each deflection of the lever arm 262 on the sensor side can be detected by means of an optical bearing detector 32 . As is generally customary with electromagnetically compensating scales, the coils 301a,b are energized by means of the control and regulating device in such a way that each infinitesimal deflection of the transmission lever 26 resulting from the application of the load 22 is immediately compensated by the application of a corresponding electromagnetic force. so that the transmission lever 26 remains in its position of equilibrium, apart from infinitesimal fluctuations.

It is of particular importance for the present invention that the two plunger coil arrangements 30a,b are arranged in opposite directions at a vertical distance from the lever arm 262 on the sensor side. The electromagnetically generated compensating force is therefore not generated and introduced in the horizontal central plane of the lever arm 262 on the sensor side, as is usual with known scales, but is generated at a vertical distance from it and introduced via vertical coupling rods 34a,b. In principle, the effect corresponds to that of a vertically offset trim weight, but the amount and direction can be precisely adjusted electrically.

With regard to the different operating modes of such a weighing device 10, reference is made to the detailed explanation in the general part of the present description.

Of course, the embodiments discussed in the specific description and shown in the figures only represent illustrative exemplary embodiments of the present invention. In particular, the person skilled in the art will understand that the purely schematic representation does not imply any limitation with regard to the actual implementation of the principle according to the invention. For example, the length ratios of the lever arms 261, 262 are not limited to the proportions shown. Likewise, a straight or vice versa, i. H. roof-shaped kinked and thus a stabilizing effect-causing design of the transmission arm 26 is possible. It is also conceivable that the plunger coil arrangements 30a,b attach to different axial positions of the transmission lever 26. The weighing-goods carrier 20 can also be connected to the load receiver 12 in a different way, for example hanging. A folded configuration of the transmission lever 26 is also conceivable, as is widely used in weighing technology to increase the transmission ratio in a space-saving manner.

reference list

10

weighing device

12

load receptor

14a,b

handlebars

16a,b

handlebar joints

18a, b

load receptor joints

20

weighing goods carrier

22

load

24

coupling strap

241a, b

Coupling Strap Joints

26

transmission lever

261

load cell side lever arm of 26

262

sensor-side lever arm of 26

28

lever joint

281

Pivot of 28

30a,b

plunger coil assembly

301a

coil of 30a,b

302a,b

magnet of 30a,b

32

position detector

34a,b

connecting rod

Claims (8)

Method for operating a weighing device (10), which has - a load receiver (12) which can be vertically deflected relative to a base, - a transmission lever (26) which is pivotably mounted in a vertical plane about a lever joint (28) fixed to the base and has a load receiver (12) articulated on it, lever arm (261) on the load receiver side and a lever arm (262) on the sensor side coupled to a sensor, - the sensor having a first plunger coil arrangement (30a), the first plunger coil arrangement (30a) comprising two sensor elements which can be moved relative to one another in the vertical direction, namely a magnet (302a) and a coil (301a) immersed in the magnetic field of the magnet (302a). and acts on the sensor-side lever arm (262) by one of its sensor elements being rigidly connected to the sensor-side lever arm (262) and the other rigidly connected to the base, wherein on the sensor-side lever arm (262) in addition to the first moving coil arrangement (30a) there is a second moving coil arrangement ( 30b) engages, and both plunger coil arrangements (30a,b) are arranged vertically spaced from the sensor-side lever arm (262) in opposite directions, comprising the steps: - placing a load (22) on the load receiver (12), - energizing the exchange coil arrangements (30a, b) with a compensation current such that a deflection of the transmission caused by the load movement lever (26) is electromagnetically compensated, - calculating the mass of the load (22) from the strength of the compensation current, characterized in that a predetermined effective system rigidity is set by appropriately distributing the compensation current to the two plunger coil arrangements (30a, b). procedure after claim 1 , characterized in that the plunger coil arrangements (30a, b) are energized in the same direction so that the resulting force effects of both plunger coil arrangements (30a, b) on the sensor-side lever arm (262) are rectified. procedure after claim 2 , characterized in that in the event that an effective rigidity of the mechanical subsystem of the weighing device (10) is greater than the predetermined effective system rigidity, that of the two plunger coil arrangements (30a, b) is energized more strongly, the one on the sensor-side lever arm (262) generated to directed force on this. procedure after claim 2 , characterized in that in the event that an effective rigidity of the mechanical subsystem of the weighing device (10) is less than the predetermined effective system rigidity, that of the two plunger coil arrangements (30a, b) is energized more strongly, the one from the sensor-side lever arm (262) away directed force on this generated. procedure after claim 1 characterized in that - before the load (22) is applied, a provisional effective system rigidity is set by the plunger coil arrangements (30a, b) being energized in opposite directions, so that the resulting force effects of both plunger coil arrangements (30a, b) on the sensor-side lever arm (262 ) are oppositely equal to each other, and - when the load (22) is applied, the energization of the moving coil arrangements (30a,b) is changed in such a way that the force required for electromagnetic compensation of the deflection of the transmission lever (262) caused by the load is derived from a difference between the Energization strengths of the two plunger coil arrangements (30a, b) results. procedure after claim 5 , characterized in that when the load (22) is applied, the change in the current flow is distributed symmetrically over the two plunger coil arrangements (30a, b). Procedure according to one of Claims 5 until 6 , characterized in that in the event that an effective rigidity of the mechanical subsystem of the weighing device (10) is greater than the predetermined effective system rigidity, the moving coil arrangements (30a, b) are energized before the load (22) is applied in such a way that one force directed in the vertical direction towards the lever arm (262) on the sensor side is generated. Procedure according to one of Claims 5 until 7 , characterized in that in the event that an effective rigidity of the mechanical subsystem of the weighing device (10) is less than the predetermined effective system rigidity, the moving coil arrangements (30a, b) are energized before the load (22) is applied in such a way that one force directed away from the sensor-side lever arm (262) is generated in the vertical direction.

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