Weighing scales – Self-positioning – Repositioning in response to deflection under load
Patent
1992-07-20
1994-09-13
Fuller, Benjamin R.
Weighing scales
Self-positioning
Repositioning in response to deflection under load
G01G 138
Patent
active
053470923
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
State of the Art
The invention relates to a compensation scale as disclosed, for example, in German Patent 3,230,998.
2. Description of Related Art Compensation scales include a movably guided component that is deflected from a rest position by a load to be determined as well as an electromagnetic arrangement which generates a force with which the deflectable component is held, for example, in the rest position independent of the load. The current flowing through a coil of the electromagnetic arrangement is a measure for the load, for example, the weight of the load. Scales generally have the characteristic that they may react with false measured values when the location where they are set up experiences shocks. The reasons for this are forces that act on the mechanical elements of the scale and on the load due to mass acceleration.
German Patent 3,230,998 discloses a compensation scale whose output signal is influenced by a correction signal that is derived from an acceleration sensor which is fixed to the placement location in the vicinity of the scale and determines the interference accelerations of the placement location.
It is the object of the invention to provide a compensation scale whose measurement signal is substantially free of interference signals over a wide frequency range.
SUMMARY AND ADVANTAGES OF THE INVENTION
The compensation scale according to the invention as defined by the features of the main claim has the advantage that the weight or the mass of a load can be determined with great accuracy after a short time. The improvement in the interference signal suppression is realized in that at least one acceleration sensor is disposed at the movably guided component that is charged by the load. This acceleration sensor puts out a signal for a correction signal processing arrangement which determines at least one correction signal for influencing the measuring result. The arrangement of the acceleration sensor at the movable component permits the detection of the actual interference signals which falsify the measuring result in that there is an additional determination of a relative acceleration that occurs between the movable component and the fixed component of the scale, something that is not possible with the known devices.
Advantageous modifications and improvements will become evident from the dependent claims.
In a particularly advantageous modification, at least two acceleration sensors are disposed at the movable component of the scale for detecting a translatory acceleration in the weighing direction and a rotational acceleration of the movable component. Rotational accelerations are particularly annoying in scales equipped with a lever with which the force to be generated by the electromagnetic arrangement can be influenced, preferably reduced, with respect to the force generated by the load. The at least two sensors are arranged relative to the pivot axis of the lever in such a way that a difference formation between the signals emitted by the sensors provides the rotational acceleration. Alternatively, one sensor is arranged in such a way that it detects only rotational acceleration.
According to a feature of the compensation scale according to the invention, it is provided that, after a determination of the current flowing through the coil of the electromagnetic arrangement, which is a measure for the weight or the mass of the load, the at least one correction signal influences the result.
An increase in the operating speed of the compensation scale is possible in that at least one correction signal influences that part of the signal processing arrangement which determines the current through the coil. Delays caused by the travel time of the signals are substantially avoided in this way.
The correction signal processing arrangement is advantageously divided into two signal paths of which one is provided for the correction of the translatory acceleration and the other for the correction of the rotational acceleration.
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Buchs Willy
Cochard Roland
Jeannin Pierre
Fuller Benjamin R.
Gibson Randy W.
Robert & Bosch GmbH
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