Digital Weighing Cell Linearization via Coil Position Feedback
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Solution Overview
Problem
Existing force measuring devices, particularly those using the electromagnetic force compensation principle, face challenges in accurately determining weight under oscillating or vibrating conditions due to position-dependent magnetic fields and dynamic effects, leading to zero point deviations and reduced precision in weighing results.
Innovation Solution
A method that incorporates a position sensor to detect the deflection of a coil within a magnet system, allowing for the calculation of weight by adjusting the coil current to return the coil to its initial position, thereby accounting for non-linearities in the magnet system and mechanical connections, and using a transmission table or function to determine the weight based on coil deflection and current magnitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electronic filters are applied to the compensation force signal to counteract vibrations, then measurement stability is improved, but response time and productivity deteriorate
Solution Approach 1:
The patent replaces the mechanical/electronic filtering approach with a mathematical correction approach. Instead of filtering the compensation force signal to remove vibrations, the invention applies a correction function that calculates the actual weight by compensating for the non-linear relationship between coil current and weight under dynamic conditions. This substitution of mechanical filtering with mathematical correction maintains measurement stability without sacrificing response time.
2Measurement precision
If the magnetic field is made homogeneous to improve measurement precision, then device complexity increases
Solution Approach 1:
The patent changes the approach from modifying the physical magnetic field to modifying the calculation parameters. Instead of creating a homogeneous magnetic field through complex magnet designs, the invention introduces a correction function that uses the measured coil current and coil position to calculate the actual weight. This parameter-based correction compensates for magnetic field non-uniformities without requiring complex magnet systems.
3Measurement precision
If the coil position is continuously monitored and adjusted to maintain equilibrium position, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent introduces a correction function as an intermediary between the measured coil current and the calculated weight. This correction function acts as a mediator that accounts for the non-linear relationship caused by coil position variations and magnetic field non-uniformities. Instead of directly controlling the coil position to maintain equilibrium, the correction function compensates for position effects in the calculation, simplifying the control system while maintaining precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables precise and quick weight determination even in oscillating or vibrating environments, improving the robustness of force-measuring devices and reducing zero point deviations, making it suitable for microbalances and checkweighers.
Implementation Method 1
the electric current through the coil is used to bring the coil and the load bearing area connected to the coil or the magnet system back into the insertion position and/or to keep them there by the electromagnetic force between the coil and the magnet system
Data Source
Figure 1~2
Figure 3
Figure 4~9
AI summary
The method involves applying a load to a load receiving part (12) causing a current-conducting coil (20) to be displaced from a settling position. An amount by which the coil is displaced from the settling position is determined. Electrical current of a magnitude calculated to generate an electromagnetic force sufficient to return the coil is applied to the position, where the calculation is achieved from an input signal to a position-controlling unit. Weight force exerted by the applied load is calculated using the magnitude of electrical current and the amount of coil displacement. Independent claims are also included for the following: (1) a force-measuring cell (2) a computer program comprising a set of instructions for determining a weight force of a load on a force-measuring device (3) a check weighing system for weighing objects.