EMF Balance Pan Deflection Calibration via Electrical Impedance
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Solution Overview
Problem
Existing electromagnetic force-compensated (EMF) scales face challenges in accurately and cost-effectively measuring the deflection of the weighing pan, particularly due to the high expense and sensitivity of laser interferometers, which can lead to alignment issues and measurement errors.
Innovation Solution
A device and method for automatically calibrating the deflection of the weighing pan using a purely electrical, frequency-dependent measurement system that includes a force introduction unit, electrodynamic actuator, position indicator, measuring resistor, adjustment weight, and signal processing unit, allowing for simultaneous voltage measurement and determination of the characteristic curve of the scale pan without the need for expensive interferometers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If laser interferometers are used to measure the deflection of the weighing pan, then measurement precision is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent replaces the optical laser interferometer measurement system with an electrical measurement system. The coil's electrical parameters (current, voltage, impedance) are measured to determine the balance pan's position and mechanical characteristics. This substitution eliminates the need for complex optical alignment while maintaining measurement accuracy through electrical impedance analysis and current-voltage relationships in the electromagnetic actuator coil.
Solution Approach 2:
The patent introduces the coil's electrical impedance and current-voltage characteristics as an intermediary measurement mechanism. Instead of directly measuring physical displacement with optical instruments, the system uses electrical measurements of the coil (which is coupled to the mechanical system) to infer position and mechanical properties. This intermediary electrical measurement system bridges the gap between electrical control and mechanical measurement.
2Measurement precision
If laser interferometers are used for displacement measurement, then measurement precision is improved, but reliability deteriorates due to sensitivity and alignment issues
Solution Approach 1:
The patent replaces the fragile optical interferometer system with a robust electrical measurement system. Electrical measurements of current and voltage across the coil are inherently more reliable than optical measurements because they are not susceptible to alignment errors, dust, or environmental optical interference. The electrical system provides stable, repeatable measurements that maintain precision without the reliability problems of optical methods.
Solution Approach 2:
The coil serves dual functions: as the electromagnetic actuator that generates force and as the sensor for position measurement. By measuring the coil's electrical characteristics (impedance, current, voltage), the system uses the existing component for self-diagnosis and measurement, eliminating the need for separate, sensitive measurement instruments. This self-service approach improves reliability by reducing the number of separate measurement components.
Data Source
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AI summary
The invention relates to an apparatus and method for automatic calibration of the deflection of the pan of a balance having electromagnetic force compensation (EMF balance). The automatic calibration of the deflection of the pan of an EMF balance according to the invention is based on a purely electrical, frequency-dependent measurement of current and voltage on the coil of an EMF balance with the aid of a reference weight (calibration weight) of known mass and the output voltage from the position indicator of the EMF balance. The most exact possible determination of the static characteristic curve represents the core of the invention.