Coin Testing Coil Assembly with Negative Feedback
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Solution Overview
Problem
Existing coin testing methods using inductive measuring techniques face challenges in effectively discriminating between various coin designs and forged coins, particularly in accurately determining the material properties and denominational values.
Innovation Solution
The method employs a specific assembly of measuring coils with a transmission coil and a smaller reception coil on a ferrite core, utilizing a secondary coil for negative feedback, and performing multiple measurement cycles with both reflection and transmission measurements to evaluate the attenuation curves, allowing for better discrimination and classification of coins based on their electric and magnetic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single reception coil is used on a single ferrite core, then the device complexity is reduced, but the measurement precision for discriminating various coin designs and forged coins deteriorates
Solution Approach 1:
The reception coil is divided into two separate coils: a first reception coil and a second reception coil. Each coil is positioned at different locations relative to the coin runway, allowing independent measurement of magnetic field attenuation from different perspectives. This segmentation enables more comprehensive analysis of coin material properties and design features, improving discrimination precision without requiring a single complex multi-element coil assembly.
Solution Approach 2:
The patent transitions from a single-point reception measurement to a multi-point spatial measurement arrangement. By positioning the first and second reception coils at different locations (one closer to the transmission coil, another farther away), the system adds a spatial dimension to the measurement, enabling analysis of attenuation characteristics from multiple perspectives simultaneously. This dimensional expansion improves the ability to distinguish between genuine and counterfeit coins with varying designs and material compositions.
2Measurement precision
If multiple measurement cycles with both reflection and transmission measurements are performed, then the measurement precision for determining material properties and denominational values is improved, but the measurement time increases
Solution Approach 1:
The system performs measurement cycles in a periodic sequence, alternating between reflection measurements (transmission coil as reception coil) and transmission measurements (separate reception coils). Each cycle comprises multiple sub-measurements at different time points during the coin's passage through the field. This periodic structure allows systematic collection of comprehensive data on material properties and denominational values while maintaining a regular, predictable measurement rhythm that can be optimized for throughput.
Solution Approach 2:
The measurement system operates continuously as coins pass through the runway, with the transmission coil continuously generating magnetic fields and the reception coils continuously detecting attenuation. The multiple measurement cycles are overlapped in time, with each cycle capturing data at different moments during the coin's passage. This continuous operation ensures that valuable measurement time is maximized without idle periods, improving precision while minimizing total measurement time.
3Measurement precision
If the reception coil diameter is made smaller than the transmission coil diameter, then the measurement precision for analyzing curve shapes and material properties is improved, but the signal strength decreases
Solution Approach 1:
The reception function is segmented into two separate coils with different diameter characteristics. The first reception coil has a smaller diameter optimized for precise curve shape analysis and material property detection, while the second reception coil has a larger diameter that captures stronger signals. By segmenting the reception function, the system can simultaneously achieve both high precision measurement and adequate signal strength without requiring a single coil to optimize for both conflicting requirements.
Solution Approach 2:
The patent merges the measurements from the first and second reception coils to achieve the desired performance. The smaller first reception coil provides precise curve shape data, while the larger second reception coil provides stronger signal content. By combining and comparing the measurements from both coils, the system achieves both high measurement precision for material property analysis and sufficient signal strength for reliable detection, overcoming the limitations of a single coil design.
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 discrimination of genuine and counterfeit coins, as well as classification of denominational values, by analyzing the curve shapes and material properties of coins, even for bicolor coins, with improved accuracy and efficiency.
Implementation Method 1
a magnetic signal is directed from a transmission coil onto a coin running along a runway and a reception coil receives the resultant signal
Implementation Method 2
a secondary coil coupled to the transmission coil the signal of which is coupled back, as a negative-feedback signal, to the reception coil
Data Source
AI summary
A method for testing coins which move along a runway, using a coil assembly which, on either side of the runway, has a transmission coil C, D adapted to be admitted by a transmission signal and a reception coil A, B on a common ferrite core wherein the reception coil smaller in diameter is closer to the runway than is the transmission coil and the diameter of the transmission coil is smaller than the diameter of the smallest coin to be assumed, and wherein the ferrite core has arranged thereon a secondary coil coupled to the transmission coil the signal of which is connected, as a negative-feedback signal, to the input of a differential amplifier in such a way that the signal of the transmission coil agrees with the transmitted signal provided to the other input of the differential amplifier.