Coin Detection System Using Dual-Axis Magnetic Gradiometers
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Solution Overview
Problem
Existing coin detection systems face challenges in accurately identifying coin authenticity and denomination due to limitations in measuring multiple signal features, particularly for coins with similar features, leading to reduced accuracy and complexity in processing signals.
Innovation Solution
A coin detection system utilizing a radial magnetic gradiometer and an axial magnetic gradiometer with symmetrically distributed magnetoresistive sensors to detect dual-axis magnetic field components, combined with an excitation coil and signal processing for real and imaginary component analysis, enabling improved accuracy and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple magnetoresistive sensors are used to form a sensor unit array to detect magnetic field distribution, then the ability to judge denomination and authenticity is improved, but the device complexity increases and processing becomes more complicated
Solution Approach 1:
The detection system is segmented into two independent single-axis magnetoresistive sensors: one detecting radial magnetic field components and another detecting axial magnetic field components. This segmentation simplifies the overall device structure while maintaining the capability to detect multiple magnetic field components, thereby reducing device complexity without sacrificing measurement precision.
Solution Approach 2:
The invention transitions from detecting magnetic field distribution in space to detecting magnetic field components along two specific dimensions (radial and axial directions). By using two single-axis sensors oriented perpendicular to each other, the system captures two-dimensional magnetic field information without requiring a complex three-dimensional sensor array, thus improving detection accuracy while controlling device complexity.
2Device complexity
If a single-axis sensor is employed to measure magnetic field, then the device structure is simple, but it is very difficult to identify coins that have similar features
Solution Approach 1:
The invention merges the functionality of multiple single-axis sensors by combining two perpendicular single-axis magnetoresistive sensors into a dual-component detection system. One sensor measures radial magnetic field components while the other measures axial magnetic field components. This merging approach maintains structural simplicity of single-axis sensors while achieving the feature discrimination capability of multi-axis detection systems.
Solution Approach 2:
The system enhances coin feature discrimination by adding another detection dimension. Instead of relying on a single-axis sensor that measures magnetic field in one direction, the invention employs two single-axis sensors perpendicular to each other, enabling detection of both radial and axial magnetic field components. This dimensional expansion allows differentiation of coins with similar features by comparing their magnetic field signatures across multiple dimensions.
3Measurement precision
If pulse field is applied for excitation and phase shifting is performed, then signal processing capability is improved, but the operation process becomes relatively complicated and resolution may be reduced
Solution Approach 1:
The invention applies preliminary action by using a DC magnetic field to magnetize the coin before detection. This preliminary magnetization prepares the coin in a consistent magnetic state, simplifying subsequent detection operations. The DC field application establishes a baseline magnetic condition that facilitates easier signal processing and improves operational simplicity while maintaining measurement precision.
Solution Approach 2:
The system employs parameter changes by utilizing both DC and AC magnetic fields with different frequencies. The DC field provides a static magnetization component while the AC field provides a dynamic detection component. By changing the magnetic field parameters (DC component for magnetization, AC component for detection), the system achieves improved signal processing capability while keeping the operation process straightforward through frequency-based differentiation.
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
The system achieves high accuracy and sensitivity with a wide dynamic linear range, effectively distinguishing between different coins by measuring radial and axial magnetic field components, reducing saturation effects and thermal drift, and providing a compact, cost-effective design.
Implementation Method 1
the excitation coil is used for providing an axial excitation magnetic field for a to-be-detected coin, the excitation magnetic field induces eddy currents inside the to-be-detected coin, and the eddy currents generate an induced magnetic field
Implementation Method 2
the radial magnetic gradiometer includes at least two radial magnetoresistive sensors and the axial magnetic gradiometer includes at least two axial magnetoresistive sensors
Data Source
AI summary
A coin detection system comprises an excitation coil, a radial magnetic gradiometer, an axial magnetic gradiometer, a signal excitation source, a drive circuit, an analog front-end circuit and a processor. After the excitation coil is excited by the signal excitation source and the drive circuit, the excitation coil generates an excitation magnetic field parallel to the axial direction of a coin, and under the influence of the excitation magnetic field, the coin generates an induced magnetic field through eddy currents induced in the coin; the radial magnetic gradiometer and the axial magnetic gradiometer detect the magnetic field components of the magnetic field in the radial direction and the axial direction of the coin, and the detected signal is transmitted to the analog front-end circuit for amplification; the processor processes and then outputs the amplified signal transmitted by the analog front-end circuit, and the material, design, denomination, etc. of the coin are obtained according to the amplitude, phase, and other information contained in the output signal.