Magnetic Sensor Discriminating High and Low Coercivity Magnets
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Solution Overview
Problem
Magnetic sensors currently fail to reliably distinguish between high coercivity and low coercivity magnets, and cannot accurately sense the strength of a magnetic field, limiting their effectiveness in authenticating banknotes with mixed magnetic security features.
Innovation Solution
A magnetic sensor system that applies a strong magnetic field to orient both high and low coercivity magnets, followed by a weak field to flip only the low coercivity magnets, allowing identification of each type based on orientation changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetoresistive (MR) sensors are used to detect magnetic security features, then the sensor can detect changes in magnetic field strength, but the sensor cannot distinguish between high coercivity and low coercivity magnets
Solution Approach 1:
The patent applies a strong magnetic field in advance to saturate all magnetic materials (both high and low coercivity magnets) before the actual measurement. This preliminary saturation ensures that subsequent weak fields can only affect low coercivity magnets, enabling reliable distinction between the two types based on their differential response to the weak field application.
2Ease of operation
If a single magnetic field strength is used for detection, then the sensor operation is simple, but the sensor cannot distinguish between different coercivity types
Solution Approach 1:
The patent employs periodic application of magnetic fields with different strengths - first a strong saturating field, then a weak distinguishing field. This periodic action sequence allows the sensor to differentiate between high and low coercivity magnets by observing which magnets respond to the weak field after being saturated by the strong field, thereby achieving both operational simplicity and measurement 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
Enables reliable discrimination between high and low coercivity magnets and senses magnetic field strength, enhancing the authentication of banknotes and reducing counterfeit detection issues.
Implementation Method 1
a first magnetic field operable to orient high and low coercivity magnets in a first magnetic orientation
Implementation Method 2
a second magnetic field, lower in strength than the first magnetic field, and operable to orient only the low coercivity magnets in a second magnetic orientation opposite to the first magnetic orientation
Data Source
AI summary
A magnetic sensor for discriminating between high and low coercivity magnets is disclosed. The sensor comprises a first magnetic field operable to orient high and low coercivity magnets in a first magnetic orientation. The sensor also comprises a second magnetic field, lower in strength than the first magnetic field, and operable to orient only the low coercivity magnets in a second magnetic orientation opposite to the first magnetic orientation. The sensor further comprises a sensor for ascertaining the magnetic orientation of each of the magnets and thereby identifying if a magnet is a high coercivity magnet or a low coercivity magnet.