Magnetoresistive Sensor with Pre-magnetization for Hard Magnetic Detection
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Solution Overview
Problem
Existing measuring devices for detecting magnetic properties of documents, such as bank notes, require close proximity and strong external magnetic fields, which complicate setup and can demagnetize hard magnetic security features, and struggle to differentiate between soft and hard magnetic materials due to similar saturation magnetization values.
Innovation Solution
A measuring device with magnetoresistive sensor elements that can only measure magnetic properties in one direction, utilizing a pre-magnetization device and support field to generate an overlapping magnetic field that prioritizes the measurement direction, allowing for separate magnetization and detection of soft and hard magnetic materials without interfering with the support field, and using a compact support field device to ensure sensitive verification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If large magnets are installed to generate a sufficiently strong field for magnetizing soft and hard magnetic security features, then the magnetization capability is improved, but the device complexity and setup difficulty increase
Solution Approach 1:
The patent divides the magnetic field generation function into two separate components: a pre-magnetization magnet for hard magnetic materials and a support field device for soft magnetic materials. This segmentation allows each component to be optimized for its specific function, reducing the overall complexity compared to using a single large magnet system.
Solution Approach 2:
The pre-magnetization magnet is positioned upstream of the sensor to magnetize hard magnetic security features before they pass under the sensor. This preliminary action ensures that hard magnetic materials are properly magnetized without requiring the support field device to generate excessive field strength, thereby reducing device complexity.
2Measurement precision
If a pre-magnetization device is added to magnetize hard magnetic security features, then the detection capability for hard magnetic materials is improved, but the device complexity increases
Solution Approach 1:
The patent combines the pre-magnetization magnet and support field device into a single integrated measuring device structure. While this adds functionality for detecting both hard and soft magnetic materials, the components are designed to work together in a coordinated manner, sharing common structural elements and control systems, which mitigates the increase in overall device complexity.
3Measurement precision
If the sensor line is positioned close to the document surface for sensitive detection, then the measurement precision is improved, but the risk of demagnetizing hard magnetic security features increases
Solution Approach 1:
The patent extracts the strong magnetization function from the detection area by positioning the pre-magnetization magnet upstream, separate from the sensor location. This allows the sensor to be positioned close to the document for sensitive detection without being in the high-field region that could cause demagnetization.
Solution Approach 2:
The patent uses spatial separation in the longitudinal dimension of document transport to resolve the conflict between close proximity for detection and distance for preventing demagnetization. The pre-magnetization magnet acts on the document at one position along the transport path, while the sensor detects at a different position downstream.
4Device complexity
If a single support field is used for both soft and hard magnetic materials, then the device complexity is reduced, but the measurement precision for differentiating between soft and hard magnetic materials deteriorates
Solution Approach 1:
The patent applies different magnetic field characteristics to different measurement zones: the pre-magnetization magnet provides strong, localized magnetization for hard magnetic materials, while the support field device provides a controlled field for soft magnetic materials. This local differentiation of field properties enables precise distinction between material types.
Solution Approach 2:
The system changes magnetic field parameters (strength, duration, spatial distribution) between the pre-magnetization phase and the detection phase. Hard magnetic materials receive a strong, brief magnetization pulse, while soft magnetic materials are measured in a weaker, sustained support field, allowing differentiation based on their distinct magnetic responses.
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 accurate and sensitive detection of both soft and hard magnetic security features without complicating the setup, maintaining the magnetization of hard magnetic materials and optimizing the measurement process by separating magnetization and detection functions, while allowing for a compact design.
Implementation Method 1
magnetoresistive sensor element (2) extending in one line direction (B), which can measure the magnetic properties of its surroundings in one measuring direction (y)
Implementation Method 2
pre-magnetization device, in particular having a pre-magnetization magnet (6), which generates a magnetic field
Implementation Method 3
support field device (5), which generates a magnetic support field, which has a magnetic field component pointing in a line direction (x) and whose field strength in the line direction (x) varies
Data Source
AI summary
A measuring device for measuring magnetic properties of the surroundings of the device includes at least one magnetoresistive element extending in a line direction, and a support field device generating a magnetic support field in an area over the line direction. A pre-magnetization device of one or more magnets is arranged at a distance from the sensor line in a direction vertical to the line direction and extending parallel to the line direction. The pre-magnetization device is arranged relative to the sensor line such that the fields of the pre-magnetization device and the support magnetic field overlap to provide an overlapping magnetic field with a field strength component pointing in the line direction that is greater at one location on the sensor line than the strength of a field component pointing vertically toward the line direction and not in the direction of the height of the magnetoresistive element.