Magnetic Sensor Shielding Stray Field Interference
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Solution Overview
Problem
Magnetic multi-turn and single-turn sensors are sensitive to external stray magnetic fields, which cause errors in monitoring the number of turns and angular position of rotating devices, such as steering wheels, due to variations in magnetic field strength rather than angle.
Innovation Solution
A magnetic sensor system comprising a magnetic single turn sensor and a multi-turn sensor, shielded by a ferromagnetic sleeve and additional shielding elements, such as discs or rings of ferromagnetic material, to absorb stray magnetic fields and reduce eddy currents, ensuring accurate measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic sensors are used to monitor turn count and angular position, then measurement capability is provided, but measurement precision deteriorates due to sensitivity to stray magnetic fields causing errors in sensor readings
Solution Approach 1:
A ferromagnetic shielding element is introduced as an intermediary component between the external environment and the magnetic sensor. This shield absorbs and redirects stray magnetic fields, preventing them from reaching the sensor. The shield acts as a mediator that allows the desired magnetic field (from the rotating magnet) to pass through while blocking harmful external magnetic interference, thereby improving measurement precision without affecting the sensor's ability to detect the target magnetic field.
2Measurement precision
If shielding arrangements are added to protect from stray fields, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent employs thin ferromagnetic shielding plates or sleeves that can be easily integrated into the existing sensor housing or mounting structure. These thin ferromagnetic barriers provide effective magnetic shielding without adding significant structural complexity or volume. The shielding elements can be positioned between the sensor and potential sources of interference, offering a simple yet effective solution that maintains device compactness while improving measurement accuracy.
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 shielding arrangement significantly improves the reliability and accuracy of magnetic sensor readings by isolating the sensors from stray magnetic fields, particularly in environments with high stray field interference.
Implementation Method 1
a ferromagnetic sleeve extending from an end of a rotating shaft, the ferromagnetic sleeve being arranged to house one or more magnets therein... a shielding element arranged in proximity to the magnetic sensing device... which combined with the ferromagnetic sleeve, protects the magnetic sensor device from stray magnetic fields
Data Source
AI summary
The present disclosure provides magnetic sensor system that includes a magnetic sensor package comprising a magnetic single turn sensor and a magnetic multi-turn sensor, and a shield arrangement for shielding the magnetic sensor from stray magnetic fields. The shielding arrangement comprises a ferromagnetic tube that houses one or more magnets and connects to an end of rotating shaft, such that rotation of the shaft causes a corresponding rotation of the ferromagnetic tube and magnets. The magnetic sensor package is positioned on a surface of a PCB substrate, which is positioned in close proximity to the ferromagnetic tube and magnet arrangement. A shielding device is then arranged in close proximity to the magnetic sensor package, for example, on the opposite side of the PCB substrate or directly between the PCB substrate and the ferromagnetic tube, to provide additional shielding of any stray magnetic fields. The shielding device may be in the form of a disc or a ring of ferromagnetic material that has a higher level of magnetic conductivity.