Annular Shielding Coil Layout for Inductive Sensor Interference Rejection
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Solution Overview
Problem
Existing inductive sensors face challenges in rejecting external magnetic field interference and reducing the influence of surrounding metal without compromising detection sensitivity.
Innovation Solution
An annular shielding coil with a smaller radial thickness is arranged outside an annular detection coil, with opposite magnetic fields that are attenuated or increased equally, maintaining constant overlapped magnetic field strength, and a testing circuit with resonant and differential amplifying components is used to manage interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a copper ring is added around the coil to weaken the radial magnetic field and obtain a directional magnetic field, then the directional magnetic field is improved, but the sensitivity of the sensor is reduced
Solution Approach 1:
The shielding structure is divided into multiple copper rings with different thicknesses arranged at different positions around the coil. Each copper ring segment handles specific interference directions, allowing the magnetic field to be shaped directionally while preserving sensitivity in the detection direction through selective shielding.
2Object-affected harmful factors
If metal rings or metal pipes are arranged around the coil to reduce the influence of surrounding metal, then the interference rejection is improved, but the magnetic field strength is weakened and sensitivity is reduced
Solution Approach 1:
Different copper rings are designed with different thicknesses and conductivities to provide localized shielding properties. The copper rings have varying shielding strengths at different angular positions, creating non-uniform magnetic field distribution that enhances directional detection capability while maintaining sensitivity in the forward detection direction.
3Object-affected harmful factors
If a ferrite pot core with self-shielded structure is used, then the electromagnetic interference resistance is improved, but the magnetic field is confined to one direction only
Solution Approach 1:
Multiple copper rings are introduced as intermediary shielding elements between the coil and external environment. These copper rings mediate the magnetic field distribution by providing selective shielding in different directions, allowing the magnetic field to extend in multiple directions while still protecting against electromagnetic interference from various sources.
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 configuration enhances interference rejection while preserving detection sensitivity by maintaining constant resonance voltages and reducing the impact of external metal on the sensor.
Implementation Method 1
the magnetic field generated by the shielding coil and the magnetic field generated by the detection coil are opposite in direction and partially offset
Data Source
Figure 1a~1c
Figure 2a~2b
Figure 3
AI summary
The invention relates to a method for shielding an inductive sensor, and belongs to the technical field of sensors. According to the method for shielding the inductive sensor disclosed by the present invention, an annular shielding coil is additionally arranged outside an annular detection coil, the shielding coil surrounds the detection coil, and the radial thickness of the shielding coil is smaller than that of the detection coil. The present invention further discloses an inductive sensor adopting the method for shielding the inductive sensor. The shielding coil is additionally arranged outside the original detection coil of the inductive sensor, magnetic fields generated by the two coils are opposite in direction and partially offset, and when interference exists, the magnetic fields generated by the two coils are influenced at the same time and are attenuated or increased by identical strength. Therefore, the overlapped magnetic field strength can be kept constant, resonance voltages cannot be attenuated, the interference rejection of the inductive sensor is improved, and the sensitivity of the inductive sensor is not influenced.