Inductive Sensor Shielding Coil Layout for EMI Rejection
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Solution Overview
Problem
Existing inductive sensors face interference from external magnetic fields and surrounding metal, which affects their sensitivity and interference rejection.
Innovation Solution
An annular shielding coil with a smaller radial thickness is arranged outside the detection coil, generating a magnetic field that opposes and partially cancels out the detection coil's field, maintaining a constant net magnetic field strength and improving interference rejection without reducing sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a ferrite pot core is used to provide self-shielding, then the sensor is protected from electromagnetic interference, but the magnetic properties of the ferrite core are affected by strong external electromagnetic fields leading to interference
Solution Approach 1:
The patent introduces a shielding coil as an intermediary element that generates a compensating magnetic field to counteract external electromagnetic interference. This shielding coil acts as a mediator between the detection coil and external magnetic fields, dynamically canceling out interfering fields while preserving the detection function.
Solution Approach 2:
The patent changes the magnetic field parameters by introducing a controllable shielding coil that can adjust its magnetic field strength and direction. By dynamically adjusting the shielding coil's current, the system can adapt to varying external electromagnetic conditions and maintain optimal detection performance.
2Shape
If metal rings or copper are added around the coil to create directional magnetic field, then the magnetic field is concentrated in the front detection area, but the magnetic field strength on the detection area is weakened and sensitivity is reduced
Solution Approach 1:
The patent employs feedback control by using the detection coil's output to drive the shielding coil. The shielding coil's magnetic field is adjusted based on the detected signal, creating a feedback loop that maintains optimal magnetic field distribution and detection sensitivity while preserving directional characteristics.
Solution Approach 2:
The patent creates a composite coil structure combining the detection coil and shielding coil into an integrated unit. This composite structure allows the system to achieve both directional magnetic field distribution and maintained sensitivity through the coordinated operation of the two coils.
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 solution effectively attenuates or increases the magnetic fields equally, maintaining resonance voltages and enhancing the sensor's interference rejection without affecting its sensitivity.
Implementation Method 1
The magnetic field generated by the shielding coil and the magnetic field generated by the detection coil are opposite in directions and partially cancel out each other
Data Source
AI summary
A method for shielding an inductive sensor includes arranging an annular shielding coil 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. An inductive sensor adopting the above method for shielding the inductive sensor, in which the shielding coil is arranged outside the detection coil of the inductive sensor, magnetic fields generated by the two coils are opposite in direction and partially cancel out each other. 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 summed 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.