Composite Ferrite Shield for NMR Eddy Current Reduction
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Solution Overview
Problem
Nuclear magnetic resonance tools face erroneous readings due to eddy currents induced in noise shields, which boost the magnetic field and degrade porosity measurement accuracy, especially since large shields are required to minimize this effect, occupying excessive space and complicating calibration measurements.
Innovation Solution
A composite noise shield comprising a metallic shield for initial noise reduction and a ferrite shield to eliminate eddy currents, constructed from high magnetic permeability nonconductive materials like ferrite film or iron powder, is used to minimize the shield effect while maintaining a compact size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a large conductive shield is used to eliminate electromagnetic noise, then noise shielding effectiveness is improved, but the shield occupies excessive space and complicates calibration measurements
Solution Approach 1:
The patent applies composite materials by combining ferrite material (with high magnetic permeability) and conductive material (such as copper or aluminum) into a single shield structure. The ferrite layer reduces eddy current effects while the conductive layer provides electromagnetic noise shielding, achieving both noise reduction and compact size without requiring a large shield volume
Solution Approach 2:
The patent changes the magnetic permeability parameter by introducing ferrite material with high magnetic permeability into the shield structure. This parameter change allows the shield to operate effectively at lower frequencies and reduces eddy current effects, enabling a compact design that doesn't require large dimensions to achieve proper shielding
2Object-affected harmful factors
If a conductive shield is used to eliminate electromagnetic noise, then noise shielding is improved, but eddy currents are induced that boost the magnetic field and degrade measurement accuracy
Solution Approach 1:
The composite shield structure combines ferrite material with high magnetic permeability and conductive material. The ferrite component provides magnetic shielding while its high permeability directs magnetic flux through itself rather than inducing eddy currents in the conductive layer, thereby reducing eddy current effects and improving measurement accuracy while maintaining noise shielding effectiveness
Solution Approach 2:
The patent converts the potentially harmful eddy current effect into a benefit by using the conductive material in combination with ferrite. The conductive layer, which would normally generate harmful eddy currents, instead provides effective electromagnetic noise shielding when combined with the ferrite material that controls magnetic flux distribution, turning a harmful phenomenon into a useful shielding mechanism
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 composite shield significantly reduces eddy current effects, enhancing measurement accuracy and maintaining a compact size, thus improving the reliability of NMR tool readings without the need for large shields.
Implementation Method 1
Eddy currents induced in the shield boost the magnetic field created by the tool at the diameter of investigation
Implementation Method 2
The composite shield is constructed from materials with high magnetic permeability, such as ferrite or iron powder
Implementation Method 3
nuclear magnetic resonance tools require a conductive shield around the antenna to eliminate electromagnetic noise from environment
Data Source
AI summary
An arrangement for shielding an NMR tool from electromagnetic noise, having a nuclear magnetic resonance tool configured to send and receive signals, a first shield configured around a nuclear magnetic resonance antenna of the nuclear magnetic resonance tool and a second shield configured to reduce the effects of eddy currents in the first shield.