High Permeability Shield for VDT Magnetic Interference
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Solution Overview
Problem
Low permeability shields in linear variable differential transformers (LVDTs) fail to effectively shield against magnetic interference from linear actuators, leading to errors in displacement measurements and inaccurate position calculations.
Innovation Solution
Employing a high permeability shield with a maximum permeability of 50,000 - 500,000, composed of alloys like CARTECH or CO-NETIC, to shield the windings from magnetic interference, thereby reducing electromagnetic interference (EMI) effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a low permeability shield is used in the VDT, then the shield structure is simple and cost-effective, but the shield fails to effectively block magnetic interference from the actuator
Solution Approach 1:
The patent changes the key parameter of shield material permeability from low (conventional) to high (50,000-500,000 maximum permeability). This parameter change transforms the shield's ability to conduct magnetic flux, allowing it to effectively divert actuator magnetic fields away from the windings while maintaining structural simplicity.
Solution Approach 2:
The patent employs composite material construction by combining high permeability magnetic shielding material with the existing VDT structure. The shield is formed as a cylindrical structure with specific wall thickness (0.020-0.060 inches) using materials like CARTECH or CO-NETIC alloys, creating a composite system that integrates magnetic shielding functionality into the sensor assembly.
2Volume of moving object
If the VDT is positioned close to the actuator for compact design, then space efficiency improves, but magnetic interference from the actuator affects measurement accuracy
Solution Approach 1:
The high permeability shield acts as an intermediary element between the actuator and the VDT windings. It intercepts and redirects magnetic flux lines from the actuator, preventing them from penetrating into the sensing windings. This mediator function allows close positioning while maintaining measurement accuracy by decoupling the magnetic fields of the actuator and sensor.
3Measurement precision
If a high permeability shield is used to block magnetic interference, then measurement accuracy improves, but the shield material becomes more complex and expensive
Solution Approach 1:
The patent specifies a quantitative range for permeability (50,000-500,000 maximum) that balances shielding effectiveness with manufacturability. This parameter optimization ensures sufficient magnetic shielding performance while working with commercially available high permeability alloy materials that can be manufactured using conventional processes.
Solution Approach 2:
The shield is designed with localized properties - a specific wall thickness range (0.020-0.060 inches) optimized for the particular application's magnetic field strength and frequency. This local quality approach allows effective shielding without excessive material usage, balancing performance with manufacturing cost and complexity.
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 high permeability shield significantly enhances the accuracy of LVDTs by mitigating magnetic interference, ensuring precise displacement measurements and correct position calculations of the linear actuator.
Implementation Method 1
The shield has a maximum permeability of 50,000 - 500,000
Implementation Method 2
When the primary winding is energized, a magnetic field is provided that induces a voltage in the secondary windings
Data Source
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AI summary
An example actuator assembly includes an actuator (32) configured to move a rod (30). A variable differential transformer (VDT) (10/380) is situated adjacent to the actuator (32). The VDT (10/380) includes a core (52/352) coupled to the rod (30) such that movement of the rod (30) causes a corresponding movement of the core (52/352). A plurality of windings (54/354, 56/356) surround the core (52/352) for measuring displacement of the core (52/352). A shield (58/358) surrounds the plurality of windings (54/354, 56/356) and shields the plurality of windings from a magnetic field of the actuator (32). The shield (58/358) having a maximum permeability of 50,000 - 500,000. A LVDT (10) configuration method is also disclosed.