Model of Magnetically Shielded Ferrite-Cored Eddy Current Sensor.

Area of Science:

• Electromagnetics
• Sensor Technology
• Computational Modeling

Background:

• Fast electromagnetic models for eddy current sensors are essential for real-time applications like model-based measurements and machine interpretation.
• Analytical modeling offers advantages over numerical methods in terms of implementation simplicity and computational speed when sensor geometry permits.

Purpose of the Study:

• To develop a computationally efficient analytical model for an eddy current sensor with a ferrite core and magnetic shield.
• To validate the model's accuracy against the finite element method and experimental impedance measurements.

Main Methods:

• Utilized a vector magnetic potential formulation with truncated region eigenfunction expansion.
• Derived analytical expressions for transmitter coil impedance and magnetic potential.
• Compared model predictions with finite element method (FEM) results and experimental impedance data (5 kHz–100 kHz).

Main Results:

• The analytical model demonstrated excellent agreement with finite element method simulations.
• Experimental validation showed agreement within 3% for resistance change and 1% for inductance change due to a conductive and magnetic half-layer.
• The model accurately captures the sensor's response to the presence of a target material.

Conclusions:

• The developed analytical model provides a fast and accurate method for eddy current sensor analysis.
• This model is suitable for applications including metallic object property measurement, sensor lift-off estimation, and nonconductive coating thickness determination.