Measuring Surface Resistance with Eddy Currents

Eddy-Current Principle for Surface Resistance Measurement

Eddy-current measurement can be used to evaluate the electrical properties of conductive materials and layers. A sensor typically contains an inductor, often built around a ferrite core, connected to an oscillator. Alternating current in the coil creates a changing magnetic field.

When a conductive sample enters this field, electromagnetic induction produces circulating currents—eddy currents—in the conductive layer. These currents create a secondary magnetic field that changes the electrical response of the sensor coil.

The instrument analyzes this change in response and uses it to infer the surface resistance of the sample. Because the measurement is based on electromagnetic coupling, it can be performed without direct electrical contact, depending on the instrument design and application.

Measurement results may be affected by the material, coating thickness, substrate, sensor geometry, distance from the sample, and calibration. For reliable comparisons, use the instrument according to its specified method and keep sample and measurement conditions consistent.

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Eddy-current sensor principle for measuring surface resistance

2023-05-07