# Measurement of permeability for ferrous metallic plates using a novel lift-off compensation technique on phase signature

## TL;DR

This paper introduces a novel lift-off compensation technique for accurately measuring the permeability of ferrous metallic plates using phase signature analysis, significantly reducing prediction errors caused by sensor lift-off effects.

## Contribution

A new phase compensation algorithm and permeability prediction method are developed, improving measurement accuracy for ferrous plates affected by lift-off.

## Key findings

- Permeability prediction error is less than 2% within tested lift-offs.
- The phase compensation algorithm effectively corrects lift-off effects.
- Validated results show improved measurement accuracy.

## Abstract

Lift-off of sensor affects the prediction of electromagnetic properties for both ferrous and non-ferrous steel plates. In this paper, we developed a strategy to address this issue for ferrous plates. With increased lift-off, the phase of the measured impedance for steel plates reduces. Meanwhile, the magnitude of the impedance signal decreases. Based on these facts, a phase compensation algorithm is developed which corrects the phase change due to lift-off considering the magnitude of the impedance signal. Further, a new magnetic permeability prediction technique is presented, which has been validated by analytical and measured results. With this new technique, the error in permeability prediction is less than 2% within the range of lift-offs tested.

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Source: https://tomesphere.com/paper/1905.13079