Eddy Current Sensor for Coating Thickness Measurement

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Solution Overview

Problem

Current methods for measuring the thickness of zinc coating layers on galvanized steel strips are either too slow for dense mapping and strict quality control, or lack accuracy, hindering effective regulation of the coating process.

Innovation Solution

A method using eddy current sensors to measure the complex impedance at low and high frequencies, combined with calibration values from X fluorescence measurements, to determine the thickness of the coating layer, allowing for rapid and accurate mapping of the coating thickness across the strip.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If X fluorescence measurement method is used, then measurement accuracy is improved, but measurement speed deteriorates

Engineering Contradiction:

Improvethickness measurement accuracyVSAvoidmeasurement speed

Core Design Contradiction:

Measurement precisionVSSpeed

Solution Approach 1:

The patent replaces the X fluorescence measurement system with an eddy current measurement system. The eddy current sensor uses electromagnetic induction to generate eddy currents in the conductive coating layer, measuring the complex impedance to determine thickness. This substitution maintains measurement accuracy while dramatically increasing measurement speed, enabling dense mapping of the strip surface.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent measures complex impedance at multiple excitation frequencies (at least two different frequencies) to extract thickness information. By changing the frequency parameter and analyzing the imaginary part of the impedance, the system achieves accurate thickness measurement with much faster response time compared to X fluorescence methods.

Inventive Principle:

Principle #35Parameter changes

2Speed

If eddy current sensor with high frequency (500 kHz) is used, then measurement speed is improved, but measurement accuracy deteriorates

Engineering Contradiction:

Improvemeasurement speedVSAvoidthickness measurement accuracy

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The patent optimizes the excitation frequency parameter by using at least two different frequencies, with the imaginary part of the impedance being measured. This multi-frequency approach allows accurate thickness determination while maintaining high measurement speed, overcoming the limitations of single high-frequency measurements.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses calibration values obtained from X fluorescence measurements to calibrate the eddy current measurement system. This feedback mechanism ensures that the eddy current sensor achieves measurement accuracy comparable to X fluorescence while maintaining its speed advantage for dense mapping applications.

Inventive Principle:

Principle #23Feedback

3Manufacturing precision

If measurement density is increased for strict quality control, then quality control capability is improved, but measurement time increases

Engineering Contradiction:

Improvequality control capabilityVSAvoidmeasurement time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent replaces the slow X fluorescence measurement system with a fast eddy current measurement system, enabling dense mapping of the strip surface without increasing measurement time. The eddy current sensor can rapidly acquire thickness data at multiple points, providing strict quality control capability while maintaining high production speed.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

Enables fast and accurate measurement of coating thickness, enabling dense mapping and real-time control of the coating process, improving quality control and detection of operational irregularities.

Implementation Method 1

by means of an eddy current sensor, for at least one area of the strip, a representative quantity of the thickness of the coating layer is measured

Methodology Applied

Scientific EffectEddy current: Eddy Currents

Implementation Method 2

The measurement made by means of an eddy current sensor comprises the measurement of the complex impedance of a coil facing the running strip for a low excitation frequency and a high excitation frequency

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS10203194B2Method and device for measuring the thickness of a coating layer on a running strip

Publication Date: 2019.02.12 ARCELORMITTAL INVENSTIGACION Y DESARROLLO S L

AI summary

A method and device for measuring the thickness of a coating material layer of a running strip according to which, by means of an eddy current sensor for at least one area of the strip, a quantity is measured, representative of the thickness of the coating layer and the thickness of the coating layer is determined from the measured quantity and from at least one calibration value. The measurement made with an eddy current sensor comprises the measurement of the complex impedance of a coil facing the running strip for a low excitation frequency and a high excitation frequency and the elaboration of a quantity representative of the thickness of the coating layer from said complex impedance measurements. A device for applying the method and a coating installation equipped with the device.