Pulsed Eddy Current Thickness Measurement Normalization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing Pulsed Eddy Current (PEC) systems for measuring the thickness of electrically conductive materials face challenges due to the need for precise coil positioning, which is impractical in applications like metal rolling, and require extensive test measurements to establish nonlinear relationships between measured values and physical parameters, making it economically unfeasible to achieve high accuracy across a wide range of thicknesses and resistivities.
Innovation Solution
A method using a PEC system with a transmitter and receiver coil, where a constant current generates an electromagnetic field, and after the current is turned off, the decaying magnetic field induces eddy currents, allowing for the measurement of voltage at specific time points. The magnetic flux is normalized to eliminate distance dependence, and time is normalized to isolate thickness and resistivity measurements, enabling unambiguous determination of these parameters without the need for precise coil positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If coil systems are placed on both sides of the plate for PEC measurement, then measurement capability is improved, but positioning precision and system complexity worsen due to the inability to maintain constant coil positions during rolling
Solution Approach 1:
The invention extracts the measurement function from a dual-coil system and implements it using a single coil that performs both transmitting and receiving functions. By taking out the separate receiver coil and using the same transmitter coil for both purposes, the system eliminates positioning complexity while maintaining measurement capability through sequential operation modes
Solution Approach 2:
The single coil is designed to perform multiple functions: it acts as both a transmitter coil for generating electromagnetic fields and a receiver coil for detecting eddy currents. This multi-functional design eliminates the need for separate coils on both sides of the plate, simplifying the positioning system while maintaining measurement precision
2Measurement precision
If extensive test measurements are performed to establish nonlinear relationships for high accuracy, then measurement precision improves, but time consumption and economic feasibility worsen
Solution Approach 1:
The invention performs preliminary calibration by measuring the decay signal at multiple time points and fitting the data to a theoretical model that incorporates material properties. This preliminary action establishes the relationship between decay characteristics and parameters, eliminating the need for extensive test measurements for each new measurement scenario
Solution Approach 2:
The system changes the temporal parameters of measurement by taking signals at multiple specific time points during the decay process. By analyzing how the decay signal evolves over time rather than using a single static measurement, the system can determine multiple parameters (thickness, resistivity, permeability) simultaneously with high accuracy without extensive calibration
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
This approach allows for accurate non-contact measurement of thickness and resistivity by normalizing eddy current flux and time, reducing the number of required test objects and enabling measurements across a broader range of parameters with improved precision, thus enhancing the applicability of PEC technology in metal industries.
Implementation Method 1
a transmitter configured to generate a changing electromagnetic field which induces eddy currents in the object arranged within the electromagnetic field
Implementation Method 2
a receiver configured to detect a changing electromagnetic field generated by the eddy currents
Data Source
Figure 1~7
Figure 2
Figure 3
AI summary
The present disclosure relates to a method of non-contact measurement of a thickness (d) of an object (1) of an electrically conductive material by means of a Pulsed Eddy Current, PEC, system (10) comprising a transmitter coil (2) and a receiver coil (3). The method comprises, after having turned off a current in the transmitter coil, at the receiver coil, measuring a voltage induced by the decaying magnetic field at a first time point, a second time point and a third time point. The method also comprises calculating a total magnetic flux which is generated by the eddy currents in the object at the first time point and picked up by the receiver coil, by comparing the measured flux at the first time point with a predetermined total flux picked up by the receiver coil when no object is present. The method also comprises normalizing measured magnetic flux resulting from the eddy currents and picked up by the receiver coil, using the calculated total magnetic flux as a normalization factor such that the normalized eddy current flux is independent of a distance between the object and the transmitter and receiver coils. The method also comprising, based on the measurements at the first, second and third time points, determining the thickness and the resistivity of the object.