Pulsed Eddy Current Transmitter Coil for Thin Plate Measurement
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Solution Overview
Problem
Existing Pulsed Eddy Current (PEC) systems face challenges in accurately measuring the thickness of thin plates with thicknesses less than 0.5 mm, requiring increased transmitter current and reduced capacitance to achieve sufficient accuracy down to 200 µm.
Innovation Solution
A PEC system with a transmitter coil comprising parallel electrically conductive coil layers and diodes, connected in series with damping resistors, and a receiver with an Over-Voltage Protection circuit, enabling higher currents and lower capacitance, allowing for precise thickness measurement of thin plates by inducing and detecting eddy currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transmitter current is increased to measure thin plates with thickness less than 0.5 mm, then measurement precision is improved, but thermal losses increase
Solution Approach 1:
The transmitter coil is divided into multiple parallel electrically conductive coil layers. This segmentation allows the total current to be distributed across multiple paths, reducing the current density and thermal losses in each individual layer while maintaining the overall magnetic field strength needed for measuring thin plates down to 200 µm thickness.
Solution Approach 2:
The patent transitions from a single-coil configuration to a multi-layer parallel coil structure, adding a spatial dimension to the current paths. This dimensional change enables simultaneous current flow through multiple layers, effectively reducing thermal losses while maintaining measurement precision for thin plates.
2Productivity
If multiple coil layers are used to reduce capacitance and enable higher currents, then productivity is improved, but device complexity increases
Solution Approach 1:
Multiple coil layers are merged into a single integrated transmitter unit with parallel connections. This combining approach reduces the overall capacitance of the transmitter system while enabling higher current capability, improving productivity for thin plate measurements without proportionally increasing device complexity.
Solution Approach 2:
The multi-layer coil structure serves multiple functions simultaneously: it reduces capacitance, enables higher current operation, maintains measurement precision for thin plates, and provides thermal management through distributed current paths. This multi-functionality improves productivity without linearly increasing complexity.
3Ease of manufacture
If parallel coil layers are connected without diodes, then ease of manufacture is improved, but circulating currents occur between coil layers
Solution Approach 1:
The patent converts the potential harmful circulating currents between parallel coil layers into a controlled feature by using diodes. The diodes allow the system to benefit from parallel current paths for reduced capacitance and improved current capability while preventing harmful circulating currents, effectively turning a potential problem into a solved challenge.
Solution Approach 2:
Diodes are introduced as intermediary components between the parallel coil layers. These diodes act as mediators that permit forward current flow for the intended measurement function while blocking reverse current flow that would create harmful circulating currents between layers, thus protecting the system while maintaining manufacturing feasibility.
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
The system effectively measures thicknesses as low as 200 µm with improved accuracy and signal-to-noise ratio, while minimizing thermal losses and preventing circulating currents, enabling stable measurement of small voltages induced by eddy currents.
Implementation Method 1
a transmitter configured to generate a changing electromagnetic field which induces eddy currents in an object of an electrically conductive material 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 1~2
Figure 3~5
AI summary
The present disclosure relates to a Pulsed Eddy Current (PEC) system comprising a transmitter (2) configured to generate a changing electromagnetic field which induces eddy currents in an object of an electrically conductive material arranged within the electromagnetic field. The transmitter comprises a switching device (24) and a transmitter coil (21) configured to be connected to a voltage source (25). The switching device is arranged for switching a current generated by the voltage source through the transmitter coil. The transmitter coil comprises a plurality of parallel electrically conductive coil layers (22) with a respective damping resistor (23) connected across each of the coil layers (22), each of the coil layers being connected in series with a respective diode (D).