Eddy Current Coil Layout for Vibration Noise Cancellation
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Solution Overview
Problem
Eddy current flaw detection apparatuses face decreased S/N ratio due to noise signals induced by vibrations and eccentricity, and require complex amplification circuits.
Innovation Solution
The apparatus includes a pair of detecting coils with opposite phase magnetic fields, sandwiched by exciting coils, with a specific distance setting to cancel out noise signals, and phase conversion of AC power to ensure opposite phases for noise signals detected by adjacent coils.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resonance coils with amplification circuits are used to improve S/N ratio, then detection sensitivity is improved, but device complexity increases
Solution Approach 1:
The patent combines the exciting coil and detecting coil into a single integrated coil structure. The same coil performs both excitation and detection functions, eliminating the need for separate resonance coils and their associated amplification circuits. This merging reduces device complexity while maintaining detection capability through the bridge circuit configuration.
Solution Approach 2:
The coil in this invention serves multiple functions: it acts as both an exciting coil to generate eddy currents and a detecting coil to sense impedance changes. This multi-functionality eliminates the need for separate dedicated resonance coils and amplification circuits, thereby reducing apparatus complexity while maintaining measurement precision.
2Measurement precision
If detecting coils are used to detect flaw signals, then flaw detection capability is improved, but vibration-induced noise signals increase
Solution Approach 1:
The patent applies preliminary anti-action by configuring the bridge circuit with exciting coils and detecting coils in opposition. The circuit is designed to automatically counteract vibration-induced noise signals before they can interfere with flaw detection. The opposite phase configuration creates a natural cancellation effect for noise while preserving flaw signal detection.
Solution Approach 2:
The patent converts the harmful vibration-induced noise into a beneficial cancellation effect. By arranging the exciting and detecting coils in opposite phases within a bridge circuit, the system causes vibration noise signals to cancel each other out, while flaw detection signals are preserved and enhanced. This transforms the harmful vibration effect into a noise-reduction mechanism.
3Power
If amplification circuits are added to resonance coils to amplify output signals, then signal strength is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges the exciting and detecting coil functions into a single integrated coil, eliminating the need for separate amplification circuits. The bridge circuit configuration provides inherent signal processing capability without requiring additional active components, thereby maintaining signal strength while reducing circuit complexity and cost.
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 configuration effectively removes noise signals caused by vibrations and eccentricity, improving the signal-to-noise ratio without increasing apparatus complexity.
Implementation Method 1
a pair of detecting coils arranged in contactless and coaxially spaced relation with a specimen... magnetic fields generated by these detecting coils are in opposite phases to each other
Implementation Method 2
a coil for generating an eddy current at a surface layer of a specimen
Implementation Method 3
a signal processing part for processing signal induced by impedance change of the coil
Data Source
AI summary
The eddy current flaw detection apparatus includes: a pair of detecting coils 10a, 10b arranged in coaxial and spaced relation with a specimen 3; and a bridge circuit two sides of which are constituted by the detecting coils so that magnetic fields generated by these detecting coils 10a, 10b are in opposite phases to each other. A pair of exciting coils 11a, 11b are arranged coaxially with the detecting coils 10a, 10b in a manner to sandwich the pair of detecting coils 10a, 10b therebetween. A distance D between the detecting coil and the exciting coil adjacent thereto is set to a distance where a vibrational noise signal excited in the exciting coil and detected by its adjacent detecting coil is in opposite phase to that of a vibrational noise signal excited in the detecting coil and detected by the detecting coil.