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US 4,061,968 AGranted
Process of and apparatus for non-destructive eddy current testing involves the suppression of displayed lobes corresponding to fault parameters to be eliminated from the display
AssigneeCommissariat a l'Energie Atomique
InventorMichel Pigeon
Life of this patent
Estimating the term…
Abstract
A process of and apparatus for non-destructive eddy current testing involves the suppression of displayed lobes corresponding to fault parameters to be eliminated from the display. Elimination circuits are provided for operating on the measurement signal to remove the undesirable parameters from the signal by compensation of the effects produced by the parameters at different frequencies.
Claims4
Process for non-destructive testing by eddy currents of the kind in which:
- a probe is displaced in the proximity of the workpiece to be tested,
- said probe is supplied by an excitation current of n different frequencies,
- the components of each of the n frequencies in the measurement signal are analysed,
- the improvement comprising the steps of determining for each component, its resistive part X in phase with the excitation current at the same frequency, and its reactive part Y in quadrature,
- modifying the phase and amplitude of the determined parts X.sub.1 and Y.sub.1 for the signal at a first frequency so that the component of that signal due to a parameter to be eliminated is made to coincide in phase and amplitude with the parts X.sub.2 and Y.sub.2 for the signal at a second frequency due to the same parameter,
- subtracting the parts X.sub.2 and Y.sub.2 from the parts X.sub.1 and Y.sub.1 thus modified, which provides a new set of resistive and reactive parts X' and Y', permitting to be obtained a representative curve for which the contribution of the undesirable parameter has been eliminated, and displaying the signal of the components X' and Y' on a plane.
3 more elements
Apparatus for non-destructive eddy current testing comprising:
- a probe disposed in the proximity of a workpiece to be tested, the probe and the workpiece moving one in relation to the other in the course of testing,
- means for supplying said probe with an excitation current resulting from the superposition of n alternating excitation currents at n different frequencies,
- means for extracting from the measurement signal provided by the probe the components of each of said n frequencies, said means comprising n analysing circuits giving, for each frequency, the resistive part X in phase with the excitation current at the same frequency and the reactive part Y in quadrature,
- means for representing the measurement signal, in a plane marked by two axes at right angles to one another one carrying the parts X and the other the parts Y of the components of the measurement signal, in such a way that, for each frequency, the point of said plane having X and Y as co-ordinates, describes in the course of testing of said workpiece, a curve generally in the form of lobes, each lobe corresponding to a fault of a parameter of the workpiece under test.
- the improvement comprising in addition means for eliminating, in the representation of the measurement signal, the parts of the curve corresponding to undesirable parameters, said means comprising:
- means for modifying the phase and amplitude of parts X.sub.1 and Y.sub.1 for the signal at a first frequency so that the component of that signal due to a parameter to be eliminated, is made to coincide in phase and amplitude with the parts X.sub.2 and Y.sub.2 for the signal at a second frequency, due to the same parameter,
- means for subtracting the modified parts X.sub.1 and Y.sub.1 from the parts X.sub.2 and Y.sub.2, which provides a new set of resistive and reactive parts X' and Y', and means for thereafter applying parts X' and Y' to display means for the measurement signal and providing a curve devoid of the lobe corresponding to said eliminated parameter.
4 more elements
Dependencies are inferred from the claim text.