Measurement with a magnetic field
US7215117B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Oct 7, 2002 |
| Grant date | May 8, 2007 |
| Priority date | — |
| Expiry date | Nov 30, 2022 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2203/0635
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Material properties such as stress in a ferromagnetic material may be measured using an electromagnetic probe. While generating an alternating magnetic field in the object, and sensing the resulting magnetic field with a sensor, the signals from the magnetic sensor may be resolved into in-phase and quadrature components. The signals are affected by both geometrical parameters such as lift-off and by material properties, but these influences may be separated by mapping the in-phase and quadrature components directly into material property and lift-off components, and hence a material property and/or the lift-off may be determined. The mapping may be represented in the impedance plane as two sets of contours representing signal variation with lift-off (A) (for different values of stress) and signal variation with stress (B) (for different values of lift-off), the contours of both sets (A, B) being curved. The stress contours (B) intersect any one liftoff contour (A) at a constant angle. Hence calibration measurements taken along a few contours of each set enable the positions of the other contours of each set to be determined.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.