Electricity: measuring and testing – Magnetic – With means to create magnetic field to test material
Patent
1993-06-25
1996-09-03
Snow, Walter E.
Electricity: measuring and testing
Magnetic
With means to create magnetic field to test material
324225, 324202, 324236, G01R 3300, G01R 3312, G01N 2776, G01N 2772
Patent
active
055527043
ABSTRACT:
A method and apparatus for performing conductance measurements on a sample using an eddy current probe, without the need for measurement or knowledge of the separation between probe and sample. The probe comprises sense and drive coils mounted in close proximity to each other (or a single coil which functions as both a sense and drive coil), circuitry for producing AC voltage in the drive coil, and a meter for measuring in-phase and quadrature components of induced voltage in the sense coil. Look-up table data can be generated for use in subsequent measurements on samples of unknown conductance by performing eddy current measurements on samples having different known conductances to generate reference lift-off curves, processing the reference lift-off curves to determine a conductance function relating each known conductance to a location along a selected curve, and storing conductance values determined by the conductance function for different points on the selected curve as the look-up table data. An unknown sample conductance can then be determined by generating a lift-off curve from voltage measurements at different probe separations from the sample, determining a new intersection voltage pair representing the intersection of the lift-off curve with the selected curve, and determining the unknown conductance as a look-up table value indexed by the new intersection voltage pair.
REFERENCES:
patent: 4000458 (1976-12-01), Miller et al.
patent: 4302721 (1981-11-01), Urbanek et al.
patent: 4351031 (1982-09-01), Flaherty et al.
patent: 4528856 (1985-07-01), Junker et al.
patent: 4727322 (1988-02-01), Lonchampt et al.
patent: 4849694 (1989-07-01), Coates
Miller et al., "Contactless Measurement of Semiconductor Conductivity by Radio-Free-Carrier Power Absorption," Rev. Sci. Instrum., V. 47, No. 7, pp. 799-805 (Jul. 1976).
Jeanneret et al., "Inductive Conductance Measurements in Two-Dimensional Superconducting Systems," Applied Phys. Lett. 55 (22), pp. 2336-2338 (Nov. 27, 1989).
Excerpt from "Nondestructive Testing Handbook," Second Edition, edited by R. C. McMaster, American Society for Nondestructive Testing, Inc. (1986), vol. 4-Electromagnetic Testing, pp. 218-222.
One-page advertisement (from the Jun. 1989 issue of the publication "Quality") by Zetec.
Soviet Inventions Illustrated, E1 section, week 8643, (abstract of SU1221-572-A), Dec. 3, 1986, pp. 14-15.
Johnson Walter
Lehman Kurt
Mallory Chester L.
Equitz Alfred A.
Snow Walter E.
Tencor Instruments
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