Method and apparatus for identifying conductive objects by monitoring the true resistive component of impedance change in a coil system caused by the object
US4263551A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 20, 1978 |
| Grant date | Apr 21, 1981 |
| Priority date | — |
| Expiry date | Jan 20, 1998 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V3/104
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The type of conductor, its property, and if a metal, its type and cross-sectional area can be obtained from measurements made at different frequencies for the amount of unbalance created in a previously balanced stable coil detection system. The true resistive component is accurately measured and thus reflects only the voltage loss attributable to eddy currents caused by introduction of the test sample to the coil system. This voltage divided by corresponding applied frequency gives a curve which peaks at a frequency dependent upon type of conductor. For a metal this peak frequency is proportional to the samples resistivity divided by its cross-sectional area.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.