Swept frequency eddy current system for measuring coating thickness
US5017869A · kind A · utility
30Cited by
6References
33Claims
0Family size
Assignee
Inventor
Key dates
| Filing date | Dec 14, 1989 |
| Grant date | May 21, 1991 |
| Priority date | — |
| Expiry date | Dec 14, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B7/105
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An apparatus for measuring the thickness of a coating on a substrate has a bridge circuit including four coils. One coil is placed near the coated substrate and another placed near an uncoated substrate of the same material. An oscillator is connected to the bridge circuit and frequency sweeps, e.g. from 10 KHz to 10 MHz. Phase differences between the voltages induced in the coils are detected to determine conductivity changes with frequency. A method for measuring coating thickness comprises generating variable frequency eddy current in coated and uncoated substrates of the same material and comparing the generated eddy current.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.