Determining the state of the surface of a moving body using eddy currents to obtain first and second runout profiles of the body
US4460869A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 23, 1982 |
| Grant date | Jul 17, 1984 |
| Priority date | — |
| Expiry date | Feb 23, 2002 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S505/843
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method and apparatus for monitoring the state of the surface of a moving body wherein a four-terminal eddy-current coil circuit is connected in a feedback loop of an RC resonator. The eddy-current coil circuit is placed in proximity to the monitored surface of the moving body and connected in the feedback loop of an RC resonator such that a change in the state of the surface of the moving body results in a change in the conductivity thereof, which conductivity change produces a phase displacement changing the output frequency of the RC resonator. During operation, a first data set is obtained from the coil circuit and RC resonator presenting a first runout profile of the body when the monitored state is in an initial state. The first data set is stored in a memory, and a subsequent profile is derived to obtain a second data set indicative of the operational state of the surface of the moving body. The second data set is also stored in the memory and then the first data set is subtracted from the second data set to obtain an effective or true profile of the surface of the body at the subsequent operational time.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.