Apparatus and method for measuring conductance including a temperature controlled resonant tank circuit with shielding
US4797614A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 20, 1987 |
| Grant date | Jan 10, 1989 |
| Priority date | — |
| Expiry date | Apr 20, 2007 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N27/023
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A meter for sheet conductance measurements does not touch the conductive surface of a sample. A probe having a resonant tank coil is positioned against a parallel supporting surface of the sample, which may be flat or curved and of unrestricted area. An oscillator incorporating the tank coil is controlled to stabilize oscillator amplitude in response to eddy current loading by the sample. An electrostatic shield in a finger configuration prevents capacitive coupling between the tank coil and the sample without hindering magnetic coupling. A readout of sheet conductance is driven by the oscillator control. Direct current can be coupled to the tank coil for temperature control preventing undesired resistance changes in the tank coil. The oscillator can be controlled by an optically coupled variable gain element. Measurements can be made with the tank coil up to at least 0.75 inch from the conductive surface of the sample.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.