Method for contactless measurement of conductivity and/or temperature on metals by means of eddy currents
US3936734A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 21, 1975 |
| Grant date | Feb 3, 1976 |
| Priority date | — |
| Expiry date | Jan 21, 1995 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01R27/02
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method for contactless measurement of conductivity and/or temperature on metals by means of the eddy current effect induced within the metal by an alternating magnetic field produced by an excitation coil fed with alternating current arranged with its axis perpendicular to the surface of the metallic test specimen, there being in addition to the excitation coil a pair of measuring coils of equal radius arranged coaxially and symmetrically with respect to the excitation coil at each end respectively of the excitation coil and having an axial length substantially less than that of the excitation coil. The two measuring coils are connected electrically in series opposition and the phase angle between the current in the measuring coils and the current in the excitation coil is taken as an indication of the measured variable. In order to reduce the so-called "lift-off" effect to a minimum and allow accurate contactless measurement such that substantial tolerances are permissible for the distance between the test specimen and measuring head which carries the coils, the radius between the excitation coil on the one hand, and the measuring coils on the other, is smaller than 1/4 or great…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.