Apparatus for magnetic inspection using magnetic shield, with specific relation of distance E between magnetic sensors and distance L between each magnetic sensor and the object to be inspected, to obtain optimum S/N
US5502382A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 15, 1994 |
| Grant date | Mar 26, 1996 |
| Priority date | — |
| Expiry date | Jul 15, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N27/82
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A magnetic inspection apparatus includes a magnetizer which generates a magnetic field in an object to be inspected, the object running in a predetermined direction, the magnetizer including a pair of magnetic poles provided in facing relation to the object, the pair of magnetic poles being arranged in the predetermined direction; a plurality of magnetic sensors arranged at small intervals in a widthwise direction of the object perpendicular to the predetermined direction, for detecting a leakage magnetic flux due to a defect of the object at locations in the widthwise direction, each magnetic sensor having sides which face the magnetic poles; a plurality of subtraction circuits, each calculating a difference signal between output signals from those ones of the magnetic sensors which are separated by a predetermined distance; a plurality of absolute value circuits, each calculating an absolute value of each difference signal output from each subtraction circuit; and an arithmetic operation circuit which evaluates the defect of the object on the basis of the absolute value signal output from each absolute value circuit, with the relationship between a distance E (unit=mm) between th…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.