The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Apr. 20, 1999
Filed:
Mar. 17, 1997
Kevin James King, Little Canada, MN (US);
Thermo Sentron, Inc., Coon Rapids, MN (US);
Abstract
A metal detector (1) having an oscillator coil (10) which radiates an electromagnetic field in the vicinity of an article to be tested. The field is detected by a primary set of receiver coils (15) which are in close proximity to the oscillator coil (10), as well as by a secondary set of receiver coils (18) located relatively more distant from the oscillator coil. Moving or vibrating metal external to the detector cavity (7) surrounded by the coils (15, 18) will produce a modulated waveform (48) in the primary coils (15) which is similar in period to the modulated waveform (56) produced by the secondary coils (18), while metal passing through the detector cavity (7) will produce a waveform (24) from the primary coils (15) which has a period which differs from the period of the waveform (31) produced by the secondary coils (18). By inverting the secondary coil output signal (42) and adding the inverted signal to the output signal (46) produced by the primary coils (15), a composite signal (68) is produced in which the effect of vibrating or moving metal external to the detector cavity (7) is reduced or eliminated.