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. 17, 1984
Filed:
Jan. 26, 1982
Grant D Avery, Loudon, NH (US);
Sprague Electric Company, North Adams, MA (US);
Abstract
A magnet is bonded to a skewed-hysteresis Hall switch in such a position that the magnetic flux, normal to the Hall element, is equal to the average of the magnetic flux required to operate and the magnetic flux required to release the Hall switch. This magnet-Hall-switch assembly is made by initially employing a magnet of much greater strength than needed. The Hall switch is energized and subjected to an oscillating field of zero average value. The on-time to off-time ratio of the magnet-Hall-switch assembly is measured. A demagnetizing field is adjusted to a strength that is directly related to the difference between unity and the Hall switch on-to-off time, and the magnet is then subjected to the adjusted demagnetizing field. These steps are repeated several times. The magnet is thus partially demagnetized to import to the magnet-biased Hall switch a symmetrical hysteresis characteristic. This symmetrical-hysteresis Hall switch is very sensitive and leads to more reliable operation in rotational speed monitoring devices such as speedometers and certain flow meters.