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:
May. 05, 1987
Filed:
Jul. 30, 1984
Robert Buck, 7992 Tettnang 1, DE;
Gerd Marhofer, 4300 Essen-Bredeney, DE;
Other;
Abstract
An electronic sensor of the contactless type has a free-running oscillator with internal positive feedback supplemented by an external negative feedback including a capacitive path whose impedance is normally high but is lowered in the presence of an object to be detected, thereby reducing the output signal of the oscillator from a normal amplitude above a predetermined level to a diminished amplitude below that level. The negative feedback is provided through an IGFET, e.g. of n-channel depletion type, with the aid of a capacitor bridging its source and gate electrodes to form with the external capacitance a voltage divider for the output signal of the oscillator.