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:
Oct. 25, 1977
Filed:
Dec. 03, 1975
Barney D Hunts, Mountain Lakes, NJ (US);
George H Hare, San Mateo, CA (US);
Bradley Eaton, Pompton Plains, NJ (US);
The Singer Company, New York, NY (US);
Abstract
A proximity switch using logic means to detect a difference in capacitance. A bias capacitance and a sensing capacitance are charged by a first voltage source, each through one of a first pair of FET devices matched for transconductance, during a charge interval. During a detection interval the capacitances are discharged to ground potential or to a second voltage source of opposite polarity than the first voltage source, each through one of a second pair of FET devices also matched for transconductance. The difference in discharge rate between the bias and sensing capacitance, which is a measure of the capacitance of each, is detected by a cross coupled latch (RS flip-flop), setting the latch in a particular state. A second cross coupled latch stores the data thus obtained for utilization. The proximity switch circuit may be embodied as part of an MOS LSI integrated circuit, except for the bias and sensing capacitances, or may be constructed of discrete bipolar devices.