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:
Dec. 27, 1988
Filed:
Aug. 10, 1987
Chih C Chang, Huntingdon Valley, PA (US);
Moore Products Co., Spring House, PA (US);
Abstract
The ratio C.sub.1 /C.sub.2 between the capacitances of two capacitors is obtained by connecting them into the frequency-determining circuit of an oscillator in at least three different combinations, namely C.sub.1 along, C.sub.2 along and both or neither of C.sub.1 and C.sub.2 ; the resultant oscillation frequencies are measured, and a signal representative of changes in C.sub.1 /C.sub.2 is derived from the oscillator frequencies, preferably by means of digital circuitry. In one preferred mode C.sub.1 /C.sub.2 is obtained by forming signals proportional to ##EQU1## and in another preferred mode proportional to ##EQU2## In still another preferred mode C.sub.1 /C.sub.2 -1 is obtained from the expression T.sub.1 -T.sub.3 /T.sub.2 -T.sub.3 and used as the indication of changes in C.sub.1 /C.sub.2. In the foregoing, f.sub.1, f.sub.2, f.sub.3 and f.sub.4 are the oscillator frequencies produced respectively by connecting C.sub.1 alone, C.sub.2 along, neither C.sub.1 nor C.sub.2, and both C.sub.1 and C.sub.2 into the frequency-determining circuit, and T.sub.1, T.sub.2, T.sub.3 and T.sub.4 are the periods of oscillations at f.sub.1, f.sub.2, f.sub.3 and f.sub.4 respectively.