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:
Jun. 16, 1987
Jurgen Kordts, Wedel, DE;
U.S. Philips Corp., New York, NY (US);
Abstract
A circuits for compensating temperature-dependent and temperature-independent drift of a capacitive sensor including two measuring capacitors (3, 4) comprises pulse duration demodulators (11, 12) in the relevant input circuits. In accordance with pulses supplied by oscillators and whose duration is proportional to the capacitance of the capacitors, a d.c. voltage (U.sub.O) is applied to respective charging capacitors (17, 18) of the pulse duration demodulators (11, 12) for a predetermined period of time in order to charge this capacitors, after which zero potential is applied thereto in order to discharge the capacitors. The output of the relevant pulse duration demodulator is connected to the input (20, 21) of a summing/substraction member (19) whose output (23) supplies a d.c. voltage (U.sub.r). A d.c. voltage (U.sub.O), supplied by a controller (16) which compares one controller input d.c. voltage (U.sub.r) with a fixed reference voltage (U.sub.ref), is readjusted so that the d.c. voltage (U.sub.r) at the output (23) of the summing/subtraction member equals the fixed d.c. reference voltage (U.sub.ref) so that the output voltage (U.sub.a) of the circuit is free of temperature-dependent and temperature-independent drift.