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. 19, 1988
Filed:
Mar. 17, 1987
Bernd Heck, Hamburg, DE;
Dierk Schroder, Hamburg, DE;
U.S. Philips Corporation, New York, NY (US);
Abstract
A measuring oscillator for detecting different physical parameters has an all-pass filter (1) which drives a current source (16) having a controllable amplification factor and a control device (17). The control device is connected to the control input of the current source (16) and controls its amplification factor so that the amplitude of the alternating voltage produced by the measuring oscillator assumes a constant value. The all-pass filter comprises a phase-determining bipolar circuit (10) comprising a voltage follower (12) having its input connected to the first pole (9) of the circuit (10) and its output connected through bridge circuit (28) to the inputs of a differential amplifier circuit (33). The four resistance elements (29-32) of the bridge circuit have resistance values varying with the physical parameters to be detected. The output of the differential amplifier circuit is connected through an ohmic resistor (41) to the first pole. The second pole (11) of the bipolar circuit (10) is connected to the junction of the two resistance elements (31, 30) of the bridge circuit. A variation of a resistance element of the bridge circuit due to a variation of the physical parameter detected by it results in a readily measurable variation of the frequency of the measuring oscillator.