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:
Jan. 12, 1988
Filed:
Aug. 04, 1986
Bernd Heck, Hamburg, DE;
Dierk Schroder, Hamburg, DE;
U.S. Philips Corporation, New York, NY (US);
Abstract
A measuring oscillator for measuring temperature has an all-pass filter (1) which drives a current source (16) having a controllable amplification factor and a control element (17). The control element is connected to the control input of the current source (16) and controls its amplification factor in a manner such 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 arrangement (10) comprising a voltage follower (12), whose input is connected to one terminal (9) of the circuit arrangement (10) and whose output is connected through an ohmic input resistor (13) to the inverting input of a first operational amplifier (14), which is fed back negatively through a measuring resistor (15) having a temperature-dependent ohmic resistance value. The output of the first op-amp also is connected through an ohmic resistor (41) to the one terminal (9) of the bipolar circuit arrangement. The non-inverting input of the first op-amp is connected to the other terminal (11) of the bipolar circuit arrangement. Small temperature variations sensed by the measuring resistor lead to comparatively large adequately measurable variations of the frequency of the measuring oscillator.