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. 15, 1991
Filed:
Feb. 27, 1990
Bruce R Long, Carlisle, PA (US);
PPA Industries, Inc., Dallas, TX (US);
Abstract
A quartz crystal resonator is situated in an enclosure whose interior is substantially a vacuum. A heating element is attached to the crystal surface. A sensor is attached to the crystal enclosure, and may be sandwiched between the crystal enclosure and the circuit board to which the crystal enclosure is attached. A control system converts the sensed temperature into a series of variable width pulses applied to the resonator heating element. Thus, the sensor, control unit and heating element comprise a temperature feedback control system which allows the crystal to operate at or very near its desired temperature. Further, the crystal enclosure may be substantially surrounded by an external material insulator. The external material insulator maximizes thermal resistance between the sensor and the environment in comparison to the thermal resistance between the crystal and the sensor. This choice of relative thermal resistances enables the temperature feedback control system to more closely emulate a closed-loop system possessing the advantages of accuracy and responsiveness. In an especially preferred embodiment, an integrated circuit from a switching power supply may be used in a novel manner to perform certain of the functions in the temperature feedback control loop.