Flame detector using a discrete fourier transform to process amplitude samples from a flame signal
Patent 5073769 Issued on December 17, 1991. Estimated Expiration Date: 
October 31, 2010. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
October 31, 2010. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesFlame detector for use with a burner Flame detector Dual spectrum frequency responding fire sensor Method of detecting a fire of open uncontrolled flames Method and apparatus for detecting flame Patent #: 4983853 InventorAssigneeApplicationNo. 608054 filed on 10/31/1990US Classes:340/578, By radiant energy250/554, Flame light source702/190Signal extraction or separation (e.g., filtering)ExaminersPrimary: Ng, Jin F.Assistant: Oda, C. Attorney, Agent or FirmInternational ClassG08B 017/12AbstractA circuit for detecting presence of a flame receives a flame signal from a standard photocell positioned to receive radiation from the flame and digitally processes the amplitude variations in the photocell's output to sense for the presence of frequencies near a frequency which is characteristic of a flame. The frequencies substantially higher than the characteristic frequency are filtered from the signal, and the remaining signal is sampled at a frequency which is preferably four times the characteristic frequency. The samples are converted to digital values and processed using a discrete Fourier transform. If the value resulting from the transform operation exceeds a preselected value, presence of a flame is essentially certain. Such digital processing allows use of a dedicated microcircuit or a microprocessor for the flame sensing function and avoids the need for many large discrete components.Other References
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