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Emerald Group Publishing Limited
Copyright © 2001, MCB UP Limited
Flame sensorKeywords: Sensors, Furnaces
Applicant: Carrier Corp. (US)Patent number: US6127932Publication date: 3 October 2000Title: Optical flame sensor having opaque hollow tube
The present invention provides a sensor which eliminates the impact of background lighting when optically sensing the presence of a flame. The sensor includes a hollow tube that is preferably closed at each end. One closed end is preferably formed during fabrication of the hollow tube from a substantially low thermally conductive material. An electrically conductive photosensitive element is preferably located at one end of the tube and is oriented towards the opposing end of the tube. The closed end tube creates a substantially dark environment for the photosensitive element. The sensor is mounted relative to the burner in a furnace so as to position the opposing end of the tube in the red hot portion of the flame produced by the burner. Heat produced by the red hot portion of the flame will cause this end of the tube to rapidly heat up so as to produce infrared wavelengths of light within the tube that impinge upon the surface of the photo sensitive element located at the other end of the tube. The photosensitive element changes its electrical conductance as a result of experiencing the particular infrared light.