Importance

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Abstract

A heat detector uses a single comparator operating in conjunction with a dynamically changing thermal reference that ensures quick response to rapid rates of thermal change and a fixed threshold that indicates an ambient temperature exceeds a threshold temperature. The inputs of the comparator receive different ones of the output signals of two thermal sensors. One thermal sensor responds nearly instantaneously to changes in ambient thermal conditions. The other thermal sensor is mounted on a printed circuit board operating as a heat sink and responds more slowly to changes in ambient thermal conditions. The difference between the thermal sensor output signals is zero at a lower ambient temperature when the rate of thermal change exceeds a preset amount and at a higher ambient temperature when the rate of thermal change is relatively slow. Thus, the comparator output indicates an alarm condition upon detection of a rapid change in ambient thermal condition or a thermal condition exceeding a threshold, irrespective of the rate of change.

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First Claim