Smoke detector including ambient temperature compensation

Claim 1

A smoke type fire detector comprising: a light emitting element; a light receiving element which receives scattered light emitted from said light emitting element and scattered by smoke particles; an amplifier for amplifying the output level of said light receiving element; a memory having predetermined temperature correction coefficients stored therein; a temperature detecting means for detecting an ambient temperature at said light emitting element and said light receiving element; and, a microcomputer coupled to said light emitting element and to said amplifier and to said memory and to said temperature detecting means, said microcomputer including (a) means for accessing said memory and retrieving a temperature correction coefficient corresponding to said ambient temperature detected by said temperature detecting means, (b) means for calculating a temperature compensated output value or a temperature compensated reference value by applying said temperature correction coefficient to a respective one of an output level of said amplifier or a given reference level, and (c) means for detecting a smoke density by comparing the temperature compensated reference value or the temperature compensate output value with a respective one of the output level of said amplifier or the given reference level; wherein said amplifier includes semiconductor elements, and wherein said temperature correction coefficients are for correcting an overall temperature characteristic of the combination of said light emitting and light receiving elements and said amplifier.