| 摘要 |
PROBLEM TO BE SOLVED: To provide a flame detection circuit capable of accurately detecting flame even by eliminating an influence of changes of an ambient temperature and of an offset voltage due to the change with time of a power source voltage for operating an amplifier on detection of the flame, for example thermal electromotive force is lowered by separation of the flame from a thermocouple due to fluctuation of the flame of a gas burner by an influence of a wind or the like, thermal electromotive force in totally lowed by irregularity of positional relationship of flame and the thermocouples due to fluctuation of mounting positions of the thermocouples in individual burners or in the case thermal electromotive force does not rise by effecting combustion at a small heating power by a burner hasing a small heating power set smaller than that of prior art by small thermal power. SOLUTION: In the flame detector for detecting presence of flame by comparing a difference of an output value of an amplifier and a measured value of an offset voltage when a thermal electromotive force is inputted with a predetermined threshold value, the offset voltage during flame detecting is periodically updated.
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