| 摘要 |
PURPOSE:To improve reliability of detecting the state of combustion by directly connecting a switching circuit in series to a condenser that is connected to a flame rod sensor in parallel and constituting so as to detect the firing condition by the time of electric discharging in the condenser when the switching circuit is OFF. CONSTITUTION:When a switching circuit 14 is OFF, a condenser 12 discharges electricity to drop the potential of a point a below a standard potential b and the output of a comparator 19 is changed over to 'high'. The time t from the OFF of the switching circuit 14 to changing-over the output of the comparator 19 to high is measured by a time keeping section 22. After this the ON and OFF of the switching circuit 14 are repeated. Because the time t is proportional to the flame electric current If, the time t is compared with a standard value at a firing condition judging section 23 to judge the firing condition. If it is abnormal a combustion stopping signal d is issued. With this constitution it is possible to improve the reliability of checking the firing condition. |
