| 摘要 |
PURPOSE:To ensure safety at the trouble such as short-circuit of resistors and the like, and to positively prevent the false flame detecting function due to loose contact of a pressure switch and a leakage current, in a combustion equipment built to use a pressure switch as a means to detect presence of a flame. CONSTITUTION:A voltage comparison circuit 3 is provided in an integrating circuit 2, the voltage comparison circuit 3 being adapted to emit a signal of level ''H'' in response to an output of pressure switch 10 which can be turned ON when a pressure in a combustion chamber increases after combustion is started for emitting a signal indicating a presence of flame. In an equipment as mentioned above, the voltage comparison circuit 3 is designed to have a negative OFF voltage when there is no voltage applied on an inversing and non-inversing input terminals 5 and 6. A flame equivalent circuit 11 is connected in series with the pressure switch 10, an AC power source 15 and a capacitor 17 formed as an impedance circuit network. The output of the capacitor 17 is connected with the inversing input terminal 5 via smoothing circuits consisting of resistors 19, 20, capacitors 21, 22 and bias resistors 23, 24. |
