| 摘要 |
PURPOSE:To improve the reliability of the flame detector having a flame rod by providing a safety device which prevents a breakdown of parts and a misoperation of firing detection in the case that the flame rod is shortcircuited to an opposing electrode for some reason. CONSTITUTION:In the flame detector, when the flame rod 1 detects out a burning flame and induces an ion current, a parallel circuit comprising a resistor 2 and a capacitor 3 outputs a flame detection voltage, which is compared with a reference voltage by a comparator 9 to determine whether the burning flame is in blue firing condition. In this instance, a Zener diode 12 is connected to a connection point of resistors 4 and 4''. This diode 12, a resistor 8 which works as a current controller and the capacitor 3 which consitutes a part of a rectifying circuit form a safety circuit for preventing a misoperation of firing detection. Thereby, if the flame rod 1 is shortcircuited for some reason, the resistor 8 and the Zener diode 12 form a path for flowing an alternating currnet signal produced by a transformer so that the relating parts are protected from breakdowns. |
