| 摘要 |
PURPOSE:To provide a combustion sensing circuit capable of checking a combustion state and sensing a deterioration of insulation in a flame rod by a method wherein an electrical potential of a burner is changed over between a plus potential and a minus potential of a DC power supply. CONSTITUTION:When a contact point 19 of a combustion sensing circuit is connected to a side (a), a flame current If is passed from a reference potential ea through a sensing resistor 15, a flame rod 16, a burner 17 and a contact point (a) to a ground potential (eb) at a minus side and then a voltage drop eb is generated at both ends of the sensing resistor 15. The combustion condition is discriminated in response to a value of an output potential eo having the potential eb amplified by an amplifier circuit 20. When the contact point 19 is connected to a side (b), a deteriorated insulation between the flame rod 16 and the burner 17 causes the flame current If to flow from a plus DC powe supply (ec) through the burner 17, flame rod 16 and the sensing resistor 15 to the reference potential (ea) and then a potential drop (-eb) is generated at the sensing resistor 15. When the output (eo) becomes higher than the electrical potential (eg), it is judged that both flame rod 16 and burner 17 show their deterioration in insulation. |
