| 摘要 |
PURPOSE:To obtain a small and light wt. smoke/gas detector having high detection accuracy, by connecting a pair of heaters also used as electrodes of the smoke/gas detector in series through a rectifier and operating this circuit by a DC power source. CONSTITUTION:The heaters 2a, 2b also used as electrodes of a smoke/gas detection element 1 are connected in series through a rectifier 13 and connected to a heating DC power source 7 through switches 9, 10. Further, the electrode 2b is connected to a constant current circuit 12 through a switch 11 and the temp. of the detection element 1 is controlled with high accuracy. This smoke/gas detector is used by such a method that the switches 9, 11 are closed at first and the switch 10 is opened to heat and degass the detection element 1 and, subsequently, the switches 9, 11 are opened and the switch 10 is closed. Biases in opposite directions are applied to the series circuit, which consists of a detection resistor 8, the heaters also used as the electrodes 2a, 2b and the rectifier 13, by the power source 7. When smoke/gas is present at this time, voltage is generated at both terminals of the detection resistor 8. |
