| 摘要 |
PURPOSE:To perform accurate detection by providing the 1st circuit which detects resistance variation depending upon the presence/absence state of smoke, gas, etc., and the 2nd circuit which detects a heater current, and turning on and off switches provided to the 1st and the 2nd circuits. CONSTITUTION:The 1st circuit 13 is constituted by connecting a DC power source 5, a heater electrode 3a, the 1st switch 9, a heater electrode 3b, and a resistance 8 in series, and the 2nd circuit 14 is constituted by connecting the series circuit of the 2nd switch 10, a constant current circuit 11, and a heater current detecting circuit 12 and a detection resistance 8 in parallel. Then, the couple of heater electrodes 3a and 3b generate heat with the 1st and the 2nd switches 9 and 10 on to heat a detection material 2 such as a oxide semiconductor sufficiently, and then both switches are turned to detect gas, smoke, etc., from the potential difference across the detection resistance. Further, the breaking of wires of the heaters is detected by a heater current detecting circuit 12 without any delay. |
