| 摘要 |
<p>PURPOSE:To provide a smoke detector which reduces a power consumption, and enables smoke, suddenly produced, to be relibaly detected for a long period of time, by a method wherein a smoke-sensitive substance (humidity-sensitive resistance), a means for heating the substance, and a means for detecting a rapid change in resistance are combined together. CONSTITUTION:Electrodes 2 and 3 are located at both sides of MgCr2-TiO2 porous ceramic (humidity-sensitive resistance) 1, and a heating substance 4 formed in a coil is placed at the outside of the electrodes so that it is prevented from making contact with the ceramic 1 to form a smoke detecting element 12 which is combined with a differential circuit 15 for detecting a change in a resistance Rs of the humidity-sensitive resistor 1 to constitute a smoke detecting device. In said device, a reference resistance RL and an A/D conversion circuit 14 convert an AC voltage from an oscillator (OSC) 13 into a DC voltage based on the resistance Rs in the smoke detecting element 12, and secondarily, a differentiation circuit 15 separates it from a change produced due to other cause to detect the sudden production of smoke. Finally, the heating substance 4 is energized from a power source 16 for heating, which results in removing contamination on the surface of the detecting element to restore to the initial condition rapidly.</p> |
