| 摘要 |
PURPOSE:To detect a signal with high reliability with lowly consumed electric power by driving the titled sensor intermittently at the ordinary time and changing over to the steady driving in case the abnormality is detected and detecting it again properly. CONSTITUTION:When gas does not exist in a detection part 2, the sensor is driven intermittently at a prescribed interval based on a signal wave with the regular pulse waveform. Then, now, when objective gas to be detected flows into the detection part 2, the pulse voltage from a heater driving circuit 3 is applied to a detection lead 1a and when the detection part is heated to 350-400 deg.C, gas molecules are adsorbed to its surface and a resistance value is reduced. Accordingly, the detection signal appears on the detection signal waveform according to this. Then, this detection signal takes a sufficient time interval to obtain the stable detection signal with a timing circuit 5 and outputs an output signal to a gate 6. Then, with the gate 6, a logical product of this output signal with the stable detection signal from a detection circuit 4 is taken and when it is formed, an alarm signal is first outputted with an alarm part 7 and an alarm to inform the existence of the objective gas is sounded.
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