| 摘要 |
PURPOSE:To reduce power consumption and to elevate the S/N ratio by detecting the resistance value at the timing of not heating the sensitive material in a sensor wherein the sensitive material is heated and the material to be sensed is adsorbed or desorbed to the sensitive material to detect the resistance. CONSTITUTION:The gad sensitive material 2 consisting of a metal oxide semiconductor is placed across the lead parts 1a, 1b to provide the sensor S. The lead part 1a is heated by the current supplied from a heater drive circuit 3 so as to be used as a haeter to heat the sensitive material 2. When a gas is present in the atmosphere, the sensitive material 2 adsorbs it so that its resistance is lowered. The detection current is conducted through the material 2 to detect the gas concentration from the electrical current passing through the detecting circuit 4. When the heating current is supplied from the drive circuit 3 to the lead 1a, it is leaked to the material 2 so that the signal output at the time of gas detection is lowered. The current is conducted intermittently to the heater 1a by a timing circuit 5 for detecting the resistance of the sensitive material at the timing of not conducting the current so that the concentration of the gas etc. may be detected by a small power consumption.
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