| 摘要 |
PROBLEM TO BE SOLVED: To provide a gas detector which generates digital signals, corresponding to an electrical characteristics of a sensor element in order to detect gas, without using A-D converters, when gas detection process is carried out as the internal processing of a microcomputer. SOLUTION: In the gas detector 1, a signal converting circuit 21 generates a transient response signal Sg, indicative of a time constant corresponding to the electrical resistance of the sensor element 23, and then the microcomputer 11 compares the transient response signal Sg with a threshold voltage Vt for deciding and obtains a count variable of high time Thi, when the transient response signal Sg exceeds the deciding threshold voltage Vt. A prescribed calculation is carried out, based on the conversion property (circuit property) of the signal converting circuit 21 and the high time count variable Thi, changing according to the electrical resistance of the sensor element 23, thereby obtaining a digital value Dsen indicative of the electrical resistance of the sensor elements 23. Then, a contamination detecting routine (S140) is carried out based on the digital value Dsen, and the concentration of the specific gas is decided. COPYRIGHT: (C)2004,JPO
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