| 摘要 |
PROBLEM TO BE SOLVED: To improve detection accuracy of a resistance value of a three-terminal type oxide semiconductor sensor wherein one terminal is used in common by a heater and a sensitive part. SOLUTION: A voltage generation part 20 applies to a heater 3 a pulse-shaped voltage whose pulse width is modulated under control by a control part 23, to thereby heat the sensitive part 2. On the other hand, an output detection part 22 reads a detection output VO to which a resistance value Rs of the sensitive part 2 is reflected during a period when the applied voltage to the heater 3 is zero. A heater resistance is almost negligible because it is remarkably small compare with Rs, and the resistance value Rs of the sensitive part 2 can be determined accurately without depending on a voltage generated in the heater resistance as hitherto. In addition, a resistance value detection part 21 reads the heater resistance during the period when the applied voltage to the heater 3 is zero, and the control part 23 controls the pulse width of the applied voltage so as to acquire a target temperature by calculating the temperature from the heater resistance. Consequently, temperature stability of the sensitive part 2 becomes excellent, and the detection accuracy of the resistance value Rs becomes higher. COPYRIGHT: (C)2006,JPO&NCIPI
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