| 摘要 |
PURPOSE:To allow a sensing device to measure the concentration of carbon dioxide gas with good precision for a long time without making calibration. CONSTITUTION:The operating temp. of a carbon dioxide gas sensor 101 is varied by a heater voltage setting means 1 having been received the output of a measuring timing output means 2, and the output difference of the sensor is measured by an output difference calculating means 3, and based thereupon a concentration calculating means 4 determines the concentration of carbon dioxide gas. Thereby, the concentration is measurable without making calibration. The lifetime of the sensor 101 can be improved by introducing the standby mode in which the operating temp. of the sensor 1 is made low besides when the measuring goes on. The atmosphere of measuring is stabilized by closing the sensor 101 at the time of measuring using a sensor closing means, which allows making calibration with good precision. The outer air is introduced only during the standby mode, and the sensor 101 is closed by the sensor closing means prior to the start of the measurement, and thereby, the measurement can be done with better accuracy and the time required for measurement be shortened. |
