| 摘要 |
PROBLEM TO BE SOLVED: To provide a method capable of calibrating an apparatus by a simple method and capable of measuring the accurate concentration of gas regardless of the temperature of sample gas, and to provide an apparatus therefor. SOLUTION: In the ultrasonic reflection type method for measuring the concentration of the sample gas using the ultrasonic reflection type apparatus for measuring the concentration of the gas constituted so that an ultrasonic vibrator 2, a reflecting plate 10 and a temperature sensor 3 are provided in piping 1 through which the sample gas flows, the kind of calibration gas with a known concentration is charged in the apparatus, and the reference length of the piping 1 connecting the ultrasonic vibrator 2 and the reflecting plate 10 is calibrated from the propagation time of the ultrasonic waves transmitted from the ultrasonic vibrator 2 and reflected by the reflecting plate 10 to be received by the ultrasonic vibrator 2.
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