| 摘要 |
<P>PROBLEM TO BE SOLVED: To extend a measurement concentration range in a gas analysis device for measuring a concentration in a particular gas within a gas to be measured by using an absorption of laser light. <P>SOLUTION: When the concentration in the particular gas is relatively high, a control unit 28 sets a modulation amplitude for frequency-modulating the laser light in a modulation amplitude controlling voltage generation unit 33 to 0 and controls a switch 26 so as to select an output from a second ADC 25. A calculation unit 27 calculates a volume concentration of a water molecule by implementing a calculation processing according to a direct absorption detection method. When the concentration in the particular gas is relatively low, the modulation amplitude is set to A other than 0. The switch 26 is controlled so as to select an output from a first ADC 24 for digitalizing a synchronization detection signal. The calculation unit 27 calculates the volume concentration of the water molecule by implementing a calculation processing according to a harmonic synchronization detection method. The concentration calculated by one of the methods is determined, and compared with a threshold. When it determines that correct results can not be obtained, a measurement is continuously implemented as the methods are switched. <P>COPYRIGHT: (C)2011,JPO&INPIT |
