| 摘要 |
PURPOSE:To obtain an inexpensive analytical apparatus reguiring no wavelength selecting means, by using a min. absorption value obtained when a pressure reduced cell of a gas to be measured is put in the light path between a semiconductor laser showing multi-mode oscillation and a light receiving element as a reference value. CONSTITUTION:At first, only a pressure reduced gas cell C1 of a gas to be measured is inserted into the light path between a laser L and a light receiving element D and the output P2 of the light receiving element corresponding to the min. value of light absorbing characteristics shown by the pressure reduced cell is passed through a first stage amplifier 1 and a lock-in amplifier 2a and the multiplied output is inputted to an A/D converter 3a where digitized to be converted to P2D. This P2D is introduced into a microcomputer 4 to be stored by a memory means 5. In the next step, the gas cell C1 is removed from the light path while a gas cell C2 into which a gas to be observed is introduced at atmospheric pressure is inserted into the light path and the absorption characteristics thereof is measured to introduce the output PT of the light receiving element D into the microcomputer 4. In the microcomputer 4, operation treatment subtracting P2 from PT is carried out to calculate the concn. of the gas to be measured contained in the gas to be observed. |
